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previous: DavidB Hey Ray, How ya bee... -- 1104339274	View Thread

Re: tube problem?

12/29/2004 1:35 PM
Ray Ivers	Re: tube problem? David, Can't complain - although right now I'm doing parts inventory so maybe I can. My Valve Arts KT66's read open-circuit cold, but I've read somewhere that 200K ohms with heaters up to full temperature was sort of the unofficial 'break point' between definitely-good and kinda-iffy. With 100R resistors routinely connected from the heater winding to ground 200K seems like a pretty high standard for the heater insulation to a grounded cathode, no? OTOH I would definitely prefer infinite H-K resistance to a first preamp stage's unbypassed cathode resistor... If you read 50R H-K obviously that's not good but I bet you won't see anything close to that. If the cathode ground connection didn't let go you shouldn't have gotten any arcing either, but it's always a good idea to check IMO. If you had a cathode-biased amp that might be a different story, and with a fused cathode w/blown fuse I would be amazed if you had no arcing or H-K burn-through. Ray

12/29/2004 1:35 PM

Ray Ivers

Re: tube problem?

David,

Can't complain - although right now I'm doing parts inventory so maybe I can.

My Valve Arts KT66's read open-circuit cold, but I've read somewhere that 200K ohms with heaters up to full temperature was sort of the unofficial 'break point' between definitely-good and kinda-iffy. With 100R resistors routinely connected from the heater winding to ground 200K seems like a pretty high standard for the heater insulation to a grounded cathode, no? OTOH I would definitely prefer infinite H-K resistance to a first preamp stage's unbypassed cathode resistor...

If you read 50R H-K obviously that's not good

but I bet you won't see anything close to that. If the cathode ground connection didn't let go you shouldn't have gotten any arcing either, but it's always a good idea to check IMO. If you had a cathode-biased amp that might be a different story, and with a fused cathode w/blown fuse I would be amazed if you had no arcing or H-K burn-through.

Ray

Replies:

DavidB Hey Ray, Yep, nuth... -- 12/29/2004 5:20 PM