Sound Skulptor forums

Build help and troubleshooting => CP554 Diode bridge compressor => Topic started by: Alex Harmer on April 05, 2024, 08:39:43 PM

Title: Can’t get 3v in step 5 in setup
Post by: Alex Harmer on April 05, 2024, 08:39:43 PM

Hi JP,

I initially successfully passed step 5 with this unit, and everything worked until step 11… when pressing down the BYPASS switch to get 0.98VAC produced no change.

After much trying, I decided to try from the beginning.

Now I can’t get past step 5.

I am getting +16vDC and -16vDC no problem.

But I only see 0.064vDC across TP2 and TP3. TR2 takes a lot of turns, and it only changes a little.

I have reflowed all solder on PCB1 and checked orientation.

Thank you!

Title: Re: Can’t get 3v in step 5 in setup
Post by: Alex Harmer on April 05, 2024, 11:19:43 PM

Here are my results from your first aid test:

Threshold switch position		TP4 & TP5 AC voltage		JMP1 between pin1 DC voltage and +input on PCB 2 (I didn't know where else to put the probe)
+6dB		0.00 (supposed to be 0.11V)		1.8 VDC (supposed to be 0.14V)
0dB		0.00 (supposed to be 0.22V)		1.9 VDC (supposed to be 3V)
-6dB		0.00 (supposed to be 0.45V)		1.9VDC (supposed to be 10.8V)
-21dB		0.00 (supposed to be 2.4V)		2.03VDC (supposed to be 15V)

Title: Re: Can’t get 3v in step 5 in setup
Post by: JPK on April 06, 2024, 04:11:31 PM

But I only see 0.064vDC across TP2 and TP3.

(Without left PCB installed)
Check the connections to the output transformer.
What DC voltage do you get on the yellow wire, against 0V ?
What DC voltage do you get on TP3, against 0V ?
Check the solder joints on Q7, trimmer TR2 and R31.

Title: Re: Can’t get 3v in step 5 in setup
Post by: Alex Harmer on April 06, 2024, 10:45:05 PM

Thanks for your reply JPK! By the way - the first unit is sounding wonderful thank you! :)

Quote

(Without left PCB installed)
Check the connections to the output transformer.
What DC voltage do you get on the yellow wire, against 0V ? = 15.42
What DC voltage do you get on TP3, against 0V ? = 14.35
Check the solder joints on Q7, trimmer TR2 and R31. = completed! No issues. I de-soldered and reflowed just in case.

Step 5 result of VDC across TP2 & TP3 is 0.046 VDC with TR2 turned all the way clockwise.

Title: Re: Can’t get 3v in step 5 in setup
Post by: JPK on April 08, 2024, 12:17:42 PM

TP3 should be around -11VDC.
Check Zener D20. It could be dead.

Title: Re: Can’t get 3v in step 5 in setup
Post by: Alex Harmer on April 08, 2024, 09:27:33 PM

Quote

Check Zener D20. It could be dead.

I think you're right! I removed Z4V7 1W3 in D20 and my meter said OL in both directions on the diode test. I then put the diode back in circuit and tested it with normal power. Same result.

Is this the correct Mouser part?

https://nz.mouser.com/ProductDetail/Vishay-Semiconductors/BZX85C4V7-TAP?qs=yIvl1B2wDi7Hji4YUWzsdQ%3D%3D

I'm having trouble finding the right replacement part in my city. No local suppliers have 1W3.

Would it be okay to replace it with a 3W?

Title: Re: Can’t get 3v in step 5 in setup
Post by: JPK on April 09, 2024, 06:59:27 PM

Is this the correct Mouser part?
Yes, correct.

Would it be okay to replace it with a 3W?
Yes, no problem.

Title: Re: Can’t get 3v in step 5 in setup
Post by: Alex Harmer on April 09, 2024, 09:07:48 PM

All sorted JPK!

Both units working perfectly, and sounding amazing.

I'll do a demonstration for YouTube if you would like to look out for it :)

Title: Re: Can’t get 3v in step 5 in setup
Post by: JPK on April 10, 2024, 08:58:54 AM

Can't wait!