ovation fuzz from the late 60's/// help me resurrect it?

[pinkjimiphoton]

For the Reverb:

all the circled numbers on the schematic have been traced, beeped, verified and corrected for which pins they actually go to. its possible i have the pnp's connections backwards, as i'm not sure if the emitter is actually the reverb drive or the ground.  that part i had to guess. if it makes sense switching ONLY those two connections, thats hip, cuz one of the two terminates in the chassis ground off the tank itself, carried there in the shield of the cable.

Hmmm, so really, that leaves up with the reverb connections unresolved/whacky.   Have you confirmed the reverb tank is internally grounded?  It's not a normal thing to do and even less normal for the drive side to be grounded even more so the tip - totally bizarre!   The PNP pin-out looks fine from the transistor data, the PCB and the way it is wired in the circuit.

somethings getting lost here in translation again. the connection there to pins 10 (HOT) and 11 (shield) on the socket are what they are.  i'm not sure which side of the drive amp is supposed to be "the output".

the tip/hot is most def NOT grounded. and the side that has the ground strap to it i believe is the reverb tank output side, not the input side. somehow things here n there got reversed, so we're both trying to figure it out. i dunno enough about reverbs to know where the output is suppposed to be taken from on the drive amp... the e of the pnp? or the 680 r resistor? i'd assume the shield would go to the e, but... in that case, the ground connection would travel thru the shield to the tank, and then terminate in the corner on the other short side of where the tank output is.

sorry... like you said, too many 3 am's lol

just curious. its 2019, be nice to let the verb "splash " when ya kill it.

Cutting the tank input line might do that since there is DC through the input coil (from what I can see).
Normally you wouldn't want that though.[\quote]

who ever said i'm normal

do ya think there's a way to kill the reverb from the footswitch, but change it from the output of the verb to the input?
maybe switch the footswitch from killing the output of the verb, to shorting the input to ground instead? or is that gonna be POP!! causing issues with noise and stuff?

There's many ways to do it.   Some methods may invoke the evil hum spirit, either due to the length of the wiring or where the grounding point are made (or due to restriction in the way the footswitch works).  I'm still not 100% sure on the foot switch and power supply.  I haven't had a chance to draw it up.  Also I wasn't sure if the terminal blocks wired one side to the other, or wired above to below  - need to look at it again.

i don't really NEED to do it, i just find it weird to here the reverb die like that in this modern age lol.
the cable to the footswitch is about 22 feet long, so yeah, hum could be an issue for sure.

right now, due to the weird wiring i stumbled on and doc'd last nite, its fairly quiet, and works well with very little "popping". every other way i tried was inSANE. popping? shit, EXPLOSIONS ffs. lol

and did i mention i'm fairly lazy?

For the Tremolo:

gonna post the graphic ,
but trem speed pot

trem intensity i had afu

The new intensity connection makes 100% sense now.   That's how I drew it before but it didn't agree with the wiring so we changed it.

Apart from the now fix green wire connection that I had the writing against, the speed pot wiring was actually correct before.  You actually flipped the speed pot and the numbers to make it the same as before.  However when you changed the numbers is now causes a disagreement between the edge connection numbers and the parts on the PCB - we can't move those.   So the correction is
- remove that dubious green wire from the trem switch to the speed pot
- wire the trem switch to the intensity pot
- leave the speed pot wires and number as they were in the V2.1 schematic.

yes, exactly... i believe that that is all 100% correct now.
sure seems to make more sense. i didn't remove the dubious green wire in the updated graphic
i digitally molested last nite.

I'll add the labels to the Trem "outputs" to the channels.   They got left off somewhere along the way.

that will certainly help MY dumb ass!! lol... btw, which of the resistors do you think are limiting the trem depth? maybe change R6 from 100k to 47k, or even 10k? or will that make it unstable?
i have barely messed with trems at all. generally me and anything that oscillates can't seem to get a long

PSU:

i'm beginning to realize we're gonna have to get the power supply right, too, unless ya wanna just say screw it and let peeps use whatever they want. for posterity sake, and any poor loser who dare tread here trying to fix one, it would be kind of us to do i guess. pretty lazy tho.

Yes, if you want to play with footswitch I think we need to get all that down on paper.  You wiring notes cover most of it.

I need to read over your new PSU pic.

it should be dead on the money. but... if something should be green and i say blue, or should be yellow and i say white, thats this goddamn glaucoma. i can't tell some colors apart without super brite light anymore.

btw, it appears the terminal blocks pass THRU the chassis i think, from the power supply side to the pcb side. i will try and beep it out to be sure.

i know the center terminals DO connect thru for sure.

