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B&W TV Going through my sets in storage .

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slidertogrid
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Number one. Sobell Dual standard that identifies as a GEC...

It is time started sorting out some of the sets I have in store in a spare room. Some of the sets have been there for many years and have never been powered up in my ownership!  I have decided to go through them and see what we have. Somewhere behind the pile is the 'Barrel' Murphy that came from Chris as a chassis and tube! It must be years since that saw mains! 

Anyway first on the bench is this 19" Sobell. It came from a friend of a friend who found it dumped on the pavement outside a house that was being renovated. I stored it in my spare room as a potential spares set for my 23" Blue front GEC. Which again has never been powered up since I got it many years ago! 

The Sobell is too good to break though, It has a knob missing and is slightly tatty but is all there and pretty much untouched. The strange thing is though it is badged as a Sobell but has a GEC model number sticker on the line output shield?

Judging by the dust the shield has been there many years maybe the wrong one was refitted years ago in a busy workshop? Maybe GEC ran out of Sobell stickers? Maybe in it's long life it has decided that it was born a Sobell but feels that it should be a GEC? These things do happen...

I had a look around the chassis, one section of the dropper has been bridged with a couple of resistors the thermistor has been replaced with a resistor not surprising as they used to fall apart and were often shorted out in the 'bangers' I saw back in the day. But no obvious horrors.

I put a meter across the HT line and wound it up slowly on the variac. The smoother was holding a charge when I wound the voltage down so it looked promising. After an hour of slowly increasing the mains voltage I wound it up to 240 Volts.

It lives! Well limps... I have a reasonable picture.

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The system switch is intermittent as is the VHF tuner and band switch, the tube is improving rapidly and the LOPT is running cool. The picture also 'swims' I am not sure if this is a line sync fault or down to poor smoothing.. It has a frame fault but it looks promising! 

If anyone has a spare knob for the UHF tuner I would be eternally grateful! The set looks to have a future! 

 
Posted : 21/07/2023 2:19 pm
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Nuvistor
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@slidertogrid 

This is the model I took my C&G Final exam in I think 1968 or 69, I had not seen one before  but it was straightforward to work on, 4 faults, sound and frame but forgotten what those were. The other two were O/C print on Line output valve cathode and S/C video detector diode.

Happy days, the exam was at Riversdale Technical college in Liverpool, it’s no longer there demolished a while ago. 

Frank

 
Posted : 21/07/2023 6:54 pm
slidertogrid
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When I did the exam we had to work on Thorn 1500s they had a row of switches on the side to set the faults all wired with green wire so you couldn't follow the wires!  You had to work on the back of the PCB no opening the chassis was allowed! I can't remember the faults they set.

 
Posted : 23/07/2023 7:22 pm
Cathovisor
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@slidertogrid They also used to that in the BBC; in my case, it was a valved Philips black and white monitor. First (and only) time I saw an EL- line output valve!

 
Posted : 23/07/2023 7:58 pm
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slidertogrid
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Number two. The Murphy that came from Chris as a chassis and tube some years ago. kindly delivered by Mike.  Chris had restored the chassis to working order but it was minus the case. It was offered for sale when Chris sold off his Mono TV collection.

The Cabinet came from a friend I hadn't seen for years 1977 in fact!  When we were at school we would prowl the local TV shops for old sets quite a few of these Murphys came our way. My friend had one as a bedroom set when I saw him again (in around 2014 I think.) I mentioned that I still had the Invicta 7070U that I had got back then and I said "I bet you haven't still got the Murphy"?  He said that he had still got the set and as he was intending to emigrate would I like it ? Some days later the Murphy arrived at my house and with it came a spares set. The spares set had no tube, no valves and a few other parts missing. So an Ideal parts donor to make the chassis Chris had complete again.

So the set consists of the Chassis and tube from Chris, the case, lid, back, mask, glass and front Bakelite surround from the scrapper.  The other Murphy was overhauled and lives in the workshop this second set after a few run ups was consigned to the spare room. I don't really need two but I didn't want to part with either set for various reasons. They are two different models one 90 degree and the other original set 110 degree so there was the excuse I needed to keep both! 

Today I dug the second Murphy out and gave it a dust off. I put it on the Variac and slowly increased the voltage over an hour or so. At 200V I was expecting some signs of life but there was none so I slid the case off to take a look. HT was present at the fuse but no signs of life from the heaters.

