Fender Hot Rod Deluxe PT Issue

[gbono]

No voltage on secondary side of PT - checked power switch, fuse, line cord, etc. Line voltage present at input/primary of PT (CP1/2). Checked the input resistance of the PT - it's open. Bad PT - bummer. Any other comments - I rarely see open PT. Who sells PT for these models? Hammond?

[pdf64]

Many current Fender PTs have an internal thermal fuse, see the export PTs http://www.webphix.com/schematic%20h...rod_deluxe.pdf
If this is your own amp, it may be worth investigating whether this is the case and if so, whether it can be safely bypassed for test purposes. If so, run it through a light bulb limiter or similar and make an assessment.
If it's for a customer, professional liability concerns may encourage you to find a new OEM part - consider contacting Fender.
Pete

[gbono]

Many current Fender PTs have an internal thermal fuse, see the export PTs http://www.webphix.com/schematic%20h...rod_deluxe.pdf
If this is your own amp, it may be worth investigating whether this is the case and if so, whether it can be safely bypassed for test purposes. If so, run it through a light bulb limiter or similar and make an assessment.
If it's for a customer, professional liability concerns may encourage you to find a new OEM part - consider contacting Fender.
Pete

The PT will be replaced since it's an amp that will be for sale as soon as it is fixed. I'm looking for sources for a new PT.

[Jazz P Bass]

Transformer - Fender® Original, Power, Hot Rod Deluxe | Antique Electronic Supply

[Enzo]

These are not unreliable transformers, even if yours failed. Chances are good something else caused that failure anyway. But I agree, instead of screwing around looking for something else to fit, just get another Fender tranny. If you want to sell it, I think being stock will be an easier sell than "I stuck something else in it."

[gbono]

These are not unreliable transformers, even if yours failed. Chances are good something else caused that failure anyway. But I agree, instead of screwing around looking for something else to fit, just get another Fender tranny. If you want to sell it, I think being stock will be an easier sell than "I stuck something else in it."

The primary side of the PT has a NTC thermistor which should have reduced any inrush current (it is still in the circuit functioning and looks like it wasn't replaced). I don't have the history on the amp but there are no charred components (or even damaged). Just ordered a new PT from AES and will see what happens after its installed.

[Enzo]

Most bad parts do not look any different from good parts. An inrush limiter does exactly that, it soft starts the system. As the NTC warms up, its resistance goes down so it essentially disappears. It offers zero protection other than inrush. It is also not part of the transformer. The fuse inside the transformer is a thermal fuse, it opens when the temperature of the transformer goes too high. That doesn;t occur at inrush, that occurs when excess current flows through the transformer over a period of time.

[olddawg]

I know the purpose if thermal fuses, but I have seen many fail for seemingly no reason at all. They just seem to randomly open. I would never do it for a professional repair, but for my own use I have replaced thermal fuses with pigtail fuses and had equipment run fine for years in personal use.

[gbono]

Searching my memory blanks, I believe that this amp came from a very large rehearsal space in Oakland CA. Plenty of possibilities for thermal and electrical abuse there including the gear

Found this related thread here: http://music-electronics-forum.com/t25580/