Tube amp guru's....help

[Patrick from Davis]

I the schematic Max posted there is a bias adjust on it.  I'll see if I can find the combo version's schematic.  This might be a fools errand for you, but the resistors R39 and R40 are in the path of the bias adjust on the posted schematic.  If they are not hard to find, check them with the multimeter.  I suppose I should find the correct schematic first, but this came to mind as an idea of something to check.
Patrick

Crap, that is the only one.  I would imagine that the same circuit boards were used.  Might be worth a look.  I can't read the layout to find the location of the part, the resolution drops too low, and trying to find the "R's" has made eyes tell me that they are not going to take much more.  More thinking...

 

[DangerousR6]

I the schematic Max posted there is a bias adjust on it.  I'll see if I can find the combo version's schematic.  This might be a fools errand for you, but the resistors R39 and R40 are in the path of the bias adjust on the posted schematic.  If they are not hard to find, check them with the multimeter.  I suppose I should find the correct schematic first, but this came to mind as an idea of something to check.
Patrick

Crap, that is the only one.  I would imagine that the same circuit boards were used.  Might be worth a look.  I can't read the layout to find the location of the part, the resolution drops too low, and trying to find the "R's" has made eyes tell me that they are not going to take much more.  More thinking...

Yes, I mentioned that earlier. The one he posted is for the head version not the combo. For some reason they decided not to put the bias adjust pots on the combo.

 

[DangerousR6]

This is about the best one I can find...

 

[OzziePete]

Look Doug, this amp is a hopeless case.

My suggestion is that you pack it up nice 'n snug in a big box and pack it off to Max... he might make some good use for it. :icon_smile:


Stick to your Blackstar from here on in. :laughing7:

(yes, I have been drinking.)

 

[DangerousR6]

Look Doug, this amp is a hopeless case.

My suggestion is that you pack it up nice 'n snug in a big box and pack it off to Max... he might make some good use for it. :icon_smile:


Stick to your Blackstar from here on in. :laughing7:

(yes, I have been drinking.)

I'm begining to feel you're right....The curse of the blue voodoo has reared it's ugly head...I've been doing some research and it seems these were prone to solder failure, maybe there's some solder joints that need reflowing..... :dontknow:

 

[Death by Uberschall]

I'm begining to feel you're right....The curse of the blue voodoo has reared it's ugly head...I've been doing some research and it seems these were prone to solder failure, maybe there's some solder joints that need reflowing..... :dontknow:

I agree, it's nothing a good old fashion bon fire couldn't fix up.

 

[mayfly]

Crap.  At this point it really has to be put on a bench.

If you really want I can make it go for you.  That is if you feel the urge to send it up to Canada.

I'll accept payment in neck plates....

 

[DangerousR6]

I'm begining to feel you're right....The curse of the blue voodoo has reared it's ugly head...I've been doing some research and it seems these were prone to solder failure, maybe there's some solder joints that need reflowing..... :dontknow:

I agree, it's nothing a good old fashion bon fire couldn't fix up.

That would definatly help reflow the solder joints....

 

[DangerousR6]

Crap.  At this point it really has to be put on a bench.

If you really want I can make it go for you.  That is if you feel the urge to send it up to Canada.

I'll accept payment in neck plates....

You're probably right, it needs to be in the hands of someone who knows what to do.....I'd take you up on you're offer....But shipping to Canada would be more than it's worth....

 

[mayfly]

Here's another thought.  Get an amp kit that uses the same output tubes.  Maybe a Blackface showman or something.  Yank out the PCBs and throw in the kit.  Then play guitar.

Even if you get someone else to work on it, that way might be cheaper than fixing it.

 

[DangerousR6]

Here's another thought.  Get an amp kit that uses the same output tubes.  Maybe a Blackface showman or something.  Yank out the PCBs and throw in the kit.  Then play guitar.

Even if you get someone else to work on it, that way might be cheaper than fixing it.

You could be on to something there....Can you point me in the direction of such an animal?

 

[OzziePete]

Look Doug, this amp is a hopeless case.

My suggestion is that you pack it up nice 'n snug in a big box and pack it off to Max... he might make some good use for it. :icon_smile:


Stick to your Blackstar from here on in. :laughing7:

(yes, I have been drinking.)

