defx Quint (Maestro USS-1) circuit challenge

[Itchy Scratcherson]

Assembled/composited Schematics attached. They're huge; I printed them on 6 and 8 sheets of paper. (Also, I hope it's okay I posted so many pics.)

Build Doc:
https://drive.google.com/file/d/1n2X3Bw3VzOeVhxAicq7RYjmCuhcRSrPX/view?usp=sharing

So I was very pleased most of it seems to work at first blush. But, I appreciate very much if someone could help me with this complex project. I have at least 2 show-stopping problems, er opportunities, though.

(1) engaging the Sample & Hold switch(es) cuts all sound off, and (2) the Filter toggle doesn't do anything (Filter Pot has no effect, nor external pedal control of the Filter frequency switched TRS jack).

Everything else seems to work: wave/fuzz, sub-octave, perc. toggle, phaser!, and envelope controls incl. the sensitivity pot.
An hour with my probe just led to frustration. also, fwiw I'm using 12V 1000mA AC adapter for now (project spec is 14-16V).

Using my ear & probe, I hit a brick wall with more complex circuits like this b/c I can't yet intuitively identify an audio path vs. an electric voltage path. So I test what seem to be all the points to probe for audio when I should maybe be identifying voltage issues, and that means thinkin'.
Or, eventually, asking.  :)

Thanks, everyone! Dino?




 

[duck_arse]

what is it with you and these monster builds? you know I'd love to help, but, it's already locked up my machine once, and I can't be doing with the 16 page schem, 100%, 400%, page 1, page 24 etc.

sample and hold is using jfets, yes? pull all the fets - even if you know they are right - and check your part numbers. make sure you have the end-gate J's in the right sockets, and the centre gate 2SK's in their right spots. then do voltage measures around the S/H section, switched on and off. and bonus points if you would edit your browser-crashing schematic down to just that S/H section, with its switches.

[Govmnt_Lacky]

1) What are you using as your S&H transistor? I had to use a 2N5088 to get mine to work well. Also, be sure to totally disconnect the Base leg from the PCB (that is what I did with the 5088 to get it to work well)

2) What do you mean by "filter toggle?" Do you mean the baton switch -OR- the 3PDT? According to the build doc, the baton switch will override the 3PDT so, if the baton switch is not ON then the 3PDT will have no effect. It works that way with ALL of the switch sets (i.e. Waveform baton/toggle + Waveform 3PDT, etc.)

EDIT: From the build doc:

"NOTE: If using the footswitch assembly for the DEFX unit, toggle
switches on the main unit override the footswitches. If main unit
toggle switch is turned on, effect will turn on even if the
footswitch for that effect is off (footswitch is bypassed). If total
control from the footswitches is desired, then ensure to turn all
toggles on the main unit to OFF."

With my build, I did not install the baton/toggle switches at all and just used 3PDT to control the on/off of the effects.

EDIT: Also, did you incorporate the board repairs and fixes that were added later to the document?

[Itchy Scratcherson]

Thanks for your responses! I photoshopped a long time this AM to get a (slightly?) more legible  schematic. So, while populating  I measured every component paying close attn. to document spec. Troubleshooting without the tethered footswitch daughterboard works. Yup, I verified same behavior using footswitches as well as (the overriding) toggles.

Very helpful that defx accomodates all pinouts with every transistor pinhole, and I've triple-checked all positions are correct. SK30's working fine for phaser section. Also, very interesting what you wrote about 5088 w/o base as S/H transistor! I'll try it. My S&H transistor is BCY58-X 'cause it's mentioned somewhere in the build doc. Probe on it is very noisy but I have no idea what that indicates. 

Semiconductors used in this build:

(I chose the closest-matched multiples in. every case using my Atlas DCA55 and diy M328 LCD 12864 Transistor Tester. I have the Stompville SV104 FET matcher, too.)

pinouts listed as when viewing flat face
2N5087 EBC x 1
2N5089 EBC x 1
PN2907A EBC x 4
PN2222A EBC (not P2N2222A, which is CBE) x 7
2N3904 EBC x 12
J113 DSG x 13
BCY58-X EBC x 1 (emitter next to tab)
2SK30A-Y SGD x 6 (50 2SK30A-GR's on the way to meet doc spec, but phasing works pretty well already)

all diodes are 4148

CD4001UBE x 1 (doc specs unavailable "4001N"; I bought buffered AND unbuffered)
CD4013BE x 1 (I *think* I have buffered AND unbuffered)
CA3080 x 1
LM13700 (I have Cool Audio on adapters)
1458 op-amp x 3 (in phase circuit)
4558 op-amp x 5

In progress:
do voltage measures around the S/H section, switched on and off.
try UBE for BE & visa-versa for 4001 and 4013 chips hiding underneath the power daughterboard

I have the revision PCB which shouldn't require any mods, but I'll investigate the doc again.