Early on you mentioned the mixer was at 22V and the reverb and fuzz were at 9V.   Is that still true?   IIRC, there are four power rails.  They had 1k resistors and there circuit didn't look like it pulled enough current to drop 22V to 9V across 1k's.

after changing the q's on the fuzz board, i get 25-0-25 off the transformer.
most of the boards seem to run about 16volts, the fuzz runs at about 11. reverb, too.
the voltage definitely has changed since we started with it.

one thing thats a bitch tho, is to get at the pinouts for the sockets, you usually gotta pull a board to get at the ones in back... and when ya pull a board? the voltage seems to go up a volt or two. so that's probably where some discrepancies came from too.

also.... while i remember... in SOME cases, sockets have multiple connections to the same pins, and in SOME cases, the color coding changes when it leaves the socket... mosty on the osc board for the tuner if memory serves, but that could account for some weirdnesses too. once i can see all the schematics together, hopefully i can match up all the connections so the whole bloody mess makes a little more sense.

i had to ditch the 3906. playing with it today, it just plain sounded lousy. yeah, it was a little louder, but really just too farty and gross. so i replaced that mofo with the ac125 i first tried in the pedal...
yeah...

You have to do what you have to do. 

now, when ya kick it in, it just sounds like natural overdrive, that nice tubey sound only ge can give. no boost in volume, and ya gotta peg the fuzz, but thats ok, i'd rather have a useable overdrive i can add fuzz to than an unruly fuzz that's just plain.... not that great.

lol.. of course, i also learned why i need to put a three prong power on it and ditch the reverse switch, as last nite this thing was humming louder than a pack of harleys lol

ok. also finished the footswitch. i smoked one of 'em. haven't done that in years!

Too many 3:00am's

messy inside, recycled amp footswitch, had to drill some holes and mess with wiring some to get it working right, so a bit ugly, but functional. i just tied the three resistors together and soldered the white wire i added to the center pin of the plug for powering the whole mess.

Things with missing footswitches are always a pain.  They get very little air-play in the docs to work it out.

And a purple mojo led ...

well, the important thing is, we CRACKED THIS SUCKAH!!
the footswitch will be handy for some poor guy someday i am sure.
it DOES make it noisier, but its not THAT bad.

we'll carry onward. gonna go hit the dungeon and see what happens. i will try and beep out the connections on the terminal blocks to see if they do indeed pass thru the chassis from one side to the next.

more later

[Rob Strand]

somethings getting lost here in translation again. the connection there to pins 10 (HOT) and 11 (shield) on the socket are what they are.  i'm not sure which side of the drive amp is supposed to be "the output".

the tip/hot is most def NOT grounded. and the side that has the ground strap to it i believe is the reverb tank output side, not the input side. somehow things here n there got reversed, so we're both trying to figure it out. i dunno enough about reverbs to know where the output is suppposed to be taken from on the drive amp... the e of the pnp? or the 680 r resistor? i'd assume the shield would go to the e, but... in that case, the ground connection would travel thru the shield to the tank, and then terminate in the corner on the other short side of where the tank output is.

I'm pretty sure the output of the amplifier which drives the tank input should go to R8 (pin #11) and ground.  I'm not overly concerned about the shield going to the output pin.  They might be flipping the phase of the reverb so it adds back to the dry signal correctly.

I'm mainly concerned with the fact with haven't proven the tip does connect to ground.  In fact if the Tank input tip *is* wired to Reverb pin10 we have already accounted for both Tank inputs.   In that case it doesn't makes sense for there to be a ground at the reverb.  If the Tank input when to ground at the reverb it would effectively short pin 10 to ground and that would kill the reverb drive entirely (as it shorts the drive amp input to ground through the reverb).

right now, due to the weird wiring i stumbled on and doc'd last nite, its fairly quiet, and works well with very little "popping". every other way i tried was inSANE. popping? shit, EXPLOSIONS ffs. lol

I don't understand it yet but when I look at the circuit the wierd R12 R13 thing makes me think someone tinkered with the values to reduce the pop when switching.

the cable to the footswitch is about 22 feet long, so yeah, hum could be an issue for sure.

So if you went down that road you would need a relay or JFET (or maybe transistor) to switch audio at the amp end and only run the control signal down the footswitch wire.

which of the resistors do you think are limiting the trem depth? maybe change R6 from 100k to 47k, or even 10k? or will that make it unstable?

R6 will probably do something.  My initial impression is R12 and R18 are limiting the depth.  So reducing those might increase the depth.   The way I look at it is the tremolo modulates the gain of the last stage of the channel amps.   The minimum gain is when the Vactrols are open leaving 6.8k's in the emitters.  The maximum gain is when the Vactrols are shorted.  The series resistance limits the the minimum resistance to 1.5k.  1.5k in parallel with 6.8k is 1.2k.    So the gain can't change more than about 6.8 / 1.2 = 5.7.     Now that assumes the Vactrols are being driven from close to short to open.  Maybe they aren't and if not R6 might work too; maybe R6 an R12 and R18 all need tweaking, it comes down to the specifics of what the Vactrol resistance is.

it should be dead on the money. but... if something should be green and i say blue, or should be yellow and i say white, thats this goddamn glaucoma. i can't tell some colors apart without super brite light anymore.

