|
General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
|
Thread Tools |
11th Oct 2005, 3:12 pm | #1 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
|
KT66 excessive current
A friend has just had to replace the KT66 valves in his quad amp.
His quandry is- and I dont know the answer- why do dieing power valves take excessive current. theroretically as the cathodes go low emission the anode current should decrease ? |
11th Oct 2005, 6:06 pm | #2 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
|
Re: Interesting question- answers on postcard please
hello Steve,
Usual cause of power valves/rectifiers/television line timebase amplifiers drawing heavy current is a tiny quantity of gas within the envelope. Caution is needed due to the fact that this is often caused by incorrect biasing or faulty [leaking] coupling capacitors. The gas is often liberated from the anode that can glow red under a fault condition. I would suggest your friend checks these points to avoid rapid demise of his new KT66's. Regards. JOHN. |
11th Oct 2005, 8:14 pm | #3 |
Administrator
Join Date: Dec 2002
Location: Cardiff
Posts: 9,060
|
Re: KT66 excessive current
I have changed the thread title to make it meaningful. Please use meaningful titles in future or your messages will be deleted.
|
11th Oct 2005, 8:52 pm | #4 | |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,549
|
Re: KT66 excessive current
Quote:
Rich
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... Last edited by Sideband; 11th Oct 2005 at 9:05 pm. |
|
12th Oct 2005, 8:37 am | #5 | |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
|
Re: KT66 excessive current
Quote:
|
|
12th Oct 2005, 9:47 am | #6 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
|
Re: KT66 excessive current
I must admit I was a bit surprised by Pauls response, I wanted to ask the question generically of power valves and not just the KT66.
|
12th Oct 2005, 10:59 pm | #7 |
Administrator
Join Date: Dec 2002
Location: Cardiff
Posts: 9,060
|
Re: KT66 excessive current
The original title was "Interesting question- answers on postcard please" which doesn't give any indication as to what the thread is about.
My new title was clearly not great either, bit it was somewhere near! |
13th Oct 2005, 7:42 am | #8 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
|
Re: KT66 excessive current
fair do's
Steve |
13th Oct 2005, 8:53 am | #9 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
|
Re: KT66 excessive current
My toys [EF50's] have been put back in my pram......
Regards. JOHN. |
13th Oct 2005, 11:05 pm | #10 |
Administrator
Join Date: Dec 2002
Location: Cardiff
Posts: 9,060
|
Re: KT66 excessive current
Thanks both. I have exchanged email correspondence with John too.
I'll close this thread now, as it's unlikely to get back on topic. Please feel free to start a new thread on the original subject. |