tubes dont glow, fuse intact, voltages awry

zlobby · 2703

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Offline zlobby

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on: March 31, 2011, 01:13:11 PM
I figured out my resistance issue, but now when I go to turn the amp on, the tubes dont glow, but the fuse doesnt blow.  My voltage readings are REALLY off from what they should be.

Any help on where to even start troubleshooting would be greatly appreciated.


1   239
2   244
3   0
4   244
5   239
6   0
7   0
8   0
9   0
10   0
11   0
12   0
13   245
14   0
15   245
20   0
21   245

A1   239
A2   0
A3   0
A4   0
A5   0
A6   238
A7   0
A8   0
A9   0

B1   238
B2   243
B3   0
B4   238
B5   243
B6   0
B7   0
B8   0



Offline Grainger49

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Reply #1 on: March 31, 2011, 02:05:52 PM
I guess that the resistance readings were close to the expected values, right?

The B+ is at the plates of both tubes and the grid of the 6080 but it seems that the tubes are not heating.  

The voltages at the tube heater pins might be missing.  The first thing to do is get the heater voltage there.

First, you need to read AC volts, not DC volts, between tube pins B8 and B7 (these readings are not to ground like in the voltage checks).  Then read AC volts between tube pins A4 OR A5 and A9.  Be certain not to short out the two pins when reading on the 6080.

If you don't get a reading at either tube read the AC volts on the transformer terminals from transformer terminal 4 to transformer terminal 5.  Those are the top right two terminals as seen on the manual on page 3.  

All these readings should be about 6.3V AC.

If there is any problems with these readings re-wet all the solder joints associated with the black and red wires coming from these two transformer terminals through any terminal strips these wires might pass through and at the tube sockets.
« Last Edit: March 31, 2011, 03:14:32 PM by Grainger49 »



Offline zlobby

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Reply #2 on: March 31, 2011, 03:50:34 PM
Re-soldered all leads leading from terminal 4&5 and voila...
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi5.photobucket.com%2Falbums%2Fy155%2FLinas03%2Fc3.jpg&hash=220ffffa9cfac92ba9731e4216e56da832f69b69)

Final pics will be posted in the pictures forum.

Thank you for your help!



Offline Grainger49

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Reply #3 on: March 31, 2011, 11:37:05 PM
Cool!  I like the glow of tubes in the dark.

Nice picture!