I'm begining to feel you're right....The curse of the blue voodoo has reared it's ugly head...I've been doing some research and it seems these were prone to solder failure, maybe there's some solder joints that need reflowing..... :dontknow:

Sorry that my playfulness after a few drinks last night is probably ringing true...  :sad1:

Surely there'd be an amp tech somewhere in your parts? If you are in a regional area you might have to go shopping in a major city (like Houston or San Antonio?). A lot of stuff I need having to be done has to come from Sydney based businesses as that is my local major city to me in Australia. There's nothing worthwhile in my own regional area here save for the odd reliable tradesman - but they are few and far between.

 

[DangerousR6]

Look Doug, this amp is a hopeless case.

My suggestion is that you pack it up nice 'n snug in a big box and pack it off to Max... he might make some good use for it. :icon_smile:


Stick to your Blackstar from here on in. :laughing7:

(yes, I have been drinking.)

I'm begining to feel you're right....The curse of the blue voodoo has reared it's ugly head...I've been doing some research and it seems these were prone to solder failure, maybe there's some solder joints that need reflowing..... :dontknow:

Sorry that my playfulness after a few drinks last night is probably ringing true...  :sad1:

Surely there'd be an amp tech somewhere in your parts? If you are in a regional area you might have to go shopping in a major city (like Houston or San Antonio?). A lot of stuff I need having to be done has to come from Sydney based businesses as that is my local major city to me in Australia. There's nothing worthwhile in my own regional area here save for the odd reliable tradesman - but they are few and far between.

Hahahaha, Houston and San Antonio are hundreds of moles away from me, I'm about 40 miles from Big D(Dallas).....There are lots of repair shops in the area, I was trying to avoid spending  a wad of moola to fix it.... :help:

 

[Patrick from Davis]

This is an odd idea, but it the tubes are not being killed by the amp, try a set of THD Yellow Jackets in there.  I'd check the EL34's in another amp and look at them with the bias doohickey.  The layout that Max posted and the pictures don't line up at all.  I wouldn't think that the circuit design would be that different, but the more things go on, the less confident I am about that.
Patrick

 

[Mor Paul]

I just reposted the schematic Cagey posted, I think.

 

[DangerousR6]

This is an odd idea, but it the tubes are not being killed by the amp, try a set of THD Yellow Jackets in there.  I'd check the EL34's in another amp and look at them with the bias doohickey.  The layout that Max posted and the pictures don't line up at all.  I wouldn't think that the circuit design would be that different, but the more things go on, the less confident I am about that.
Patrick

Exactly, the head schem. is totally different than the combo. And I only have one other amp to check the EL34's in, but it's a brand new amp, and I ain't jacking around with it. And I don't think the tubes are being harmed 'cause the #3 fuse is blowing almost instantly when I switch it off standby...

 

[Cagey]

Do you have a multimeter? If so, be sure everything is powered down and discharged, then pull the power tubes and check the resistance between pin (3) on the tube socket to ground. It should be open, or very nearly so. If not, then it's likely your output transformer has gone to ground internally. That'll take out the HV fuse instantly coming off standby. It's also not an unusual thing to have fail in a tube amp.

 

[DangerousR6]

Do you have a multimeter? If so, be sure everything is powered down and discharged, then pull the power tubes and check the resistance between pin (3) on the tube socket to ground. It should be open, or very nearly so. If not, then it's likely your output transformer has gone to ground internally. That'll take out the HV fuse instantly coming off standby. It's also not an unusual thing to have fail in a tube amp.

Yip I have a meter, I'll have to give that a shot... :icon_thumright:

 

[mayfly]

Here's another thought.  Get an amp kit that uses the same output tubes.  Maybe a Blackface showman or something.  Yank out the PCBs and throw in the kit.  Then play guitar.

Even if you get someone else to work on it, that way might be cheaper than fixing it.

You could be on to something there....Can you point me in the direction of such an animal?

had a quick look.  The best is likely ceritone.  Not sure if Hoffman is still doing it, but they were providing board kits back in the day.

 

[Patrick from Davis]

Hoffman doesn't build boards anymore, but there are several places that make Hoffman boards.  EL34 world will have the list.  Sorry that the amp is being such a booger, hope something comes up that solves it.
Patrick