Speaker issue or Resistors? - 410 Blues Deville Reissue

[thoushaltjam]

Hi all. I have a 410 Blues Deville Reissue that I'm experiencing some issues with. I've recently noticed that I have hardly any headroom with my amp. It breaks up really soon (around 2, 3, on the volume) and sounds really trashy. I peeked at the plate resistors in the amp and I didn't notice any burn marks or anything (I have yet to check the resistors with a multimeter). So, I did the next easiest thing and checked the speakers thinking that they were perhaps blown (uncommon, I know, but I had an unfortunate experience with a loop station and a drum machine. i.e., it was turned on w/ max "bass kick" volume...it was loud! ha). Anyway, all the speakers measure 2 to 2.6 ohms. Is this low? Considering that they are 8 ohm speakers, shouldn't they read somewhere around 6 or 7? Do I have four blown speakers??! Please help!

[Chuck H]

What is a "Blues Deville Reissue" I'm not even aware that it was ever out of production!?!

The speakers should ohm out higher. But all speakers are different. DC resistance and AC impedance are two different things. Try the amp through another cabinet and see if the performance improves.

BTW... The thread title is very presumptive. There's no reason as yet to think your problem is either of those things.

[Enzo]

Are you measuring the speakers with the wires disconnected?

And when they are all wired up, are they all IN PHASE?

Plug the speakers into some other amp to see if they sound OK. And connect some other cab to this amp. That will tell you if either has a problem.


MAKE SURE to plug the speakers into the main speaker jack, and NOT the extension speaker jack. IT MATTERS. Wrong jack can sound as you describe.


On all those DeVille family amps, look VERY close at the solder on the power tube sockets. I just automatically resolder them if I open the things.

Then with power on, look at the phase inverter tube, the tube next to the power tubes. Is there B+ voltage on BOTH pins 1 AND 6? An open plate resistor will result in one of those being dead and the sound will become as you describe.


Blues DeVille was a 1993 design. The reissue is 2004 or thereabouts. And by then they had moved to one board as the basis for all the Blues/HotRod Deluxe/DeVille series.

[thoushaltjam]

Are you measuring the speakers with the wires disconnected?

And when they are all wired up, are they all IN PHASE?

Thanks for the reply. I'm measuring while they are all plugged in - as if the amp were ready to be played, but power turned off. Is this the incorrect method? Also, I've checked all the solder for the power tubes and they are okay. Now, for the phase inverter, which pins are 1 and 6? I'm a newbie at this stuff. Thanks for the help!

[52 Bill]

I'm measuring while they are all plugged in - as if the amp were ready to be played, but power turned off. Is this the incorrect method?

If this is true, I'd expect the reading to be even lower, as the output transformer secondary will read almost as a direct short. You need to measure each speaker disconnected from the others as well as from the amp itself. If there are push on connectors, just pull off one of the two at each speaker as you test it.

Now, for the phase inverter, which pins are 1 and 6? I'm a newbie at this stuff.

If you have to ask this, then I'd suggest that you test the two phase inverter plate resistors instead of reading the live voltages, it will be much safer. There are two resistors that often go open in the PI circuit. One is a 100K and the other is an 82K resistor. They are both located on the tube socket pc board. Make sure the amp is off and unplugged and use your meter to read the resistance of these two resistors.

[Chuck H]

I'm measuring while they are all plugged in - as if the amp were ready to be played, but power turned off. Is this the incorrect method?

If the speakers are all connected then their resistances are all connected. If you want to measure the electronic properties of any one component it needs to be isolated. It's the way all the components work together that makes them do electronic stuff. In the case of your speakers, they are wired together in a way that provides the amplifier the correct load impedance. Which is different from one individual speaker.

Counting pins on preamp tubes, one is clockwise of the gap.

Solder joints don't need to look grossly bad to be bad. Sometimes just a little flux line around the component lead on an otherwise nice shiney joint is the only evidence that it may be bad. It's easy enough to just reflow the joints and be sure. Enzo is very experienced and often, if not always, suggest inspection or reflow of these joints in these amps.

