Boss CE 2 semiconductor voltages

[ponce]

Could someone analyze these voltages next to the correct ones and tell me what's wrong with my build. Been trying to troubleshoot this for weeks, ordered ICs from various selles with no success. Many, many thanks in advance!

[duck_arse]

we would like some more information, like a circuit diagram, and what the actual fault/problem is - what is it doing/not doing?

while you're thinking about that, the collector of Q4 (7V39) is shown on the vero as connecting to pin 1 of IC4 (8V19). why are your voltages not the same? [this is all that I can point to, others may find more "stuff".]

can we see photos of the thing that you have built?

[Govmnt_Lacky]

Before going through the rough stuff... I recommend reviewing the east stuff first.

- Verify ALL resistors, caps, and transistor values for correctness and orientation
- Verify your wiring. ALL of it.
- MOST IMPORTANT.... verify all of your jumpers and cuts (this is my bet on where the problem is)

[ponce]

This is the only photo I have at the moment, but I can make better ones later.  I've checked all the traces, eventual bridges, parts values, cuts and orientation at least ten times, but there are so many components that its not hard to overlook something. I get the signal (boosted) through, when the pedal is engaged but no effect. I get wobbly sounds sometimes when touching some contacts with my fingertips and I've also tried the audio probe but It's hard for me to follow the schematic. It's my last complicated build for sure. From now on, only silicon fuzzes

[Djentronio]

Have you tried switching the transistors to lower gain devices like 2n3904? If the transistors are Q1-Q5 directly comparable to Q1-Q5 on the board, which looks like the case since Q5 in both schems are connected emitter directly to ground, I might try replacing the 2sc945 transistors with 2n3904 and see what results I get.

[Govmnt_Lacky]

I have never.... ever seen an MN3101 made by Signetics 

The only ones I have seen were by Matsushita (like your MN3007) and Belling

Wondering if your clock chip is a counterfeit.

[Djentronio]

Every single value is slightly lower than it should be, and since the ac current gain of transistors matters for emitter followers and since ac current gain is really high for 2n5088s, and really low for the original circuit's transistors, I thought that might be a place where the transistors are causing universal voltage sag by having too high a gain.

I mean DC current gain. I woke up this morning and that was my first thought.

[ponce]

I have never.... ever seen an MN3101 made by Signetics 

The only ones I have seen were by Matsushita (like your MN3007) and Belling

Wondering if your clock chip is a counterfeit.

Interesting. I bought it from a professional electronics dealer here in Croatia. I thought it was some kind of an old stock, but who knows. Is there another way to test the chip?

[Kipper4]

Is that the right schematic for Harolds "with mods" vero layout?

I love this ^

[ponce]

I don't know if such schematic exists, I sure cannot draw it

[Slowpoke101]

The schematic supplied does not quite match the vero layout but the correct one may be found. Using the tonepad schematic does help.
Q4 is of the most interest at the moment. The base and emitter voltages are too low. Did you remember to cut the track under R36? If you have not cut it you will have a short to ground on the depth pot's centre pin (pin 2, the wiper). Have a look.
A Signetics MN3101? Odd. Worry about this a bit later. Just have a look at Q4 first.

[Djentronio]

slowpoke how can you tell? I'd like to look for this vero.

[antonis]

Q1 & Q3 are back-biased and you shouldn't take no signal at all... 
(Q3 in cut-off region should be responsible for not taking modulated signal but Q1 in cut-off region should be responsible for not taking any signal..)




As long as you say:
<I get the signal (boosted) through, when the pedal is engaged>
your measurements are probably inaccurate.. 

[PRR]

> Q1 & Q3 are back-biased

If we assume 470K base resistor and a 1 Meg meter, those are the expected readings including meter-loading.

Since it passes signal, and as you say it could not if truly bad-biased, I'd assume the voltages are reasonable when not poking it with the meter.

[ponce]

I've made a mistake - confused Q4 and Q5 while measuring. These are the corrected voltages. Not much difference either, but what do I know. Maybe it sheds a new light on the problem. A few more things.. I did actually cut the trace under the R36. Signal is boosted only when the vibe switch is engaged and there is a noticeable ticking which changes in speed when the rate knob is turned. I've ordered yet another MN3101 from a different source, it's the third now. Saw yesterday a new BOSS CE-2w in a local music shop, sells for 320$, > crazy. If I don't succeed with this BBD chorus, would you recommend something PT2399 based like a Little Angel or the Glam Chorus?

[ElectricDruid]

What's clear there is that Q4 and Q5 are still wildly wrong. So it's unlikely that anything you changed before the new measurements is the problem.

Q4 and Q5 both deal with the LFO modulation of the clock, so I'd be double checking components around the LFO, and around those transistors and the clock. If something there was wrong, it could throw the clock out and make people think the clock itself was bad.

I've fried a few of those clock chips in my time by going a bit wild with the modulations, so I feel I've earned the right to an opinion on this one. Unfortunately for me, that doesn't make it any more likely to be right

Tom

[ponce]

Here are additonal pics:

[Djentronio]

is that a 1590b footprint btw?

[ponce]

is that a 1590b footprint btw?

I don't know the exact Hammond specs but it's a bit taller than usual mid size boxes I used.

Btw. this build has been debugged and the pedal works perfectly now. The member Slowpoke made it happen. His suggestions were spot on and his guidance unparalleled.

I had two microscopic trace breaks, therfore a continuity loss, bad blend pot and bunch of faulty MN3007 chips. Upon solving that stuff, there was audible LFO ticking, but he had a fix for that too. It's supposed to be a mod implemented by BOSS in the later CE models.That silenced it completely. I tried the fix I read in M. Hammer's posts, but it didn't help. I probably haven't applied it correctly.

Thanks for your help everyone, and if somebody experiences difficulties with this build, I'd be glad to help. Just send me a p.m. This is one great sounding chorus.

[ElectricDruid]

Glad to hear you got it going. Good work!

Tom