PYE 815 - 1st Steps in its renaissance

[brianc]

Please don't expects a Col saga but I'll do my best .
I took it into the workshop after clearing away a couple of TV22s (anyone got a back for sale?). Two basic problems have come to light. The first is that the knobs are stuck fast. They are of the pull-off variety but they don't! No way to get to the shafts in any way as the knobs have a shoulder which passes through the cabinet aperture, so I will have to resort to string or similar, hopefully, without damaging the pots.
There is a fibre panel underneath to gain access to the innards so I put the cabinet on it's side (making sure that the chassis was screwed down) to access the panel. The second problem then showed it's face - the dreaded woodworm. It looks as though it has been active recently so as soon as I get the chassis out of the cabinet, I will start treating it. There are not too many flight holes in the veneered faces but a few underneath. Nothing like Colin's Ekco though.
I took some pictures of the "works" underneath and it looks as though the phantom plumber has been at work with his blowlamp and the rubber covered wiring is mostly very sad but hey, this is why we love this hobby - isn'tit? . I have added a few pictures which sum up the initial investigation but the upside is that on the upper chassis, there seems to be total originality with the wet electrolytic caps still in place so I will be able to get rid of those dreadful twistlock substitutes.
The state of the rubber insulation is a bit worrying and it looks as though I will need to replace most of the wiring. I will use silicone rubber wire and will, therefore, need to stock up on the less common colours as I normally keep red, black, green and the standard mains colours.
The mains transformer looks as though it is beeing eaten by mould. I know it works because it was plugged in by the previous owner so careful cleaning using an anti-fungal cleaner - ideas anybody?
Now to get down to those bl**dy knobs!!!

[Heatercathodeshort]

Hello Brian,
Pye EHT transformers tend to look a bit tired but seem to hold up well. I would clean it off dry with a toothbrush and leave it at that. The less induced damp the better. Wood worm looks a doodle and a syringe used for filling ink cartridges normally floods the tunnels and puts an end to any invaders. By the look of those electrolytics I would say the receiver looks as if it was used well into the 50's and was probably working to a greater extent when laid up for a lovely new Pye V14..[I bet the 815 had the last laugh!] The MW22-1 is very similar to the first post war Mullard tube the MW22-7 and should be capable of a brilliant picture. By the look of that picture I would say the H.T. supply is missing leaving just an unfocused blob. The EHT is present but no current in the focus coil and inoperative timebases. I want to play with it..Regards, John.

[murphyv310]

John.
Don't be selfish WE ALL want to play with it. Great Fun!

[brianc]

You're both welcome to come and play. Unfortunately Trevor, it's quite a long way for you but for you John, I'm just around the corner. Shall I be seeing either of you?
By the way, string got the knobs off! The chassis is about to come out - I've just had me lunch !

[Herald1360]

For some reason (possibly the laminating glue?) woodworm seems to have a particular taste for old plywood- the bottom of this set clearly being suitably tasty.

I'm not generally a fan of old TVs, but this one I'll be following......

[mark pirate]

Great news that it is almost original, i bet it was used well into the 50's!
I will be following this thread with great interest, i would love to get my hands on a prewar set, alas my funds wont stretch that far

Mark

[brianc]

We'll try and make you a fan Chris .
The chassis is out and the full extent of the work required is exposed. Someone has been at it and there are quite a few disconnected wires and realy terrible joints so I'll have to trace a fair amount of the circuits to find out where the connections go. It really is a difficult set to work on. Indeed, in the service instructions I have it says "This receiver is likely to present difficulties ....." and suggests that the RF and TB sections need to be removed from the chassis to gain access to them - too true blue - it's a nightmare. For some reason, the valves are mounted on sub-plates hung under the chassis and pass through the chassis. In the case of the RF section, there are screening cans on top and below the chassis. The Marconiphone 703 construction is similar but on a much larger scale so easier to work on.
The mask is very brittle and beyond redemption so I have to wing it somehow, starting with advice from the rubber company I mentioned earlier.
Next, I removed the tue. It came out fairly easily but the coils were impossible to move. However, 1A DC through the line coils for 5 minutes softened the goo and enabled me to remove them. The picture shows how badly they were connected and also shows the line linearity control, a really crude type of variable resistor. The slider is simply a bent piece of spring wire bent to form a handle and a small spring looped behind the resistive element to form the contacts. There are several of these, including one without it's slider.
Fortunately, all the capacitor cans are there including a rectangular block which is mounted under the chassis. The photo shows what I assume is a date code on one electrolytic - 392 which could mean Feb. 1939.
Before I remove the RF and TB assemblies, I need to take lots more pictures and make some sketches as it is very tightly packed under the chassis and, of course, all the connecting wires look the same colour.
Slowly, slowly, catchee monkey - is that non-PC? I'm not sure.