[Govmnt_Lacky]

I tried using various BCY-58 transistors in the S&H section and just couldn't get it to work. After some research (and a few questions) I found that the higher gain 5088 worked (with the Base lead removed from the PCB)

Are you still getting NO sound when the S&H is engaged? Or, are you just not getting the bee-bop??
Is the Filter pot/circuit working now? Maybe double check your wiring for the external Filter CV jack...

[digi2t]

I'm going strictly from memory here, so bear with me...

If I'm not mistaken, the S/H and filter section are integral to each other. That's to say, while you can have S/H on without the filter on, what the S/H is doing in this case is randomly modulating the filter section throughout it's entire frequency range, from high to low, and everything in between. When the filter is engaged, the frequency control sets the filter frequency range limit. With filter and S/H on, the frequency pot now sets (limits) the frequency range of the S/H modulation, as well as setting the filter frequency.

With this in mind, I would first concentrate on figuring out why the filter isn't working. Could it be that the frequency CUT.T. trimmer is so far out of range that the audio is cut off completely when the frequency is engaged (dog whistle territory)? Since the S/H modulation range is also dependent on this, it would explain why the S/H isn't happening either. Get the filter working first, then worry about the S/H.

[Itchy Scratcherson]

Dino, with the CUT.T trimmer setting in mind, does it make sense that at one point yesterday I got the S/H toggle to activate the Filter? No Sample & Hold sounds but it was the first time I got the Filter pot and Brilliance pot to respond. Turning the actual Filter toggle ON seems to mute everything, so I'll follow your advice & carefully experiment with that trimmer setting & troubleshooting Filter not S/H. (Something I did subsequently deactivated the Filter & Brilliance Pots again... that's where I'm back to now.)

Govmnt_Lacky, redoing the wiring on my external switched TRS jack for the Frequency control is next on my list! Currently I get no sound at all when either the Filter toggle or the S/H toggle are engaged. Everything else works. Digging the Fuzz and rather unique Phaser sounds, though. 
How high are your high-gain 5088's? I tried a 5088 yesterday but made no difference. I think the hFE was around 400 or 450, and that's not far from the BCY58-X's gain value. I see pin 2 on the schematic is hanging there, but I'm surprised that leaving it out on your build got some things to work.

Duck Arse, I'm neuro-divergent, man. Thank You for the basic voltage checking tip/necessity. Still on task & especially studying the schematic carefully before responding to that.
 
Thanks again, everyone.

[PMowdes]

Hey Itchy

If you had asked we would have sent you a pdf copy of the full schematic.  It's only over so many pages so we can get it in the build doc and so you can actually see it.

Don't be afraid to ask, you could have saved yourself a bunch of time and headache.

Cheers

Phil [DEFX]

[Govmnt_Lacky]

How high are your high-gain 5088's? I tried a 5088 yesterday but made no difference. I think the hFE was around 400 or 450, and that's not far from the BCY58-X's gain value. I see pin 2 on the schematic is hanging there, but I'm surprised that leaving it out on your build got some things to work.

If I remember correctly, the gain on my 5088 was close to 800-900. As for the Pin 2, there are many S&H circuits that were found to work better if the transistor Base was totally removed from the circuit. Once I found the perfect 5088 for my Maestro, I just cut it off and hot glue'd the other two legs to the socket.
As for the Filter issue, it sounds like Dino has you on the right track. He and Phil are the creators so I would follow their lead on that 

[Itchy Scratcherson]

Success! I traced a voltage leak to the soic-16 V13700 Cool Audio chip I evidently didn't construct properly. Subbing a different 13700 chip, now I have the Filter working! I just need to dial-in the S/H —which is responding now, just not doing much.

[Itchy Scratcherson]

Yep. Thanks SO much guys. I just got the unmistakable sounds of Sample & Hold happening, and *I think* everything's working now. I replaced that section's 4558 (again, my diy SOIC on a converter board... must've assembled it a long time   ago.), and voila! re:S/H transistor: I tried 2N5088, BC108C, and currently using an MPSA18 with an hFE around 750. My BCY58-X was around 510.

I do need to revisit the foot-pedal control of the Frequency. My Moog EP-3 expression pedal controls the Speed parameter nicely, but I couldn't tune it to properly control the Frequency parameter.

And then... on to the Pompei sitting so patiently on the shelf! Steve Hackett, here I come! I just wanna play the solo from Counting Out Time from The Lamb.

[digi2t]

Excellent!!