Voltages on vintage tube amps

[VintageAmps]

Hi guys , new to the forum and had a question about voltages. I am working on my first amp , a 1965 Fender deluxe and noticing the differences between measured voltages and schematic voltages. I realize this is due to wall voltages today vs then so the question is : do you fret any over the higher plate voltages or just concentrate on setting your plate current and dissipation?

[mresistor]

Hi.  Is it a real '65 or a reissue '65?   Most of the vintage original DRs I have worked on are in the 440-460 range and this varies with how you set the bias.  Hotter bias results in lower plate voltage.  I haven't fretted much over it.

[VintageAmps]

This is the real deal, not an ri. I had been working on it while it was plugged into my dim bulb tester. When I plugged it into the wall and had adjusted the neg dc bias for around 9.5 W plate dissipation and saw 440 V on the plates of the output tubes I got a little nervous.

[mresistor]

I think the amp will be fine.. 

[VintageAmps]

Thanks for the input friend. I can't wait to get home from the day job and get back to work on this DR. I think shes about ready to slip back into the cabinet.

[HotBluePlates]

... a 1965 Fender deluxe ...

This is the real deal, not an ri. ... adjusted the neg dc bias for around 9.5 W plate dissipation and saw 440 V on the plates of the output tubes I got a little nervous.

I assume this amp has a 125P23C power transformer?

You didn't mention what your wall voltage or heater voltage was.  While you can't get an exact ratio of these a.c. voltages to the rectified high voltage.  However, you can get an idea of how high you might be.

I have a 1964 Deluxe Reverb with the 125P23B power transformer, and get 6.3vac on the heaters when 120v is at the wall outlet.  After comparison to another person's 1965 DR with the other transformer, we found the 125P23C transformer has slightly higher B+ voltage.

[VintageAmps]

Actually the PT was replaced in this unit I'm thinking maybe sometime around 1968. It shows a 025130 p/n with a manf/date code of 606-8-02. The wall voltage I'm dealing with is 122 V. The filament voltage is around 6.7 Vac. All the other transformers date 1965 and are p/n listed in the schematic. Of course the PT could have been replaced later and someone found this one to be closest to the original at the time. From what I could tell this would have been a direct replacement for the original , but you might know different.

[HotBluePlates]

Actually the PT was replaced in this unit I'm thinking maybe sometime around 1968. It shows a 025130 p/n with a manf/date code of 606-8-02. ... All the other transformers date 1965 and are p/n listed in the schematic. ...

"025130" is the correct part # for the Deluxe Reverb, starting in ~1966.  If there is no letter preceding it (as in "L025130") then it probably is a 1968 transformer.  I'm unsure of the significance, but I've only seen the letters L, J, and M preceding the part # on 70's and 80's Fender amps.

Here are measurements from that 125P23C (I was wrong, it was a 1966 DR), which delivered 431vdc with 19.65mA plate current at the 6V6s under conditions similar to yours.

So the amp you're checking out is right where it should be, all things considered.  My DR's 125P23B resulted in 394v on the 6V6 plates when drawing 24.9mA, and a wall voltage of 120vac.

[VintageAmps]

Thank you HotBluePlates, I am just getting started and felt fortunate to land this DR as a first of what I hope to be many more to come. Really glad to have joined the forum and look forward to hopefully being able to contribute and learn as I go.