After a few checks of the easy to access valves and tube heaters I went 'round all the valves giving them a rock and ensuring they were all pushed home. There are a lot of valves in this set and I wasn't relishing chasing the heater volts 'round the set. Didn't need to as switching on again I had heaters! So it was either a valve not seated or not making contact or removing and refitting the Boost diode and line output valve restored the circuit.

After a while the screen lit up so I connected the converter and lashed up a speaker. The set has what appears to be an AGC fault there is very little screen activity until I attenuate the signal then I get a buzz on sound and lots of wiggery lines on the screen. Giving it full signal results in a blank screen and no sound.

Hopefully nothing serious! I'll have another look tomorrow.... Chris? How long was the Guarantee? 😉

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Posted : 23/07/2023 8:40 pm
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crustytv
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Posted by: @slidertogrid

Hopefully nothing serious! I'll have another look tomorrow.... Chris? How long was the Guarantee?

Good lord, now there's a blast from the past. Nice to know the V410 finally found some trousers!

I can't believe I restored the V410 back in 2012, that's 11-years ago, not surprised it might cough up a fur-ball or two by now. I'd only started on my TV repairing journey just two years prior to working on that TV. It was a fantastic set and I was also just learning to drive a scope too.

Now, as to the guarantee, unfortunately, Rich, that was only for 10-years. You're 1-year, 4-months too late, isn't it always the case.  😉 

CrustyTV Television Shop: Take a virtual tour
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Posted : 23/07/2023 9:44 pm
slidertogrid
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Damn ! I knew I should have taken out the extended Guarantee!  Joking apart it didn't take a lot of fixing.  I assumed wrongly that the BBC setting on the tuner was channel 1 I was running the set on my Pineapple converter which is channel 1 only.  Putting the set on the Hedgehog and clicking through proved that BBC is set to channel 5 the set only has two sets of coils one for BBC and one for ITV which I seem to remember was common for these sets, they weren't fully loaded. It is puzzling as I definitely ran the set up when I first got it and thought that back then I only had the Pineapple but I must have had the Arora as well. Anyway turning down the contrast and setting the brightness has resulted in a very nice picture! 

I just did a search and found the post Chris did in 2012 when he had the set I am going to re read it. I think I will swap it over with the set in the workshop which I think is a V310 ? (110 degree version) and give this set a few runs and the other one a rest. 

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Posted : 25/07/2023 11:44 am
Cathovisor
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Posted by: @slidertogrid

I think I will swap it over with the set in the workshop which I think is a V310 ? (110 degree version) and give this set a few runs and the other one a rest. 

The V310 is the 70° set - the V500/V510 are the 110° models.

http://www.murphy-radio.co.uk/murphybilia/cats/Better.pdf

 
Posted : 25/07/2023 12:06 pm
slidertogrid
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Ah sorry yes my other set must be a V510 then it's on a reasonably high shelf so I can't check until I swap it over, but as I am going through the sets in the spare room the workshop is somewhat cluttered at the moment! I have a lovely little brochure booklet that features the V410 amongst others I have no idea where it came from maybe from the shop I used to get the sets from in the '70s there was always interesting things to be found in the bin!

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Posted : 25/07/2023 2:38 pm
Nuvistor
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@slidertogrid 

I only saw a few of the V410 series but they did work very well, I think the 30P4MR problems were in the 310 series.

A scan of the brochure would be a nice addition to the library.

 

Frank

 
Posted : 25/07/2023 4:43 pm
Cathovisor
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@nuvistor That's interesting, because if you go to http://www.murphy-radio.co.uk/murphybilia/murphy_bilia5.html you'll note that in this case, there are separate radio and TV catalogues; is Rich's a "combined volume", as us trainspotters once used?

 
Posted : 25/07/2023 5:45 pm
slidertogrid
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Yes my Brochure features Televisions V410 V410K V410C V430D V420 V430K V440D V350S V350. Radios B385 B283 U501 U502 U512 U506 U472 A482 A474. Record players A316G A316R A492R and Radiograms A494SR and S1. including prices, quite a range. I may be able to get it scanned if required. 

 
Posted : 25/07/2023 6:51 pm
slidertogrid
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Number Three. One of my favourites a late 20" A640 Coop Defiant.  This set came from a local collector that had done a lot of work on the set and it worked well before it was stored.  I had high hopes that it would work and it pretty much did. I gave it a fairly slow warm up on the Variac  when it was up to 200 volts I had a small picture so I gave it full mains.

The hold controls and the system switch were a little iffy but a few twiddles later they settled down and the set produces good pictures on both standards. The line lin is a little out and it looks as if the coil has been rewound.

