Fender 5F6-A + PL36. OK?

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Hojvaelde

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Joined 2005
#1
Hi
Here in the summer, I was at the flea market / garage sale. There I bought a half-finished chassis for approximately $ 15.
Now I have time to see what I bought. It is a clone of Fender model 5F6-A (Written inside with a speedmarker). Of course, without tubes.

It is the only input/pre and the phase splitter. Most components are mounted on a board. A couple of the potentiometer is broken. The components connected with the output tubes are not installed, only two empty 8-pin sockets are mounted. No holes for transformers / choke etc.

Now comes the question: I have no 5881 but I have a lot of PL36 , 35 Watt output transformer with Ra-a = 4k. As well as a suitable main transformer and a ring core to 25 V heating.

Is it worth the effort?

Benny
 
#3
The problem with this tube is that there is only one data sheet that has English on it, also having two other languages. The data sheet doesn't give the load resistance because this tube wasn't made for this application. But you still can use it for an output tube. If you are fairly confident you can set up the amp so it operates properly into that 4k a-a impedance, you should be good. Most data sheets seem to indicate 250v is the max for the plate, but again, only one had English on it but the others seem to also point to 250v. And the plate curve sheets stop there as well. The Phillips data sheet has the most complete info. http://frank.pocnet.net/sheets/010/p/PL36.pdf It has multiple plate curve sheets if you know how to use these for design purposes.

Remember, an OT reflects an impedance back to the primary. It has a fixed ratio. So let's say your tranny has 4k for a 4 ohm sec. If you hook up an 8 ohm speaker, this will make your pri 8k a-a. This is a useful tool for using on-hand OTs and not having to buy new ones.
 
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#4
Well, i used EL36/PL36 quite nice tubes similar to EL503 , i used them in amps where EL503 where used , Philips used them in theri amps, they produce around 60W from a pair in pushpull and sound well to me, lot of headroom.

But i recall using them with a plate load around 2.5 / 3 K ohm , they will work in your amp but expect lower power, also the problem with those tubes is providing a screen voltage (g2) around 160 - 180V , also i never exceeded a plate supply of 350V.

Is it worth the effort?
Click to expand...

I would use 6L6GC / 5881 since they're cheap, the output xfrmr goes well with them and you won't need a 25V for heaters .
 
#5
The EL36/PL36 main application was as a 'sweep tube'/horizontal deflector in TV's. This is a hard life, so the ratings in the datasheets are very conservative.
The EL36 is actually one of the few sweeps that has published audio use data. Phillips used them in PA amps.
Sweep duty: Max 250V, audio duty 300V Max.
I use them in my daily audio amp well over 425V.
Keep the screen grid low! Phillips used a tap on the power tranny, I use a regulator set at 150V.
Official application: 300V anode, 150V screen grid, 3,5k Raa, 45W out (class B). At higher volts increase Raa to keep the current/dissipation under control.
I haven't used it in guitar amps (yet), but since it has a big cathode you can expect it to pack a punch (big current reserve).

One other thing to keep in mind: use quality top cap connectors. There are cheap ones around that are known to get loose and in guitars amps they will have to stand lots of moving and vibration. Without anode connection, the screen will take a lot more current and could melt.
 
#7
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