Pye MM

[AlanBeckett]

David,

Yes, that's what I feared. However, it all looks very dry so I suspect it was well stored, although probably accidentally. The worm probably implies a nice dry warm attic.

Alan

[Joe]

I had the same concern which is why I didn't just reach for the jump-leads.

- Joe

[AlanBeckett]

A short update just to show that I haven't gone into hybernation.
Power supply next. The first step was to tack a couple of strips of wood on the bottom. The transformer leads all exit at the bottom so scraping it about on the bench might well damage the cotton/rubber covered wires.
Next, what about connecting the Mains? The original plug is long gone. The 'Socket' consists of two flat blades of different widths. After a bit of cleaning up and straightening it was clear that one was 1/4" and the other a bit bigger. The bigger one goes to the Voltage Selector so, although it doesn't say so on the Diagram, I propose to make that Live. A 0.25"/6mm Faston will fit the small one with a bit of 'easing'. The big one will take the next size up. So, with some Heat Shrink and a mains lead it can be powered up.
Now for the connections and interconnections. So far I'd been working with the Trader Sheet from the BVWS CD. According to that there were a number of different versions, and the information was, to say the least, scanty. That's no big deal 'cause it can all be worked out, but why struggle? I decided I might as well have a look on the VRRF and there was the Manufacturer's data, all 22 pages of it. So for the princely sum of £1.99 I downloaded it. It actually consists of a series of numbered Pye Sheets, each one detailing different aspects of the set, including various modifications. Not to put too fine a point on it it's wonderful. In reality the Trader Sheet is pretty pathetic, although better than nothing. I have to assume that Industrial Espionage was less well developed in the '30s.
Apparently there were two different Capacitor Blocks fitted and this is the later one. Apart from a wire colour, which might simply be due to fading over the years, it all matches - insert big sigh of relief.
So, 'all' I have to do is make a Mains cable, reconnect the wires and fire it up. I've actually got all the parts except the Frame Aerial in the house now so I propose to do the wiring here then I'll have to bite the bullet and transport it all to the garage and start it up with the Variac. One advantage of the Metal Rectifier is that I can do that slowly and hopefully reform the Electrolytics slowly. Some heating will be needed unless there's a sudden thaw, but don't worry David, I'll avoid Extension Leads

Alan

   
  MainsFastons.JPG (Size: 3.35 MB / Downloads: 109)    

[Yorkie]

Interesting to note the AC mains frequency range on the voltage selector, which suggests that back in the 30s, they hadn't standardised on 50Hz as it says 40 - 100Hz. The metal rectifier will be doing well if it's still behaving itself Alan, and it will be interesting to see if the smoothers are still OK.

As to Service Data, Paul Stenning still has his DVD (and Valve Data disc) on special offer for a few more days. You can soon recoup your money, and though the freebie BVWS trader sheet discs are better than nothing, the makers' data sheets - for obvious reasons - tend to be much more comprehensive, and some of the ERT ones are good too. It's rather a pity that they use different component numberings between the trader sheets and makers' sheets for the same models.

As to extension reels, I still can't believe I did that! A drill for five minutes is one thing, but a 2KW heater for a couple of hours drawing >8 Amps?

If someone else had done it, I'd be laughing them off the face of the planet. It's no wonder my kids try to stop me climbing ladders and going on the roof!

[AlanBeckett]

David,
I hadn't noticed that frequency range although it was fairly standard with Pye sets.
Alan

[AlanBeckett]

Back to work

The next job was to sort out the connections and do a bit of tidying up. After that it's just a matter of getting connecting everything up and getting on with testing.

Just to recap the set consists of four units; The PSU, The Speaker Assembly, the Main Chassis (Valve Platform in Pye terminology) and the Frame Aerial. The wiring between these had been disconnected, as Pye advises, by either Joe or me. Despite having labelled and photographed I decided I'd better recheck, and it all looked fine, with three exceptions.

