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

[Rob Strand]

Today progress is slow from my side as well.  Can't seem to get things to match-up.  Maybe I'll post what I have and you can kick the wheels back into shape.

i think it would make a great little standalone project. but.. the trem is kinda weak, the REVERB is incredible tho.

I suspect the tremolo could be fixed there's some resistors in series with the Vactrols which are going to limit tremolofication  .    Reverb is a very simple ckt.  Has a low-pass filter.  Looks like in between voltage and current drive, ie. voltage drive through a resistors.

i started reading mad when i was about 4, stolen from my brother. no wonder i'm all messed up.

somebody somewhere is gonna be glad we did all this someday.

I'm sure of it.  Doesn't matter how obscure something is some poor bugger will get stuck on an obscure beastie.

watch... i'll make a freekin video extolling its virtues, and suddenly they'll pop out of the woodwork like %^&*roaches lol

Be good to hear it.     Roaches - lol!

[pinkjimiphoton]

unh hunh huh huh... hey, beavis, he said....

lmao. love it. what me worry?

so i didn't do anything i set out to do. i messed with some fuzzboxes with it, dialing in various things, running both channels paralleled with a jumper like we used to do on marshalls before all the modern amenities got added all the 13 year olds with daddy's credit cards needed <g>.... holy cow. interesting. the #2 input on each channel is slightly different gain and voice it seems like from the # 1 inputs, but ONLY when jumpering channels. so like, plug in channel one, input 2, and run a jumper from channel 1 input 1 to channel 2 input 1 or 2, 2 will be slightly hotter.
the interaction of the two channels is really strange too, particularly after i
molested the fuzz slightly like we all knew i was gonna do.
just for shits n grins i tacked 3 .1u caps shunting across the .001u caps, which i guess is .101u there instead.
NOW the fuzz actually sounds fairly good, and if ya jumper the channels right you can get a real nice brownish overdrive out of it.
the fuZz is in parallel, so theres always an element of clean to it sorta. it does a REAL good mimic of a warm old tube amp, and i was playing it with no other effects and getting real close to the same tones i normally would use live.

so i think the fuzz will be a keeper. but i think the preamp card, or part of it, is part of the fuzz circuit. how you drive the preamp determines how hard the fuzz drives, too. the higher the preamp volume, the hotter the fuzz seems to get. the tone controls have a little to do with it too, but not much. of course, this is AFTER changing the cap values to let some bass in.
still works good with a ge fuzzface into the front end.
sounds a lot like a brown or early blackface fender when ya dial it in right.

yeah, if we can un-neuter the tremolo and give it slightly bigger bollocks that could be fun, too. its pretty faint as is.

checked the filter caps, all three FIFTY volts. i can't see all the markings clearly, i gotta do that in bright daylight.

i also tacked an inline fuse holder across the blown circuit breaker. it said the circuit draws .100 amps from the wall, i figure a 1 amp should be ok, the parallel courtesy outlet is rated for 3 amps, so i know its a bit high but should be fine as long as i don't throw a spanner in the works somewhere or something equally stupid.

we ARE talking me, here

so anyways, after playing a bunch of guitar (i shouldn't have) with this damn finger <good for it AND my soul> and finally being asked super nicely by the young lady upstairs to turn the @#$% down i gave in for the nite.
i gotta be in playing shape, handwise, by thursday, by hook or by crook. the wyld west medicine show must go on! lol

i will endeavour to get it finished up tomorrow or the next day, for posterity sake

damn little purple berries.

been eating them for weeks now, haven't got sick once

its got that kinda sound.

its hip.. its now... its 50 freekin years ago

and ALL the kids are gonna be doing it, hick-a-doo-laaah

too many bad pop culture refs ina  row that are completely random, hippy needs sleep.
catch up more tomorrow.

peace out bro

[pinkjimiphoton]

btw, this is scary shit for a guitar player... this is a week into treatment. its WAY better than it was.

