Gut shots - Uberschall ultra EL34

[OldGtrGuy]

Had some recent amp failure. Hoping its just the tubes but I wanted to look inside to see if I could spot any clear as day damage. Figured some of you may like to see the inside of the amp.

 

[311boogieman]

Looks complicated


Here is another gut shot:

ultra gut shot

 

[griff10672]

Cool stuff

 

[OldGtrGuy]

Looks complicated


Here is another gut shot:

ultra gut shot

I could be color blind but his PCB looks green and mine looks blue.

 

[311boogieman]

I could be color blind but his PCB looks green and mine looks blue.

IIRC - Reinhold used different colored boards for different tube versions but don't quote me on that.

 

[OldGtrGuy]

IIRC - Reinhold used different colored boards for different tube versions but don't quote me on that.

I think you're right. IIRC Leib got the KT88 version.

 

[70 Mach 1]

Looks complicated


Here is another gut shot:

ultra gut shot

that was my exact first thought. my goodness all the crap in there lol

 

[311boogieman]

^ it is quite versatile form what I've heard and honestly a cleaner layout than say a Dual Rectifier.


It looks like there are 2 - biasing variable resistors we can mess with. One for each pair. It almost looks like he cut out a section of PCB on that upper board to allow for a screwdriver to access the pot. There better not be two more under that board

 

[harddriver]

Those white ceramic 5W 1K wirewound power resistors numbered R890, R891, R892, R893 on the circuit board are your screen grid resistors for your power tubes, all 4 look fine with no discoloration or evidence that any of them burned. You should test them with a digital multimeter if possible but if you can't I don't see any obvious evidence of any failures there.

Unless you can test the power tubes that are in the amp, I would not try to run the amp until you have a new set of power tubes. From what you described in the Tech section it sounds like a power tube/tubes shorted or partial shorted out and probably took out the HT fuse. I hope you get things sorted out.

 

[OldGtrGuy]

^ it is quite versatile form what I've heard and honestly a cleaner layout than say a Dual Rectifier.


It looks like there are 2 - biasing variable resistors we can mess with. One for each pair. It almost looks like he cut out a section of PCB on that upper board to allow for a screwdriver to access the pot. There better not be two more under that board

Nope I believe they have a pin from there to the top, allowing bias while inside the headshell, if I am not mistaken.

 

[OldGtrGuy]

Those white ceramic 5W 1K wirewound power resistors numbered R890, R891, R892, R893 on the circuit board are your screen grid resistors for your power tubes, all 4 look fine with no discoloration or evidence that any of them burned. You should test them with a digital multimeter if possible but if you can't I don't see any obvious evidence of any failures there.

Unless you can test the power tubes that are in the amp, I would not try to run the amp until you have a new set of power tubes. From what you described in the Tech section it sounds like a power tube/tubes shorted or partial shorted out and probably took out the HT fuse. I hope you get things sorted out.

Thanks, thats kind of the info im looking for.

I do have a meter...but im not trying to die. Honesty no idea what im doing there.

But yes, new tubes and new fuses in route.

 

[OldGtrGuy]

Those white ceramic 5W 1K wirewound power resistors numbered R890, R891, R892, R893 on the circuit board are your screen grid resistors for your power tubes, all 4 look fine with no discoloration or evidence that any of them burned. You should test them with a digital multimeter if possible but if you can't I don't see any obvious evidence of any failures there.

Unless you can test the power tubes that are in the amp, I would not try to run the amp until you have a new set of power tubes. From what you described in the Tech section it sounds like a power tube/tubes shorted or partial shorted out and probably took out the HT fuse. I hope you get things sorted out.

They look in tact.

 

[harddriver]

They look in tact.

Yep those 4. If they had failed they can look tan or the actual solder joints can melt at the solder terminal on the circuit board and I don't see any evidence of burning or failure visually. Just from what you have described I think a new quad of power tubes and a new HT fuse probably will fix your situation. I've have had JJ's 6ca7's fail just like that and they were brand new.

Really Really inspect your power tubes looking for any possible arching on the cathode or anode plates inside and either whiteish. or greyish coating on the inside of the glass envelope.

Make sure you bias your new tubes.

 

[311boogieman]

Nope I believe they have a pin from there to the top, allowing bias while inside the headshell, if I am not mistaken.

Even better

 

[Geo]

I would re flow the solder on all the tube sockets since they are so accessible.

 

[harddriver]

I would re flow the solder on all the tube sockets since they are so accessible.

I don't he has that capability Geo, and I think the amp is relatively new so it would probably go back to Bogner anyway and thank God Bogner stands behind it's amps and works on them for their customers.

 

[Geo]

I don't he has that capability Geo, and I think the amp is relatively new so it would probably go back to Bogner anyway.

May I suggest then that he takes a good close up look at them.

 

[OldGtrGuy]

I don't he has that capability Geo, and I think the amp is relatively new so it would probably go back to Bogner anyway.

Yeah any major repairs would be me talking to a tech here or mailing to Bogner.

Ive soldered my own pickups, like an amateur. There's no way im soldering a $3k amp. Just not in my skill set

 

[70 Mach 1]

I bet most of those cards can be swapped out like the old 90s RAM cards
problem is troubleshooting which one is bad

 

[harddriver]

Yeah any major repairs would be me talking to a tech here or mailing to Bogner.

Ive soldered my own pickups, like an amateur. There's no way im soldering a $3k amp. Just not in my skill set

Since the amp is relatively new that's fully understandable. I don't like working on PCB amps myself.