AMPEG B15 issue

[Colas LeGrippa]

Hola my friends, my V4B friend came back with an Ampeg B15 amplifier that keeps on blowing fuses even with all the secondaries disconnected. My tester measures 3 ohm accross the 2 black primary leads and I am wondering if this is low resistance enough to blow the fuses.
Other question: the trannies black covers are just snapped over the transformers or do I have to unscrew the nuts.by underneath to remove them ?
Thanks

[PRR]

The 3 ohms on a DC ohm meter will/should be much higher at 60Hz AC.

If you are sure "all the secondaries disconnected" and it still blows, it has an internal short.

[Colas LeGrippa]

Yeah,obviously.  The hv taps, heater taps and 5 v taps are disconnected.  I have measured the dc resistance of  the primary of a brand new tranny laying on a shelf in my shop
 My meter read 12 ohm. So the 3 ohm of the ampeg tranny is still confusing me 'cause it might indicate a short circuit...or not.
I ll hook up a temporary power t in there to perform the very last test b4 replacing it


Thanks for hint

[kagliostro]

https://www.ozvalveamps.org/repairs/trannytest.html



Ciao

Franco

[SoundmasterG]

The Ampeg B15N power transformers seem to fail more often than other makes. I've got a 63 and the power transformer had failed sometime in it's past. I also am repairing a 67 and the power transformer had failed so badly it left a lot of black tar inside the chassis. You can get a new one to specs from Fliptops.


https://www.fliptops.net/catalog/p-100561/power-transformer-pt108-for-ampeg-b15nb12n



Greg