[Rob Strand]

the interaction of the two channels is really strange too, particularly after i
molested the fuzz slightly like we all knew i was gonna do.
just for shits n grins i tacked 3 .1u caps shunting across the .001u caps, which i guess is .101u there instead.
NOW the fuzz actually sounds fairly good, and if ya jumper the channels right you can get a real nice brownish overdrive out of it.

Cool.   There may be some issue with the phasing of the two channels through the mixer.   I haven't finished deciphering the channel preamps yet but channel 2 output driving the fuzz might be different to the channel 1 driving the mixer.

yeah, if we can un-neuter the tremolo and give it slightly bigger bollocks that could be fun, too. its pretty faint as is.

There's probably more than one way to do it.  The oscillator drives a gain stage for each channel so you could beef-up the output.  However, the resistor in series with the Vactrol is going to limit what you can do with just the drive.  The LFO is AC coupled.   If the tremolo is disabled by shorting the Vactrols the means decreasing the series resistors will mess with the non-tremolo gain.  You might need change the way the switching is done to disable it.

i gotta be in playing shape, handwise, by thursday, by hook or by crook. the wyld west medicine show must go on! lol

Good luck, looks like you should be able to do it.    (A few times I've sliced the tips of my fingers and it totally stops you from playing.   Bending ... huh ... just tears it open. )

btw, this is scary shit for a guitar player... this is a week into treatment. its WAY better than it was.

Yeah, I was the other thread.  That stuff is freaky.

BTW, I'm hoping to put up some info today.   There's no doubt it will need some fixing.   I'm having trouble bridging between the wiring lists you wrote out and the what I see on the schematic.   Maybe you will need to do another scan over it.

[pinkjimiphoton]

cool!
not a problem, just let me know what ya need me to look at!

i'm gonna go mess with it a while... just got outta my coffin for the day.

i'll permanently change them three caps i think, and remount the mixer board to the chassis etc..  while i got the switch buss taken off, i'll check where the wires go to. still not sure how the top boost works, i'm suspecting it may be part of the fuzz board. there's really nothing i can see on the switches themselves.

if my band wasn't so loud, i'd try it live tomorrow.. but i suspect it may be too noisy to use til i at least CHECK the filter caps... and i'd disconnecte a big cap to ground from the power supply i suspect was there to nuke rfi and stuff, i didn't fire it up after that so it may be quiet again tonite.

my girl gotta get up early, so limited time to really mess with it tonite. so i got time to check connections, etc.

more later. rock on bro!

[Rob Strand]

still not sure how the top boost works, i'm suspecting it may be part of the fuzz board. there's really nothing i can see on the switches themselves.

The top boost connects back the channel preamps.   There is a series resistor before the James Tone Control (Passive Baxandall)  The top boost shorts a cap across that resistor.    It's sort of like the bright switches on a Fender except it doesn't go across a pot.

I've nearly finished three boards.    Another two partially done.

In your wiring list you have the fuzz yellow wire pin 11 (your reversed numbering) going to channel 2 pin 17 (your reversed numbering).   From what I can see the tremollo is also connecting there to channel 2 pin 17.  Is that right?  If the tremolo switch short to ground that would take out the fuzz as well.

[pinkjimiphoton]

i will check on that when i go down stairs, been dealing with ebay crap.

as i recall, yes, theres a few spots where socket pins share more than one connection.
the fuzz will still work if the tremolo is off or on, tho only on channel two, now.

before, there was a bit of "bleed" from the fuzz that came thru on channel one, now its gone since the mixers working right.

before that, i think the whole thing was "bleeding" thru the switch on the channel 2 only jack... if i opened the connection, it died, where as now the normal outs still work.

curiouser!
i will verify the wiring and post as soon as possible bro.
thanks!

[Rob Strand]

curiouser!
i will verify the wiring and post as soon as possible bro.
thanks!

I'm really struggling to make sense of the Reverb wiring.   I can match it up to the circuit.
There also a bit of ambiguity between the Reverb *Board* in/out  and the Reverb *Tank* in/out.
Can't see how the Reverb pot works either.

