Yes, I’ve started on another project, and no, I haven’t finished any of the earlier ones yet! Although, you could look at it this way, this project actually arrived long before any of my current ones! I think I’ve had the set since around 2004, purchased from the NVCF as it was known back then, and almost certainly when it was at the NEC in Birmingham. I can remember it cost me £60, which was rather a lot for what I actually came away with, which turned out to be a total shed!! Let’s just say that ‘got at’ would be the understatement of the century, it looks like Barry the Bodger got a new pair of side cutters for Christmas, and thought he’d try them out on this poor old PYE.. There were wires just snipped for the hell of it, components snipped out and missing, valves missing, anudio output transformer missing and the top cap connection missing from the PL38.
Back in 2004 I didn’t really know enough to be able to do much with it, I managed to collect enough valves to complete the set, but as for the snipped wires, I was lost! It also turned out the dropper was O/C on the 365 ohm section too.
I can’t remember when, but I must have had a go at it at some point, as I’d connected up the heater circuit, and stuck an under rated polo section on the dropper, and also tacked in some new caps in the line stage where the old ones had gone missing from, but obviously never got much more than the heaters lit. The CRT was good, I know that because it got robbed for another set! So it currently has a duff one fitted.
I decided to have a poke at the poor thing this weekend, after seeing a member on UKVRRR revive one. If I could get it to produce EHT, then it’s a go-er, if not it’s scrap! So with that in mind I checked over the replacement caps, which were wrong, and checked the wiring was connected mostly, certainly the wiring for HT to the line stage, then gave it some mains!
The heaters lit, except the tube because it’s heater is toast, and the HT came up to about 210V, and not much seemed to be happening, no whistle. I poked the meter about on the Lopty primary with it set to read frequency, and it showed around 18KHz, so something was oscillating! After a while there was a very faint whistle which could be varied with the line hold control, and a tiny spark from the anode of the EY51, checking with an EHT meter with a rectifier stick attached showed only about 250V coming out of it.
I then looked at the power circuit closely and came to the conclusion that it was wired wrong according to the manufacturer’s data, and wasted some time re-wiring it, only to find that if you look at the trader sheet, it was actually correct the way it was! It seems there were 2 different versions of the set, and I’m not talking about the BV30, even the layout under chassis is different between the manuals. So I put it all back again!
The one part I’m missing from the set is the thermistor on the dropper, a CZ1, and so far I haven’t found any info on what it’s resistance should be when hot, so I’ve been running without it, much to the disgust of the 400 ohm polo dropper! A dig through some power resistors unearthed some big 560 ohm wirewound ones, so I croc clipped one across the 400, and wound up the variac slowly. The heaters came up a bit brighter than before, and the line whistle started up before the HT had got past 170V, once the HT got to 210V the whistle was much louder than it had been before, and the EY51 was lit! A check with the EHT meter showed 5KV! The frame stage also began making noises too, a sort of quiet screeching noise that varies in pitch with the hold control. I think it’s time to pull a tube from another set to see what, if anything, will be visible!
Regards,
Lloyd
I will tidy those caps up eventually!
I like it Lloyd. 👍
Just think of all the knowledge you have gained since 2004.... you have the power to restore !
To understand the black art of electronics is to understand witchcraft. Andrew.
The one part I’m missing from the set is the thermistor on the dropper, a CZ1, and so far I haven’t found any info on what it’s resistance should be when hot,
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Cheers Chris! That’s just what I needed 🙂 looking at that the resistance drops to 44 ohms when it’s operating at its maximum current, so I could probably get away with sticking an even lower resistance in there for test purposes. I think I’ve got a CZ1 on another TV22 chassis that’s in the lock up.
I certainly have come a long way since 2004, I cringe at some of the things I used to do back then!
Regards,
Lloyd
The PYE doth glow!!
first light at last, something I never thought I’d see! I’ve pinched the tube from my TV12, which I think may actually be the original tube from the PYE in the first place, I do keep playing musical tubes with these 9” sets… I really must find another 9” tube!
I have straightened the scan coils after that, the frame circuit is going to be next on the hit list, I think it’s running too fast by the sound it’s making, the height doesn’t have much effect, and the hold varies the speed a little. The RF part is not going to be easy, there are bits missing, and one of the coils wound on a resistor is trashed. I might try bodging in the RF chassis from a TV22! I could even make this just a monitor and do away with the RF part..
Regards,
Lloyd
Ouch! Now that is one thing I would add if I were to make this a monitor (I could change the model to MV30!).
Looking at the RF chassis it is looking more likely that a monitor conversion could happen, there’s several coils missing that will be very hard to find replacements for. Someone really didn’t like this set!
I got a bit more life out of the set tonight, I found a big 50W 36 ohm resistor and stuck it in place of the missing CZ1, wound it up on the variac whilst monitoring the voltage on the CRT heater, I still didn’t get 6.3V, just made it to 6.1V, that got more height, and more EHT, which is now 5.5KV with a bright raster, and 6KV with the brightness turned down.
Regards,
Lloyd
More fun and games! I’m slowly working through the mangled tag strip, where most of the components have either been snipped at one end, or totally removed. On this tag strip are the components for the video amp, audio amp, sync separator and interlace filter. I have managed to work out that the resistor and capacitor that go from the cathode of the video amp to ground had been removed, so no video amp action, having reinstalled them I now have activity on screen! So to just for fun I connected the video output of the Hedghog to the grid of the video amp and we have a picture! Albeit a floating one with no sync at all, because I now need to rebuild that too.
For safety’s sake I should add that I have the set powered through an isolating transformer, and also the Hedghog is powered by its own isolating transformer rather than a switch mode brick. This should NOT be done on a set connected to the mains directly, and should also not be done by anyone inexperienced, these sets are LIVE CHASSIS.
