This beautiful radio I manage to get hold off.
And whatever you do, NEVER EVER power a radio up from that age!!
Not even on a variac!!
You could be very very sorry in a flash literately.
The radio is from the outside very complete and in a very good condition.
Everything seems to be present, I will take a peak inside the radio shortly.
I expect him there to be in the same condition.
Obviously, this radio needs re capping after all those years(80)
The resistors will be checked as well, they will be probably out off tolerance.
So, a nice job to keep me of the streets,and I will enjoy this restoration.
At first glance you get the impression the set is not worked on.
Unfortunately there is somebody being working on the radio!
Looking closer something's don't look right, some wiring is being cut and two capacitors linked together and going no where.
I checked some resistors they are out of tolerance as expected.
Capacitors are leaky, the mica capacitors are OK.
Electrolytic caps needed replacement they are also leaky.
By further checking the choke seems to spilled his insides,after checking the choke, he is open.
This means trying to rewind him, but I have my doubts getting him apart.
This also means the iron core will be damaged.
The option that I have here to wind a new choke.
I checked the electrolytic capacitors in the power supply they have also have a high resistance, they need replacing.(Cause? Valve 80 looks OK for now, but will be tested)
Probably the reason why the choke spilled everything? and burnt out, that remains for now a mystery .
On the chassis I can see the marks of heating from the connecting wires.
Unfortunately, fuses are here absent.
At the end stage 6F6 the output transformer is not originally what was in this radio.
Also this has to be checked.
The impedance for this valve is 7500 ohms.
The transformer primary is 286 ohms, the secondary what is connected to the (5000 ohms)measured 1 ohm.
In comparison, primary and the connection to the secondary is wrong for 500 or 5000 ohm.
The transformer is connected up for a speaker or a normal headphone.
The values from primary = 150 ohm middle 136 ohm total 286 ohm.
The values from secondary = 0.2 ohm 1ohm 1.6 ohm 2.2 ohm.
I am considering to wind a new output transformer to match 500 and 5000 ohms including a winding for a normal speaker or headphone.
The headphone originally is 5000 ohms.
After giving my attention to the output stage, I came to the conclusion this would never have worked.
It is actually a bad job and I say it nicely,bare wiring everywhere apart from the mistakes,(400 volts!) this is asking for it.
If somebody doesn't know what he or she is doing, refrain from working on such radio's.
You do damage to it.
More importantly, these are lethal voltages, they can cause death or serious injury.
So think twice before you start out on such venture.
Just Imagen I would plugged this radio in, fireworks and serious damage would occur.
Having said so, perhaps they tried to power the radio up, that's is the reason why the choke was open?
A Big short occurred?
Checking the choke.
I heated up the choke with a hairdryer, he came with some help from a tiny hammer apart.
First I tried to discover or find the broken end from the windings,firstly removing the paper.
That didn't work, I tried to remove the first layer the wire broke easily, to easy for my liking.
Then I discovered the burn marks on the lower layer copper windings, so recovering those layers wouldn't work.
So I removed all the layers present.
Here is what is left of it.
Next thing to do, is rewinding the coil on the machine.
I have a fair idea how many turns go on.
Imperial standard wire Gauge S.W.G. 40 or 0.15mm.
The paper former can't be used that way, so I have construct a support for the wire so that it is trapped between the sides of the former.
And I have to support the paper former with some plastic pipe what fits in there precisely so that it won't damage or distort the former with rewinding.
Now rewinding can start and will be easy to perform.
Start of rewinding on the machine.
The finished coil.
The testing.
Building in of the repaired choke.
Checking the power transformer.
Firstly I took measurements of the windings primary en secondary.
They al seem to be alright.
Then I made sure that there were no connections to the transformer and hooked him up on the variac.
There were no problems,smoke or overheating.
Rewinding the output transformer.
Well on his way!
Winding finished, primary 7500 ohm and 4 ohm visible.
On the back the 500 and 5000 ohm.
Start stacking.
The almost finished transformer and comparison in size.
The flaw in the design of the schematic and consequences for the output transformer.
It shows the short-circuit of the transformer when connected to the headphone.
I have to find a solution for this problem.
What I have done is, I wired the telephone plug up with the 4 ohm speaker.
As soon you plug in then the speaker shuts down.
I tried also a headphone from 2000 ohm this worked as well.
Refitted and connected the new re winded output transformer
Start of recapping the receiver.
Recapping done,and removed the out of tolerance resistors.
All capacitors are very leaky,because of there age.
Now it is time to do the smoke test.
With everything replaced this should be no trouble.
As expected everything worked out.
The only valve inserted was valve 80.
The front lights came on and the voltage went up to 300 volts.
No problems.
Now the moment of truth, will the receiver work??
I put all the valves in the receiver now.
The only thing I will do is to test the LF section.
I will power the receiver up and see what happens.
The LF output works!!
Next thing to do, to power the rest up.
Unfortunately, the receiver doesn't work he is totally mute.
No signal gets true,so I have to investigate why.
As I early on stated,somebody is being working on the radio.
I did find marks from a short on one of the capacitors.
My fear was that the coil from the detector was burned out.
Fortunately that was not the case,what I did find was a mistake in the circuitry.
I corrected the connections and replaced the resistors they had the wrong value.
Concerning, R15 and R17, R15 was 250K should be 30K, R17 was 250K should be 500K.
The resistor R19 1M, was connected on the wrong side of R15.
The receiver was still not working.
After checking the voltages in the receiver I discovered the the bias voltages on the RF and IF valves were not correct.
They suppose to be 8 volts but instead Ive got 80 volts this means the bias circuit is open.
After checking this and re soldering everything, the radio came to live.
So after I had done this and checking the bands,the tuning cord broke.
After replacing this,I checked all the bands.
Band 1, 2, 3, are totally detuned, a lot of screw driving took place here.
Band 4 oscillator is 350 kHz off but is working.
Band 5 oscillator is 2 MHz off but is working.
This receiver needs definitely re aligning.
Firstly I checked IF.
1 and 2 IF cans were miss aligned, after correction gave that a big improvement in sensitivity.
All the bands are re aligned, and the radio works perfectly now.
The band spread tuning I had to re adjust the dial mechanically as well.
On the right the S meter, two resistors was out of tolerance I replaced them as well.
The last thing to do is fitting the fuses to protect the transformer and the valve 80 the rectifier.
So the receiver is now in perfect working order, it is a performer he works extremely well.
For realigning I used my self build RF signal generator, he was very accurate and also worked perfectly.
I enjoyed this restoring.
