Pye MM

[Joe]

There's no nasty niffs, yet. It's remarkable to compare the size of that metal rectifier with a couple of 1N4007s and think that they do the same thing, in fact the silicon things are probably capable of both higher voltages and currents.

I've now done the inside with worm killer. I know it isn't the flight season but feel a bit safer knowing it's done.

- Joe

[Tedzed1]

ooooh, I do like that Joe,:D

Very Nice, that is the largest rectifier I have seen in a radio so far.

[AlanBeckett]

That looks very tidy young Joe.
The Capacitor block should be fun.
I'd also be inclined to replace the rectifier, sympathetically.
Alan

[Retired]

Hi,

I repaired one of these sets in 2005. In those days I knew little of radio restoration but I had a friend called Roger who had a large collection and Roger would kindly loan me sets to practice on to gain experience.

Even so long ago I kept a log of all the work I carried out and I hope I'm not hi-jacking this thread but I hope my notes are of interest and I've copied them from a floppy disc.

Good luck Joe but please be very careful of the alloy castings which break so easily as I found out to my grief. I hope my notes are of use.


7 March 2005. I paid my usual visit to see Roger today taking with me a repaired Ekco AW69 that Roger had kindly loaned me to play with. I expected to collect a K.B. which was in need of a bit of loving care and was surprised when Roger handed over this Pye MM. This is quite an expensive receiver and I know that Roger had travelled a long way by car to collect it. These receivers are very desirable and becoming rare to find. Its very good of Roger to let me play with it. As I write the set is on the bench in my workshop awaiting a start to be made on repairs. I haven’t repaired this kind of set before so will find it an interesting challenge. I’ve repaired a number of TRF sets but none with this power supply arrangement. Roger pointed out that an original mains lead wasn’t available as it’s a special lead unique to this type of set and a “choc block” had been fitted for connection to the mains, this will obviously be the first job to investigate in order to supply a safe mains connection. Also HT is missing and Roger did wonder if it was down to the MRI Westinghouse metal rectifier unit being faulty? The cabinet has a number of dents and scratches but given the sets age this is to be expected. As I opened the rear “door” to obtain the serial number I thought this is a bit of alright! I don’t recognise many of the components so I’m in for a steep learning curve once more.

11 March 2005 First job was to make up a mains cable, one end with a plug fused at three amps and the other end connected into the choc block. Now at least a good supply was connected. Out of curiosity I plugged the set into the workshop test panel and after first checking for any signs of danger switched on. As Roger had told me, the set appeared dead. The series 100W test lamp wasn’t showing any signs of life so I left the set switched on and started taking voltage readings. What a surprise to find HT on the main condenser bank? With no sound or crackles from the loudspeaker I gave the set a while to sort itself out after all I didn’t want to start pulling it apart when it was only tired from being asleep for many years. I had by now pulled out the power supply panel just to confirm that the Westinghouse rectifier was in working order and was proved by a continuity test. After quarter of an hour the HT had come up prompting a bit of knob twiddling. The wave change switch wouldn’t budge, it was seized solid on SW. I wound up the gain control and experimented with the reactance and station knobs and was highly delighted when it pulled in Virgin radio, this was with low gain so the set was left an hour to run on soak. After this the set was plugged directly into the mains which brought more gain and more stations so its improving.

Its been left on soak for three hours and today I spent a number of hours playing with it. After a bit of a fight the chassis was removed and all the de-soldered connections marked for re-assembly. The wave change switch refused totally to turn so after a liberal dose of WD40 was applied and firm pressure applied to turn the knob it proved to be very obstinate and still wouldn’t budge at all!! At this point I gripped one of the “contact blades” attached to the spindle with a large pair of pliers and jolly well forced it into submission. At first the spindle was extremely stiff to rotate but with more lubrication and much twisting it can now be turned but its still a bit stiff. In order to get at the spindle a fair bit of stripping was required. The die cast end panel was removed after first taking off the two knobs. This was a huge mistake. The tuning gang is mounted between two centres and of course by removing this end panel the rotating part of the tuning gang just dropped and then followed the most frustrating job ever trying to get the lot to re-align. This took a couple of hours and more stripping to find out what had happened. It tested my patience somewhat.