Regards,
Lloyd
Sync separator is now sort of working! Line lock is just about there, but weak, and frame lock is so weak it might as well not be there, but it’s a start! The picture has a really nasty hum bar running through it, not sure if that’s another dead electrolytic or a ground loop problem from my dodgy lash up. Still nothing from the RF side of things, but that’s probably down to the lack of HT to that part, there is still a couple of wires hanging loose. I haven’t rebuilt the audio stage yet either, mainly because I don’t have the output transformer for it! I’ll have to search eBay for something suitable, or stick a small mains transformer in there for a test.
The picture focus is rubbish too, I have a feeling that may be my fault, back in 2004 I did rather like stripping things down to polish them, and almost certainly did the focus magnets… I’ll have to play with them and see if I can get them back to somewhere sensible!
regards,
Lloyd
The frame sync on Pye sets is normally very solid because of that twin-diode circuit they use; as ever, make sure that the components around the sync. sep. are up to spec but also, check that the video feed to the sync. sep. is not lacking in LF due to loss of capacity in the coupling components - loss of capacity in C10A on the Pye service sheet would not help in this instance!
C8A video output screen decoupler would also cause poor LF response and could cause poor frame sync.
Frank
I’m working from the trader sheet currently, as it matches up with my set, while the manufacturers data has quite a few differences, some of which are in the area mentioned. C10A is still in the same place (can’t remember what is number is on the trader) and I have still to change it, I’ll have to look up what C8A does when I get back.
I have managed to get frame sync now though! Mr Snippit had been at the components between the cathode of the interlace filter EB91 and ground, the wire looked like it was connected, but I was getting zero volts on the resistor and cap, and sure enough poking the wire it came away, sorting that out the frame sync began working, still a little weak, but it does lock at least!
Regards,
Lloyd
C10A is still in the same place (can’t remember what is number is on the trader) and I have still to change it,
C28.
I’ll have to look up what C8A does when I get back.
C8A (C26 on the Trader) is the screen grid and anode feed decoupler for the vision output valve, as Frank stated a couple of posts back.
Ah, he did 😳
I hadn’t changed that one, so tacked in a replacement, I haven’t got any 12uf’s so fitted a 22uf, and it has improved even more! It seems all the small electrolytics are past their best, all the others have had to be replaced too. The tag on it came away from the rubber bung when I tried to un solder it, looked like it had rotted off inside, so I’ll get a list together and put in an order for some. I’ll try C10A (C28) tonight, see if that also improves things!
I have some thermistors on order too, I spotted some TH1A’s which sounded very similar to CZ1’s, then I can tidy up the dropper, and then tidy up my tacked in components underneath, it needs it, it actually looks worse than when I got it at the moment!
Regards,
Lloyd
A long time ago I encountered weak sync in a Bush TV80; this was due to there being DC getting on to the control grid of the sync sep which actually crushed out the sync! Once we'd replaced the leaky cap causing that, it had the strongest lock of any TV set I have seen in ages.
I’ve stuck the scope on it, see what you think? I did wonder if the Hedghog outputs enough signal to drive the video amp directly. The sync coupling cap is brand new, as the original was totally missing!
The sync does seem to be working ok, it does take quite some time to settle down from cold, but once it’s settled it stays locked.
I thought it’d be interesting to see if I could get a proper RF signal through this thing, after looking at the RF strip it seems that it’s been mostly left alone, nothing snipped out underneath, just bits chopped off above chassis, some of the little chokes in the heater chain were missing, and I bridged them out to complete the chain, the only other notable destruction was on the little tag strip at the back, L21 was destroyed and most of the caps are either Hunts, missing, or snipped at one end! The video signal from the RF chassis goes through L21, so nothing was getting through, just for a test I bridged it out totally, and fed in a channel 1 signal from the Hedghog, to my utter amazement a picture came through! It needed the contrast turning up, but it actually works! No tweaking of the tuning required either. It’s a bit noisy, with some patterning, which could be a number of things, the missing parts, my naff lash up RF lead, something noisy in the shed… but it’s looking like this set is going to be a good one, if I can work out what I can replace that coil with.
The picture focus is still awful, I’ve tried a few things, like rotating the tube a bit, different ion trap, new EHT rectifier, but it’s still crap. One thing that did work was sticking a magnet to the focus assembly, but that’s not a good cure.
New thermistors arrived, and I’ve fitted one, it seems ok so far! I also found the break on the dropper, and have managed to reconnect it, not a permanent fix, in fact I may remove the 365 ohm section and replace it with a big metal clad resistor, as the original dropper runs really hot.
Regards,
Lloyd
That's great work indeed. The little choke you have in your hand is for HF frequency correction in the feed to the tube's cathode. Now, the choke is wound onto a resistor not just because it's expedient to do so but it also offers some damping of the 'Q', thus minimising ringing.
If you tend to use the Hedghog video out on tv chassis, it would be a good idea to add the 330uF ceramic capacitor on the video out as protection. It is something i have had to repair several times for people, it only usually only damages the video amp chip.
thats a good idea, I’ve just checked and I didn’t fit those. I did however connect a 400V 0.1uf between the TV and the Hedghog, just in case! I always check for voltage before connecting it too.
interesting, I wonder if one from a TV22 RF chassis would do it? The TV22 one isn’t wound on a resistor, but in the circuit is shown with one connected in parallel with it.
Im going to have to put a wanted ad out for this set, mainly for the focus assembly, I think my cleaning efforts back in 2004 knackered it! That photo from yesterday the focus looked great, but I can’t get it anywhere near that today.
Regards,
Lloyd
