71

CP5176 FET compressor / Re: Modification HPF cp5173

« Last post by PMswing on January 08, 2026, 07:08:26 PM »

R = 2 x 3900 = 7800 ohms
C en Farad
Avec les valeurs standard: 204Hz

Merci !
 
Afin que je comprenne clairement, cet exemple correspond aux valeurs du hpf du cp5173 ? :

-dans cet exemple que représente la valeur R= 2x3900 ohms ? Une ou plusieurs résistances déjà présente dans le circuit du cp5173 ?
-Qu'entendez-vous par "valeurs standard" ? 204Hz correspond au coup bas du cp5173, ou au début de l'atténuation ? J'ai lu dans sa présentation que son HPF était  80Hz !?

Merci pour vos précisions !

72

CP4500 Stereo Bus Compressor / Re: Bad power voltages and reversed THAT1246

« Last post by MRMNW on January 08, 2026, 06:32:41 PM »

OK I'm up to step 8 on the setup guide. I have a reading of 0.5VAC on the DMM but the trimmer T4 isn't affecting the meter at all. Turned it a considerable amount in both directions. No movement at all. 

73

CP4500 Stereo Bus Compressor / Re: Bad power voltages and reversed THAT1246

« Last post by MRMNW on January 08, 2026, 06:15:01 PM »

78L12 AND 79L12 were in the wrong place! 

Thanks for your patience and help. (I may be back once I get past the first stage of setup!)

74

CP4500 Stereo Bus Compressor / Re: Bad power voltages and reversed THAT1246

« Last post by JPK on January 08, 2026, 05:59:28 PM »

Are the fingers on the back connector clean and making a good contact?
Check that you didn't break the vias between the top and bottom pads of the components you replaced.
Is U23 getting hot? This is the last active device connected to V+.
If true, remove it.

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CP4500 Stereo Bus Compressor / Re: Bad power voltages and reversed THAT1246

« Last post by MRMNW on January 08, 2026, 01:23:11 PM »

Still getting the same readings when it's just PCB (A). 
R41 Doesn't seem to be getting hot. 
I've replaced all the 1N4004 diodes.
Still the same. 

76

CP5176 FET compressor / Re: Modification HPF cp5173

« Last post by JPK on January 08, 2026, 12:16:10 PM »

R = 2 x 3900 = 7800 ohms
C en Farad
Avec les valeurs standard: 204Hz

77

CP4500 Stereo Bus Compressor / Re: Bad power voltages and reversed THAT1246

« Last post by JPK on January 08, 2026, 11:57:03 AM »

do you mean R41 and R42?
Yes, sorry.

Do you still get V+ at +4.59 when you only power the left PCB (A), without the front PCB being connected?
Check the diode D4.
Is R41 getting hot?

78

CP5176 FET compressor / Re: Modification HPF cp5173

« Last post by PMswing on January 08, 2026, 10:23:13 AM »

Super merci !

Il y a t'il une formule qui permet de déterminer la valeur de C24 en fonction de la fréquence de coupure désirée ? si oui, pouvez vous me la donner ?

79

CP4500 Stereo Bus Compressor / Re: Bad power voltages and reversed THAT1246

« Last post by MRMNW on January 07, 2026, 11:49:28 AM »

pictures:

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CP4500 Stereo Bus Compressor / Re: Bad power voltages and reversed THAT1246

« Last post by MRMNW on January 07, 2026, 11:42:32 AM »

Yes, sorry V- = -16.40

I've triple checked all diodes, BRs and polar caps are correct. Not seeing any solder bridges or forgotten joints - reflowed all the joints too.
I have R52 as 5K1 in the parts list, do you mean R41 and R42?
R41 and R42 both read 1.2 ohm.
I've given it a good clean too with Isopropyl alcohol.

I'm still getting the same results.

Trying to add pictures but the spam filter won't allow me to embed them or post a link.

Thanks