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TUBE BIAS, socket to me!

BIAS: (I'm starting from zero understanding) 

I have never measured/adjusted bias in the 3 tube amps, 3 tube receivers, and 2 tube preamps I have acquired over 47 years. I just switched my current Cayin from 6550's to KT88's. Adjust bias? Adjusters inside, scary electrocution warnings. I could pay someone else to do it, i.e. Steve at VAS 1 hr away in NJ, soooo, 

What really counts? (personally I don't care about either heat or life, but would like to understand)

Heat?
Life?
Output stays Matched when adjusted?
Acoustic Performance?
_________?

Over the years, fronts off, bottoms off, I hose em down with contact cleaner/lubricant, compressed air, all controls and switchers, any adjusters, swish full spin back and forth. Kill any spiders, look for, replace the rare burnt resistor. 
Then leave any adjusters (whatever they are) in the middle position, button it back up.

Two tube testers, my big hickock always agrees with small portable one, test strength, shorts, matched strength old and newly purchased. Large collection of NOS, used. Often used test essentially same strength as new ones.

When they go, it's usually a short.
elliottbnewcombjr
elliottbnewcombjr OP
5,563 posts
 
Thanks Bill,

I've been asking this because I knew that, thanks for sending me the instructions.

Working inside, plugged in, serious warnings: You know I love to do it myself, but not this, at least not until I see it done by someone who lives to explain what not to touch!

Steve at VAS will do it while I wait/watch, so I'll schedule something when you and I can get together to go there.
jjss49's avatar
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jjss49
6,612 posts
 
https://forums.stevehoffman.tv/threads/tube-integrated-with-autobias-equivalent-to-cayin-a88t.784890...

if you haven't seen this elliott - some interesting background and discussions
twoleftears's avatar
twoleftears
5,318 posts
 
Strange.  No mention of adjustment here.
https://elusivedisc.com/content/pdfs/CAYIAA88T.pdf
jjss49's avatar
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jjss49
6,612 posts
 
that sino made a88 amp has been out there for years, sold under various brands subbrands (line mag, cayin, grant fidelity yaqin etc etc) and with different front panels and biasing features (or lack thereof) as the chinese manufacturer matured and tried to move up market and sell effectively into different overseas markets

elliott if yours doesn’t have meters or accessible biasing pots you are best off getting it in the hands of a tech who knows tube gear...
oldhvymec
5,101 posts
 
OK yours is older.. Still no biggie.. I was taught by an OLD guy in the 70s.
I looked at a newer one..

You can looked up the pin out on the valve.  Find the ground, find the plate, you could see the wire going to the bias pot.

There are a lot of the older ones with internal bias pots..

If you don't feel confident, best to watch someone do it. Pretty easy though..

Regards
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