PYE MM advice required

[chriswood1900]

I am seeking some advice on how to repair my PYE MM, I have two, one with a nicely restored cabinet which has developed some problems with the tuner and another which was bought as a compete wreck but it had a rear door which was missing from mine and it has a complete original tuner with the die cast still in good condition, my intention is to make one good and complete one.
I started in a previous post asking for some advice on the mains connection which I did with a captive mains lead, I started some tests and whilst it partially works the volume control has virtually no effect on the PU input and tuner and the tuning is poor. On closer examination the wave-change switch S2 has a broken contact where the paxolin paddle has sheared off the shaft.
My original MM is serial FGA0XXX the donor is EGA0XXX and whilst I have service sheets for the former I can find no mention of any sets with EGA prefixes and if is later or earlier than the F prefixed ones.
I have extensive experience of modern electronics and repair but virtually zero of old TRF radios.

As I see it I have some options:-
1. Try and repair the wafer which needs a major strip down of the tuner and possible repairs to the volume control, which I’m still trying to understand.
2. Transplant the other chassis with an overhaul and repairs with the PSU which I already have and is working OK.
3. Swap out just the tuner unit from the EGA to the FGA chassis
4. Rip out the existing tuner and PSU and replace with modern units to provide Bluetooth and make it more usable, the Radio sits in my main lounge mainly to match the 1930s theme but has not been much use for listening. I like to keep originality but want something easily usable by the family and tuning TRF sets seems to be a problem.

I would be grateful for some insight into the differences in the 2 models and advice on what to do and particularly how the volume control is supposed to work.

[Ed_Dinning]

Hi Chris, if you can post some pics of the wafer you need I may have something suitable in my spares. They are quite nice sets when working, I have the MM, GB and also the S.
I was surprised to find that most of the very old capacitors were "just about " passible (apart from the wet electrolytic), but the resistors were miles out.
I do have a collection of "dogbone " types and a sort through produced some that were about the values needed (but not what was painted on them). A repaint and occasional use over the past 20 years and they appear not to have shifted any further.

Ed

[John_BS]

Chris: the action of the "volume" control is desribed in Trader Service Sheet 745. It comprises a variable resistor R10, whose wiper sets variable -ve bias on the input valve AC/SG. Also on the same mechanical shaft is differential capacitor C20, which only swings into action once maximum gain is reached on R10. C20 provides a variable amount of regeneration around V2, hence increasing the gain further. If set too "loud" the set can hoot.

John

[chriswood1900]

Ed& John Thank you.
I went for option 1.
I have taken a wafer out of the other tuner and with the help of tweezers managed to change it so the radio works well now the new power lead is on and the radio is back in its home.
Another couple of questions?
1. In the Gram position faint radio sound can still be heard, the volume control does not seem to affect the Gram/PU input and if any low impedance source is plugged in like a CD player the radio volume falls off is this normal.
2. I wanted to add a safety earth, I notice the 2 chassis are not connected together so should I earth the radio chassis or the PSU at the moment the Radio has the earth connection.

Regards

[vinrads]

Like many sets of the period ,the volume is controlled in the rf stage rather than at the audio stage , I suppose you could fit a vol control on the input socket , and turn down the set vol control to reduce the radio break through , or another way is to use a switched vol control and somehow disable the radio cct when you switch to input , if that makes sense .Mick.

[chriswood1900]

Mick thanks I thought that might be the case, I will probably feed the PU input from a Bluetooth or Airplay input which will have volume control.
It must have been awkward using the input with a typical ceramic output deck as my memory of the one we had in early 60s had no volume control on the deck and used the PU input via the volume control of our Ferguson 383.

[ms660]

Just to note, according to a schematic I'm looking at, the PU needs a DC path to ground when PU is selected, if not the valve won't be biased.

Lawrence.

[Nickthedentist]

Originally Posted by chriswood1900

It must have been awkward using the input with a typical ceramic output deck as my memory of the one we had in early 60s had no volume control on the deck and used the PU input via the volume control of our Ferguson 383.

But I think some record decks of this period did have their own volume control, precisely for this reason: https://www.vintage-radio.net/forum/...2&d=1535626570

N.

[chriswood1900]

I finally got round to repairing the turntable on the radio today. It was seized solid and initially could not see how it would work, however on dismantling by removing the 4 small screws I could see the crimped in rubber? had stuck to the aluminium fixed plate and the grease had taken on the consistency of Evostick. I washed the ball and the guides in turps and cleared the gap between the fixed plate and rubber with a knife and lubricated the edge of it with some silicone spray which freed it up. I re-assembled the races (seemed a bit short of balls but that was how many were in it) using a light LM grease and reassembled and all seems to be well and I can now move freely to get the best LW reception.
The radio is now back in pride of place in the Sitting Room.