Sobell T171 help needed - UK Vintage Radio Repair and Restoration Discussion Forum

jay_oldstuff · 22nd Jul 2006, 9:39 pm

I seem to have one problem stopping me getting this TV running again, someone has been in there and pinched a valve, now the only service data I have is for a McMichael M17T; the T171 being a set with a similar chassis according to Trader sheet 1310/T131, but it doesn't have a valve where I have one missing (under where the aerial socket is).

Anyone out there know what my missing valve should be?
Then I can get some power through and see whether she is a good'un

Jay

mickjjo · 22nd Jul 2006, 10:08 pm

Hi Jay, Attached is a list of the valves used in the Sobell T171 from R+TV servicing 1957/8. You should be able to work out the missing one.

.

Regards, Mick.

Steve_P · 22nd Jul 2006, 10:31 pm

Right, well, I don't know where the AE socket is on this set, but...

V1 - PCC84
V2 - PCF80
V3 - EF80
V4 - EF80
There seems to be no V5 in the list, but the diagram says EF91
V6 - PCF80
V7 - ECL80
V8 - PL81
V9 - EY51
V10-PY81
V11-EBF80
V12-PCL83
V13-PCL83
V14-PY32

Does this help?

Cheers,

Steve P

P.S. Well as I was typing, Mickjo was scanning. Ah well....

jay_oldstuff · 25th Jul 2006, 4:32 pm

Hi all
This one is turning into a bit of a saga; first I bridged the faulty section of dropper with a big 110 ohm wirewound, gave it some juice again and most of the heaters fire up, all but the last four in the chain.
First thought is that one of the caps on the end of the heater string has shorted but all test OK.

Then I pull that PCL83 and the rest of the heaters go out - there's a nice heater cathode short on the PCL83 and I do mean a dead short (0 ohms with my DMM).

Now some more hunting through my verry small stock of TV valves produces another PCL83, well actually a LN309 but they're the same thing aren't they?
Anyway, popped that in and gave it some juice and all the heaters light this time and the line whistle comes up but still a blank screen.
Now, a quick look at the circuit diagram the; I find the EHT rectifier is an EY51 but it's missing so back to the valve junk box and lo and behold, I have one so I go to fit it and realise the LOPT on my set is not the original and doesn't connect up like the one in my service data.

So after a bit of head scratching I work out how to connect it up hoping it should still be an EY51 with the LOPT change. Fired up and after a couple of minutes up comes a raster of sorts.
A little small and flickery but a raster so at least the CRT is OK.
I then glance at the EY51 and it is glowing blue inside and not just a gentle purple so I am guessing it's duff and I dont think I have another.

So, that's where I am up to; never really worked on a TV that has had this kind of tinkering done to it in the past so I am not sure where to go from here, any suggestions apart from obtaining another EY51?

Jay

Steve_P · 25th Jul 2006, 4:45 pm

Good stuff so far! I think from what you say that the transformer is OK, phew!

If you can't get an EY51, you can fit a socket and an EY86/87. That's the same valve but connected with a Socket rather than soldered! Just make sure everything is insulated. Or of course get an EY51. I reckon yours is soft, at a guess.

I don't think there's a lot wrong here. Well, that's my head on the railway line....

Cheers,

Steve P

jay_oldstuff · 25th Jul 2006, 5:38 pm

Thanks Steve
I'm just a little worried that it might not be an EY51 that this LOPT should use, as I mentioned it is not the original LOPT nor do I think it is some RadioSpares pattern kind of part.

I think it was probably just pinched off a scrap chassis to keep this set going, judging by some of the caps in the set it must have been used up until sometime in the mid 70's.

I am just hoping it was not designed to run with a DY51 (think that's the valve

) as I have no way of checking.
Anyway I've found a U151 on a scrap chassis so I am going to try that in a bit, I'll report back

Jay

Steve_P · 25th Jul 2006, 7:03 pm

Just checked - that'll be fine.

Cheers,

Steve P

jay_oldstuff · 1st Aug 2006, 10:09 pm

Now this really is turning into a saga. My new EY51 turned up today (thanks Andy) and I had it fitted in no time.

