CS-800C with a problem or two.

[cabinover]

Hi folks, new guy with limited electronic experience although I have replaced outputs and successfully biased my own Bose 1801 amps. Still just a mechanic that wishes he could fix electronic stuff.

Years ago my brother in law and I used to rent a CS-800 and a pair of SP-2s from Ezra Sound in Rutland, VT to DJ with, back when lots of music didn't suck Get them folks out on the dance floor with the Beatles, The Hollies, or some other 50s-80s group and life was great for 4 hours.

Moving along...I've always wanted a CS-800, just because. Bought one the other day from someone that had no idea if it worked or not. It was $50, how wrong could I go?

Brought it home, the L channel had gaffers tape over the input/outputs and a different knob. Right side looked ok besides normal wear and tear. Plugged her in expecting smoke and nothing! Cool! Threw a multimeter on the R channel outs and pretty close to 0VDC. Even better, let's hook up a speaker...works fine.

So today I start looking around after blowing 30 years of dust out and see the left amp board is unplugged. Hmmm...someone has been here. Throw the amp with R channel connected onto a dim bulb tester. 60W, lamp lights then dims slightly. Unhook R channel and hook L channel up, same thing with no VDC on outputs. AWESOME!!!

Hook R channel back up, L channel is already hooked up, attach them back to the amp chassis and fire it up. Lamp stays fairly bright. Just one problem..15VDC on both outputs. I've forgotten much that I learned about electricity but I know that's not right.

I found a schematic but it's really small from my printer so I thought maybe I'll ask you guys that work on these all the time what you thought.

The old girl has a couple other cosmetic issues like a left knob is now a chicken head and the DDT pull section either doesn't work or this isn't the correct stalk as it came out in my hand when I pulled it out.

Thanks a ton.

[GTC]

With an apparent 15 V DC offset, it's just as well you did not connect speakers to those outputs.

Step 1: Remove the dim bulb, and measure the DC offset again. Let us know what you get.

[cabinover]

With an apparent 15 V DC offset, it's just as well you did not connect speakers to those outputs.

Step 1: Remove the dim bulb, and measure the DC offset again. Let us know what you get.

Sorry for not replying until now but I can explain. While writing the initial post I may or may not have had a couple short glasses of bourbon on the rocks. Satisfied I'd said all I could mention, I posted and shut down for the night. The next morning there was no sign of my post. Then I got to thinking about the bourbon and figured I may have had more than enough and forgot to post after all. Today I finally got to get back to the amp and after unplugging from the dim bulb, smoked the fuse as soon as I reconnected channel A. Channel B will level out to pretty much 0VDC.

Let me procure some fuses and I'll be back. Thanks GTC.

[cabinover]

My fuse is labeled 311 3AG, then underneath that is 254 32V. I'm guessing that this is not the proper fuse for it. Up here we call that "Farmerized"

Is this supposed to be a slo-blo, 15A fuse? I'm in the US so only 120V.

BTW, measured across the output banana jacks, L channel dead short. R channel rises as charging caps. Guessing that Triac is smoked on L, and probably trouble prior to that. Good! Been studying and learning about retirement and finances for a month, ready to do something different for the rest of winter anyway!

[cabinover]

I still cannot reply to the post I started...

[GTC]

My fuse is labeled 311 3AG, then underneath that is 254 32V. I'm guessing that this is not the proper fuse for it. Up here we call that "Farmerized"

Is this supposed to be a slo-blo, 15A fuse? I'm in the US so only 120V.

Have been away. Just getting back to this forum.

I think that should read: 3AG 311 25A 32V ... which is 25 amp 32 volt normal/fast blow in a 3AG size.

Ordinarily I'd expect that to be an automotive fuse.

From what I can see on a schematic, that ought to be a 15 amp 120 volt fuse. I tend to use slo-blo for such applications if inrush current is an issue.


Yes, seems something has gone short. Could be more than one component in that channel. Continuity testing should find the culprit(s).