Is this KT88 gone?

[jcalvarez]

I may have done something stupid, I bought a Fatman iTube 182 on Gumtree. The owner reported "motorboating", and that sounded OK at low volume. The amp was recapped, I can see that all capacitors are new. I paid £80, hoping that at least the chassis and power transformer is worth that, the rest is a bonus.

I have not plugged the thing yet, just looking at the KT88 tubes, one seems to be on the way out, do you guys agree? The other tube seems to be OK.

Thank you!

Jose

 

[kodabmx]

Does it work?

I've seen tubes that look new and test poor, and I've had tubes that look like that one and work fine.

 

[jcalvarez]

Does it work?

I've seen tubes that look new and test poor, and I've had tubes that look like that one and work fine.

That's my next step, plug the thing on. The amp was reported as "working" at low volume, and "motorboating" at higher one.

 

[RJM1]

The getter is gone, but not white. It could be that there was insuficient getter material to begin with and when they flashed the getter it all disapeared.
The tube may work but also may be gassy, best to check it on a tube tester.

 

[jcalvarez]

The getter is gone, but not white. It could be that there was insuficient getter material to begin with and when they flashed the getter it all disapeared.
The tube may work but also may be gassy, best to check it on a tube tester.

Unfortunately I do not have one of those. Maybe it's the right time to buy or build one

 

[PRR]

Getters can be mostly brown and still be good for decades.

White is bad.

 

[jcalvarez]

Getters can be mostly brown and still be good for decades.

White is bad.

I think so, white is the getter reacting with oxygen. Bad indeed.

 

[RJM1]

From the pictures that I see, where te getter was deposited it is now clear *** you can see the tube internals through wher it was.
Manufacture iinsufficiency.

 

[pcan]

The tube may still work. I've worse looking ones that still measure good. The motorboating may be a consequence of the recapping. It may happen if the factory capacitors have been replaced with new ones with far higher capacitance value, or if the ground connection has been moved, maybe because they are bigger in size and don't fit on the original mounting anymore.

 

[jcalvarez]

The tube may still work. I've worse looking ones that still measure good. The motorboating may be a consequence of the recapping. It may happen if the factory capacitors have been replaced with new ones with far higher capacitance value, or if the ground connection has been moved, maybe because they are bigger in size and don't fit on the original mounting anymore.

They reason the original owner did the re-cap was the motorboating. It did not fix it. I had the impression the guy spent more money than he wanted to trying to fix it, then decided that life is too short
I need to get some me time to plug it on and see what's going on.

 

[OldHector]

Probably the first thing to do is try and get hold of the original schematic and compare the circuit. There is always the temptation when fixing an issue to jump straight to improvements, and maybe the previous owner excaberated an issue by moving away from the original design.

 

[jcalvarez]

Probably the first thing to do is try and get hold of the original schematic and compare the circuit. There is always the temptation when fixing an issue to jump straight to improvements, and maybe the previous owner excaberated an issue by moving away from the original design.

I found on the net an excellent report on repairing the same amplifier, the guy this a great job, all well documented, is going to help a lot.