Fired the set up and a slightly better raster came up this time - not yet perfect though - so I measured the HT and it was a little down, the PY33 looked well worn so I popped in a nice brand new one, powered back up again and was rewarded by a nice bright raster then disaster.
Just as I was considering going and getting my pattern generator and giving it a go, clouds of smoke came billowing out of the turret tuner.

I switched off quickly, after alot of hassle I have managed to remove the turret tuner, opened it up and all I can find wrong is one resistor charred beyond recognition.
I have no data for the tuner unit so:

does anyone have any data relevant to this turret tuner or
does anyone have a spare?

thanks
Jay

Steve_P · 1st Aug 2006, 10:52 pm

I've got the ERT sheet here, and I'll try to upload it, but in the meantime....

1: Clear some space on the bench for the tuner unit. Then dismantle.
2: Clean the thing out thorougly.
3: Change the duff resistor. And see where it feeds.
4: If you're not sure which one, try subbing both valves.
5: Try it Gently....

Cheers,

Steve P

Steve_P · 1st Aug 2006, 11:05 pm

Here's the circuit of the tuner.

Cheers,

Steve P

jay_oldstuff · 19th Aug 2006, 11:24 pm

I've finally fixed the tuner, that Hunts cap was actually OK despite the fact it was falling to bits (replaced as a precaution, though).

Once I had removed the resistor I could see what had happened; the resistor had been rubbing on the moving part of the turret tuner - this had eventually rubbed through part of the resistor taking HT to ground, the replacement is smaller so the same shouldn't happen again.
Anyway back to the rest of the set and to the task of changing the last of the Hunts caps around the line output stage, I might even try to get a picture out of it tomorrow.

Jay

jay_oldstuff · 20th Aug 2006, 10:20 pm

Well she's running

I spent a couple of hours changing caps in the line timebase area.
After that I had a very good raster so a quick check with the old sig gen and nothing - not a peep out of the tuner.
One PCC84 later and, bingo, we have bars across the screen so hook up the standards converter and up pops test card C.
Gave it a video signal and hey presto we have a fairly good picture.
I know it stilll needs a little fine tuning but not bad and the CRT appears to have plenty of life left in it.

Jay

22nd Jul 2006, 9:39 pm	#1
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Sobell T171 help needed I seem to have one problem stopping me getting this TV running again, someone has been in there and pinched a valve, now the only service data I have is for a McMichael M17T; the T171 being a set with a similar chassis according to Trader sheet 1310/T131, but it doesn't have a valve where I have one missing (under where the aerial socket is). Anyone out there know what my missing valve should be? Then I can get some power through and see whether she is a good'un Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

22nd Jul 2006, 10:08 pm	#2
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: Sobell T171 help needed Hi Jay, Attached is a list of the valves used in the Sobell T171 from R+TV servicing 1957/8. You should be able to work out the missing one. . Regards, Mick. Attached Thumbnails

22nd Jul 2006, 10:31 pm	#3
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Sobell T171 help needed Right, well, I don't know where the AE socket is on this set, but... V1 - PCC84 V2 - PCF80 V3 - EF80 V4 - EF80 There seems to be no V5 in the list, but the diagram says EF91 V6 - PCF80 V7 - ECL80 V8 - PL81 V9 - EY51 V10-PY81 V11-EBF80 V12-PCL83 V13-PCL83 V14-PY32 Does this help? Cheers, Steve P P.S. Well as I was typing, Mickjo was scanning. Ah well.... __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

25th Jul 2006, 4:32 pm	#4
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Sobell T171 help needed Hi all This one is turning into a bit of a saga; first I bridged the faulty section of dropper with a big 110 ohm wirewound, gave it some juice again and most of the heaters fire up, all but the last four in the chain. First thought is that one of the caps on the end of the heater string has shorted but all test OK. Then I pull that PCL83 and the rest of the heaters go out - there's a nice heater cathode short on the PCL83 and I do mean a dead short (0 ohms with my DMM). Now some more hunting through my verry small stock of TV valves produces another PCL83, well actually a LN309 but they're the same thing aren't they? Anyway, popped that in and gave it some juice and all the heaters light this time and the line whistle comes up but still a blank screen. Now, a quick look at the circuit diagram the; I find the EHT rectifier is an EY51 but it's missing so back to the valve junk box and lo and behold, I have one so I go to fit it and realise the LOPT on my set is not the original and doesn't connect up like the one in my service data. So after a bit of head scratching I work out how to connect it up hoping it should still be an EY51 with the LOPT change. Fired up and after a couple of minutes up comes a raster of sorts. A little small and flickery but a raster so at least the CRT is OK. I then glance at the EY51 and it is glowing blue inside and not just a gentle purple so I am guessing it's duff and I dont think I have another. So, that's where I am up to; never really worked on a TV that has had this kind of tinkering done to it in the past so I am not sure where to go from here, any suggestions apart from obtaining another EY51? Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

