- Joined
- Apr 17, 2014
- Messages
- 111
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I had an intermittent channel in my Phase Linear Series II 3500 preamp. I thought it was a bad RCA connector, because wiggling the cabling caused the channel to come back in. Took the thing apart.... and that wasn't it at all. It was ALL of the connectors between the various daughter boards and the motherboard. The frame for the PL 3500 has no internal bracing, and when you remove the top and bottom panels it becomes SUPER flexy. Even with the panels securely attached, there is flex when attaching tight connectors -- or even just wiggling the RCA cables up and down. There are three or four places where heavy-duty ribbon cables bridge between various boards inside the amp. These cables are very thick and have solid-core wires inside, so they do not flex at ALL. Instead, the solder joints and PC boards flex. This causes the solder joints for the connectors to crack. Easy fix, just re-flow and add a little solder to each one.
I did this to the main cable that was causing my intermittent problem (so bad I could SEE the crack plain as day, without any magnification), and on a whim I decided to fiddle with the other cables in there, just press on them gently... and low and behold wiggling the volume control cable also caused intermittent channel - on the other channel! So, I soldered all of the connectors in there. I'm debating going back in and replacing the ribbon cables with stranded wires, so they can happily flex. I'm also debating internal bracing of some sort. But in the on the other hand, it lasted 30-some-odd years before having a problem, so I might just leave it as-is
It was an easy fix... so if you see a 3500 with an intermittent channel, chances are pretty good it's a dirt-simple fix!
Charles.
I did this to the main cable that was causing my intermittent problem (so bad I could SEE the crack plain as day, without any magnification), and on a whim I decided to fiddle with the other cables in there, just press on them gently... and low and behold wiggling the volume control cable also caused intermittent channel - on the other channel! So, I soldered all of the connectors in there. I'm debating going back in and replacing the ribbon cables with stranded wires, so they can happily flex. I'm also debating internal bracing of some sort. But in the on the other hand, it lasted 30-some-odd years before having a problem, so I might just leave it as-is
It was an easy fix... so if you see a 3500 with an intermittent channel, chances are pretty good it's a dirt-simple fix!
Charles.