Redplating 6L6 - shall I let it burn in?

Boromedic

So I bought a new matched set of 6L6's for a cathode biased amp, the old JJs work but one of them is really microphonic. Other than that they're great.

Stuck in the new set, amp started to smell hotter than previous or so it seemed? Not burning as such, just hotter. Then there was an increase in noise floor so I had a look. One of the valves was redplating so it seemed.

Tried them again after switching off, this time there was a few crackles and I got the pics below, kind of a time lapse from standby to on, to a minute or so after. I removed them and put the JJs back and aside from the rattle, they're working fine with no redplating.

I spoke with the vendor and they're asking me to try the valves again and switch them around to see if the problem stays with the valve. They even suggested it's just the valve settling and burning off contaminants. They have offered a replacement once I've tried that stuff so they are being decent.

What do the techs here think? Can I damage the amp running redplating valves to see if they settle? The fact the old JJs are fine is throwing me off!?

Thanks all,

Al

ICBM

No, that’s faulty.

(Assuming it stays with that valve when you swap them round.)

Don’t run it any longer than just to check that.

Boromedic

I never swapped em John, too scared to run it!! Should I test it on the other socket?

The JJs run without issue.

fretfinder

Boromedic said: the old JJs work but one of them is really microphonic.

The fact the old JJs are fine is throwing me off!?

But they’re not fine, one of them is ‘really microphonic’!     Dunno about you but I can’t live with a really microphonic power valve. 

Good luck sorting your issue. I’d be tempted to send them back personally and get a replacement pair.

Boromedic

fretfinder said:

Boromedic said: the old JJs work but one of them is really microphonic.

The fact the old JJs are fine is throwing me off!?

But they’re not fine, one of them is ‘really microphonic’!     Dunno about you but I can’t live with a really microphonic power valve. 

Good luck sorting your issue. I’d be tempted to send them back personally and get a replacement pair.

Hahaha, no neither can I hence the replacement pair , but at least they're not glowing in fire!

Currently chatting with the vendor as they're seemingly asking me to pay return postage.

ICBM

Boromedic said:

I never swapped em John, too scared to run it!! Should I test it on the other socket?

The JJs run without issue.

Yes, swap them in the sockets and run it just for long enough for the problem to show - I’m almost certain it’s the valve, but you need to eliminate a possible amp fault, even if the JJs appear to work.

Boromedic said:

Currently chatting with the vendor as they're seemingly asking me to pay return postage.

Hotrox or Watford?

If so, expect the faulty valve to magically test fine when returned…

Boromedic

ICBM said:

Boromedic said:

I never swapped em John, too scared to run it!! Should I test it on the other socket?

The JJs run without issue.

Yes, swap them in the sockets and run it just for long enough for the problem to show - I’m almost certain it’s the valve, but you need to eliminate a possible amp fault, even if the JJs appear to work.

Boromedic said:

Currently chatting with the vendor as they're seemingly asking me to pay return postage.

Hotrox or Watford?

If so, expect the faulty valve to magically test fine when returned…

I'll give at a whirl!

Luckily neither of those vendors, Watford I wouldn't patronise if he was the last valve dealer on earth, and Hotrox I haven't used for a while

Dealer has agreed to return shipping and replacement luckily, so I might even avoid switching them around now, even though I'm sure it's the valve.

hywelg

Be sure. Swap em just to test. 

fretfinder

hywelg said:

Be sure. Swap em just to test. 

Why bother, if the dealer has agreed to return shipping and a replacement? You take the risk of accidentally snapping the guide pin off or causing some other damage and there goes your free replacements!

p90fool

fretfinder said:

hywelg said:

Be sure. Swap em just to test. 

Why bother, if the dealer has agreed to return shipping and a replacement? You take the risk of accidentally snapping the guide pin off or causing some other damage and there goes your free replacements!

I'd definitely swap them, if the problem stays with the socket rather than the valve then the amp has a fault that perhaps the JJs weren't highlighting and were robust enough to mask. 

I know it's unlikely, but still. 

ICBM

fretfinder said:

Why bother, if the dealer has agreed to return shipping and a replacement? You take the risk of accidentally snapping the guide pin off or causing some other damage and there goes your free replacements!

Because if you don’t and the fault is with the amp, there’s a risk of damaging one of the new valves too. The JJs being fine is fairly strong evidence that it’s not the amp, but proving conclusively that it *is* the valve is better.

Boromedic

Thanks all, in the end I switched them and the problem followed the valve, the amp is going to a tech soon though because it's still noisy. I will of course update the thread with the outcome