Tube socket replacement

I had heard some funky noise coming from my amp kinda stayic sounding. As i looked it over for visable failures i started pulling power valves. This is what i found.

20220404_101049.jpg
The one pin had some etching on it. I was told this happens from wrong OHM setting for running a full stack.
 
I started to inpect the socket and was unhappy with what i saw. Theres a bit of discoloration on that pin.
20220404_101914.jpg
 
LRT said:
@Amp Mad Scientist
I could use a little bit of assistance on procedures here
Click to expand...
When a socket burns it's caused by an impedance mismatch.
You have to correct the speaker impedance and speaker cable, inspect the speakers wiring, and check the speaker jacks for defect contact with the cable...measure the speaker cab with an ohmmeter....
You need to test and replace the screen grid resistors because at least one could be toasted.
or else it will happen again.
The 4100 needs to be rebuilt because the PC mount electrolytic caps will fail from age.
The can caps will also bulge and fail.

The electrolytic caps will cause the bias to fail, and fry the output tubes from red plating...
You have to verify the plus minus 16 volt power supplies, I usually replace the 2 zener diodes and filter caps for those low voltage supplies.

You have to have really good PC soldering skills.
Or else the PC board could be damaged. It is quite fragile. Don't try to learn how to solder by working on the amp, it could be destroyed.
If you do not have the equipment and skills, get a professional.

Determine if the amp is built for EL34 or 5881 output tubes. This is critical for the bias set up.

So as you can see, there's quite a lot more to it than replacing a socket.
If you want you can PM me,or use my phone number and I can give your tech some directions.

But remember what I told you. If all that above stuff doesn't work right the amp will not keep working.
It must be verified and should be scope tested.
DO NOT operate the amp until all tests have been made. It could destroy the new tubes and worse.
DO NOT put the tubes in until all voltages and tests are passed.
Correct and verify everything FIRST, put the tubes in LAST.

Do not put the tubes in to "see what happens."
That's the Charvel Dan method.
That method is a very bad idea.

I offer to help you through all the tests. Do all the tests.
 
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syscokid said:
The burn mark seems to be centered around one of the socket's heater terminals. Hmmmmmmm... :unsure:
Click to expand...
It will arc between plate and filament happens all the time when speaker is mismatched.
It will arc pin 6 to pin 7....
all this happens when the speaker is wrong. Very common seen it happen 100 times.

If the speaker is correct, never happens.

This is a major problem because people ignore speaker impedance.
People ignore using a real speaker cable....
and it fries the tubes /sockets / transformers.

Now we tell people this all the time. They rarely pay attention.
15 minute speaker test will save $500 repair bill.
But do they listen? No.
Most people think that speaker impedance is a joke.....they never check anything.
Bad idea, and I warned everybody. Now Suffer.
 
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It's not my amp, but I do know a few things about it. @LRT will pop in here when he gets a chance.

Originally from the factory it's a 5881 amp. However, this one has successfully been converted to an EL34 amp by changing out all the necessary resistors to do so, all with the proper values. This happened 4 or 5 years back, and I do believe you assisted with that project too, AMS....back on the MF.

The other thing I know about this project is that indeed, this was caused by an impedance mismatch, when connecting to two 4x12 cabs, but leaving the amp set at 16ohms...before that single incident, it had been a strong running and great sounding amplifier, ever since the conversion to EL34s, way back when.

...and that's about all I know about it.

Aside from that, there are no other visible failures other than the discoloration on the one socket, caps don't look like they're bulging or anything, no fried resistors, etc, but that will all be thoroughly tested and looked at closer a bit later, I'm sure.
 
Amp Mad Scientist said:
It will arc between plate and filament happens all the time when speaker is mismatched.
It will arc pin 6 to pin 7....
all this happens when the speaker is wrong. Very common seen it happen 100 times.

If the speaker is correct, never happens.

This is a major problem because people ignore speaker impedance.
People ignore using a real speaker cable....
and it fries the tubes /sockets / transformers.

Now we tell people this all the time. They rarely pay attention.
15 minute speaker test will save $500 repair bill.
But do they listen? No.
Most people think that speaker impedance is a joke.....they never check anything.
Bad idea, and I warned everybody. Now Suffer.
Click to expand...
Lol we're usually pretty good about making sure of that....I can't attest to why it was overlooked this time....but you're right; it was. We always use proper speaker cables between amps and cabs too, no instrument cables.

The good thing is that the suffering has been at least minimal, as it's not LRT's only amp. So we've been able to jam the whole time this 4100 has been down, so at least we're not getting rusty.

The other plus here, is that I watched it happen, so not only has LRT learned a valuable lesson from this, but so have I.
....at least I think that's a plus, anyway :LOL:
 
Blink is correct about 4 or 5 years ago AMS helped me to properly convert 5881 to EL34
This consists of changing the grid resistors and screens to proper values. This is what the local teck of our areia didnt do it was jus put tubes in and bias.
Yes i failed to switch to 8ohms when adding the other cab , shame on me for not reading instructions.
 
Ams i will be doing the work and am ready to follow your instrutions.

First question is proper resistor to dischsrge capacitors?

Amp has set for several months and power switch is set to on and standby in operate but i fell thats not enough to make sure caps are discharged
 
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