Silverface Deluxe Reverb Issue

[jkey04]

I recently obtained a 1975 Deluxe Reverb and it sounds amazing! But...

The longer it is on the HOTTER the power tranny gets. So much so, that the chassis and faceplate get hot to the touch. I have played it for a couple hours at practice a few times and it seems to hold up but this heat problem cant be good.

I will note that upon inspection of the amp when i first brought it home it has new Sprague filters, several orange drop signal caps and carbon film resistors replacing orginal components, replacement PT and OT from AES (their DR drop-in replacement), artificial 2x100ohm center tap for heaters. The PA plates are 415vdc. It has possibly has the original 5U4 rectifier (its an old one). All the work was done professionally and is VERY tidy. I will post pics later in the week if that will help.

Before i replace the PT, I wanted to pick the forum's brian for suggestions of things to look for first. Would replacing the 5U4 possibly solve the problem or is it probably a short in the tranny? Thanks ahead of time - this forum is great!

[martin manning]

I suspect the 5VAC rectifier filament winding in your PT is rated at 2A, for a 5AR4. The 5U4 is probably there to lower the B+, but it draws 3A. A JJ 5Y3 might be a better solution. It only needs 2A and has the voltage drop you need. It's current capacity is just adequate, but it's also pretty inexpensive to try out.

Edit: I see a Fender replacement at AES that has a 3A 5VAC winding, so it may be ok there. Still, the 5U4's 3A draw from the PT and the 15W of heat produced by the filament are certainly contributing to the temperature rise.

[jjman]

What are the heater voltages running?

[Stevem]

You can still get NOS 5V4 rectos that will not break the bank!
They have a 2 amp heater and the heater is the soft start type that is indirectly heated,these will work great and work great for a much much longer time than a aftermarket made recto.
This would be my pick!
Also note that having each output tube pulling more than 22 ma in these amps is just wasting power supply current as any other output tube but a JJ brand sounds too washed out and flabby for me, in fact dependant on the speaker 18 ma each works great!

[jkey04]

Sorry for the delayed response back but I really appreciate the good input!

Interesting statement about the PT 5v winding 2A rating vs 3A rating. I'll check the number on the tranny later in the week and have a look on AES to see which it is as well. I was kinda thinking the problem was related to the 5U4 myself as well. I actually have some NOS 5V4's and 5Y3's laying around. I'll try them both out and report back.

Thanks again!

[Stevem]

Fender made some sort of change in 68 with these amps.
The blackface PT part number 125p23b rated at 325 volts and powering a 5ar4 recto was changed at some point in 68 when the PT was swapped out for a Fender musical instruments part number 025130 with a voltage output listed as being 330 with a 5U4 recto.
Both transformers are the same size and I would bet my bottom dollar that the 5 volt heater winding is still rated at 2 amps for the 5ar4 recto, seing as the CBS guys where all about saving penny's where they could !
This same Trans was used by them right thru the 70's.