Hi guys,

I am another step closer to having a working valve radio, I have replaced all the capacitors, fixed a broken solder joint and put in a new set of valves. I then built up the courage to plug it in and turn it on. After a couple of minutes all five valves had a dim orange glow to them, I think this is good? I had a temporary speaker connected as my other one is getting reconed, I could hear a slight hum an a little faint crackle from the speaker but no radio station would tune in. I lete it warm up for about 10 minutes but still nothing. Has anyone got any ideas where I should start looking.

Cheers

Shane

The hum could indicate that the amp may be working?

Would be handy to know what we are dealing with? eg the Monster on my bench has 18 valves. Several of which are wired up with wrong parts.

If you have the circuit compare. I always take photo's, so that when I have an interuption, or senior moment, I have something to refer back to.

Faint crackle is not good.

Believe it or not, with a dead set you start at the power ssupply then amplifier & work towards the aerial. A signal generator could be handy.

Advise please, what it is & valve compliment. &what are they?

Marc

Hi Marc,

The Valves are as follows:

6N8
6BD7
6AN7
6V6GT
5Y3GT

They are all new and they all have a dim orange glow when I power up the set. Here is a picture of the circuit after I replaced the capacitors.

Image Link

Cheers

Shane

Still like to know what breed it is so as I can see if I have a circuit. It looks early fifties.

I will enlarge pic & see if there is something obvious to the eye.

Valves of these types normally run dull red

I would have a look at the plates on the tuning gang, these can be bent when servicing & handling. The moving rotor plates should not touch the fixed ones.

Marc

Hi Marc,
I am unsure what model it is but here is a pic of it.

Image Link

I have had a little bit of progress, the 6V6GT that I just bought has only got six pins on it compared to the old one that has seven. I placed the old one back in even though it was all black and the plastic base was cracked and I managed to get one radio station (the horse racing station). It was very weak and had a lot of static even when I added a longer bit of wire on the aerial. The tuning gang seems to be in very good condition, no physical damage anyway (i'd love to know how it actually works though).

I hope that is helpful.

Cheers

Shane

Still have not studied pic.
Someone is bound to recognise the dial & logo

It's not unusual for there to be six pins on a 6V6. in most Pin 1 is not used and six never used. The 6 pin is often used as a tag bettween a 50K grid stopper and the 500K grid leak, which are both notorious for going out of spec. I have replaced several.

I would like an idea on the HT Voltage at pin 8 of the 5Y3. Watch the fingers it will be in the order of 250V DC if all is well.

Look at the screws on the IF cans (literally .. no touch) & see if there is evidence of them being played with?

We may have to plod on this one as we get more info.

Do you have any signal generating equipment?

Tuning gang itself is simple, its a variable capacitor. It works in conjunction with coils of fixed inductance. By varying the capacity you vary the resonant frequency of the circuit ( one can get more bogged down in theory) The cap can be parallel or in series with the coil.

Marc

Need clearer indication of what is on 6V6 photo pixelates in the area when enlarged.

I would expect a cap coming off of pin 3 & going to a tone control or ground.

Speaker transformer is between screen pin 4 and plate pin 3.

Cathode is pin 8 check the soldering and the value of the resistor it's two hundred & something. There should be about minus 12.6 volts between cathode and pin 5, grid. The positive end of the cathode bypass electrolytic should be on pin 8.

From pins 5 to 6 a 47K grid stopper resistor, with cap to previous valve (prob 6N8) going to pin 6.

There should be a 470K resistor to ground from pin 5 and I cannot see it?

If its not there the valve will be a diode & not work.

Marc

Pin 8 on the 5Y3 has 322 VDC.

I can't rally tell if the IF cans have been played with, I know I haven't played with them though.

I don't have any signal generating equipment at all.

When I measured the value of the resisitor on 6V6 pin 8 I got 465 ohms.

The resistor on 6V6 pin 5 goes back to pin 1.

Here is a closer picture of the 6V6 and 5Y3

Image Link

Ok depending on the band colour if its white or grey

Red is 2, White is 9, brown = multiply by 10 = cooked replace it, it should be 280 or 290 Ohms.

The input to the 6V6 is strange check between pin 1 & ground with an ohm meter ( set off ) There should be 500K ( 0.5M ) between that and ground if not there is a problem with that tone pot.

There is a switch. This switches from Phono to Radio ......and it is in which position?

Like also to see voltage on pin 4 If that is too high a valve is not conducting.

Has the set got numbers stamped on the back of the chassis?

Marc

Hi Marc,

I am going to get a new 280 ohm resistor today.

That switch you mentioned I did not know what that was for but I had been toggling between it and in one position there was no sound coming out of the speaker and in the other position I could recieve that one radio station, this switch now makes sense.

Between pin 1 and ground on the 6V6 I got 1.08M, does this mean I need a new tone pot?

I am not sure if I understand the controls on the radio entirely, I have a tuning control and a phono radio control. I also have what I thought to be the on/off/volume control, it works fine as an on/off switch but only alters the volume ever so slightly at the start of its motion and then it appears to do nothing. The other control seems to also be a volume control as it changes the volume a lot more than the one on the on/off switch. I am not very sure here but maybe it has something to do with the tone pot that you referred to?

One thing I had noticed but didn't think much of is when I touched the on/off/volume knob the volume of that one radio station I could recieve would rise significantly. This has now changed.........just today my new power cord arrived (one of those brown fabric ones with a moulded three pin plug). I fitted the cord the only difference being there is now a earth wire connected to the chassis, now I have no more volume variations when I touch the controls (there are no knobs on the shafts) and I can get a couple more faint stations

On pin 4 of the 6V6 I got 302 VDC.

The numbers stamped on the back of the chassis are TG2387 these appear to be roughly stamped with a set of punches and a wobbley hand.

Thank you for your help so far it has been greatly appreciated.

Shane

Just did a little research, the tone pot/potentiometer with the on/off on it reads 22 ohm to 1.097 M ohm and the other one reads 1.284 M ohm to 205 ohm. The both have 500M written on them.

If it's got 500M on it it should be 500K. Bit unusual for both to go.

You will get capacitive effects if the set is not earthed, via mains.

How much wire have you got on the antenna if any? None ... problems.

Normal lenght is 25 feet. but in a City you should get something with less.

302V sounds high but I don't know what the set is? Normally high voltage is valves not conducting. with a high cathode resistor it will not conduct fully. I would check a few other cathode & Plate resistors.

Any with yellow tend to be the worst offenders. 10% high is my normal evict tolerance. ie 110K for a 100K is out. Beware of erroneous readings with some resistors "in circuit".

Marc

I did contact Brad re this as there appears to be a hassle where the site reverts to the host not the Forum. Even when you login.

I would note that you have reported three resistances that are twice what they should be. The Pot one's have made me suspicious.

Get some known good resistors say 470K & 470 Ohm & 270 Ohm & check them. I think we need to establish if that meter has a problem with a shunt in the ohms ranges?

Marc