Not good.  I haven't had a chance to go over it in detail.

after changing the q's on the fuzz board, i get 25-0-25 off the transformer.
most of the boards seem to run about 16volts, the fuzz runs at about 11. reverb, too.
the voltage definitely has changed since we started with it.

OK thanks - cool.

one thing thats a bitch tho, is to get at the pinouts for the sockets, you usually gotta pull a board to get at the ones in back... and when ya pull a board? the voltage seems to go up a volt or two. so that's probably where some discrepancies came from too.

Yeah, that whole area is a mystery to me.

well, the important thing is, we CRACKED THIS SUCKAH!!
the footswitch will be handy for some poor guy someday i am sure.
it DOES make it noisier, but its not THAT bad

Yes we aren't too far off.   I guess we have gone a lot further than just fixing the thing

[pinkjimiphoton]

somethings getting lost here in translation again. the connection there to pins 10 (HOT) and 11 (shield) on the socket are what they are.  i'm not sure which side of the drive amp is supposed to be "the output".

the tip/hot is most def NOT grounded. and the side that has the ground strap to it i believe is the reverb tank output side, not the input side. somehow things here n there got reversed, so we're both trying to figure it out. i dunno enough about reverbs to know where the output is suppposed to be taken from on the drive amp... the e of the pnp? or the 680 r resistor? i'd assume the shield would go to the e, but... in that case, the ground connection would travel thru the shield to the tank, and then terminate in the corner on the other short side of where the tank output is.

I'm pretty sure the output of the amplifier which drives the tank input should go to R8 (pin #11) and ground.  I'm not overly concerned about the shield going to the output pin.  They might be flipping the phase of the reverb so it adds back to the dry signal correctly.

I'm mainly concerned with the fact with haven't proven the tip does connect to ground.  In fact if the Tank input tip *is* wired to Reverb pin10 we have already accounted for both Tank inputs.   In that case it doesn't makes sense for there to be a ground at the reverb.  If the Tank input when to ground at the reverb it would effectively short pin 10 to ground and that would kill the reverb drive entirely (as it shorts the drive amp input to ground through the reverb).

the tip doesn't connect to ground bro. the tip connects to the tip. that's pin 10. the sleeve connects to pin 11, and pin 12 is grounded, but to a specific point.

what i'm not sure is where the signal comes from that goes down the shielded wire, if it exits the circuit from the 680r resistor, or e of q2 is what i mean. to me, it seems either would probably have signal on it.

ok. just compared the overlay to the schematic. we definitely are still reversing some connections.
pin 10 becomes pin 3 when ya flip the board. which appears to have happened.

again.

so... we'll reverse shit and go with the pinout you prefer, which is 180 opposite of mine.

reverb socket pin 1 reverb send shield (reverb drive amp)
reverb socket pin 2 no connection
reverb socket pin 3 blue wire to terminal block #2, side a #3
reverb socket pin 4 reverb level 2
reverb socket pin 5 key
reverb socket pin 6 reverb send hot/tip (reverb drive amp)
reverb socket pin 7 green wire to reverb level 3
reverb socket pin 8 purple wire to mixer pin #11
reverb socket pin 9 orange wire to terminal block #1, side b, pin #5
reverb socket pin 10 reverb return tip/hot (reverb recovery amp)
reverb socket pin 11 reverb return shield (reverb recovery amp)
reverb socket pin 12, ground at mixer pin #8

i just messed with the drawing a little, compared my notes to the schematic and the parts overlay,
and this is definitely gotta be it on this drawing. we had the pinouts opposite each other.
remember, i was describing from the COMPONENT side of the board, not the trace side when numbering, as in the amp its opposite the way the fuzz is.
so all our connections are backwards from each other.

right now, due to the weird wiring i stumbled on and doc'd last nite, its fairly quiet, and works well with very little "popping". every other way i tried was inSANE. popping? shit, EXPLOSIONS ffs. lol

I don't understand it yet but when I look at the circuit the wierd R12 R13 thing makes me think someone tinkered with the values to reduce the pop when switching.

r12/13 on which board?

the cable to the footswitch is about 22 feet long, so yeah, hum could be an issue for sure.

So if you went down that road you would need a relay or JFET (or maybe transistor) to switch audio at the amp end and only run the control signal down the footswitch wire.[\quote]

yeah, probably the easiest way to do it, but i'll really need help cuz i haven't tried a transistor as a switch yet, tho it looks kinda easy... still gotta pass power down the cable tho to power the led's, wondering if its worth it to add another daughterboard inside the unit or not.
if ya crank the preamp fairly loud, and turn the amp down, its pretty quiet.

which of the resistors do you think are limiting the trem depth? maybe change R6 from 100k to 47k, or even 10k? or will that make it unstable?

