Fender DeVille 212, low low power

[featuringbirds]

'96 Fender DeVille 60w 212

Started out as a low power issue, now no response from the master volume. Whether it's at "0" or "12" there is a very weak and bad sounding distorted signal coming through the speakers. The amp had been knocked off an amp stand when the problem started. All of the tubes glow a faint orange, none are microphonic. One of the 6L6's has a broken center guide pin, but it looks like the glass is OK and it lights up. Amp hasn't blown any fuses or smoked or anything. I am thinking that it's something to do with the power section of the amp, but I don't have a lot of experience.

Also input #1 has been cutting out for some time, I figured I would re-solder it when I pulled the amp apart.

I am familiar with deadly voltages and the idea of discharging caps, I've been doing research on and off for a few years about repairing tube amps. It hasn't been until now that I need to actually do any repairs.

Any help is appreciated. Thanks.

[Enzo]

First, is the speaker plugged into the correct jack? If you plug it into the extension speaker jack, it will act as you describe.

Look VERY closely at the solder on the pins of the power tube sockets. ANy little cracks in it? Whenever I am inside this series of amps, I always resolder the power tube sockets - solder cracks are common.

[featuringbirds]

Speakers are plugged in to the right jack. Checked for cracks, wiggled the tubes and checked some more, all looking solid.

Should I look for somewhere to get the power tubes tested?

[Prairie Dawg]

Speakers are plugged in to the right jack. Checked for cracks, wiggled the tubes and checked some more, all looking solid.

Should I look for somewhere to get the power tubes tested?

If I had to take a guess I'd say start by eliminating the tubes as a source of discomfort and then start looking for weak/broken solder joints particularly on the tube circuit board.

[booj]

Check your tube voltages

Hot Rod DeVille.pdf

Maybe this will help

[Klugetone]

My Blues Deville 212 had a similar problem several years ago. Finally, in the middle of a high profile show it got really bad and would cut in and out whenever I played a loud chord or cranked it for a solo. Turned out to be the two large screen resistors (I seem to recall) that were poorly soldered and worked their way loose under heat and vibration. They were still in their through-holes but were intermittent. Reflowed the solder and added extra and that solved that issue. I just went ahead and reflowed everything else while I was in there.

edit: just saw the schematic...check and reflow solder connections at R61 and R62 for starters. They are 1 watt, 470 ohm resistors. I believe that's the two I had to fix on mine.

Just FYI

Dave

[Enzo]

And we should not forget the classic...

Plug a spare cord from FX send to FX return. Any help?

[seeley]

Further to what Klugetone had to say, I've seen those resistors cause trouble in a couple of these. Won't hurt to replace them with higher wattage ones either

[Klugetone]

While you have the thing apart, look closely at the two 5W, 330 Ohm resistors in the 32 Volt supply circuit on the main board. (R78 & R79) I recall the soldering on these was substandard as well. They get hot during operation and could probably benefit from a solder reflow too. Easy to find as they are the largest resistors on the board right in the middle, side by side.

Good Luck! The DeVilles are nice sounding amps. Working on them does suck though.

Dave

[MWJB]

Try the power tubes one at a time in the same socket, do they sound resonably similar, & work (they will be more distorted with only 1 fitted)? If so carry on...

Check voltages at pins 1 & 6 of the phase inverter tube (12AX7 next to the 6L6s), should be reasonably similar (within 15 or so v)?

Check voltaeg at pin 4 of both 6L6s?

[Prairie Dawg]

My Blues Deville 212 had a similar problem several years ago. Finally, in the middle of a high profile show it got really bad and would cut in and out whenever I played a loud chord or cranked it for a solo. Turned out to be the two large screen resistors (I seem to recall) that were poorly soldered and worked their way loose under heat and vibration. They were still in their through-holes but were intermittent. Reflowed the solder and added extra and that solved that issue. I just went ahead and reflowed everything else while I was in there.

edit: just saw the schematic...check and reflow solder connections at R61 and R62 for starters. They are 1 watt, 470 ohm resistors. I believe that's the two I had to fix on mine.

Just FYI

Dave

David, you are a frackin' genius and saved my butt.

I have a Bassman Reissue here that was hardly ever used. A friend of mine bought it on Craigslist for a good price, but the tone really sucked. I checked bias and found 13 ma either side. I installed an adjustable bias, got it up to about 36 or so, changed a few tubes and called the customer. It would crackle and spit, but only when real hard bar chords were played. So playing around with preamp tubes and I happened upon your post here. Just this minute I put my finger on the resistors and thought one moved. I got out my needlenose pliers and sure enough, one of the resistors was loose.

So I gotta go back in and resolder the resistors but now I know for a fact what it is going to take to fix this amp and it'll stay fixed.

[Klugetone]

David, you are a frackin' genius and saved my butt.

Thank You! I just get lucky now and then. Glad to have been able to help a bit!
I just hope the OP gets his DeVille sorted out.

Dave

[Prairie Dawg]

Thank You! I just get lucky now and then. Glad to have been able to help a bit!
I just hope the OP gets his DeVille sorted out.

Dave

For sure. I am thinking that part of my examination is going to be giving board mounted items like this a very gentle tug with a small pair of pliers. I removed the board last night and went over the connectors, found another loose one and a number of dodgy looking joints. In this particular case the solder was there, but it had not grabbed the wire where it came through the hole-leaving me to believe that the surface of the resistor lead was contaminated or insufficiently cleaned before assembly.

Thanks again.

[featuringbirds]

Thanks for all the replies. I've got the day off tomorrow and will be doing some noodling around. I'll let you know what I come up with.

[featuringbirds]

Thanks for all the suggestions.

Checked and re-flowed solder at R78 and R79, also at R61 and R62.

Patched the FX loop, nothing.

I noticed that when the channel is switched to the "drive" channel, the master volume has an effect on the very small amount of distorted volume coming through the speaker.