12 March 2005 I was keen to get started this morning so was in the workshop at 9am. With the heater on and a wireless tuned into Classic Gold I was soon feeling settled. I tried to turn the wave change switch but it had just about seized up again, it took a lot of force to budge it so all the work on it yesterday was to no avail!! This is turning into a major job, just to gain access to the wave change switch spindle meant a number of leads required de-soldering in order to release the cover which was secured by some dozen screws. All the leads were marked for re-assembly and a plan drawn on paper for good measure. I didn’t completely remove the cover but just enough to enable it to be propped out of the way. Once again the end die cast panel had to be removed together with the two knobs. After a bit more stripping I finally had reasonable access. How the heck do I withdraw this spindle without destroying the set? I couldn’t drift it out with a punch and shudder at the thought of damage to the die cast case should I even attempt it. I put the knob back on and had to remove more items so that I could get a good grip and turn it. This spindle is extremely tight indeed and just didn’t want to be withdrawn. I spent a long time and with a lot of patience kept spraying with lubricant and twisting. In the end I removed the knob as by now my hands had become very dirty and sore. This is a real problem. Out of desperation I selected the largest pair of pliers available and jolly well got a firm hold on the exposed square end of the spindle and forced it to turn. I must have spent the best part of an hour twisting and lubricating in the end the spindle broke into two parts!!! Drat, I hate it when things break, I don’t think our local DIY store will be able to supply a new spindle after all the sets only 70 years old. What a dilemma, I’m well and truly up the creek, how do I explain this to Roger?

With nothing to lose now I grabbed the remaining length of spindle in the pliers and after a struggle finally removed it. Boy was it tight. Looking at the two bits I was not amused to see that the spindle appeared to be a die cast aluminium item. It had broken across one of the contact mounting holes. The surface was very poor and what should have been bright machined bearing surfaces were in fact straight from the casting still with the casting lines intact. No attempt had been made to fettle it and I’m not surprised that it finally locked up. A lot of die casting has been used on this set but it’s a mistake to use it for this spindle!! After a pot of tea there was only one solution. Make a new spindle which given my resources and training should be possible. I took Bronwyn along for the ride an went to Blackgates Engineering to obtain suitable spindle material. I purchased 2ft of 1/4" dia brass rod and 2ft of precision ground mild steel again at 1/4" dia. This cost £4.58 but will give me plenty to experiment with and hopefully some left for stock. After dinner I spent the full afternoon in the garage working on the Triumph lathe. This lathe is a monster for this kind of work requiring a gentle touch because it would easily destroy a spindle of this size. I cut a 6ins length of brass to start with because it would be more in keeping on this old set. Getting it to run true in the large 3 jaw chuck took a while but I got it pretty near for this job. The short end with the small dia. section for the control knob was first to do. This brass soon let me know to sharpen the lathe bit, it started to chatter which was a bit worrying. I put a razor point on the lathe bit and completed this first bit of the job. Its not a perfect finish but at least its turned down to size comparing it to the original. The spindle was then removed from the chuck and a brand new milling cutter was installed and tightened up. Using packing the spindle was then secured into the tool post at the correct height and with the spindle marked for length a cut was taken to the correct depth, this was done in a number if passes. I don’t have an indexing head for the lathe so the spindle was lined up using an engineers square, using this method a square was formed next to the small dia. next job was to sort out the problem of how to mount the spindle in relation to the newly machined square section, the square was not in line with the contact mounting recesses.

After a bit of searching I found a lump of square steel which I bored at 1/4ins throughout its length and a tapped hole was added to enable the spindle to be gripped through a full rotation. The whole was set up using my woodworking planer cast iron table as a surface plate and a sliding bevel was adjusted using the original for reference. Using this method it was a slow job but one by one the flats were machined taking light cuts. The new slots of course had rounded ends so once the lathe work was complete it was a case of hand filing to finish this part of the job off. The final part of the job was to drill the two clearance holes and the four holes for tapping. But as I’ve run out of time and don’t wish to destroy the job after so much work by trying to rush it knocked off for the day. I’m well pleased so far and wish the weather was warmer, I have great patience for this kind of work and as such excelled in my days as an apprentice mechanical engineer. As an apprentice I was sent on a training course to Crigglestone Colliery were I had a file in my hand for 3 months and learnt how to file flat, the second 3 months were spent on various machine tools including lathe work which I have never forgotten. If this Pye thinks its beaten me with its broken spindle its picked the wrong person.

