startup testing.

2nd harmonics for the masses

startup testing.

Postby hembrook » Wed Jan 30, 2008 10:31 am

Not wanting to wreck my tubes, I set up just the rectifier tube and
fired the board up to see what I get. I am getting very funny readings.
Is this because I don't have the preamp and power tubes in?

I am using a NOS CBS 6AX5GT that tests fine, kinda at the bottom of the range, but still good on my Accurate 157.

My power and standby switches are on. I am using J6 pin 3 as the test
ground.

Here are some of my voltages.

Pin Should Is
V1
1...............0 .............0
2 ...........147.............330
3............1.8..............0
4 ..............0..............0
5 ...........147..............330
6.............1.8.............0
7............6.3 +51.........3
8............6.3 +51.........3

V2
1..............0..............0
2..............6.3 + 51....not measured
3..............324 AC......~300 AC
4..............0..............0
5..............324 AC......~300 AC
6..............0 ..............0
7 ..............6.3 + 51.. not measured
8 ..............333 ........ 430

V3,4
1..............0..............0
2..............54..........+3.5
3..............308...........420
4..............0..............0
5..............0..............0
6..............0..............0
7..............48...........-3.5
8..............0..............0

J6
1..............324...........410
2..............0..............0
3..............0..............0
4..............324...........410

J7
1..............319..............410
2..............319..............410

Am I doing something wrong?

Power transformer doesn't get warm, all seems in order.

I obviously don't want to risk my tubes until I know more.

Thanks,
hembrook
 
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Joined: Wed Oct 31, 2007 3:36 pm

Postby Shannon Parks » Thu Jan 31, 2008 5:50 am

The 6SL7 and the power tubes are all self biasing, so you'll need the tubes in there for further voltage testing. But eyeballing your numbers, it looks A-OK.
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Shannon Parks
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