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CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« Last post by vwyf11 on March 23, 2026, 02:12:37 AM »

I couldn’t get consistent voltage on a couple of the readings so I just decided to pull everything apart.  I made an incredibly stupid error and skipped over the last two diodes on the front panel pcb.  I couldn’t find the 1n914 diodes included but I had some 1n4148 diodes so I put them in their place at d10 and d11.  Testing seems to be going much better so far.  I know these diodes are almost identical so shouldn’t be an issue.  Will these be any problem?

92

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« Last post by JPK on March 21, 2026, 09:48:02 AM »

You could look for a continuity between ground and C8, C9, C10. But the best thing to do will be to shorten the pins.

93

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« Last post by vwyf11 on March 18, 2026, 03:33:37 PM »

I did notice now that I forgot to trim the leads of T2 and that may have shorted to the case.  Is there a test while that is still soldered to check for issues there?

94

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« Last post by JPK on March 18, 2026, 12:14:19 PM »

I only get resistance from 0.3ohms to about 1.6Kohms
Normal because the trimmer is in parallel with R31+R32.

I have added some DC voltage checks to do here. Please compare with your values.

95

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« Last post by vwyf11 on March 18, 2026, 02:54:25 AM »

R26, TR2 and R31 all look fine and no bridged pins etc.  The resistance on the 5k pots don’t test the way I would expect.  If I measure from the wiper to another pin on TR2 I only get resistance from 0.3ohms to about 1.6Kohms.  Not sure if there’s a problem there.  I tested between tp2 and tp3 again and the voltage swings from 2.7V to 3.1V and will never settle

96

CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« Last post by vwyf11 on March 17, 2026, 05:51:07 PM »

Sorry, step 7 was where I was hung up.  I could not match bypass on and off level.  I was reading 1VAC between pins 2 and 3 when bypass was up and 0VAC when depressed regardless of how much I turned tr1

97

CP5176 FET compressor / Re: My CP 5176 is very quiet on the input stage

« Last post by JPK on March 17, 2026, 05:33:08 PM »

I changed Q1 but that was not the issue
Did the sound return when Q1 was disconnected?

I see that R56 and R57 changed color a little.
This means you have a short circuit somewhere. Are they getting hot? 

A little burned the resistance is correct and they are just for power right? But that cannot be an issue?
You can check their value with your ohmmeter (in circuit).

Do you think it might be transistor or capacitor?
Not a capacitor. Neither a transistor if you got the DC voltages right in the picture here.

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CP554 Diode bridge compressor / Re: Cant get 3v at step 5

« Last post by JPK on March 17, 2026, 05:23:21 PM »

I moved on and could not get past step 6
What happened at step 6?

Check the solder joints on R26, Tr2, R31.
Check the wire connections to the transformer, look for a thread that might be causing a short circuit.

I was checking for shorts anywhere and did find continuity between two pins on U3
Pins 1 and 2 are connected by a 7R5 resistor, whick way look like a short.

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CP5176 FET compressor / Re: My CP 5176 is very quiet on the input stage

« Last post by Denis on March 17, 2026, 04:17:02 PM »

Try removing Q1 on the broken unit. If the sound is back then Q1 is the culprit.

Hi Jean-Pierre

I changed Q1 but that was not the issue..any ideas what it can be? I dont want to swap out all pre stage
I see that R56 and R57 changed color a little. A little burned the resistance is correct and they are just for power right? But that cannot be an issue?
I swapped the SK25 and the front assembly with no effect either. 
Do you think it might be transistor or capacitor? I would swap the caps out first.

Thanks
Denis

100

CP554 Diode bridge compressor / Cant get 3v at step 5

« Last post by vwyf11 on March 17, 2026, 03:25:12 AM »

Hey,

I’ve gotten to the testing point and I’m trying to adjust tr2 to get 3v between tp2 and tp3.  The voltage when I initially tested at these points gave me 3v steady with good consistency when changing tr2.  I moved on and could not get past step 6.  I remeasured between tp2 and tp3 and was no longer getting 3v but instead bouncing around 2.7 to 3.1v sporadically and tr2 no longer seemed to make the same consistent change when turning.  

I was checking for shorts anywhere and did find continuity between two pins on U3 either between output and adjust or output and input.  I will have to double check which pins exactly.

I’m not sure where to go from here or what may need checking

Thanks