13 March 2005 First job this morning was to wash the car. It’s not half cold outside with a frost during the night. By 9.30 am I was absolutely frozen so came indoors for a drink and to get warm. Next job was to drill and tap as required to complete the spindle, this job took about an hour but the spindle is now completed to my satisfaction and what a joy it was when I tried it in the chassis. It slides in with just a bit of clearance so there is now no chance of it seizing up. I’m going to visit Roger tomorrow as usual and will take the new spindle for his approval.
15 March 2005 More work has been completed on this set over the last couple of days. The new spindle has finally been installed and appears to work ok but can be tested once the set is powered up again. Also the 1uF 250V AC working can has been stripped out. This can had been bridged with a 0.05uF 1500V tubular item, this was tested on the Hunts Component Tester and found to be ok on capacitance but electrically leaking on the 100V/200V range, out of curiosity I also tested the original can which gave identical readings?. The can was taken into the garage and using a blowlamp it didn’t take long to remove the old condenser unit. This also destroyed the paint on the can. This is always a messy job. I soldered extension leads onto a new 1uF 275V Class X2 condenser, cut a wooden close fitting plug to seal the open can end with and drilled the plug for the leads. Then the plug was given a coat of black marker ink making it look more original. The can decided to come apart at the seams when the blowlamp was applied, this melted the solder. The can was cleaned up and then re-soldered using the soldering iron, this actually proved easier than expected. The new condenser was installed together with the plug and for good measure I drilled a single hole to accept a screw securing the can to the plug making the repair reversible. With the can secured the chassis could be put back together again. The leads that had been unsoldered to enable access were resoldered and once completed the wave change now works easily. What a lot of work just to achieve this though!!

18 March 2005 This set just refuses to be repaired. I re-assembled the chassis into the cabinet soldering it in etc., but then it refused to pull any station in, it was totally dead on signal? So it was out with the chassis once again to investigate. This was a bit of a disappointment as I did expect the set to work better after all the attention it had received, no such luck though so its back to the long route. I ended up stripping all the outer chassis panels off just to get at the tuning gang, this is buried deep in the set and even with the panels off the moving part of the gang couldn’t be removed. What a strange way of mounting, as already stated its mounted between two centres but it won’t adjust as one centre is actually cast into the cast end panel, the other end does adjust but only to take up end play? Of course its rubbing badly and I believe this is the cause of the poor reception. I’ve spent hours playing with it and by 9pm last night it was pulling in Virgin Radio quite strongly, but this is the only station it receive so I really need to resolve this tuning gang problem. A number of options are available to me but care is needed if the set is to remain original. I’ve just returned from a visit to Roger so he is up to date on repairs so far.

20 March 2005 I’ve spent a good deal of time on the set over the last couple of days and what a challenge its been!! The tuning gang has been a right old pain to sort out. I tried many times to adjust the vanes on the spindle in relation to the fixed vanes, this job was very interesting but most frustrating as well. The gang was adjusted from rubbing at one side to rubbing on the opposite side but I still couldn’t get rid of the crackles on the last half inch of dial, it was so near but refused to give in and work. This morning I spent about an hour trying once again to get the adjustment correct in the end I accidentally broke one of the vanes completely off, it just pinged and snapped, this upset me somewhat as I hate to damage these old sets. What made the break worse was the fact that I was trying a suggestion by Roger to part the vanes which were rubbing manually, this particular vane was leaning to one side so that it would not run clear from min. to max. and this was giving me all the grief!! I know it was the problem because the set is now working well with absolutely no rubbing. I would have liked to achieve this without the damage though so am disappointed as I didn’t use much force to snap it off.

The set is now totally rebuilt and working well on a number of stations. It takes a fair bit of knob twiddling to get the stations in tune but output is well up. Its also working on its own internal aerial so I will be pleased to try it out tomorrow when I return it to Roger. This set has been different to all the others that I’ve repaired as the faults have been mostly of a mechanical nature. The job has tested my patience to the limit with the tuning gang and the wave change spindle but at least the end result has been worth the effort. A toggle switch has now been fitted for switching the mains and this job alone took around two hours to complete today. I cut out suitable mountings from thick black plastic and both look well in keeping with the age of the set. The toggle switch supplied by Roger was dead on one of the poles so was not used. I stripped out a suitable switch from an old power supply, the casing and lever are in plastic so didn’t require an earth for safety, I used twin double insulted cable for the mains and am pleased at the appearance, the old original switch unit is in a plastic bag for safe storage by Roger. One quite alarming discovery was as I wired up the new mains connection I tested for safety to earth. The mains voltage tappings were set correctly but as I put the meter on the securing screw at the back of the chassis to the workshop earth it was well and truly live at full mains potential. The lead was red rubber insulated and one would have thought it to be the live side, the other lead was nondescript cotton covered which appeared to be the negative. A new black lead was made up and fitted and the live side was run through the new toggle switch as this switch is only a single pole item. The chassis only shows very low voltage to earth now so is much more safe. This was potentially lethal as with the rear cabinet door opened the dangerous connection could but touched easily. What a lot of work for a set that originally was just down on HT?