[thoushaltjam]

Safety certainly is a concern, but I do have some basic knowledge about what not to do (I've done a good bit of electrical work in a residential setting). If I were to test the voltage at the pins is there anything special I should be concerned about? Personally, I'd like to learn how to work on this amp anyway so any advice is welcome.

Also, when I checked the solder joints I used an orangewood stick and gently pressed each one. I noticed no loose or broken joints.

[Chuck H]

There are some good books on the subject of tube guitar amp electronics. It's not hard to find one at a book store most of the time. Poking the joints won't always reveal a bad one. If the amp is operating the chances are better because you might hear a pop or some other noise. Poking the joints with a soldering iron doesn't take much longer than poking them with an orangewood stick.

Remember this... your bodies conductivity combined with typical household AC can give you a nasty shock. Possibly mortal if your health is compromised in certain ways. But the high voltages in tube amplifiers are much more likely to electrocute you. As in, shock you to death. There should be safety instructions for working in tube amps available in any book on the subject as well as your search engine.

Back to the issue at hand... Did you check to see that all your speakers are wired in correct phase?

How old are the power tubes?

When and how did you first notice the problem? was there any odd noises? Was it immediately after the drum machine incident? Or did you just realize one day "Hey, my amp hasn't been working like it should."?

[thoushaltjam]

Back to the issue at hand... Did you check to see that all your speakers are wired in correct phase?

How old are the power tubes?

When and how did you first notice the problem? was there any odd noises? Was it immediately after the drum machine incident? Or did you just realize one day "Hey, my amp hasn't been working like it should."?

Okay. I re-checked the speakers w/ the multimeter. The ohms for each speaker read normal (6-7). However, this still doesn't mean that I might not have a blown speaker, correct? As for the power tubes, they are brand new and the amp has been re-biased to the low end of the factory suggestion (62mv).

Initially, after the drum incident I noticed that every time the amp heated up the tubes would start to buzz/rattle. So, I bought new power tubes thinking that my old ones were about to go. After I biased the amp for the new tubes (SED winged Cs, which were supposed to provide more headroom) I noticed that it sounded really crappy past 2 or 3 on the volume, but the buzz/rattle was gone. I'm not sure how long it had been like that because I rarely turn it up past 2, due to the fact that I have house mates and I want to be courteous.

So, honestly I have no idea what to do next. I guess I need to measure the voltage at the pins as suggested earlier.

[52 Bill]

Yes, you may still have a bad speaker, but if they test with your ohm meter as you say they do, they usually do not cause the problem that you are describing.

If you still have the old output tubes put them back in the amp and see if the distortion clears up. If that doesn't have any effect try swapping the driver tube (the one closest to the outputs) with one of the other preamp tubes. Does this help?

Did you check as Enzo had pointed out to see if you were plugged into the main speaker out jack and not the extension speaker jack?

Did you try reading the resistance of the two driver tube plate resistors that I suggested earlier?

[thoushaltjam]

Alrighty. I've tested pin 1 (@276V) and pin 6 (@267V) of the phase inverter. Are these normal readings?
The jack is definitely plugged into the internal speaker jack.

[Enzo]

Those look fine.

Isolate the problem.

You have a couple of jacks - preamp out and power amp in. Plug the guitar into the power amp in jack. This will bypass the preamp. How does that sound? Clean and strong, or still has the problem.


Likewise, you can play through the amp like normal, and run a cord from preamp out to the input of some other amp. How does that preamp signal sound coming out the other amp?

[Jazz P Bass]

You need to verify that it is not a speaker problem.
Thoes speakers sre really only good for 15 watts, in an open back cabinet.
You could try each speaker separately (without getting carried away, volume wise. Remember, 15 watts)

[thoushaltjam]

Plug the guitar into the power amp in jack. This will bypass the preamp. How does that sound? Clean and strong, or still has the problem.

I plugged the guitar into the power amp in jack - sounded great. Clean and strong is a good description. What would this suggest? Think this might just be a preamp tube issue? Also, I would try the preamp out, but unfortunately I don't have another amp at the moment to test it through.

[Jazz P Bass]

Simply to prove out a jack issue, plug a cord from the preamp out into the power amp in.
See if that helps.