Voltage problem [solved]

[mbbarton]

Hi
I liked the crack amp so much I got another for my daughter. But..
Voltage at B3 reads 0. B6 reads 170v. Power output tune does not warm or light up. We have checked all the wiring and joints. Re-soldered those around B3. Took the tubes out and put them in the other crack amp where they work fine. The LED attached to A3 lights up but when voltmeter attached to B3 it flickers!
All advice gratefully received.
thanks
Michael

 

[Grainger49]

If the 6080 doesn't light it is probably a problem with the heater wiring.  That is the wiring that comes from transformer lugs 4 & 5 and ends up on pins 7 & 8 on the 6080. 

There should be about 6.3V AC between those pairs of pins/terminals.  Rewet those 4 points.

 

[mbbarton]

All joints re-wetted. The voltages at 4 & 5 and 7& 8 are 6.2V. 9 pin socket and tube heat but the 8 pin tube does not heat. This 8 pin tube heats in the other amp. 8 pin tube from the other (working) crack amp doesn't heat in this socket. this doesn't explain the lack of voltage in B3. B6 shows 170V

 

[Paul Joppa]

Is the 8-pin socket rotated 180 degrees?

Just asking because a fair number of people have made that mistake. You can measure the DC resistance between tube pins 7 and 8 to determine if the tube itself has a functioning heater. If the heater is good and the socket is correct, then the socket isn't making contact - bad pins or bad socket or something.

 

[mbbarton]

The 8 pin socket is 90 degrees to the image because its locator pin only lines up in this configuration.
Locator notch lines up in one configuration only. See attached image. I attach the image from the manual for comparison. Of course we should have  checked the numbers. Probably better not to use this brand of sockets or warn builders.

All the wiring will have to be shifted 90 degrees!

 

[Paul Birkeland]

You need to rotate the socket 90 degrees.  The retainer clip will slip over the socket properly (see the images in the manual).

See page 13 in the manual, and the red arrow.

-PB

 

[mbbarton]

Fixed. the problem was the wiring of the socket which was wrong becuase the socket locator did not match the orientation in the illustration.