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I can't get it to adjust so I may replace the coil with a spare I have on a spare panel.

I noticed a tell tale sign on the tube neck and sure enough the tube is a re-gun a really good re-gun as well! Other good news is that the LOPT is a replacement and runs cool. The set has had some capacitors replaced and remains stable.  This is another one that deserves to be in the workshop, running!

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Posted : 27/07/2023 2:38 pm
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Tazman1966
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You really can't beat the Rank A640 chassis for performance in that era. I have a Bush TV161 and after a lot of replacement resistors that were MILES out of tolerance causing all manner of faults, and a few capacitors too, it is working beautifully. It's on the bench at the moment though as I need to glue a coupe of the speaker slats back on. I'll have to get a suitable clamp to hold them in place when the glue sets though.

 
Posted : 29/07/2023 9:48 am
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slidertogrid
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Next is a Murphy V929U which is the same chassis as the Bush TV135RU Which I also have in my collection. The Bush uses a direct vision 'Panorama' Tube. This Murphy has a Mazda Goldstar with a Fenbridge guard. This set has been stored since I bought it about seven years ago so I thought today I would see what it is like.

The first thing was the 405 contrast control is broken the good news is that the LOPT is a replacement so fingers crossed! I brought it up slowly over an hour or so I found I had sound on 405 but nothing on the screen, on 625 I just had a background noise but no signs of any sound. 

So i plunged in and demonstrated an afternoon of arse-about -face fault finding! Ht was present on the top caps so I tried a new PL36 then a new PY801. Then I did what I should have done first and checked the screen volts on the PL36. None! Screen feed resistor open circuit. Result! Plonked in a new resistor and no change! 

The resistor was definitely open circuit and I had HT on the PY top cap but nothing on the resistor... System switch not making on the 405 contact. Clean contact but find switch only just makes it over enough to the 405 contact maybe out of adjustment...

Anyway finally screen volts and a picture of sorts on 405. 

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Switching to 625 showed a blank raster. Checking the system switch on the IF and I found it wasn't going fully over to UHF it looks as if there is a problem 'button end' of the cables... I took the cable off the switch and pushed it home onto UHF. Now I could tune in a picture with the same problems as on VHF, cogging and pulling with weak sync. It looks like i may have capacitor problems ! The LOPT is holding up and the tube is good so another set with potential! 

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Posted : 29/07/2023 6:52 pm
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Nuvistor
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@slidertogrid 

The screen decoupler of the video amp  and the one on the sync sep dry up, the flywheel sync diodes fail and also the chassis connection on the time base PCB goes high resistance.

Frank

 
Posted : 29/07/2023 10:17 pm
slidertogrid
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Thanks Frank, I will check those points. There are at least two of those black and red Plessey electrolytics that are held together with yellow sticky tape I bet they are duff for a start.   

 
Posted : 30/07/2023 6:32 pm
Jayceebee
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@slidertogrid You mention you replaced the boot diode with a PY801, I'm not 100% sure but I think the correct valve is a PY88? If I'm correct here's a 13v difference in heater voltage between the two so using a PY801 will overun the heater chain a bit.

John.

 
Posted : 30/07/2023 7:26 pm
slidertogrid
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@jayceebee I wondered about that when I changed it, A PY81/800 was fitted so I replaced with the same.  Checking the diagram today shows that is the correct valve i think maybe the PY88 was used in the earlier non-PCB chassis set like the TV125? 

I pounced on the Electrolytic capacitors first changing them one by one they all tested miles out. That restored the contrast control operation. I have linked the wipers of the two controls so the un-broken 625 control works on both systems for the time being.

The capacitor that cured the cogging fault was a yellow .1uf now I have a fairly good picture on 405. There is a little 'swimming' of the picture which seems common on this chassis and the A640 probably as suggested by Frank caused by the sync diodes. I have checked and me made the earth connections on the frame/line osc PCB just to be sure. The next job will be to reinstate the system switch cables and adjust them to see if I can get the switch working properly. Then I can recheck 625 to see what that looks like.

Considering how little work has been needed, the set works well especially when it still has a lot of original capacitors which must be pretty much expired...

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Posted : 31/07/2023 12:13 pm
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Jayceebee
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The PY88 as most of us know was used in the A640 styles of chassis. I had thought it was used in that style also, maybe in the versions with the transistor IF?.

That CRT looks amazing, excellent corner focus by the looks of things and it's a Mazda. Must be an optical illusion 🤣.

John.

 
Posted : 31/07/2023 12:28 pm
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