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Post subject: '94 Blues Deville 410 Has No Sound
Posted: Wed Jan 09, 2013 12:02 pm
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First time posting anything ever. Here's my issue. I bought the amp about 4 months ago. It had the original tubes in it and the guy who owned it before never played it above 2 on the volume. So after I buy it I started using it in practices at higher volumes, and after a while I start noticing a buzz in the bottom right speaker. Reasearch told me the tubes could be going out. I don't know if that's true (and if it has nothing to do with this, then I won't worry about that now), but I continue to play until one day the sound just kinda fizzles out. The amp still turns on and when you play through it you can very faintly hear something. I replaced all of the tubes, and tried again and still get the same results. Can someone tell me where to start looking? I have experience with circuits and soldering and the like. I just don't know what I need to be looking for first. This is my first foray into noodling around with circuits in a tube amp. Thank's for the help.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Wed Jan 09, 2013 3:19 pm
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Not sure I understand well .
Look you have problem in power supply . Bad solder or resistor.
Power tubes need a bias check/ adjust when new .

Blues de ville schematic and layout;

support.fender.com/schematics/guitar_amplifiers/Blues_DeVille_schematic.pdf


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Wed Jan 09, 2013 4:02 pm
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It's fixed bias. I assumed, if you replace the tubes, they needed to match the bias since it can't be adjusted. The tubes I got from Euro tubes and they said it was good for the older fixed bias DeVilles. Other than that, like I said, it powers on, the tubes heat up, and there is sound coming from it when I play through it. It's just barely there.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Wed Jan 09, 2013 4:46 pm
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B+ voltage reading is the first thing to do. . With looking carefully you can find something wrong.

Second , audio signal generator and 'scope to follow the path . But you don't have those tools.

Be carefull , tube's amp have lethal voltage


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Wed Jan 09, 2013 4:54 pm
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Okay. Can you tell me the location is on the schematic for the bias resistor? R87 is my guess, but I watched a video of a guy biasing a HRDv and it was R82. That doesn't seem to match on the diagram though. Thanks for the help.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Wed Jan 09, 2013 5:35 pm
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Yes it is R87 in schematic I show you , but not sure if you have this version ?

Just read if you have aroud -49 volts , that's all you need to know if your tubes are safe and your amp should work with this bias. This -49 should also be at each 6L6 's grid

Go to read other volts ; B+ . IMO there is your problem not bias.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Thu Jan 10, 2013 7:15 am
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Okay. This is a start. I'll get in there this evening to take a look. Is there anything else I can look for, say if B+ voltages are good?


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Thu Jan 10, 2013 3:26 pm
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Look carefully for any trace of burn on circuit board, loose solder , on some burn resistor. If you can take some pictures , close-up of power supply section . It could help.

Be careful ; lethal voltage.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Sat Jan 12, 2013 7:43 am
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"a buzz in the bottom right speaker" -->Did you remove the speaker to control if there is something in ?

Probably bad soldering as stated by stratele, check all supply first, specially on big resistors (R85/86) that are on +/- 16V

However, on the devile
- you have a preamp out that you can connect on another amp, doing that can help to say that the preamp is OK or not
- you have a power amp in, you can connect another preamp, doing this allows to check if the power amp is OK.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Thu Jan 24, 2013 11:24 am
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Thanks for the help guys. My work on this is slow going. I tested the continuity of the two transformers and both are in good shape. The power tubes are soldered in well and I don't see any burn on the board. I haven't taken it off, though, to see the other side. Unfortunately, my meter doesn't go over 300V, so I haven't been able to check B+. I'll have to wait till the weekend to get with a friend who has a better one. I'll report what I find and post some pictures of the power section while I'm at it. Also, I haven't done anything with the speaker. It was just something I noticed in passing. At the time, I assumed it was the tubes going bad, which I had intentions to replace them anyways as they were terrible.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Thu Jan 24, 2013 11:28 am
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Have you checked the speaker wiring for proper continuity?

Arjay

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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Sat Jan 26, 2013 11:01 am
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Speaker wiring is fine. I actually was able to go in there today and test B+. I was getting 50V at pin 6 on the power tube. I also did a check further up the line at R82 and got the same reading. I'm going to re-run the tests on the power transformer to see if there was something I missed. Are there any suggestions as to what can drop voltage like that? Sorry no pictures. I will have some up soon.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Sat Jan 26, 2013 1:12 pm
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andthedevilmakes3 wrote:
Speaker wiring is fine. I actually was able to go in there today and test B+. I was getting 50V at pin 6 on the power tube. I also did a check further up the line at R82 and got the same reading. I'm going to re-run the tests on the power transformer to see if there was something I missed. Are there any suggestions as to what can drop voltage like that? Sorry no pictures. I will have some up soon.


Pin 6 is not connected on a 6L6GC. Plate voltage will be on pin 3.

50 VDC at R82? Bad caps, bad rectifier, or bad power transformer.

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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Mon Jan 28, 2013 10:46 am
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Can someone explain the rectifier to me? I've tried to find some info on the webs and the best I can get is that it's a solid state (circuit?). I assume it's diodes. Would that be this bit attached to CP17 and CP18? Transformer checks out. I'm down to caps and the rectifier. I'm just not sure I fully understand what that is. Thanks for the help.


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Post subject: Re: '94 Blues Deville 410 Has No Sound
Posted: Mon Jan 28, 2013 3:42 pm
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Uh, no.

The main power supply rectifier consists of CR14, 15, 16, and 17. They are connected to the power transformer and C34/C35. According to the schematic, you should be measuring 471 VDC (+/- a few volts) from R82 to ground.

Are you sure that you are measuring at the right test points?

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Last edited by bluesky636 on Tue Jan 29, 2013 3:59 pm, edited 1 time in total.

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