R6 will probably do something.  My initial impression is R12 and R18 are limiting the depth.  So reducing those might increase the depth.   The way I look at it is the tremolo modulates the gain of the last stage of the channel amps.   The minimum gain is when the Vactrols are open leaving 6.8k's in the emitters.  The maximum gain is when the Vactrols are shorted.  The series resistance limits the the minimum resistance to 1.5k.  1.5k in parallel with 6.8k is 1.2k.    So the gain can't change more than about 6.8 / 1.2 = 5.7.     Now that assumes the Vactrols are being driven from close to short to open.  Maybe they aren't and if not R6 might work too; maybe R6 an R12 and R18 all need tweaking, it comes down to the specifics of what the Vactrol resistance is.

should i get a reading off of them? would i have to unsolder one end like with resistors, or just clamp my meter to them? pink don' knows nothin' bouts no vactrols....
the trem is actually pretty sweet since i changed the fuzz around.

it should be dead on the money. but... if something should be green and i say blue, or should be yellow and i say white, thats this goddamn glaucoma. i can't tell some colors apart without super brite light anymore.

Not good.  I haven't had a chance to go over it in detail.

yeah, when i hooked up power for the footswitching, i looked EVERYwhere for the "white" wire i'd found the nite before... only to discover in daylight it was yellow, not white. glaucoma sucks... even with COPious amounts of... cof.. medicine

after changing the q's on the fuzz board, i get 25-0-25 off the transformer.
most of the boards seem to run about 16volts, the fuzz runs at about 11. reverb, too.
the voltage definitely has changed since we started with it.

OK thanks - cool.

one thing thats a bitch tho, is to get at the pinouts for the sockets, you usually gotta pull a board to get at the ones in back... and when ya pull a board? the voltage seems to go up a volt or two. so that's probably where some discrepancies came from too.

Yeah, that whole area is a mystery to me.

well, the important thing is, we CRACKED THIS SUCKAH!!
the footswitch will be handy for some poor guy someday i am sure.
it DOES make it noisier, but its not THAT bad

Yes we aren't too far off.   I guess we have gone a lot further than just fixing the thing

yeah, we done good bro.
when all was said and done, i ended up with a pair of ge's in the amp itself, i had to go a bit higher gain than i wanted, but it got a nice overdrive to it. as ya turn the fuzz mix pot, it actually phases against the channel settings, allowing quite a wide range of tones.

i used an ac176/ac128 combo for the npn/pnp respectively.

in the standalone, its gonna either need some values tweaked or really low gain q's.
right now i've been trying to choose between two different ge npn's for q1. i've got an ac128 in q2 which seems happy there.
but its so weird. it wants LEAKAGE to be happy in q1. not too much, not too little.
in q2, the ac128 reads 89hFE with 108mv leakage <i can't do math, best i can offer, sorry>
in q1, i tried using a switch to choose transistors. it was actually kinda amusing, cuz at first i tried tieing e's and c's together and just switching b's. THAT was interesting. frankly, i liked it better... i could get a clear difference tween a nice overdrivey kinda warm ge tone, and a boosted much louder FUZZtone.

i may go back to it. still trying to decide. the other way leaves the b's connected and switches the e's and c's. it pops more, and i lose a bit of fuzztone and volume. interestingly, if i reverse beta one q, it gets a better fuzz and is about 4x louder!

anyways, in q1,
the first q on the switch is
2n1302 ge
hFE 36(!!!) with 226mV leakage.
reverse beta gives a very unapologetic 60's style fuzz, correct its like a warmish overdrive.

but the OTHER transistor, shit, i dunno what to make of it. its ge, marked o73 and is a VERY old q, one of the first that was available, a real antique. i picked a couple up years ago, and thought their gain too low. but man, in this fuzz, it really rips!
http://dsmcz.com/prestashop/unknown-spec-transistors/6466-transistor-4-073.html
i can't say what the gain is, cuz neither my meter nor my transistor tester can seem to read it.

it comes up as two opposing diodes with a tap in the center...
                                            2
like...  1--------I<--------------+----------------->I---------3
the left side reads 1.11v, the right side says 419mv

no idea!!!!! above my paygrade!
wondering if what its actually doing is conducting the input to the base thru to the collector to get amplified by the second stage.

every @#$%ing thing about this circuit is beyond weird!!!!!!!!!!!!!!!!!!!!

anyways, i await what ya think... let me know if the reverb looks right above.
it gets confusing for sure.. and often stuff got reversed between your notes and mine, so i've started looking at stuff the opposite way if it doesn't make sense, and then things seem to start to work. i think.

its like... take neon green. if you make it the opposite, ie negative, it becomes hot pink.

these sockets are like that. i think now, we're getting 'em right.

i'm gonna go play with transistors for another hour or so trying to find the optimal ones for the standalone. i've spent a good chunk of a couple days doing this, and got it narrowed down to the two.. do i go with the fuzzier tone, or the more overdrivey one?

