I'm recapping a Heathkit TT-1 and I have no schematic, so I would like to know how the switching is implemented with dual triode tubes under test, such as the 12AX7.
The problem I am seeing is the readings with the K,P,G switches in the #2 position (down) are 1/3 the readings of the #1 position. I have tested numerous 12AX7s to minimize the possibility of a bad #2 triode, as well as some new tubes right out of the box. The problem is consistently low readings on #2. 1900 for #1 and 600 for #2, typically.
Normally, I would assume these switches just move the connections from triode 1 to triode 2, however, I am not so sure because of the abnormally low readings for position 2.
Are there any active components in line with #2 K,P,G switches that are not shared with #1 positions? Ie., separate resistors, in which one may be out of tolerance or open? Does anyone have a schematic?
Thanks!
The problem I am seeing is the readings with the K,P,G switches in the #2 position (down) are 1/3 the readings of the #1 position. I have tested numerous 12AX7s to minimize the possibility of a bad #2 triode, as well as some new tubes right out of the box. The problem is consistently low readings on #2. 1900 for #1 and 600 for #2, typically.
Normally, I would assume these switches just move the connections from triode 1 to triode 2, however, I am not so sure because of the abnormally low readings for position 2.
Are there any active components in line with #2 K,P,G switches that are not shared with #1 positions? Ie., separate resistors, in which one may be out of tolerance or open? Does anyone have a schematic?
Thanks!
> Heathkit TT-1 and I have no schematic
https://ia802600.us.archive.org/33/...tic/Heathkit TT-1 Tube Tester (schematic).pdf ?
https://ia802600.us.archive.org/33/...tic/Heathkit TT-1 Tube Tester (schematic).pdf ?
Fantastic! Just what I was looking for.
From the schematic, it sure looks like pure switching between triode section A and B, and no components exclusive to either A or B, so that deepens the mystery of why section B always tests 70% lower than section A. Owner claims it worked fine for the first few days after purchase. But I keep wondering if something was miswired in this unit...
...or... one of the 100uuF caps connecting from the 9 pin sockets through 100 ohms to ground is shorted.. Now I have a good lead. Thanks for providing the schematic link!
From the schematic, it sure looks like pure switching between triode section A and B, and no components exclusive to either A or B, so that deepens the mystery of why section B always tests 70% lower than section A. Owner claims it worked fine for the first few days after purchase. But I keep wondering if something was miswired in this unit...
...or... one of the 100uuF caps connecting from the 9 pin sockets through 100 ohms to ground is shorted.. Now I have a good lead. Thanks for providing the schematic link!
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I have a TT-1 with similar issues and just wondering if you were able to identify and fix the problem.
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