[TNC]

This going to be a truly fascinating project - to say I am envious is the understatement of the decade!
Working out how far to restore will probably be a bit daunting but I am sure we will all be rooting for you.

Just a word about the dreaded worm...I note John's comments about the ease with which it can be sorted but I would just mention that my Invicta T105 appeared as easy to treat and I abslutely soaked it in Rentokil woodworm fluid before re-veneering/polishing and restoring the cabinet...yet it still took about 3 years before the odd flight hole finally stopped appearing. What I regret I couldn't do at the time was to put the cabinet in a freezer for a couple of months...this I have been told is the best cure of all - freeze the b.....s solid!!

Best wishes with this exciting project,

Trevor

[Line whistle]

Hi,
Well done on getting this set.
I'm looking forward to reading your progress with it.
Best wishes,
Des.

[brianc]

Originally Posted by TNC

Working out how far to restore will probably be a bit daunting....

I know what you mean Trevor. The wiring is in quite a poor shape and I will have to replace a fair amount of it so do I go the whole hog and replace the lot? I would make sense to do so but it's a rare set and the purist thought will be to leave as much as possible but I will definitely have to use some new cable - the mains I will do in the modern colours anyway. The screening cans are rusty on top so they will be resprayed and so where do I stop. As I said earlier, a plumber has been at it so it cannot ever be "original" again so it will be a majority rewire, respray and cap rebuild - but not to concours condition.
As to woodworm, it's a pity the really cold period is over because I could have left the cabinet under our covered awning over winter to kill the bu**ers. Rentokil and a plastic bag for as long as the project takes will have to do. By the way Trevor, I have an Invicta T105. A strange combination of two Pye models.
Thanks for your encouragement Des. More anon.

[brianc]

To give a better idea of the 815, here are a few more pictures - underneath is worse!

[FERNSEH]

Hi Brian,
My Pye 838 TV-radiogram combi employs an similar TV as your 815.
The set has been in my possession since 1988, a time when one find pre-war TVs at reasonable prices.
The EHT transformer was rewound by the Majestic Transformer Company shortly after I acquired the set. The wet HT electrolytic capacitors have been reen replaced along with a few paper capacitors in the frame timebase.
The sound output valve in the Pye 815 is a Mullard EL3N, it is electrically similar to the EL3 except it has smaller diameter bulb. The valve is used as a focus stabiliser in the 838. The sound output valve on the radio receiver does the TV sound.
Possibly the most difficult valve to find for the 815 and 915 TV receivers is the specially made for Pye 6153T frame output valve. It's a modified ECH2 radio frequency changer valve, the oscillator injection grid is removed in the heptode section. The Mullard maintenance manual suggests that the ECH21 can be used as a replacement.
The CRT is a Mullard MW22-1 which has a 4 volt heater or the Mullard MW22-2 which has a 6.3 volt heater.
Both tubes employ a complex hexode gun assembly even though normal magnetic focusing is used.
I look forward to seeing results of your work on the 815. The picture quality one can get from these little Pye sets is quite amazing.

DFWB.

[Heatercathodeshort]

Looks good to me Trevor. I think the R.F. strip uses EF8 side contact valves hence the strange 'sunken' look. I agree with TNC Trevor about the woodworm but with a little care it should not be difficult to eradicate it. It amazes me the bodges that take place with these vintage receivers but looking at the access you can imagine how the service guys heart sank when he came across a pre war receiver compared to say a Bush TV22, Ferguson 941T or a Pye B18T/LV30. Get it working and get out! That must have been the general idea and I would have wholeheartedly gone along with it.. I reckon it's going to be a real nice job when finished. J.

