SOLVED Me again...........Tayda EA Tremolo PCB not working

Jeff C

Jeff C

Active member
Hoping I don't set another record with this one, but I've just finished building an EA Tremolo from a PCB from Tayda. The Tayda forum is useless. No answers, no activity. So, I hope the patient and helpful folks on this forum who got me eventually across the Cobalt Drive finish line (which by the way sounds fantastic!), can figure out what my problem is. Once I finished it and plugged it in, I got audio but no effects. The LED stays lit up whether the switch is off or on. Volume trimmer potentiometer seems to work fine. I do have the input and output jacks wired correctly :)p), and am getting positive (not negative :rolleyes: ) 9 volts to the board. I've posted four pics below (figured out the magnifying bar on the mag-lite app -doh!). Given my transistor trauma of the Cobalt Drive build, I'm suspicious of mine on this one, so I took some close up pics of those. They Tayda build instructions were confusing. https://www.taydakits.com/instructions/ea-tremolo/pages/designators-and-components--43. For one, it lists a C4 cap, but there is no place for it on the PCB. It also says to use the N5457 and the SMD for Q1 and Q3. Tim (Fig) told me to use one or the other so I used the 2N5457, perhaps unwisely. They look pretty gnarly in the pics.
Here are some voltage readings from the transistors:
Q1: G: 9.3; S: 5.65; D: 4.46. Q2: E: 2.24; B: 2.8; C: 2.18; Q3: all 0's (hmmmmm); Q4: E: 0; B: 4.61; C: 2.55.
Also, C2 reads 4.4 on the negative pin and 5.6 on the positive one.

I tested with the audio probe and get a signal most everywhere but nada from any of the pot pins.....

Any suggestions on where to start would be appreciated! Tks.

Jeff
D01F7FA4-026A-4026-ACA3-600137BE4269.jpeg E3A09D66-D151-427A-BF18-897394B9F3C5.jpeg 480462DC-AE1B-49DF-BEB9-9A85F3CF16CF.jpeg 2A97B54C-6D90-479C-8A11-2C7A5DCF7FFE.jpeg
 
Sort by date Sort by votes
Stompbox parts (not Amazon this time……) And yes, they are oriented correctly. You can check that out in the close up pics, but if somehow I misread that, let me know! Tks!
 
Upvote 0 Downvote
I wanted to help, but then Chris posted a meme so I'm outta here.

BTW, you read Q1's voltages backwards. Should be D-S-G.

Q1 is ok.

Q2 is saturated. Verify R9 and look for shorts.

Believe it or not, Q3 should be all zeroes. The gate voltage will vary if the LFO is running, which it's not.

That brings us to Q4. The only reading there that makes sense is E = 0. If B is really 4.61V then that transistor is FUBAR. Which might explain why the LFO is not running. Recheck your readings, inspect for shorts, etc.

I forget, what was the root cause of the Cobalt failure?
 
Last edited:
Upvote 0 Downvote
Well, Cobalt Drive remains a mystery to me. When I replaced the transistor we were focused on, I still didn’t have success. But when I replaced the IC, suddenly everything worked. But you were skeptical it was the IC, thus the mystery - to me at least.

I will recheck my readings tomorrow and report back. I‘ll have to order another 5088 if that one‘s shot, unless I can use something else……….
 
Upvote 0 Downvote
BuddytheReow said:
The 5088 is pretty cheap so buy a handful
Click to expand...
👍. Just out of curiosity, why does Tayda write this:

Q1 2N5457 2N5457 JFET N-CHANNEL TRANSISTOR
Q2 2N3904 2N3904 NPN GENERAL PURPOSE TRANSISTOR
Q3 2N5457 2N5457 JFET N-CHANNEL TRANSISTOR
Q4 2N5088 2N5088 GERENAL PURPOSE TRANSISTOR
(SMD Q1 and Q3: SMD SOT-23 2N5457 JFET N-CHANNEL TRANSISTOR and SMD TRANSISTOR PCB)

the link in their instructions just takes you to a standard thru-hole 2N5457, not an SMD one. And the link to the SMD Transistor PCB takes you to a “SMD TRANSISTOR TO TO-92 PCB”. Very confusing. But that is of course for the 2N5457, not the possibly faulty 5088…….
 
Upvote 0 Downvote
Jeff C said:
Well, Cobalt Drive remains a mystery to me. When I replaced the transistor we were focused on, I still didn’t have success. But when I replaced the IC, suddenly everything worked. But you were skeptical it was the IC, thus the mystery - to me at least.

I will recheck my readings tomorrow and report back. I‘ll have to order another 5088 if that one‘s shot, unless I can use something else……….
Click to expand...

Over 90% of the time, the root cause is workmanship. Unless you find out otherwise, assume that's the case here. Keep inspecting until you find something. The root cause is very rarely bad parts.
 
Upvote 0 Downvote
Jeff C said:
Just out of curiosity, why does Tayda write this:
Click to expand...
They’re saying that you could use an SMD 2n5457 on an SMD-to-through hole conversion board instead of a TO-92 package through hole 2n5457 device. For each position (Q1 and Q3), it’s either/or—not both. As noted above, the product link to the SMD device is incorrect. The link should be to an MMBF5457.
 
Upvote 0 Downvote
Yeah, that’s why I got them from Stompbox. Re the 5088, I understand it’s an “all purpose” transistor. Do you think it can be replaced with a J201? (and Chuck, I did order a transistor tester…..but it’s on a slow boat from China…..)
 
Upvote 0 Downvote
Jeff C said:
Yeah, that’s why I got them from Stompbox. Re the 5088, I understand it’s an “all purpose” transistor. Do you think it can be replaced with a J201? (and Chuck, I did order a transistor tester…..but it’s on a slow boat from China…..)
Click to expand...
No. A 2n5088 is a BJT and a J201 is a JFET. They are not interchangeable. You could replace it with any NPN BJT of a similar hFE range.
 
Upvote 0 Downvote
You must log in or register to reply here.

Similar threads

A
  • Question
SOLVED Moonshot Tremolo rate LED always on
Replies
1
Views
95
airetex
A
PAGOON
  • Question
Need help with fuzz face wiring
Replies
3
Views
213
Fontelroy
Fontelroy
N
  • Solved
SOLVED Aion Andromeda - Bass not working
Replies
17
Views
400
Noodles
N
N
  • Question
Thumb Sucker Not Working
Replies
4
Views
377
nate_noise
N
C
  • Question
SOLVED Aion Xenotron/? Flange LFO issues
Replies
5
Views
572
comradehoser
C
Back
Top