@#$%! said pink... i likes 'em both!!

but, saith the voice of reason... dude... yer using GE. its gonna sound different EVERY SINGLE TIME
lol

i think i've found my own private hell    

[Rob Strand]

the tip doesn't connect to ground bro.

When you were talking about the reverb being grounded at the reverb end I thought you meant, *in order to fix the reverb drive issue* the Tank input "tip" was ground *at the reverb*. I understand the tip is not ground at the Reverb board side and goes to Reverb #10.    I think I misunderstood which terminal you said was grounded at the reverb.   It's the shield on the Tank Output - yeah?    Sometimes that *is* done whenever the Reverb Tank casing cannot come in contact with chassis ground - like when it is mounted on the wooden base of an amp, or isolated with rubber gromets.   The Tank Input usually floats both terminals.

ok. just compared the overlay to the schematic. we definitely are still reversing some connections.
pin 10 becomes pin 3 when ya flip the board. which appears to have happened.

again.
...

so all our connections are backwards from each other.

I'm pretty sure all the connections on the last dump of "revision 2.1" schematics are correct.    If you look at your reverb markup and my latest Reverb V2.1 schematic all the connections now agree.  Your markup was on V1.0 which *did* have the reversals.

what i'm not sure is where the signal comes from that goes down the shielded wire, if it exits the circuit from the 680r resistor, or e of q2 is what i mean. to me, it seems either would probably have signal on it.

Ok the drive definitely comes out of Q2's collector then though R8 (680R) then to the reverb tank input (shield).   That's part makes 100% sense to me.

The hanging issue is where the other end of the drive goes ie. the Tank Input tip.   Based on the current wiring and schematics:  it goes to Reverb #10 which then goes to R1 on the schematic.  This matches the V2.1 Reverb Schematic and your wiring.   You can see pin #10 goes to R1 on the overlay,



So if all the checks point to that - it must be like that?

r12/13 on which board?

On the reverb board.

should i get a reading off of them? would i have to unsolder one end like with resistors, or just clamp my meter to them? pink don' knows nothin' bouts no vactrols....
the trem is actually pretty sweet since i changed the fuzz around.

It's a bit tricky as the resistance gets modulated and you will end-up with fluctuating results, which could be useless.   Given we have nothing to lose give it a try.   You could measure the resistance across the vactrols when the both Trems are disabled.  Measure both Vactrols.   That might help work out the centre.  However it doesn't really tell us if it swings closer to open or closed.

even with COPious amounts of... cof.. medicine

One of my bosses had that (he was a good guy).   He had it under control but I'm sure there's varying degrees of the symptoms.

when all was said and done, i ended up with a pair of ge's in the amp itself, i had to go a bit higher gain than i wanted, but it got a nice overdrive to it. as ya turn the fuzz mix pot, it actually phases against the channel settings, allowing quite a wide range of tones.

You might as well put all you can into it.

nterestingly, if i reverse beta one q, it gets a better fuzz and is about 4x louder!

Hard to say what will happen.  It comes down to specifics and where the bias points end-up.

2
like...  1--------I<--------------+----------------->I---------3
the left side reads 1.11v, the right side says 419mv

If I saw that the first thing I would think of is it is a Darlington:  1=e, 2=b 3=c

anyways, i await what ya think... let me know if the reverb looks right above.
it gets confusing for sure.. and often stuff got reversed between your notes and mine, so i've started looking at stuff the opposite way if it doesn't make sense, and then things seem to start to work. i think.

I think were are in agreement now.

I"m still not 100% happy about the Tank Input tip going to the input of the amp - it just looks totally whacked to me.

[pinkjimiphoton]

the tip doesn't connect to ground bro.

When you were talking about the reverb being grounded at the reverb end I thought you meant, *in order to fix the reverb drive issue* the Tank input "tip" was ground *at the reverb*. I understand the tip is not ground at the Reverb board side and goes to Reverb #10.    I think I misunderstood which terminal you said was grounded at the reverb.   It's the shield on the Tank Output - yeah?

yeah!!!!!!!

Sometimes that *is* done whenever the Reverb Tank casing cannot come in contact with chassis ground - like when it is mounted on the wooden base of an amp, or isolated with rubber gromets.   The Tank Input usually floats both terminals.

yeah, this is floated completely, rubber washers, and it connects funny... weird machine!

ok. just compared the overlay to the schematic. we definitely are still reversing some connections.
pin 10 becomes pin 3 when ya flip the board. which appears to have happened.

again.
...

so all our connections are backwards from each other.

