No Voltage at PT Secondaries.

[Ghetto_Soundwave]

I built this SS bridge rectifier/12ax7 pre-amp/12ay7 PI/EL84 push-pull amp about ten years ago. It's been a solid amp without issues until a few weeks ago. The preamp tube was getting microphonic so I slipped a couple o-rings around it in hopes it might help (it didn't). Within a few times operating the amp with the o-rings installed the amp died, which may or may not have been related. Troubleshooting lead to the PT (Triad VPS230-190) with no voltage readings on the secondaries. This amp employees a second dedicated 12v transformer for the heaters. Also, it has a main fuse and a fuse between the PT secondaries and PSU filter section, but neither are blown.
I purchased another PT ($30) from Mouser, however my concern is was it simply a PT failure on it's own or possibly the SS bridge rectifier, tube(s) PSU cap or other issue that caused a current spike to overheat the power transformer?  Looking for troubleshooting help please before I install the new PT.  I have a new rectifier on hand as well.

[sluckey]

First off, how did you measure the voltage on the secondary? One probe connected to chassis is not a valid check in this case. You must measure from one HT lead to the other HT lead, IOW, measure across the secondary winding. And was your meter set to AC Volts?

my concern is was it simply a PT failure on it's own or possibly the SS bridge rectifier, tube(s) PSU cap or other issue that caused a current spike to overheat the power transformer?  Looking for troubleshooting help please before I install the new PT.

Any of the things you mentioned could have caused the PT to fail, including the PT itself. Before replacing the PT I would disconnect all wires from the bridge and check the diodes in the bridge. Then check resistance from each filter cap to ground. Low or zero resistance is not good. If these checks are OK then you should be able to replace the PT. Then pull the output tubes and check for B+ (using a lamp limiter is a good idea).

[Latole]

Sluckey ; And was your meter set to AC Volts?

 

[Ghetto_Soundwave]

First off, how did you measure the voltage on the secondary? One probe connected to chassis is not a valid check in this case. You must measure from one HT lead to the other HT lead, IOW, measure across the secondary winding. And was your meter set to AC Volts?

I  measured V across both secondary wires and not separately to ground. Yes, set to AC volts.


"Any of the things you mentioned could have caused the PT to fail, including the PT itself. Before replacing the PT I would disconnect all wires from the bridge and check the diodes in the bridge. Then check resistance from each filter cap to ground. Low or zero resistance is not good. If these checks are OK then you should be able to replace the PT. Then pull the output tubes and check for B+ (using a lamp limiter is a good idea)."Will do. Thanks.

[Ghetto_Soundwave]

thanks