My brand old C39 just came today, it's in really good condition except for no remote, which isn't a big deal.

I bring it home, plug it in, set all controls to 0/default, hook up my CD player, plug in a pair of headphones and get BLASTED BY HUM. Super loud. I plug in my amp through the balanced outs, same thing. I unplug the CD player, same thing. Doesn't matter what input is selected. Doesn't matter what the volume is set to. No control settings make a difference, the second you plug in an amp or headphones, horrible, painfully loud HUM.

The seller said it was working fine when he sent it (he has good feedback on Audiogon, as well.) Any ideas?

I have a C-39. I've never had that hum problem with mine. Mine is as quiet as a church mouse. Sounds like you've got some kind of a faulty ground connection. Could have happened in shipping. Try opening her up and visually inspect all solder points. Good luck.

If you have any component that has a 3 wire plug use a ground lifter (3 to 2 wire adaptor), sounds like a ground loop.

LOL!! Can you handle a visual inspection?? That's what the inside of my C-39 looks like. Check all those connections, make sure none came loose. Thankfully most of the connections are push down types. Easy to work loose - easy to fix. Hope it helps - good luck!

http://www.rycher.net/DSC02534.JPG

Huh, it seems to have fixed itself. I left it on over dinner and it works fine now. I'll see what happens tomorrow, I'm gonna call up my local Mac repair shop just in case. Is there some kind of recertification program for used Mac gear?


JimmyNeutron- LOL!! Can you handle a visual inspection??

Nice pic! Actually I work for an electronics company, and we have a pretty well decked-out lab, I was going to run it through an Audio Precision test suite before taking it home but I ran out of time, and was to anxious to play with it :)
Maybe a service manual would be a worthy investment.

If you have any component that has a 3 wire plug use a ground lifter (3 to 2 wire adaptor), sounds like a ground loop.

It's a captive two prong AC connector, so no ground loop. The sound coming out was way beyond ground loop hum, it was at maximum loudness, probably would have blown my eardrums if it was attached to something larger than my small maggies.

It fixed itself for a while, then happened again. I pulled the top off and started poking around, the tall black caps in the power supply (upwards and right of the transformer on the left hand side of the picture above) are loose to the touch. They must have vibrated loose in shipping. The waveform coming out of the outputs was a truncated sinewave, so the AC was probably shunting into ground or something equally nasty. Thanks for everyone's suggestions, but it's going into the repair shop, as I'm not up to disassembling half the preamp to get at that one board, especially with no service manual.

The power supply is only under all seven boards! They all come out and can be unplugged and unscrewed from the rear panel. Re-solder all of the power board connections with some good silver solder and all should be well again.

Ron-C

Here is a closer nudie of the C-39. Hope they help. :thmbsp:

http://www.rycher.net/10.JPG

:yes:

The two regulator transistors on the 'U' shaped heatsink, towards the front, should have their solders checked also.

Ron-C

Dial-up beware!!

How about just posting the link to the picture and letting 56k'ers decide. ;)

We have a gallery that you can use to host your all your gear pics. :)

Carl

The power supply is only under all seven boards!

Actually it's on the right hand side of the smaller picture above, the black shield/heatsink surrounds the capacitors that are loose. It isn't under any other circuit board, but it's affixed to the front panel somehow, and I got to the point where I was going to have to remove the whole front assembly, glass, drawer and all, just to get at that one board. The caps aren't a big deal, but if I break the faceplate, or drawer, or some other esoteric part up front it's going to cost.
I'd rather have a certified and *insured* tech ripping everything apart.

On another note, which is the THX board? I'm thinking it's the board directly below the transformer in the smaller pic above, as it has a big Analog Devices DSP on it. There's nothing wrong with it, I'm just wondering what the internal layout is.

On another note, which is the THX board? I'm thinking it's the board directly below the transformer in the smaller pic above, as it has a big Analog Devices DSP on it. There's nothing wrong with it, I'm just wondering what the internal layout is.


Hello Jb, my C-39 (which is the one that's pictured) has no THX board. It's a mint virgin C-39 - no mods what-so-ever. I use mine strictly for 2 channel stereo listening in my bedroom, so no $500.00 THX module is needed. As for where is goes, it gets "mounted" right on top of that board next to the cap/heatsink with additional plastic risers. It is mounted kinda in-line with that board. Unplug come cables from their current positions, plug them into the THX module, then plug the module into the left over plugs. Very simple and easy install if anyone wanted to do it themselves. I've seen the THX modules going for $400.00-$500.00 on ebay, but I just don't think it would do anything even for the resale value of the C-39. Besides, those modules cost what I paid for my C-39 anyway! Personally, I think an original, minty virgin would fare better - resale wise, no?