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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Re: Matching power tubes with a temp probe posted by Jim McShane on March 12, 2006 at 07:04:48:
I have a lot of 36 NOS 7C5 tubes all of same manufacture. This lot was tested on a Hickok 575A tester for plate current at 300 VDC & transconductance.Interesting that lower current & lower transconductance tubes do operate much cooler in circuit. The spread of tube operating temperature is from 40 to 60 degree C as measured at top of glass with regard to low to high GM & current tubes. I noticed temperature matched within 3-4 degree C are also current & transconductance matched within 5%. I also noticed a higher plate current tube as measured on the Hickok 575A does not necessarily has highest transconductance.
Variances due to tube placement on the chassis seem to be within 1 degree C when I swap tubes around. The tubes are spaced about one tube diameter from one another.
Accuracy is not exactly scientific, but these measurements are interesting.
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Follow Ups
- Re: Matching power tubes with a temp probe - Jimmy 07:44:35 03/12/06 (8)
- I might add..... - Jimmy 07:52:37 03/12/06 (7)
- More to add..... - Jimmy 08:31:40 03/12/06 (6)
- Another odd measurement........ - Jimmy 10:32:17 03/12/06 (1)
- Finally, what are we hearing....... - Jimmy 10:46:13 03/12/06 (0)
- Once had a friend match the PL519 tubes... - Allen Wright 09:48:50 03/12/06 (3)
- Hey, that was pretty funny .... but it does make a point! - Naz 20:48:59 03/12/06 (0)
- so much as keeping there! - Allen Wright 01:34:42 03/13/06 (0)
- I get it Don... - Jimmy 10:15:22 03/12/06 (1)
- Opps- Allen - Jimmy 10:33:10 03/12/06 (0)
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