[ianm]

Hi Brian,

Thinking about the challenge presented by the poorly screen mask, you may recall that forum member taipai_royal is also restoring one of these sets. From memory, the mask on his set is in very good condition; perhaps worth keeping in mind should you need a reliable reference to look at.

[Retired]

Hi Brian,

I too will be following this thread with great interest and in particular your chassis work as I hope to pick up a lot of tips whilst work is in progress so plenty of information please to help novices like me.

It certainly looks a great challenge and could well turn into a saga; after all my own story started with nothing more than a simple enquiry and grew out of all proportion.

Woodworm is a major problem and usually the flight holes are the least of the worries as the worm cause so much unseen damage inside panels and framework; much of my cabinet had been eaten hollow hence I resorted to completely replacing large sections of the cabinet. filling worm holes is difficult although over veneering with new veneer would completely hide them but then of course you end up with a mother of all restorations.

The very best of luck with this restoration Brian; take your time and enjoy it.

Kind regards, Col.

[brianc]

Originally Posted by Heatercathodeshort

I think the R.F. strip uses EF8 side contact valves hence the strange 'sunken' look.

It uses EF6s, John. The sunken look comes from the method of construction. I've seen pictures in 1930s books on VHF receivers showing the valves mounted in alternate orientation (head to tail) so the anode pin in the base of one valve is close to the grid top cap of the following one - this is the first time I have seen it in the flesh! The valve bases are mounted on pillars about 7 eighths inch high recessing the valves. The pictures tell all. I'm sure you are right about the erstwhile service guy back in the '04s & '50s meeting one of these service nightmares! The chassis had to come out just to change some of the valves.

I've located a 6153/T Dave, so if mine's duff, I have a replacement standing by. I tested the one in the set and the hexode section tests very high but the triode is spot on (no gas). The envelope is one of those tall, parallel tube affairs which seem to be fairly unusual.

Thanks for the tip about Taipai-Royal, Ian. I have PMed him.

As to the woodworm, Col, there seems to be no real "cavitation" so no reconstruction will be required (TG). The few flight holes in the external finish will be filled with wax. I have a furniture restorers (bodgers) cabinet which is full of different coloured waxes so I can get a match.

[Boom]

Would a TV24 mask help at all? I have a good one under the bench but I suspect the aspect ratio will be wrong.

[FERNSEH]

Hi Brian,
Here's two pictures of my 838.

David.

[brianc]

Originally Posted by Boom

Would a TV24 mask help at all? I have a good one under the bench but I suspect the aspect ratio will be wrong.

The TV24 uses, I believe, a CRM121 which is 12" so no thanks Boom but kind of you to offer.

Thanks for the pictures, David. I'm glad mine's not so big (the 703 is enough for SWMBO .

A bit of bad news this afternoon. I know that the vendor of this set showed a picture with light on the screen, but I now find that the mains transformer has a couple of problems. One half of the HT winding is O/C - the feedout wire has snapped off and I can't find the end inside the winding-yet!! The second is that the EHT winding is O/C. I can't see any sign of arcing but it could be that it happened because it was switched on with full mains after 20 years . The transformer will need rewinding so I will have to strip it down, removing the mains tap panel, the tag board and the rectifier platform, carefully marking each lead. A problem will be that the systoflex used to insulate the wires is brittle and could snap off.

The good news is that the RF side looks to be in very good condition thanks to the screening cans. The pictures show the strange construction, and the push-pull vision detector with its 2 diodes. With the transformer removed, access is much better but I will remove the TB and RF chassis in order to rebuild them. I can power them up using bench power supplies to ensure their function before refitting them to the chassis. It's a pity about the transformer but not the end of the world - well, not quite!

[FERNSEH]

Sorry to hear about the condition of the mains transformer. I had the same problems with the original transformer in the 838.

The full wave video detector is unusual for a TRF receiver. It employs two T6D (EA50) diodes. Also, the detector drives the CRT direct, there is no video amplifier. The CRT has special characteristics and will operate with a low video drive of 20 volts, rather like the Emiscope 6/6.

DFWB.