I might just post what I have in about 1/2 hr and see if you can kick it into shape
with the unit in front of you.

Oh,  on the fuzz there is an orange wire going back to the PSU (Fuzz board pin 8, with 1 at the key end).
Can't work that out either.

[pinkjimiphoton]

hahah still trying to walk away from the computer, wheeling and dealing with a cat in oz on the bay.

the orange wire i'm betting i got wrong... not power supply, i bet it goes to the footswitching. i thought it went to the power supply, but i'm not sure how the hell the terminal block connections work. stuff goes all over, i dunno what goes thru the chassis, i will try and take pics to show what i mean.

i will check the wiring. i am betting any wires that totally don't make sense have to do with the footswitching.
stay tuned

[Rob Strand]

i will check the wiring. i am betting any wires that totally don't make sense have to do with the footswitching.
stay tuned

I forgot about those.  Yeah!  where do they fit into the story.

Here's the stuff which is nearly there,

[pinkjimiphoton]

holy shit rob!!
you been busy!!

i STILL haven't made it downstairs. lol look good!
i'm-a gonna check 'em real quick

the only thing i see weird is the preamp board picture appears to be mirrored from whats actually there.
but i just realized its seeing "thru" the board. looks good.
i can verify values n crap too.
printed the connections you posted so i can check.

hopefully, i can get down there now!!

[Rob Strand]

i STILL haven't made it downstairs. lol look good!
i'm-a gonna check 'em real quick

No hurry.

I've traced the channel preamps and the tremolo but I haven't drawn them up.
Trying to make sense of the external connections *and* the schematics is really killing me 

[pinkjimiphoton]

ya got popcorn, and a cold beer ready?
blaze a yule log and gimme a couple minutes.
dude, we're just about there.

[pinkjimiphoton]

OK!

to answer questions first

does fuzz socket pin 11, yellow wire, connect to channel 2 socket, pin 17?

yes

does trem socket 3 also connect to chan 2 pin 17?

yes

fuzz board, orange wire, fuzz socket pin # 8, (1 at key end) to FOOTSWITCH orange, fuzz

channel 1 , socket pin 5,l-r,  orange wire to tuner socket # 10, key 2 l-r

footswitch connections.... i got extra pins, so i can run led's in it and power them remotely 6 pin DIN, only 4 used...
orange  fuzz
green  trem
blue    reverb
black  ground

trem oscillator vactrols
GE 6535 appear to have three connections
i will get proper values at another time...

reverb tank appears to be standard accutronics type, kinda "gray" rather than laquered only thing i see on it for numbers is 1122 stamped on top. it might have more inside, i'll open the plate and look at some point.

fuzz board wiring appears to be right i think

reverb is like this, as per your picture you posted

1   reverb out, tank recovery, black rever tank out shield
2 n/c
3  blue, not +v, reverb footswitch
4  rev lev 2,  tank recovery, reverb blend pot #2
5  key
6  reverb out signal? yes  is this tank input? no. this is tank output tip
7  rev lev green.... does really go to rev pot? yes, rev # 3
8  mixer 11 purple   ...... i gotta look at that again, its weird, its ultimately part of the switching, but after the pots.
9  +v orange +vr1  psu
10    rev in (hot)  reverb in   does this go to mixer pin 8? (blue wire) YES
11 rev in grnd /shield tank drive out , reverb tank input (hot) yes
12, grnd, black, mixer pin 8? not 8, pin 8 is the blue one. i gotta look fresh.

stay tuned, if yer still out there, i gotta scan a page of notes for the power supply.
be right back.