First here is a cable between the PSU and the Main Chassis. This has four black wires with coloured traces in it. When I was disconnecting I blithely chopped the wires off at the Main Chassis end - well, they're bound to be connected to tags behind the Paxolin panel, and the loss of 1/2" is no problem. It turns out that that's not the case at all. The wires are connected directly to their destinations in the set. So, I'll either have to rejoin them - Heat shrink - or make a new cable.

Second, someone had done a bit of jiggery-pockery with the PU Socket wiring. There were a couple of bits of dangling bell flex, one to the 'Live' socket and one to the wire to the set. That was easy to undo, just a bit fiddly.

Finally, while I was working on No. 2 I noticed a very unhappy looking resistor - see attached. The Trader and Pye sheets give a different layout for the Group Board, no doubt reflecting the modifications that were done during the life of these sets. This one appears to be somewhere in between. As far as I can tell from the wiring it's R2, which is the bottom half of V1 Screen Pot. Divider. I measure it at 50k. which is miles out. Also, I can't see how it could have been damaged, unless there was a serious valve fault at some stage. Anyway, I propose to leave it for now and see what the Screen volts are.

So, connect and fire up next

Alan


  GroupBoard1.JPG (Size: 3.24 MB / Downloads: 98)

[AlanBeckett]

It was very mild and dry yesterday and I managed to escape for a bit

So, the first job was to connect some nice long wires to the various places where I'd chopped the originals. Next I set the whole lot up on the bench and interconnected the wires with choc blocks - see attached.
Then it was just a matter of plugging in to the Variac and turning it up slowly, while monitoring the ht and heater voltages. I only ran it up to 220v input as the capacitors are only rated at 275v. I did that over a couple of hours by the end of which the ht was at 270v and the Heaters at 4.2v. Bearing in mind that I hadn't put the valves in I thought that was pretty good to start with. In fact I was congratulating myself that things were going splendidly and the next step was to install the valves when I noticed a wisp of smoke from the main chassis. Sure enough one of the resistors is getting hotter than I think it should. I'm not certain where it is in the circuit yet, as at that stage I was recalled to base to assist with Christmas things, and I haven't managed to escape again yet.

A few extra comments:-

The mains switch works fine.

The eagle eyed will notice that the AVO 8 is switched to AC, despite the fact that it's measuring the ht. I wondered why it gave a strange reading when I changed ranges.

There were encouraging scratching noises from the speaker when I was poking about with the AVO

So, next job is find out what the problem is with the resistor and try the valves.

Alan

   

[Andrewausfa]

Here's to you getting away for a bit Alan as this has been a good read so far. Just looking through the MM service sheets I like the fault-finding sections and had a smirk at the strap-line "THESE TABLES APPEAR INCOMPREHENSIBLE". Looking forward to reading some more on the MM.

Andrew

[Retired]

Hi,

You're on the the home straight now Alan and the smoking resistor should be easy enough to sort out; perhaps a crossed wire due to playing around a bit as this is easy to do. On the set I worked on the electrical components appeared to be more robust than the alloy castings so hopefully you are in with a good chance of it speaking to you shortly.

The most interesting part of this restoration for me was watching how you resolved the broken spindle problem bringing it to a successful conclusion. This spindle problem could have rendered the set useless. I'm pleased you explained in full and supplied detailed drawings as this will encourage others to have a go at making components. I used my lathe but you used your mill for cutting the spindle flats; I don't own a mill but had I done so this would have been my first choice of machine.

Doesn't Christmas get in the way of us playing with our toys? Keep up the good work.

Kind regards, Col.

[AlanBeckett]

Andrew,
It is indeed an 'interesting' turn of phrase especially when it's compared with a Railway Timetable :D
I've only just noticed that the 0745 Trader Sheet says that it's a TRANSPORTABLE AC SUPERHET. However, the description is correct.
Nothing done today as expected. Sorry Joe, it's going to be after Christmas.
Merry Christmas.
Alan