Blowing fuses in a '68 Sentura I

[Mark]

Hi all..

Just picked up new tubes, etc, for my '68 Sentura I.
I haven't played this in years, and it blows fuses within approx 3 seconds after powering it up.
I've removed all the tubes (rectifier tube as well) to eliminated a shorted tube causing this..

Should I be looking next at the filter caps and the primary or output transformer ? If it is either a primary or output, where might I find a replacement ?

Thanks much !

[Joe]

: I haven't played this in years, and it blows fuses within approx 3 seconds after powering it up.
: I've removed all the tubes (rectifier tube as well) to eliminated a shorted tube causing this..

Pulling the rectifier tube and still blowing fuses eliminates most of the amp circuitry with the exception of the power transformer.  

Have you taken the amp out of it's case?  Depending on how you were storing it, there might be some critter well cooked across the transformer lines!!

[Ryan Phelps]

: Hi all..

: Just picked up new tubes, etc, for my '68 Sentura I.
: I haven't played this in years, and it blows fuses within approx 3 seconds after powering it up.
: I've removed all the tubes (rectifier tube as well) to eliminated a shorted tube causing this..

: Should I be looking next at the filter caps and the primary or output transformer ? If it is either a primary or output, where might I find a replacement ?

: Thanks much !

Mark;
You're on the right track. If the fuse blows with all of the tubes removed (including the rectifier tube)then your power transformer is most likely blown. With the rectifier tube removed the filter caps and output transformer are effectively removed from the circuit, so they aren't the problem. Your options are either rewinding the blown transformer, cannibalizing one from another amp or buying a generic replacement transformer from Mojo, New Sensor, Antique Electronic Supply, Angela Instruments or any number of boutique amp builders such as Hoffman. Your local amp tech can locate a suitable replacement and install it. It could easily cost $100 - $125 installed.
Good Luck!
Ryan

[Mark]

Thanks Ryan..

I had a nasty feeling that's what I was looking at. This week, I'm going to unsolder the tranny and do a reading on it. I knew it was going to be some $$, but the main thin I'm interested in is retaining it's stock value. Will look around for someone that can correctly rewind it, paying attention to the interleaving..

So glad it's not my '68 plexi 50 that went south !!!

: : Hi all..

: : Just picked up new tubes, etc, for my '68 Sentura I.
: : I haven't played this in years, and it blows fuses within approx 3 seconds after powering it up.
: : I've removed all the tubes (rectifier tube as well) to eliminated a shorted tube causing this..

: : Should I be looking next at the filter caps and the primary or output transformer ? If it is either a primary or output, where might I find a replacement ?

: : Thanks much !

: Mark;
: You're on the right track. If the fuse blows with all of the tubes removed (including the rectifier tube)then your power transformer is most likely blown. With the rectifier tube removed the filter caps and output transformer are effectively removed from the circuit, so they aren't the problem. Your options are either rewinding the blown transformer, cannibalizing one from another amp or buying a generic replacement transformer from Mojo, New Sensor, Antique Electronic Supply, Angela Instruments or any number of boutique amp builders such as Hoffman. Your local amp tech can locate a suitable replacement and install it. It could easily cost $100 - $125 installed.
: Good Luck!
: Ryan