Pye MM - UK Vintage Radio Repair and Restoration Discussion Forum

mancunian69 · 29th Aug 2021, 3:08 pm

Hi all,

The next set I have for resto is a Pye MM sent to me by the same customer as the HMV 501 that I restored earlier this year.

Anyone who has ever worked on these will no doubt tell you that they are an abosolute pig to work on. It must have taken me all afternoon to figure how to get the 2 part chassis out.

However, once out it is relatively easy to work on, and, unlike the HMV, all parts are easily accessable,

Now, I have replaced most of the caps and resistors on the main tag board and a few others too, but:

There are a couple of caps which I need some advice on. Namely, the rectangular square section types. I have attached an image of one of them.

This one has 3 terminals and no identification marks at all other than the value and voltage rating.

Can I assume it is a regular non polarised cap but having an earth shielding around it. If that is the case if I replace it with a modern poly cap is it going to cause any issues?

Thanks in advance

Michael.

Herald1360 · 30th Aug 2021, 10:04 am

Does the set correspond to the MM in the service data "up top"? If so which capacitor is it? There doesn't appear to be any 1.5uF in there.....

Whatever, it's AC rated so definitely non polarised!

PJL · 30th Aug 2021, 4:38 pm

The usual problem with these is distorted tuning capacitor frame and disintegrating knobs as they were made of Mazak. Are yours OK?

ms660 · 30th Aug 2021, 6:41 pm

The block capacitor in question could be a 1uF and a 0.5uF, the top tag being the common ground, the next tag down being a 0.5uF that's connected to the junction of V1's g2 potential divider, the bottom tag a 1uF that's connected to V2's cathode and it's cathode bias resistor etc.

Lawrence.

mancunian69 · 4th Sep 2021, 5:35 pm

Cheers guys. Over the last few days I have managed to figure out from the schematic that the 1.5uF stamped on the can is the combined value of the 2 caps inside. 1uF and 0.5uF.

These have now been replaced with separate poly items.

So, now on to my next issue.
The set powers up fine and has no hum. However, I can only receive Gold at the top of MW band, below which there is nothing, and nothing on LW too. I need clues on what to check next.

The chassis has some capacitor/inductor units in a sealed cans by the looks of it. Also, according to trader sheet, there is no alignment procedure available, just the adjustment of C22. I have tried this, but makes no difference to reception, only volume level which I have adjusted to max.

Any ideas?

Michael.

29th Aug 2021, 3:08 pm	#1
mancunian69 Pentode Join Date: Apr 2013 Location: Manchester, UK. Posts: 177	Pye MM Hi all, The next set I have for resto is a Pye MM sent to me by the same customer as the HMV 501 that I restored earlier this year. Anyone who has ever worked on these will no doubt tell you that they are an abosolute pig to work on. It must have taken me all afternoon to figure how to get the 2 part chassis out. However, once out it is relatively easy to work on, and, unlike the HMV, all parts are easily accessable, Now, I have replaced most of the caps and resistors on the main tag board and a few others too, but: There are a couple of caps which I need some advice on. Namely, the rectangular square section types. I have attached an image of one of them. This one has 3 terminals and no identification marks at all other than the value and voltage rating. Can I assume it is a regular non polarised cap but having an earth shielding around it. If that is the case if I replace it with a modern poly cap is it going to cause any issues? Thanks in advance Michael. Attached Thumbnails

30th Aug 2021, 10:04 am	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Pye mm Does the set correspond to the MM in the service data "up top"? If so which capacitor is it? There doesn't appear to be any 1.5uF in there..... Whatever, it's AC rated so definitely non polarised! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

30th Aug 2021, 4:38 pm	#3
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Pye mm The usual problem with these is distorted tuning capacitor frame and disintegrating knobs as they were made of Mazak. Are yours OK?

30th Aug 2021, 6:41 pm	#4
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Pye MM The block capacitor in question could be a 1uF and a 0.5uF, the top tag being the common ground, the next tag down being a 0.5uF that's connected to the junction of V1's g2 potential divider, the bottom tag a 1uF that's connected to V2's cathode and it's cathode bias resistor etc. Lawrence.

4th Sep 2021, 5:35 pm	#5
mancunian69 Pentode Join Date: Apr 2013 Location: Manchester, UK. Posts: 177	Re: Pye MM Cheers guys. Over the last few days I have managed to figure out from the schematic that the 1.5uF stamped on the can is the combined value of the 2 caps inside. 1uF and 0.5uF. These have now been replaced with separate poly items. So, now on to my next issue. The set powers up fine and has no hum. However, I can only receive Gold at the top of MW band, below which there is nothing, and nothing on LW too. I need clues on what to check next. The chassis has some capacitor/inductor units in a sealed cans by the looks of it. Also, according to trader sheet, there is no alignment procedure available, just the adjustment of C22. I have tried this, but makes no difference to reception, only volume level which I have adjusted to max. Any ideas? Michael.