I'm pretty sure all the connections on the last dump of "revision 2.1" schematics are correct.    If you look at your reverb markup and my latest Reverb V2.1 schematic all the connections now agree.  Your markup was on V1.0 which *did* have the reversals.

hahahha i think i need sleep

what i'm not sure is where the signal comes from that goes down the shielded wire, if it exits the circuit from the 680r resistor, or e of q2 is what i mean. to me, it seems either would probably have signal on it.

Ok the drive definitely comes out of Q2's collector then though R8 (680R) then to the reverb tank input (shield).   That's part makes 100% sense to me.[/quote]

The hanging issue is where the other end of the drive goes ie. the Tank Input tip.   Based on the current wiring and schematics:  it goes to Reverb #10 which then goes to R1 on the schematic.  This matches the V2.1 Reverb Schematic and your wiring.   You can see pin #10 goes to R1 on the overlay,[/quote]

yep, thats right. i agree. somehow i guess i lost one of the graphics with a puter issue or something, or i AM that braindead or possibly both





So if all the checks point to that - it must be like that?[/quote]

yes exactly correct

r12/13 on which board?

On the reverb board.

i will take a peek in the morning when i have good light.

should i get a reading off of them? would i have to unsolder one end like with resistors, or just clamp my meter to them? pink don' knows nothin' bouts no vactrols....
the trem is actually pretty sweet since i changed the fuzz around.

It's a bit tricky as the resistance gets modulated and you will end-up with fluctuating results, which could be useless.   Given we have nothing to lose give it a try.   You could measure the resistance across the vactrols when the both Trems are disabled.  Measure both Vactrols.   That might help work out the centre.  However it doesn't really tell us if it swings closer to open or closed.

tried, my shitty meter is acting up and i couldn't get a "range" where anything seemed to show up.

even with COPious amounts of... cof.. medicine

One of my bosses had that (he was a good guy).   He had it under control but I'm sure there's varying degrees of the symptoms.

stuff just slowly gets.... dimmer.

when all was said and done, i ended up with a pair of ge's in the amp itself, i had to go a bit higher gain than i wanted, but it got a nice overdrive to it. as ya turn the fuzz mix pot, it actually phases against the channel settings, allowing quite a wide range of tones.

You might as well put all you can into it.

when i get a chance to actually breadboard the thing, i'll play with values to adjust it to sound a bit better. i'm imagining the bias is way off from where it should be to get the circuit to sound its best.

nterestingly, if i reverse beta one q, it gets a better fuzz and is about 4x louder!

Hard to say what will happen.  It comes down to specifics and where the bias points end-up.

and a whole lotta leakage!!

2
like...  1--------I<--------------+----------------->I---------3
the left side reads 1.11v, the right side says 419mv

If I saw that the first thing I would think of is it is a Darlington:  1=e, 2=b 3=c

wow. weird, the only time i've seen it on the little chinese transistor checker do that is with really leaky germanium. sometimes it will read them as jfets. weird.
did they make germanium darlingtons?

anyways, i await what ya think... let me know if the reverb looks right above.
it gets confusing for sure.. and often stuff got reversed between your notes and mine, so i've started looking at stuff the opposite way if it doesn't make sense, and then things seem to start to work. i think.

I think were are in agreement now.

I"m still not 100% happy about the Tank Input tip going to the input of the amp - it just looks totally whacked to me.

wayyyyyyyydaminnit... i think i'm suddenly misunderstanding this again. where the hell does the signal to be reverberated COME from? cuz yeah, it sure seems weird looking at it, but its gotta be what its gotta be.
the only explanation i can get would be reverse #11 and #2 again, cuz it can only be one or the other. #2 has no connection AFAIK!

so... the input to the reverb drive amp comes from ? would have to be the mixer, right?

[Rob Strand]

So if all the checks point to that - it must be like that?

yes exactly correct

It's just weird!  weird weird weird ...  (skips off in the distance with a crazed laugh)

tried, my shitty meter is acting up and i couldn't get a "range" where anything seemed to show up.

Well, you could do an experiment and put a 470R ohm in parallel with the 1k5's.

wow. weird, the only time i've seen it on the little chinese transistor checker do that is with really leaky germanium. sometimes it will read them as jfets. weird.
did they make germanium darlingtons?

Leakage could make cause the tester to show dodgy results.  Maybe check the "diode" voltages directly with a DMM.

wayyyyyyyydaminnit... i think i'm suddenly misunderstanding this again. where the hell does the signal to be reverberated COME from? cuz yeah, it sure seems weird looking at it, but its gotta be what its gotta be.
the only explanation i can get would be reverse #11 and #2 again, cuz it can only be one or the other. #2 has no connection AFAIK!

so... the input to the reverb drive amp comes from ? would have to be the mixer, right?

