Redplating el84
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- StrummersOfThunder
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Redplating el84
Question for the amp heads
Noticed last night that the lb30 has a red plating el84
When i was inspecting it earlier I did see a charred looking ??grid stop (I think) resistor tho it tested normal so I left it in (100r I think)
Assuming - bad tube
- shorting tube
- bad cap (cathode bias)
Once I can find my tube stash Ill replace that el84 and the resistor.
Anything else I should do ?
Noticed last night that the lb30 has a red plating el84
When i was inspecting it earlier I did see a charred looking ??grid stop (I think) resistor tho it tested normal so I left it in (100r I think)
Assuming - bad tube
- shorting tube
- bad cap (cathode bias)
Once I can find my tube stash Ill replace that el84 and the resistor.
Anything else I should do ?
Last edited by StrummersOfThunder on Mon Jan 29, 2024 7:45 am, edited 1 time in total.
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Re: Redplating el84
That looks like a resistor to pin 3, which would make it a cathode bias resistor. Looks like it was working hard to do its job. You don’t have to replace it and since the amp seems to have individual biasing you can just pop in another valve. Just to be safe, I’d try one of the other old valves in there and then put your new valve in a different spot. Have the amp on for a bit and then check for redplating again. Ideally you’d want to measure the voltage across all of those 100r bias resistors, just to make sure there’s nothing else going on except a worn out valve. The voltages should be roughly equal.
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Re: Redplating el84
With a burn mark like that I'd replace the resistor at a matter of principle. It'll take 30 seconds. I'd use a vishay 5 watt as well for peace of mind.
Good shout on swapping tubes around to see if the same tube goes wonky in another socket. Hopefully it's a just a bad tube and not something more serious.
Good shout on swapping tubes around to see if the same tube goes wonky in another socket. Hopefully it's a just a bad tube and not something more serious.
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Re: Redplating el84
A very good example of me not knowing what I’m talking aboutRectifiedAmps wrote: ↑Mon Jan 29, 2024 6:31 am That looks like a resistor to pin 3, which would make it a cathode bias resistor. Looks like it was working hard to do its job. You don’t have to replace it and since the amp seems to have individual biasing you can just pop in another valve. Just to be safe, I’d try one of the other old valves in there and then put your new valve in a different spot. Have the amp on for a bit and then check for redplating again. Ideally you’d want to measure the voltage across all of those 100r bias resistors, just to make sure there’s nothing else going on except a worn out valve. The voltages should be roughly equal.
Thanks for the advice and info
- MikeC
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Re: Redplating el84
Strummers, do let us know if it is the valve.RectifiedAmps wrote: ↑Mon Jan 29, 2024 6:31 am That looks like a resistor to pin 3, which would make it a cathode bias resistor. Looks like it was working hard to do its job. You don’t have to replace it and since the amp seems to have individual biasing you can just pop in another valve. Just to be safe, I’d try one of the other old valves in there and then put your new valve in a different spot. Have the amp on for a bit and then check for redplating again. Ideally you’d want to measure the voltage across all of those 100r bias resistors, just to make sure there’s nothing else going on except a worn out valve. The voltages should be roughly equal.
Whakanuia o mea kei a koe
- jeremyb
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Re: Redplating el84
Nothing to add but some humour!
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Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.
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Re: Redplating el84
Is this how vapes work?!?!??!
Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.