Voltage check problem

[JamieMcC]

Hi would you be kind enough to take a look over my voltage checks as I have a couple of voltage errors on the octal sockets and one LED went out during testing.

Resistance checks were all very close both.

Voltage checks going well but during testing LED at A8 it went out

Voltage check for 1-21 all very close within 2 volts except

1 expecting 90 had 82
5 expecting 90 had 82

Octal socket

A1  81
A3 1.5
A6 145
A8 13

B1 145
B2 162
B3 145
B4 80
B5 170
B6 102

Something is not quiet right but I have not got the foggiest about where to start.

Cheers Jamie

[Paul Birkeland]

82 is within 10% of 90, so there's no problem there.

The 13V at A8 generally means an LED that isn't well soldered on the striped end, has been shorted to the adjacent high voltage pin, or has a floating grid (wire coming from the potentiometer).

Was there anything that precipitated the LED going dark?

Do both halves of the 12AU7 glow?

[JamieMcC]

Yes the led went dark as I was testing A8

[JamieMcC]

And yes both halves of the 12AU7 glow

[Paul Birkeland]

Yeah, you may have shorted A8 to an adjacent tube pin. 

E-mail replacementparts(at)bottlehead(dot)com and we can get you a new LED.

FWIW, if you have 75-90V at terminals 1 and 5, the LED's will glow and will be at the correct voltage, so there is no need to measure them. 

[JamieMcC]

OK will do and thanks for the help and speedy reply.

[JamieMcC]

Problem resolved, I found a local supplier for the HLMP-6000 which saved on shipping a spare to the UK. I am pleased to report after replacing the shorted led the Crack is up and running with absolutely no background noise.

Thanks

Jamie