CP650 Issue

[Neal Scanlan]

Hello All,

I have an issue with my CP650:

From cold the processor powers up and works fine. After about 15-20mins it drops into bypass mode and then reboots. Thereafter it repeats this cycle with a descending period of time between moments of stability. After the first restart the sound is also much reduced.

Has anyone experienced this or could help me resolve the issue?

Thank you

[Frank Cox]

My first guess would be a cracked solder joint that separates when it warms up. You might (or might not) be able to see it if you go over the motherboard with a magnifying glass.

[Steve Guttag]

I'd start with the power supply...sounds like it is cycling.

[Adrian Avram]

I would suspect the PS as well!
Does it have the PS model AM-120U-T133-171 installed? there is a sticker on the golden chassis of the power supply .

[Marcel Birgelen]

Besides an obviously leaking capacitor or cracked lead, I'd say that replacing the Power Supply is the lowest hanging fruit as a potential fix for this.

[Sam Chavez]

Almost certainly power supply. Lots of them around these days. BACP carries new ones if you can't source one locally.

[Mark Gulbrandsen]

This is often what happens when CP-650 supplies go bad, it's not Dolby's fault... it's just more of the Capacitor Plague. Millions of boards and power supplies still out there that have it. I had quite a few do this, so I carried capacitor kits in the truck and rebuilt them, in the booth. It also hit DTS...

[Neal Scanlan]

Hello,

Thank you all for getting back back to me. I toook the power supply out today and have photographed it. I am guessing that it is the four capacitors on the right that could be the culprits?
I live in the U.K. can I ask who BACP is?

[Mark Gulbrandsen]

BACP is Bay Area Cinema Products... Sam Chavez is the owner and they supply parts for most new and older Dolby products. He also worked for Dolby for many years. If you want to replace the supply, which I recommend doing, you can get one from him. The caps on your board are not leaking, so the issue is not obvious. Recapping the board might fix it and might not but replace the large cap on the upper left as well. It's the AC line input cap. ...

[Neal Scanlan]

Hello Mark,
Thank you, I will replace them and let you know if that cures the problem.

[Kieran Hall]

Not sure how much they cost these days but www.allpsu.co.uk are the UK dealer for the IPD PSUs and according to the IPD site they still stock this unit. We managed to get a replacement for our CP500 from them a while back.

[Leo Enticknap]

CP750 power supply boards have a habit of going bad after a few years, too, and they were all made post-capacitor plague (2000 to '07, approx.).

[Sam Chavez]

BACP provides the entire Cat. No. 776 power supply and carrier or sled. There were three different power supply modules used during the 650's production, each with a slightly different wiring harness and and attachment points.

[Mark Gulbrandsen]

The most solid power supply in any Dolby processor was the one in the CP-100.

[Sam Chavez]

Mark,

You mean 200? The one in the 100 was entirely built in and no fun to repair.