CHASM REVERB

[pinkjimiphoton]

ok.... found some bridges and some cold solder... got the thing kinda running.
i baked one chip and one 7805 so far.

got clean signal... and loud... with the volume all the way down. if i turn it up whatsoever, the brick starts motorboating like crazy, sounds like a damn airplane.
the modulation is working. i can hear it on or off. so THAT's good...

any ideas as to where to look to find the motorboating problem? i had a hell of a hum, i thought it may have been from having the 1u cap backwards... i had oriented it with + to the right originally, tried it the other way and lost the hum.

i've tried subbing the 2n5457's, no change at all, so assuming they are working. i haven't tried the 2n7000, do you think that may be the culprit?

funny... yesterday i had reverb. today, i have an airplane synthesizer.

help!!! please

[bluebunny]

ok.... found some bridges and . . .

ok.... found some bridges and . . .

So you may not have any reverb, Jimi, but you sure as hell got an echo!   

[pinkjimiphoton]

wtf??? weird!!! windows on acid!!

[deadastronaut]

ok.... found some bridges and some cold solder... got the thing kinda running.
i baked one chip and one 7805 so far. ....why, wrong way around?

got clean signal... and loud... with the volume all the way down.( should be the same level as bypass when fully CCW) if i turn it up whatsoever, the brick starts motorboating like crazy, sounds like a damn airplane.
the modulation is working. i can hear it on or off. so THAT's good...(that's not good )

any ideas as to where to look to find the motorboating problem? i had a hell of a hum, i thought it may have been from having the 1u cap backwards... i had oriented it with + to the right originally, tried it the other way and lost the hum.

i've tried subbing the 2n5457's, no change at all, so assuming they are working. i haven't tried the 2n7000, do you think that may be the culprit? (i used a 2n7000 ) and 2 of 5457 or j201 will be ok)

funny... yesterday i had reverb. today, i have an airplane synthesizer. lol..


hi jimi, theres something quite wrong if you have massive volume with it all the way down...theres a lot of wiring on this man, check you haven't got anything crossed, especially the brick wires.

help!!! please

[pinkjimiphoton]

ok.... found some bridges and some cold solder... got the thing kinda running.
i baked one chip and one 7805 so far. ....why, wrong way around?

mayyyyyyyyyyyyyyybe.... i figured better safe and popped a new one in there. the voltage is good.

got clean signal... and loud... with the volume all the way down.( should be the same level as bypass when fully CCW) if i turn it up whatsoever, the brick starts motorboating like crazy, sounds like a damn airplane.
the modulation is working. i can hear it on or off. so THAT's good...(that's not good )

well, i mean it's unity with the volume fully clockwise, anything above that and the motorboating starts. i meant good, in that obviously it's passing clean signal, the modulation is working, and the reverb must be too, or it couldn't keep making that godawful racket.

any ideas as to where to look to find the motorboating problem? i had a hell of a hum, i thought it may have been from having the 1u cap backwards... i had oriented it with + to the right originally, tried it the other way and lost the hum.

i've tried subbing the 2n5457's, no change at all, so assuming they are working. i haven't tried the 2n7000, do you think that may be the culprit? (i used a 2n7000 ) and 2 of 5457 or j201 will be ok)

i do have some j201's. i could try them i guess. i don't think that's it tho, i think it's working... but somewhere is a feedback loop.

funny... yesterday i had reverb. today, i have an airplane synthesizer. lol..


hi jimi, theres something quite wrong if you have massive volume with it all the way down...theres a lot of wiring on this man, check you haven't got anything crossed, especially the brick wires.

help!!! please

[/quote]

hmmmm.... i connected pins 2 and 4 together with a jumper (i mounted my brick on a small piece of vero ) at the brick, it's circuit and signal ground... on the schematic, both are shown being wired to ground... do you think that may be where the problem is?

[pinkjimiphoton]

the motorboating is audible even in bypass. something is wrong somewhere... have checked the damn board and wiring, sucked/reflowed with fresh solder and checked for unwanted continuity AND wanted continuity... something is way weird.

i disconnected the right side of the mix control. if i touch the wire of it, i get a strong reverbed buzz. but... that should be the output of the reverb there, right? or is it the input to the reverb?

if i temporarily connect the wire from this node to the input jack tip, i get a huge swampy reverb.

i HAVE dry signal, and the volume works fine with the wire disconnected.

the dwell and decay knobs make audible difference when turned with said wire jumpered to the input signal.

if connected to the pot, they change the sound of the cacophanous noise. i do not get it... unless somehow i got the wiring wrong, but it matches the layout. i'm thinking it's more likely  someplace in the switching part of the circuit, but i'm scratching my head hard on this one. am i right the mosfet is the switch, and the two jfets are for mixing clean and effected signal?

maybe i need to draw a proper schematic up, cuz i'm getting lost on this one i think.

where the hell could a feedback loop be happening that would do this?

i've swapped out the jfets for the j201's you suggested rob, and have changed the 2n7000, the chip, and the regulator.

shorted pot maybe?

i tried to connect pin 4 of the brick to it's own ground, made zero difference.

i'm looking at this really hard, and i've gotta wonder if it's the brick itself that may be defective, but then why would it work hooked up wrong?

dumb question... but rob, we're looking at the back of the pots on the layout, correct? pin 3 would be to the right?

where would be a good spot to try bypassing the switching...wondering if maybe i'm better off just with true bypassing it.

so... good news... all things working. bad news... not working right.

hellllllllllllllllllllllllllp..... it has to be someplace a strong feedback loop would be happening, or somewhere limiting the signal being sent to the reverb i'd think. in a tube amp, it would be a blown cap in the reverb send amp letting dc thru to the springs i'd think, but i don't know if the same would apply here.

[deadastronaut]

jimi: pm'd...

[loylo]

Well, there could be many explanations:
As you fried the 7805, chances are you have also fried the brick.
Maybe, you have a wrong value of resistor, like the feedback resistor at 47R (instead of 47K) or 10R (instead of 100K), explaining why the reverb goes into wild oscillations, sounding like motorboating.
And/or you don't respect DA's layout, with that ground thing with pin 2 and 4 of the brick (I don't understand what you did with your build).

[deadastronaut]

^ fried brick...oh dear.. maybe,

the pots are left to right 3 2 1 btw (looking at the back of pots)..if you are getting motorboating when on/bypass, then the switching might be ok..

but it must be another issue..maybe osc switch wiring?..

[loylo]

^ fried brick...oh dear.. maybe,

I hope it's not that, but the brick may be the culprit.
I suggest to verify everything else first, like component's values, wiring...

[pinkjimiphoton]

well, no, the brick works. if i go directly to the input of it, i get a reverbed signal.
it's happening somewhere in the feedback loop. i'm thinking it's gotta be a hosed chip.

the 805 never fried per se, i just felt it better to try a fresh one.. i've found with them they can be a real bitch.

i've been over the wiring a gazillion times. it matches deadastro's exactly. it has since it was built.

it switches on and off, so i assume the fets are all working.

it passes dry signal.

but as soon as i hook up pin 6 of the brick, it goes @#$%ing batshit. if i turn the volume all the way down, no oscillation. as soon as i crack it open, it starts.

it sounds like a blown reverb transformer blowing dc into some springs almost. wondering if something in the brick internally hosed itself.

noticed lead dress seems to be an issue too... it will start oscillating if the wire is removed from pin 6 of the brick and even put anywhere near pin 1 or 3.

that said... if i remove pin 6, i get no oscillation. so it's gotta be in the stage that goes to the input of the brick, and bugger if i can find the problem. i mean, all that's there is a
couple parts... and i've even disconnected the osc switch, that makes no difference.

if every thing on the board is right, and the wiring is right, i mean, what the hell else can it be? gotta be the brick... but if it WERE the brick, why the hell would it work directly?
also....

i have one HELL of a loud hum if i don't jumper the grounds of the input/output jacks together.

the oscillation is the part i'm not getting... something has to be leaking dc, right? but what the hell is there to leak? and the brick is supposed to be ok for ac coupling...

i'm stumped.. the interweb is no help.

[Jdansti]

The chip will not operate correctly without a high enough resistance to ground on pin 6. What happens when you put 5-10k from pin 6 to ground?

Brick-not PT2399. Ignore this post. 