From what I can see with the current set-up:  one side of the drive comes from the 680ohm (Reverb pin #11), the other side comes from Reverb pin #10.   However, the input to the reverb drive amp (ie. the input of the reverb "block" in the bigger picture)  is also on Reverb pin #10  the input signal to the drive amp comes from Mixer pin #4.     The weird thing is the reverb spring is wrapped from the out back the input of the reverb drive amp.   So that *is* how it appears to be connected.  However, to me it makes no sense and every time I look at it red lights flash and I hear a robot voice saying does not compute.   To me the input and output are at wrong phase for that connection and the impedance driving the input is too high.

Anyway I can explain where an input the Reverb is coming from (Mixer pin #4 to Reverb pin #10)  but the connection of the Tank Input is screwed.

[pinkjimiphoton]

ok, that all makes sense... at least as much as can be made with this monstrosity!!

i'm ASSUMING the weird shit is cuz everything is in parallel. right up until ya peg it its fairly weak to normal, but when ya peg it... the channels, reverb, or fuzz... everything kinda saturates.

this is the weirdest thing i ever dealt with!

if you're as sick of messing with it as i am getting to be, let me know, and i'll call this nut cracked, at least cracked enough. the main missions were to remake the fuzz, and get it working, so mission accomplished, the rest is cake i think.

i wanna thank you for the help, and more, for the hang, bro.  you rock. let me know what ya wanna do... if ya wanna finish the beast off for posterity, i can get whatever data remains. if ya think we're good, i'm good with that, too. my job has been the easy part, you've done all the heavy lifting, so i'm leaving the final decision up to you!



now, i'm-a gonna go build me a flangerlicious pedal while i await your reply.

[Rob Strand]

this is the weirdest thing i ever dealt with!

Same here.   It's just different enough to put you off the scent at every step.  Normally I can guess what is going on but I can only put a 20% confidence on any guesses with that thing.

i wanna thank you for the help, and more, for the hang, bro.  you rock. let me know what ya wanna do... if ya wanna finish the beast off for posterity, i can get whatever data remains. if ya think we're good, i'm good with that, too. my job has been the easy part, you've done all the heavy lifting, so i'm leaving the final decision up to you!

No worries at all.  It would probably be a good thing to polish off the switching and PSU.  I scared to go there because it might open another can of confusing worms.   I had a dream about tracing the tuner.  That might take a while.

[pinkjimiphoton]

heheheh

well, since its in parallel, ummm... want me to pull the dang board n just mail it to you?

may be easier than me messing stuff up again.
i must warn you tho
that some of the missing connections, or connections that make no sense probably jumper to the tuner board.

but what the hell, in for a dollar, in for a dime, i'll start getting the last of the info asap.

and hey!!!
them "vactrols" ain't vactrols i don't think. they only have three legs, and appear to be some kind of diode-y thing. i found one almost identical to the ones on the tremolo in my semi junk drawer and it had the same markings. tried to look it up, i don't see anything else like it.

the preamp, by itself, now has a really nice vintage tone, the fuzz sounds like tube distortion, the reverb is pretty much killer AND the tremolo sounds almost more like a vibe on the lower strings.. very phasey.

i will get a picture of the dang component, i meant to bring it upstairs with me but forgot all about it. need sleep. lol

rock on bro

[pinkjimiphoton]

rob,
on the tremolo board, could it be some kind of weird schotke diode?
cuz them black things on the tremolo board have three terminals pokin' into the board, and the markings on the front look just like the ones on this, but double, kinda...

[Rob Strand]

well, since its in parallel, ummm... want me to pull the dang board n just mail it to you?

may be easier than me messing stuff up again.
i must warn you tho
that some of the missing connections, or connections that make no sense probably jumper to the tuner board.

I wouldn't separate it from the unit.  The board is pretty much irreplaceable and should be kept with the mothership.   Whatever I get done is fine.  If you feel like getting the values in the future that's fine - I'll pencil it in for 2030  .

and hey!!!
them "vactrols" ain't vactrols i don't think. they only have three legs, and appear to be some kind of diode-y thing. i found one almost identical to the ones on the tremolo in my semi junk drawer and it had the same markings. tried to look it up, i don't see anything else like it.

To be honest, I'm not 100% sure what they are.   I drew them as vactrols with a common "LED" + resistance terminal.  That configuration should work (there are some issues with feedthrough in the Ovation ckt).     The part numbers looked a bit like some opto part numbers I've seen in the past.   I could not find any info on them.    It's on my "to do" list.   In 1969 there was probably all sort of weird parts floating around.   Parts that didn't work out disappeared and by the mid 70's the electronics world was largely what we see today.

