Hi
I'm having trouble with my CPS650. It is fully recaped and works flawlessly up to ~ +0.7A/~ -0.7A (12 ch + 3grps+ master section). If I load the PSU with more than ~0.7A per rail (add another channel ) , +/-17VDC drops to like +/-0.5VDC and mixer goes into crazy, noise, random LEDs going on, meters go full up etc. Taking just one modul out puts everything back to perfect order, voltage goes up to +/-17 etc. It can work for hours like this.
All channelss. groups. and master are tested OK, one by one, and all are recaped and in perfect condition. I can plug in any combination of Venue 2 moduls, but, I can not load the PSU with more than ~0.7A per a rail.
I disconnected the sensing circuit (BTW sensing circuit transistors tested OK), and tested the PSU with a dummy load. The regulators will give up holding steady voltage around 0.7A per a rail,at which point the voltage soares to almost 0V.
Think that regulators are broken. Why they work up to 0.7A or so flawlessly and then give up, I have no idea.
Question : LT1038 is obsolete(10A)! Can I replace it with LM338K - it is 5A and the same pinout. I don't think this console draws more than 2.5-3A per a rail (24ch-8grps-Master).
Also, why are those transistors in the sensing circuit so "esoteric", couldn't the same function be achieved with ordinary BJTs like BCs and MPSAs? I must be missing something.
Schematic attached.
Thank you
Uploaded CPS 650b U.G. with schematics to Soundcraft tech page (as well as Venue 2 service manual).
I'm having trouble with my CPS650. It is fully recaped and works flawlessly up to ~ +0.7A/~ -0.7A (12 ch + 3grps+ master section). If I load the PSU with more than ~0.7A per rail (add another channel ) , +/-17VDC drops to like +/-0.5VDC and mixer goes into crazy, noise, random LEDs going on, meters go full up etc. Taking just one modul out puts everything back to perfect order, voltage goes up to +/-17 etc. It can work for hours like this.
All channelss. groups. and master are tested OK, one by one, and all are recaped and in perfect condition. I can plug in any combination of Venue 2 moduls, but, I can not load the PSU with more than ~0.7A per a rail.
I disconnected the sensing circuit (BTW sensing circuit transistors tested OK), and tested the PSU with a dummy load. The regulators will give up holding steady voltage around 0.7A per a rail,at which point the voltage soares to almost 0V.
Think that regulators are broken. Why they work up to 0.7A or so flawlessly and then give up, I have no idea.
Question : LT1038 is obsolete(10A)! Can I replace it with LM338K - it is 5A and the same pinout. I don't think this console draws more than 2.5-3A per a rail (24ch-8grps-Master).
Also, why are those transistors in the sensing circuit so "esoteric", couldn't the same function be achieved with ordinary BJTs like BCs and MPSAs? I must be missing something.
Schematic attached.
Thank you
Uploaded CPS 650b U.G. with schematics to Soundcraft tech page (as well as Venue 2 service manual).
Attachments
Last edited: