Identifican request - 3 Valve mains superhet

[Crackle]

Nice find, these are quite popular sets and often sell for upwards of £40.
How much was it from the boot sale Bob.
Mike

[ppppenguin]

During WW2 and its aftermath there was a shortage of almost everything. This, along with many skilled technicians being in the forces easily accounts for many bodged repairs. Mains transformer burned out? Use what's to hand and if that means making the set live chassis well so be it. At least it's working and the owner can listen to the news.

[Sparks]

He wanted £10, but I got it for £7!
Bob

[Bassoonbloke]

Excellent,
Bit of a bargain then.

Alan.

[Sparks]

Yes!
I have now removed all the superfluous old (modified) power unit components.    This has left me plenty of space under and over the chassis to put in a new PSU with isolating transformer.     I believe that the 8uF can capacitor, visible on top of the chassis in the original images had every right to be there, as the hole does not look like it was added as an afterthought.    It was connected between the screen grid of V3 (HT+) and earth, leading me to think it is just part of the HT smoothing circuit.    I can check it outside the receiver, and it will be easy enough to put it back if it is OK.     Some wiring will need to be replaced.   I will then power the heaters with a 6 Volt sealed lead acid, and apply HT, gently from my variable PSU that can supply from 0 Volts to 350 Volts DC via an isolating transformer and a variac - and see what happens.     The tray contains the componets removed so far. 
Bob

[Sparks]

It isn't far off working now (I think). Before I tried it, a few quick checks revealed two resistors o/c and I replaced the worst of the rotten wiring. Connected the heaters up and started by raising the HT gradually to 150 Volts. Bit of crackling and buzzing, but nothing else. Found shorts on the oscillator coil wiring where it passed through the chassis. After replacement, I can now get some hetrodyning whistles and what sounds like a teleprinter at the higher frequency end of the band. No commerical stations though. Will probably leave it for a couple of days, but feel I am getting there.
Bob

[Sparks]

It lives!
I have a dreadful struggle with this one, I don't recall ever seeing a receiver in such a bad way.     I have had to change a number of resisors and capacitors, made much more difficult because their colours were so grimy and faded that I had a job to identify them.    The Trader sheet was a lot of help, but was not all that clear in component locations.     The volume control was o/c as well.    Eventually, I got some faint sations with lots of crackles and whistles, and then got round to trying different valves.    The output valve was the worst for emmission, and things were a lot better with a 6V6 in it.    Now, with only 150 Volts HT, it is quite loud when tuned exactly on stations, but whistles and howls if slightly off tune.   I noted that the 25uF cathode bypass on the o/p valve had gone down to about 100pF, but  didn't replace it at that time, thinking it would not stop it working.   Maybe things will improve when I put a new one in.    I will definitely have a rest now, as it was beginning to bug me something awful.     Lots of wiring to replace, and after it is working properly, will have to build a new PSU.   Also led astray by one of the leads in my capacitance meter becoming o/c about an inch from one end, and only discovered when, clutching at straws, I metered both leads.
Bob

[pwdrive]

So far so good, a new cathode bypass capacitor should up the volume, upping the HT should bring a better performance too.

Lawrence.

[boater sam]

Check that the metalized coating of the EF39 is still connected to pin 1, they have a habit of going o/c where the wire comes up the base cap and is bonded in the coating usually with a paper washer. This causes all sorts of whistles and shrieking.
I have had lots of EF39 do this. Sometimes a replacement is the only answer.
Lots of equivalents, 0M6, VR53, and others. 6K7 should work too.

[Sparks]

That ocurred to me as well, as I have come across the same thing. I have tried two or three, and some are better than others. But the EF39s immediately to hand last night have pretty poor coatings although I have some good ones out in the shed, and I will try them today. Replacing the cathode by-pass did not make the slightest bit of difference. Volume is good and tone fine, but decreases if I increase the HT. There is so much left to check and replace - the wiring is in a dreadful state, but I am at last getting somewhere.
Bob