[pinkjimiphoton]

i can try that... at the moment, i have the chip hooked up on my breadboard...the brick is working fine.

whats happening is somehow theinput is bleeding into tghe output... i can reproduce it outside the pedal.

i need to take a break and look again. every semi i've swappe4d out still works in other circuits. has to be something with the pcb or the wiring, it melted the 22k pot... @#$%er was smokin

very very very weird. and this was the cleanest build i'd done. WAS.

[pinkjimiphoton]

took all the semis out. checked continuit everywhere, and for shorts. the straight guitar comes thru. the buffered guitar comes thru.

the brick was even working, tho it wasn't really loud. it has a reset, if you unplug it for a few seconds it seems to come back. i'm suspecting something burned out inside... i mean, it is 2399's, right?

what i can't understand tho is why i can plug the guitar right into the input, and take either output to my amp... totally wet, but working like that.

i re-wired the switches and pots, and even put in good jacks. same result.. when all appears to be right, as soon as ya crack the volume knob, all hell breaks loose.

it's a VERY cool airplane simulator, lol... but for the life of me i can't see what the hell i've done wrong.
the ass end is working. the front end is working. the buffered straight thru guitar is working... could the chip short internally between the input and output somehow?

or is it the brick itself? man... what a bitch this one is.

i thought it was a dc hum, but it's definitely a feedback loop happening from the output to the input somewhere.

[Jdansti]

Do you have another 2399?  Sometimes they can become damaged and sometimes they're bad right out of the package. Of course, the problem may lie elsewhere. This wouldn't be fun if it were easy!  

Please ignore anything I say. There is no PT2399. I should know-I've built one of these. 

[deadastronaut]

Are those diodes for the fet switching round the right way?

resistor values?...

im not sure what could be giving you grief....

i know the feeling of doing a nice neat and tidy build then having to pull

it all out man, been there too, what a bummer....

soemething is defo wrong with wiring if you smoked a pot....

[loylo]

Let me try to understand:
My understanding is that  the sound goes weird as you soon as you connect pin 6 of the brick.

If you don't connect pin 6, do you still have reverb?
Because pin 6 is one of the output of the brick (assuming you have a BTDR-2, not a BTDR-1), the other output is pin 5.
And the circuit is able to function properly with only one of the two outputs connected.

[bluebunny]

Please ignore anything I say. There is no PT2399. I should know-I've built one of these. 

Take the cat off your head, John.  It's affecting your brain!   

[samhay]

jimi - If you melted the delay pot, then you probably put 9V across it. One of the lugs (#2) connects right next to V+ on Rob's layout. Any chance you have a solder bridge?

[pinkjimiphoton]

sam, thanks... exactly what i'm looking for, cuz it SOUNDS and acts like the power supply and audio are connected somehow.

the pot smoked while i had all the chips and fets taken out, i was afraid i may nuke them doing continuity tests. so i'm wondering if that is where i'm gonna find the problem.

i'm trying to take some time away from it so i can be a bit more objective.. i have it narrowed down to where it's messed up, stage wise... it has to be somewhere either in the audio switching or the stage feeding the input of the brick...

other wise, i can't see how the heck the brick can work on the breadboard.

speaking of..yes, disconnecting pin 6 of the brick (it's the newer 6 pin btdr2hl)  will stop the oscillation, but then the reverb doesn't work. the oscillation is always happening, i can turn it down with the volume control soit has to be somewhere between the input (chip a) and output (chip b).... so it's gotta be in or near the feedback circuit. i'm betting sam may have found it, i will check.

could the brick be shorted internally? the original regulator is fine, it's putting out a solid 5.1v, and the brick works fine on my breadboard. i can get the exact same effect as the problem if i connect pin 6 to pin 5 or pin 3 of the brick (out of the circuit, on the breadboard).
i can get reverb out of either side, but pin 5 is definitely wimpier than pin 6.

it's hard to describe and troubleshoot, cuz each power up it seems to do something different.

i hate to buy ANOTHER brick to find it wasn't the problem. but maybe i should.  worst case, i can build a verb with this one that doesn't have the fancier accoutrements.

i bet i spelled THAT wrong.

gonna smoke a doobie and guzzle a couple huge cups of coffee and go have a look-see... i am gonna go out on a limb and misquote larry/armednready and pronounce it's something i must have done wrong

i'm wondering if it's a latch up problem? i've had 2399's act like this.. maybe it burned a feedback path inside the chip?