Vibrolux Reverb ~ 5U4GB

[wui223]

Hi everyone. Servicing a Vibro Reverb at the moment, rectifier not light up at all. All other tubes are light up, but no sound coming from speakers.

Checked rectifier pin 2 & 8, gives 15VAC when tube rectifier not insert.

My guess is the heater winding for rectifier is faulty, 5U4GB called for 5V/3A as seen from datasheet.

My question is:
1) Should I conclude that the heater winding of PT is faulty and need replacement?

2) Could I add another transformer rated 5V/3A just for the rectifier, instead of replace the whole PT?

Thanks in advance for any input.

[tubeswell]

So you tried another rectifier tube?

[wui223]

hi. right now no spare tube to try.
is it abnormal to have 15VAC at the heater winding pins?
or should i remove the B+ wire before taking reading?

thanks

[MWJB]

Wait. You need to get a new 5U4 tube anyway, so when you have that, take your readings again.

Does your meter read AC RMS, or peak to peak?

You have no load on the rectifier winding anyway & susequently no load on the B+ winding either, so voltages are pretty meaningless right now.

[wui223]

For AC measurement, the handbook stated "mean value response". Does it mean RMS or P-P ?

[MWJB]

RMS. Either way, wait til you have the new rectifier, you can only really measure the secondary voltages when they have a load (tubes) on them. Out of interest what do you get at the 6L6 heaters (pins 2 & 7)?