So I had a friend tell me his Deville is randomly dropping volume. Sounds like the typical resistor issues these things are famous for, right? Well, I get it home, plug it in, jam a few minutes with no issues. Then, it does this: http://youtu.be/4rEh8OTTqmw
So I uhh, not sure where to begin poking around. Tried all the obvious options, different guitar, cables, outlets etc. Happens regardless of having and input, and *** you can see it in the video, doesn't matter what channel or if any of the pots are up or not. Looking for ideas here before I go shotgunning the thing and test every component with the ole DMM. Thanks for any advice guys.
So I uhh, not sure where to begin poking around. Tried all the obvious options, different guitar, cables, outlets etc. Happens regardless of having and input, and *** you can see it in the video, doesn't matter what channel or if any of the pots are up or not. Looking for ideas here before I go shotgunning the thing and test every component with the ole DMM. Thanks for any advice guys.
Hot Rod DeVille? Hot Rod DeVille III? Blues DeVille? Blues DeVille Reissue? We have to know what circuit we are discussing.
The power rresistors that unsolder themselves tend to cause channel switching things. Dropping output has various causes that come up: bad loop jacks, cracked solder on tube sockets, PI plate resistor opening, etc.
You now have a loud hiss? Isolate the problem. Is it in the power amp or preamp, first question.
The power rresistors that unsolder themselves tend to cause channel switching things. Dropping output has various causes that come up: bad loop jacks, cracked solder on tube sockets, PI plate resistor opening, etc.
You now have a loud hiss? Isolate the problem. Is it in the power amp or preamp, first question.
Pull the preamp tubes and see if you still get the noise. And yes, post the schematic or tell us what specific DeVille model it is.
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Sorry guys, not at the house right now, but I'll get the exact model and board rev later this evening. I'll pull preamp tubes this evening as well and report back on any effects it has. The noise persists regardless of anything besides turning the amp off. I've tried it with no input, as well plugging my guitar into the preamp and power, and the noise still persists and is unaffected. I'm not sure if you can tell from the video, but there is also a very high pitched whine coming through the amp that oscilates a bit.
The first time I fired up the amp I let it sit for about 15 minutes on standby, and cut it on and played it for a minute or two before the noise began. I then let it sit for about half an hour to cool down (trying to troubleshoot cold solder joints) and when I cut the amp on it began making the noise immediately. Cut it off, for a minute or two, cut it back on and there was no noise. Played for a minute or two, boom noise was back agin. The intermittent of the issue seems to be a component(s) on the board going bad, I'm just not sure where to look. Haven't peaked at the board yet, so for all I know I could pull it out and find something noticeably baked, but baked components are normally just a symptoms and not the underlying cause. Just my two cents though, you guys would probably know a bit better than me.
I'll take a better look and gather some more info that you guys need tonight. If anything looks amiss on the board, I'll post pictures as well. Thanks.
The first time I fired up the amp I let it sit for about 15 minutes on standby, and cut it on and played it for a minute or two before the noise began. I then let it sit for about half an hour to cool down (trying to troubleshoot cold solder joints) and when I cut the amp on it began making the noise immediately. Cut it off, for a minute or two, cut it back on and there was no noise. Played for a minute or two, boom noise was back agin. The intermittent of the issue seems to be a component(s) on the board going bad, I'm just not sure where to look. Haven't peaked at the board yet, so for all I know I could pull it out and find something noticeably baked, but baked components are normally just a symptoms and not the underlying cause. Just my two cents though, you guys would probably know a bit better than me.
I'll take a better look and gather some more info that you guys need tonight. If anything looks amiss on the board, I'll post pictures as well. Thanks.
Alright, back plate says Type😛R 247, serial starting with B-31xxxx, and the PCB is dated 2002. Google suggests this is a Blues Deville, but that's just from forum posts and not fender themselves. Nothing looks to be burned out on the top side of the board (haven't removedit to check the bottom yet) any one have a link for the scheme, or voltages to measure as a place to start/components to check as a start? Or if more information is needed let me know.
The back plate is worn down some. But it looks to only say "Fender Deville 2x12" but some of the lettering is faded. I'm not at the house, but when I get home I'll take photos of the back plate and post them to see if that helps any one. Worse comes to worse I'll call fender and give them the serial and ask to identify the make and model.
Do you have a "more drive" function? I believe the Hot Rod series has this and the Blues DeVille series did not. BTW, I have a Hot Rod DeVille and it also says type PR247. I believe they overlap. I think it stands for "Product Release". The Hot Rod is a direct descendant of the Blues DeVille. They found 1/2 of a 12AX7 that was unused, so they used it and released the Hot Rod series.
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yes, the product release numbers do not correspond one to one with model names, they refer to engineering projects. It often has a note on the manual that the PR number is not used for warranty claims.
Yes there is a more drive function on the amp. So I guess it is the hot rod version. Really annoying that the back plate is messed up. The amp was bought used from a local music shop (hung out with owner tonight and got what info I could from him.)
Awesome man, thanks for posting it.
Anyone have suggestions on where to start specifically, or should I just go and test every test point, and post the voltages here? I don't have a sig gen, so some of the voltages may be a little off from the scheme. Also, should I test the amp under load, or disconnect the speakers?
Have you tried to pull the preamp tubes to see if this makes a difference? Sometimes by doing this, you can isolate the problem to either the preamp or power amp. If it still makes the noise after pulling these tubes, it would almost have to be in the power section. Also, you can substitute, one at a time, with a known good tube going down the line to try all three preamp tubes.
Have you worked on amps with power on before? This amp has 485v in a few places and lower but still lethal voltages in several places. I just want to be sure that you are good with doing this as these voltages can KILL YOU!