[pinkjimiphoton]

i'm betting the transformer output is more like 25v-0-25, not 50. maybe even less, b+ seems to be about 21v.
maybe even 12-0-12... center tapped.
resistors between the can pieces are 1k. the 10,000uf cap only uses one of its three sections, there's two left over
the 100uf cans are double caps
CLR for the pilot lamp 680r to star ground
all the case connections of all the power supply caps are connected, to the ground shown on the first 100u cap
the terminal block is a double sided one, the connections on one side go thru to the other.
diodes i can't read the markings, bullet shaped kinda, about the size of a pencil diameter. not sure which side is cathode, but one side of each is black, i marked it on the crappy drawing
i didn't add the power on or phase reversal switches,
the power on is just a spst
the phase reversal is the typical x pattern dealio
i DO need to finish tracing the last couple switch connections for the tremolo and top boost, but other than that, we have now
gone all the way thru the circuit, other than proper values on some of the boards.
i will start working up graphics of cap values for the whole mess, i think you can probably see the resistor values better than i can.

we done nailed it. well done, everyone!




my widdle bwain hurts. i don't think its in kansas anymore.

little bit further, to get farther back...

its hip, its now, its 50 @#$%in years ago lol

[Rob Strand]

Wow heaps of info.  Thanks.

my widdle bwain hurts. i don't think its in kansas anymore

Now mine does too.   

Didn't get too far yesterday.   I just rechecked the trace of the preamp and fixed a few bugs.  Volume control is a bit whacky.

I'll check over all that stuff you posted in a bit.

[pinkjimiphoton]

i think the volume control is set up kinda like a pan. i can nab ya pix if ya need them.
gotta gig tonite tho, so won't really be able to do much til i get home at 3am or sometime tomorrow.

look forward to buttoning it up. wondering about adding some relays, so i can switch them 3 caps in and out remotely. never really worked with them before, but thinking i may be able to steal a b+ voltage for the footswitch leds and send it down the cable to the switches...and still have one wire left over to power the relays with.

this is way above my paygrade lol

i'll check in later. later!

[Rob Strand]

i think the volume control is set up kinda like a pan. i can nab ya pix if ya need them.

It looks like the input sockets wire to one part of the volume pot.

gotta gig tonite tho, so won't really be able to do much til i get home at 3am or sometime tomorrow.

How did your finger go?

look forward to buttoning it up.

Yes, the fixing job is done.     

We don't need to back-engineer the thing to the point of cloning it - unless you want to.    Most of the details have been captured.  If anything happens to it you have a good map to fix it.

wondering about adding some relays, so i can switch them 3 caps in and out remotely. never really worked with them before, but thinking i may be able to steal a b+ voltage for the footswitch leds and send it down the cable to the switches...and still have one wire left over to power the relays with.

That will work.   If the supply is 24V you could use 24V relays.  Another way is Vactrol, like some of the old Mesa Boogies.

this is way above my paygrade lol

Nah,  you could do it easily. 

i'll check in later. later!

No, problem - same here.

BTW, the channel preamps have some sort of "voicing" EQ build-in on top of the tone controls.   The tone controls aren't quite normal either they have an interesting twist.

[pinkjimiphoton]

input wires go right to the socket for the channel, each to its own pin. the ground from the jacks goes to them i think, but i will have to look. i don't think the volume controls come off the inputs, but off the outputs of the channel.
not sure tho, i will check more closely when i get home.

relays. hmm! maybe it would be cool! but i think its easier to just hardwire the new caps in, and use the onboard fuzz modded. it sounds about 20000000000000000000x better i think.

duty calls.. will check back when i can. probably in the wee hours. entirely too sober for a formerly lush musician lol

[Rob Strand]

input wires go right to the socket for the channel, each to its own pin. the ground from the jacks goes to them i think, but i will have to look. i don't think the volume controls come off the inputs, but off the outputs of the channel.
not sure tho, i will check more closely when i get home.

I think the problem was the inputs do go to their own pin (2nd and 3rd pin from one end) *but* on the board it is a dead-end.   The signal has to come out on the 4th pin (from the same end).  That's where I think it goes to the volume control. Then comes back from the volume control and into the 5th pin (from the same end).
There's also a 220k resistor stuck across pins??? of the Vol pot.

The manual talks about some volume control scheme to reduce clipping.

I was trying to work that out yesterday but only got this far.