5e5 Pro, 1955

[Greeny]

Can anyone tell me something about the power this amp should deliver?
It's an original 1955 5E5, with a N.O.S. set of TungSol 5881, original Outputransformer and recapped.
I measure 19-20WATTS on my scope, just before clipping.
I always thougth the PRO was about 26Watts, or should this only work for the fixed-biased 5E5-A?

Thanks

[Bruce / Mission Amps]

...original 1955 5E5, with a N.O.S. set of TungSol 5881, original Outputransformer and recapped.
I measure 19-20WATTS on my scope, just before clipping.
I always thougth the PRO was about 26Watts, or should this only work for the fixed-biased 5E5-A?
Thanks

A really good one will make about 18-20 watts so you are right on the money.
The fixed bias 5E5A amps will make about 5-8 watts more then the cathode biased ones.

[Greeny]

A really good one will make about 18-20 watts so you are right on the money.
The fixed bias 5E5A amps will make about 5-8 watts more then the cathode biased ones.

Thanks, Bruce. That's the answer I was looking for and does reassure me that there's nothing wrong with the OT.

[Greeny]

A really good one will make about 18-20 watts so you are right on the money.
The fixed bias 5E5A amps will make about 5-8 watts more then the cathode biased ones.

My second problem will be the HUM there is in this amp. I located it as coming from the inputs. In a 5E3 (almost the same circuit) I also once had that hum. Only way the amp was dead quiet was to use only 1 inputjack (with a 34K inputresistor) and bridge the channels on the tube itself, worked great. But the 5E3 also has the 68K's whicht the 5E5 has not.

Could you tell me if this HUM is an layout error of that circuit? ALL 4 jacks are mounted on the chassis, so grounded. And it sounds just like a ground-loop.

I also had an oscillation on the Instrumentchannel, which was caused by the inputs, or something in that area, because when I took that set of inputs out of the amp, the oscillation was gone.

[Bruce / Mission Amps]

First thing to do is go right to the grids of the first preamp tube and ground them with a set of test leads.
If the humming noise stops, there is a very very good chance you have a miswired input jack set or one or two switching jacks are not working correctly.

[Greeny]

First thing to do is go right to the grids of the first preamp tube and ground them with a set of test leads.
If the humming noise stops, there is a very very good chance you have a miswired input jack set or one or two switching jacks are not working correctly.

Done that just right now, no improvement. I have done about everything I could think off.
I did not know untill now that those inputs are wired differently than other Fenders, f.e. the 5E3.
Both of the inputs 2 are in fact normal inputs into one half of a tube. But the inputs 1 go also to the inputs 2 so if you plug your guitar into input 1 you are using both halves of a pre-amp tube. Is it because of this linking that this hum is present?
That's the reason why I thought this amp really broke up very quickly.

[Bruce / Mission Amps]

If there is no plug inserted into either jack, the grids are still at ground on these triodes and the hum can not be generated there.
You bypassed the jacks with grounded test leads so that eliminated the bad jack issue. My first guess would have been worn out jacks.
If you pull the first preamp tubes does the hum quit?

[Greeny]

If there is no plug inserted into either jack, the grids are still at ground on these triodes and the hum can not be generated there.
You bypassed the jacks with grounded test leads so that eliminated the bad jack issue. My first guess would have been worn out jacks.
If you pull the first preamp tubes does the hum quit?

No, it still is there. When I take out the .02 couplingcap then the hum is practically gone.
I also have an oscillation on the 2e channel (instr.), between 10 and 12 on the volume. With the comple tonestack taken out both channels should be the same but 1 is fine and 2 has that squeeal.
Two tricky problems I know. I did change all the Astroncaps for blue moldeds that still measured perfectly, no DC-leakage at all. The Astrons were very bad. Also installed new filtercaps and a couple resistors. New Tubes (a nice N.O.S. set of TUngSol5881's) installed also.

update:
I just now found the oscillation problem:
The .02 couplingcap after gaintstage 2 going into the P.I. was too close to the inputjack 2 from the instrumentchannel.
It is often a tricky littl thing, but solved.

[Jammin'John]

Big Tweed Deluxe

A really good one will make about 18-20 watts so you are right on the money.
The fixed bias 5E5A amps will make about 5-8 watts more then the cathode biased ones.

Kinda like a BIG tweed deluxe. I like it.
I am playin' a homebrew and it's just right. More headroom than a deluxe reverb and it SINGS a lot better than a DR.

JJ