Always have a load connected to a tube amp when power is on unless you for some reason do a test with the power tubes pulled. This way there can be no output so don't need a load. As far as I know, this is the only time you don't need a load, otherwise always have one. If you don't have one, wait to get one. And you should get a 50watt value so as not to fry it. If this happens, it easily could be an open and thus the same as no load and other serious problems can result.
Google "Dale Power resistors" for a good one to use. 8 ohm, 50 watt
Here is a link to Fleabay for 5 of them for $8, free shipping. This way, you can hook two up for 16 ohm in series or 4 ohm in parallel and these two will also handle 100 watts. Or just use one for 8 ohms.
http://www.ebay.com/itm/Dale-Wirewo...025?pt=LH_DefaultDomain_0&hash=item41960d9de1 Get a standard 1/4" jack and some speaker wire or lamp cord to do this, don't use standard shielded instrument cable.
I'm certainly not the greatest troubleshooter in the world, so maybe someone else has some input hopefully.
If the preamp tube pull or sub doesn't work, you can start to take readings. You do this without a signal at first to see if B+ voltages and tube bias voltages are correct but I always start with tubes because it is easiest and you don't have to open up the amp.
Have you worked on amps with power on before? This amp has 485v in a few places and lower but still lethal voltages in several places. I just want to be sure that you are good with doing this as these voltages can KILL YOU!
Always have a load connected to a tube amp when power is on unless you for some reason do a test with the power tubes pulled. This way there can be no output so don't need a load. As far as I know, this is the only time you don't need a load, otherwise always have one. If you don't have one, wait to get one. And you should get a 50watt value so as not to fry it. If this happens, it easily could be an open and thus the same as no load and other serious problems can result.
Google "Dale Power resistors" for a good one to use. 8 ohm, 50 watt
Here is a link to Fleabay for 5 of them for $8, free shipping. This way, you can hook two up for 16 ohm in series or 4 ohm in parallel and these two will also handle 100 watts. Or just use one for 8 ohms.
http://www.ebay.com/itm/Dale-Wirewo...025?pt=LH_DefaultDomain_0&hash=item41960d9de1 Get a standard 1/4" jack and some speaker wire or lamp cord to do this, don't use standard shielded instrument cable.
I'm certainly not the greatest troubleshooter in the world, so maybe someone else has some input hopefully.
If the preamp tube pull or sub doesn't work, you can start to take readings. You do this without a signal at first to see if B+ voltages and tube bias voltages are correct but I always start with tubes because it is easiest and you don't have to open up the amp.
Thanks for all the advice man. First time working on an amp with voltages this high, but I've been doing the electronics hobbiest thing for over a year, and have read up on all the safety precautions a good number of times for servicing tube amps. Luckily, my wife is a nurse, I told her she has to be in the room when I open this amp up haha.
Thanks for the fleabay listing. I've actually been wanting to build a dummy load for a while to test out some stuff.
I've got some known good tubes, so I'll just start by pulling all 3 preamp tubes and replacing them. If the noise persists, onto the power section. I may have some tubes laying around I can swap in to make sure this isn't some kind of internal short in the power section also. I'll report back tonight after doing all the tube swaps.
Thanks for the fleabay listing. I've actually been wanting to build a dummy load for a while to test out some stuff.
I've got some known good tubes, so I'll just start by pulling all 3 preamp tubes and replacing them. If the noise persists, onto the power section. I may have some tubes laying around I can swap in to make sure this isn't some kind of internal short in the power section also. I'll report back tonight after doing all the tube swaps.
I don't know if you noticed but that link I sent also has the component layout on page 2, so with Fender's generous amount of voltage readings and the layout, you should be able to find the voltages that are critical and where to measure them if the tube option doesn't fix things. On the schematic, the rectangle shaped test points are DC readings and the oval ones are for AC with signal applied which is a 4mV, 1kHZ sine wave at the #1 input, so don't worry about those right now, just the B+ and other DC voltages. It cross-references the test points between the two sheets so the schematic page gives you the voltages and page 2 shows where it is on the layout.
I had noticed that, other than the difference in the AC and DC symbols, thanks for the heads up though. Hopefully while testing the DC points I'll find one/some that are either way over or under. That way we'll have a good place to start sniffing around. Well, hopefully it's just a bad tube, and I don't even have to open this up haha.
So I don't have any 6L6's. The only pair I have are in my Peavey Classic VT, which ironically; the owner of the Deville is currently borrowing haha. I have a set of 6V6's which I could adjust the bias and drop them in, but I feel like altering anything (even the bias current) in amp could cause a false positive. However, dropped in known working preamp tubes, and so far can't get it to act up. Played it for about 10 minutes just fine, and now I'm just gonna leave it on for several hours and play it every so often to see if anything changes. Fingers are crossed. Gonna be really surprised if simply a bad tube caused that much noise. I mean I've heard the buzz amps get whenever a tube does a heater-cathode short, and it was nothing like the noise this Deville was putting out. But hey, if all it needs are new tubes, I'm alright with that.
I would not advise you to put in those 6V6s. The plate and screen voltages are too high for them and I doubt you could get the bias adjusted correctly. Plus the output transformer primary impedance is not right for them.
Yep, hopefully it's just a tube. You could sub in the ones you pulled one at a time to find the bad one and keep the other two.
Yep, hopefully it's just a tube. You could sub in the ones you pulled one at a time to find the bad one and keep the other two.
Yea, I've read split opinions on subbig in the 6v6, i'll forgo it and grab the 6l6's from my amp if the problem comes back with known good tubes in the preamp section. Going to keep in testing with these good tubes all night, and try the old ones one tube at a time tomorrow evening if it stays well behaved this evening.
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