An original lead from the loudspeaker case to a terminal on the chassis back tag strip shows a low voltage which is a bit strange? I’ve connected this as it was supplied to me but as the set appears to be working ok with it connected have left it as such. I’ve not done much work on the components because with the set working quite well its still very much original in appearance and it would be a shame to lose this just to improve on output quality. The rear door is a tight fit and I wouldn’t recommend playing around with it as its possible some damage could be caused to the cabinets joints, once again its original and to start planing it to fit it would be hard to copy the finish colour. I’ve got to know this set very well indeed over the last couple of weeks, its been in my thoughts most of the time and certainly kept me out of trouble in the workshop. I’ve enjoyed playing with it and on the whole am happy to have got it working. Roger has paid a lot of money for this set and I’m very happy to have had the pleasure of its company. It will be returned back to Roger tomorrow with many thanks. Hope Roger is happy with it.

Kind regards, Col.

[Joe]

I'm pleased to be leaving the chassis to Alan. Thanks for confirming the wisdom of this, Col.

I treated the inside of the case yesterday and the next thing will be to scrape, fill and re-polish it.

- Joe

[Retired]

Hi,

Good luck with the cabinet Joe; you could always pop it into Sheffield A&E and say it has been shot with a 12 bore and leave them to sort it out!!

To be on the safe side I gave my restored Ekco TV cabinet a good dose of wood worm treatment; I hate the little blighter's.

Kind regards, Col.

[Coherers]

I just thought I would share an experience I had with woodworm a few years back. It has to be said that this wasn't in a radio, but in the plywood back of a 1930's chest of drawers. However, the chest was quite similar to a wireless of the same era really, in that it was rectangular with knobs and made of wood, so humour me.

The solid timber body of the chest was unaffected, but there was woodworm in the plywood panel at the back (circa 3/8" thick). Not too bad an infestation it seemed, just a few dozen holes rather than the hundreds one can see in really badly affected objects - but clearly active. I decided to treat it chemically and used Rentokil Woodworm Killer. But rather than just brushing/spraying/injecting it as per the instructions, I decided to "go medieval on their ass". I laid the chest face down so the rear panel was horizontal and flat and poured the stuff on so the panel was completely flooded, and so the liquid drained down into the flight holes giving maximum penetration. (I really hate woodworm, and thought if this doesn't poison them, it will drown the nasty buggers first!).
Not being one for underkill, once dry, I inverted the chest of draws and repeated the process for the inside face of the panel.

Great, job done - the evil little monsters are dooooooomed, if not writhing in their death-throws already, I thought.

A few years passed before I next had the opportunity to examine the item to ensure I had cured the problem. However, when I pulled the chest out, I was confronted with an horrendous sight - the entire panel was literally covered with exit holes - even the exit holes had exit holes. One of the worst examples of worm I have ever seen. It was if the woodworm "killer" had just acted as food for the buggers. I still feel itchy at the thought of it.
It is supposed to poison them as they tunnel out rather than kill them in situ but if my extreme treatment had so little effect, I wonder what the point of chemical treatment is? Perhaps, once out, the little monsters snuffed it before they could breed, but that is little good as the affected item was essentially destroyed by them first.

As a result, I have no faith in the permethrin-based killers, and am not even convinced as to the effectiveness of the likes of Borocol as an insecticide. Several deep freeze / defrost cycles is the only thing I would use now on active worm. Either that or a napalm flame-thrower.

Jeremy

[Joe]

I must say I wonder about how well it can deal with un-hatched eggs as if it was potent enough to be effective it wouldn't be on sale.

I had a similar experience to you but with moth balls. Rather than being repelled by the smell it seemed to work as a aphrodisiac!

It was interesting to not that the plywood of the frame aerial former was un-touched despite other bits that were glued to it having holes. They obviously have their likes and dis-likes.

- Joe

[Mark Hennessy]

Hi Jeremy,

I've heard similar stories before, and it's one of the reasons I shy away from chemicals - they might reduce the chances of further infestation, but in reality, it's really bolting the stable door after the horse has bolted... And I've often speculated on whether they prefer plywood - perhaps because of the glues - and your story just adds further weight to that theory. I know that in softwood, they prefer sapwood to heartwood, so they definitely exercise preference.

Drying out wood is another sure way of stopping them in their tracks, although that isn't always possible.

Cheers,

Mark

[Joe]

I've developed a certain admiration for wood-worm. I stripped the case today and the old finish was rock hard and I'm surprised they could nibble through it.

It actually proved easier to sand than scrape off. I made some progress with a Stanley knife blade but even that needed frequent sharpening. Eventually I resorted to paint-stripper.

The veneer is a very nice colour and it's making me think about re-doing my Fergy.

Unfortunately, as usual, I was thinking more about what I was doing than taking photographs. Here's one of it stripped and with the first rough filling applied.

   

More tomorrow.

- Joe