[pinkjimiphoton]

its some kind of diode bridge or rectifier... wondering if thats why it sounds so phasey?

this is what was in my junk drawer, the markings are the same... i googled a metric arse load of vintage diodes and found nothing particularly close other than maybe this:

https://www.silicon-ark.co.uk/rvd10dc4r-dual-diode-by-international-rectifier



we need to get rg and mark n paul and jc in here so somebody can figure this out! lol





these are the two best crappy pics i could get of the things. they are marked with the same thing as the one i have and ones i've seen. apparently the "dot" is where the common cathode or anode ends up, depending on which way the diodes drawn on it face.

i will endeavor to get readings off the one i found tomorrow.







the ones in the unit, the top is epoxyed, makes me suspect its like, just two diodes in there. i have heard of diode based phasers AND trems, maybe this is what it is?

[Rob Strand]

these are the two best crappy pics i could get of the things. they are marked with the same thing as the one i have and ones i've seen. apparently the "dot" is where the common cathode or anode ends up, depending on which way the diodes drawn on it face.

i will endeavor to get readings off the one i found tomorrow.

Cool.  Yes!!!! They definitely are a dual diode device.

I can't quite make it out but to me it looks like, from left to right
(1)---A1--->|---K1---(2)---A2--->|--- K2---(3)

So the diodes point in the same direction.   Is that how you see it?
(In your "red and black" rectifier the diodes point to the centre terminal (2) which is much more common.)

So in the trem circuit, the general connections are,
Rectifier pin 1 to Collector
Rectifier pin 2 to channel amps
Rectifier pin 3 to Emitter

The lower diode, pin 2 to pin 3, is the variable resistance.
I can only assume the diode, pin 1 to pin 2, helps the tremolo transistor keep in the good range of bias voltages.

[pinkjimiphoton]

i forgot my bol, am on my way out the door to my thursday thing, so i will check cuz i gotta go down there anyways... gimme a second bro

[pinkjimiphoton]

0---->I--0--->I----0 is the marking in the ovation, and the same as the diode thing i found bro. so its def a dual diode!! cool!!

so thats in/anode cathode /center tap/ to anode to cathode/out?
i wonder if thats why it sounds so phasey. more of phase shift maybe than a trem?

stay tuned to this bat station!!! lol

[Rob Strand]

so thats in/anode cathode /center tap/ to anode to cathode/out?

in/anode
out/center tap
common point/ cathode

i wonder if thats why it sounds so phasey. more of phase shift maybe than a trem?

[/quote]
Normal diodes dont make it sound phasey, more distorted or you get ticks in sync with the LFO.
Phasey might the be due to the coupling cap between trem and the channel.

[Rob Strand]

This is the only info I could find,



The part number you gave kind of follows the pattern even though there are a few holes.
I'm pretty sure there's a datasheet somewhere elaborating on more options and details.

[pinkjimiphoton]

https://www.digchip.com/datasheets/5897984-ld6935l-dual-low-dropout.html

LD6935L
Category   
Title   Dual low-dropout regulators, high PSRR, 300 mA
Description   The LD6935 series consists of small-size dual Low DropOut regulators (LDO). Each device delivers two times 300 mA with a typical voltage drop of 240 mV at 300 mA for each LDO. Each device offers two individual fixed nominal output voltages (VO(nom)) from 1.2 V to 3.6 V.
The LDO has an integrated Soft start to control the inrush current during start-up. The output states when disabled can be high‑ohmic 3‑state or auto discharge. Optionally a delayed output circuit is available for the second output. The devices are available in DFN1612‑8 (SOT1225) plastic package with a height of 0.4 mm.
Extremely low standby current in shutdown mode (≤ 0.1 μA)
Low quiescent current
Low output noise
Fast turn-on time
High Power Supply Rejection Ratio (PSRR)
Auto discharge or high‑ohmic mode for output states when disabled
Delayed output circuit for second LDO (optional)
DFN1612-8 (SOT1225) leadless package 1.6 x 1.2 x 0.4 mm
Pb-free, Restriction of Hazardous Substances (RoHS) compliant, free of halogen and antimony (Dark Green compliant)

i thought this may be it until i saw the damn datasheet
https://www.digchip.com/datasheets/parts/datasheet/1019/LD6935L-pdf.php

the one in my junk drawer is a dual SELENIUM rectifier. assuming the ovation is the same. google and nte searches have turned up ONE OTHER ONE very similar to the one i have.

gonna keep lookin'!! its just a matter of time... all there base are belong to us lol

[Rob Strand]

LD6935L

I'm pretty sure that's the date code 69 = 1969.

It's like a fluke that the date code is the same as a part number.
There's no way that regulator was around in 1969.

[pinkjimiphoton]

agreed. i'm gonna take some measurements of the one i found in my junk drawer, and will post them to see what's what... hopefully can narrow it down.

from what i've been reading on the hifi sites, these can often be replaced with 2 diodes and a current limiter resistor.

still trying to find an exact-ish example somewhere, but i have a feeling its gonna be wicked hard to find. not that it's not out there...

maybe i should contact haveyouseenhim and see if he still has access to that surplus electronics place