25th Jul 2006, 4:45 pm	#5
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Sobell T171 help needed Good stuff so far! I think from what you say that the transformer is OK, phew! If you can't get an EY51, you can fit a socket and an EY86/87. That's the same valve but connected with a Socket rather than soldered! Just make sure everything is insulated. Or of course get an EY51. I reckon yours is soft, at a guess. I don't think there's a lot wrong here. Well, that's my head on the railway line.... Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

25th Jul 2006, 5:38 pm	#6
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Sobell T171 help needed Thanks Steve I'm just a little worried that it might not be an EY51 that this LOPT should use, as I mentioned it is not the original LOPT nor do I think it is some RadioSpares pattern kind of part. I think it was probably just pinched off a scrap chassis to keep this set going, judging by some of the caps in the set it must have been used up until sometime in the mid 70's. I am just hoping it was not designed to run with a DY51 (think that's the valve ) as I have no way of checking. Anyway I've found a U151 on a scrap chassis so I am going to try that in a bit, I'll report back Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

25th Jul 2006, 7:03 pm	#7
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Sobell T171 help needed Just checked - that'll be fine. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

1st Aug 2006, 10:09 pm	#8
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Sobell T171 help needed Now this really is turning into a saga. My new EY51 turned up today (thanks Andy) and I had it fitted in no time. Fired the set up and a slightly better raster came up this time - not yet perfect though - so I measured the HT and it was a little down, the PY33 looked well worn so I popped in a nice brand new one, powered back up again and was rewarded by a nice bright raster then disaster. Just as I was considering going and getting my pattern generator and giving it a go, clouds of smoke came billowing out of the turret tuner. I switched off quickly, after alot of hassle I have managed to remove the turret tuner, opened it up and all I can find wrong is one resistor charred beyond recognition. I have no data for the tuner unit so: does anyone have any data relevant to this turret tuner or does anyone have a spare? thanks Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

1st Aug 2006, 10:52 pm	#9
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Sobell T171 help needed I've got the ERT sheet here, and I'll try to upload it, but in the meantime.... 1: Clear some space on the bench for the tuner unit. Then dismantle. 2: Clean the thing out thorougly. 3: Change the duff resistor. And see where it feeds. 4: If you're not sure which one, try subbing both valves. 5: Try it Gently.... Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

1st Aug 2006, 11:05 pm	#10
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Sobell T171 help needed Here's the circuit of the tuner. Cheers, Steve P Attached Thumbnails __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

19th Aug 2006, 11:24 pm	#11
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Sobell T171 help needed I've finally fixed the tuner, that Hunts cap was actually OK despite the fact it was falling to bits (replaced as a precaution, though). Once I had removed the resistor I could see what had happened; the resistor had been rubbing on the moving part of the turret tuner - this had eventually rubbed through part of the resistor taking HT to ground, the replacement is smaller so the same shouldn't happen again. Anyway back to the rest of the set and to the task of changing the last of the Hunts caps around the line output stage, I might even try to get a picture out of it tomorrow. Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

20th Aug 2006, 10:20 pm	#12
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Sobell T171 help needed Well she's running I spent a couple of hours changing caps in the line timebase area. After that I had a very good raster so a quick check with the old sig gen and nothing - not a peep out of the tuner. One PCC84 later and, bingo, we have bars across the screen so hook up the standards converter and up pops test card C. Gave it a video signal and hey presto we have a fairly good picture. I know it stilll needs a little fine tuning but not bad and the CRT appears to have plenty of life left in it. Jay Attached Thumbnails __________________ The light at the end of the tunnel is probably the headlight of an oncoming train