21st Feb 2021, 8:02 pm | #161 |
Heptode
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 988
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Re: My first telly TV22
Hi Travellingwave,
that's a great picture. I've had a little look and I don't think I have a TV22 focus magnet here. It will have to wait until restrictions relax. I will look in a couple of other places though just in case. and I will send you a PM if one does turn up. Anyway, time to enjoy watching it! Cheers Andy
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22nd Feb 2021, 7:55 pm | #162 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
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Re: My first telly TV22
Hi Andy
Thanks for the offer - any way would you believe it , I got to putting the case back on and guess what dropped out of the case - the focus magnet follower pin. So Im all sorted. Just getting my raspberry pi sorted as a media player Then I have to negotiate with SHMBO about where it can live!! |
22nd Feb 2021, 8:41 pm | #163 |
Heptode
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
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Re: My first telly TV22
Hi Travellingwave,
That was a lucky find! I hope the negotiations go well. I find that kind of thing much harder than the actual restorations! Cheers Andy
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23rd Feb 2021, 10:01 am | #164 |
Pentode
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Location: York, North Yorkshire, UK
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Re: My first telly TV22
I have secretly placed it in the dining room - see how long it takes SWMBO to notice!
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23rd Feb 2021, 9:42 pm | #165 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
Oh dear
Been giving it a bit of a soak test ( running for and hour or so) and have lost picture , still have audio so presumably heaters are still up. Will have to investigate tomorrow |
24th Feb 2021, 11:02 am | #166 | |
Nonode
Join Date: Feb 2005
Location: Worcestershire, UK.
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Re: My first telly TV22
Quote:
Steve
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24th Feb 2021, 11:48 am | #167 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
So got it back on the bench
Looks like the line output stage has died - No line whistle no EY51 heater. I have checked the voltage at the grid of the PL81 and get -10v wrt chassis - so I take it this means I have line drive - interestingly when I apply my DMM to the grid I seem to get a line whistle coming back (I think) nothing on the screen though - and I can probe and check the EY51 for life at the same time. I have checked the windings of the LOPT for resistance and they seem somewhere near right though I know this proves nothing much as there coud be a shorted turn. Any ideas what I can check to prove health of LOPT? I have a NOS PL81 arrived just this morning. |
24th Feb 2021, 11:50 am | #168 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
SWMBO notice it and did not protest too much so I think I got away with it!!
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24th Feb 2021, 11:50 am | #169 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
She was more upset by the smell of T cut as I polished up the cabinet
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24th Feb 2021, 11:53 am | #170 |
Heptode
Join Date: Jan 2003
Location: Tewkesbury, Gloucestershire, UK.
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Re: My first telly TV22
Were the flowers a peace offering?
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Keith Yates - G3XGW VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm |
24th Feb 2021, 1:19 pm | #171 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
Flowers were already there!
So there is definately some line whistle coming from the LOPT , but no lif at the EY51 , anode 1 volts on CRT measures 40v using the peak hold function on my DMM (I got 300 volts before) the line whistle sounds a bit erratic almost as though there may be some sparking going on within the primary of the LOPT. So I'm fearing the worst - but this is always a danger when fault finding. Any other things I can check?? Thanks |
24th Feb 2021, 2:28 pm | #172 | |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
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Re: My first telly TV22
Quote:
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24th Feb 2021, 2:45 pm | #173 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
Hi Helder
No I didn't I was a bit worried that if I covered the whole thing in varnish inside the primary that it would not neccesarily get to where it needed to go and would make a hell of a job to dismantle if a fault subsequently occured. SO I just coated the overwind. I have just checked and I have have about 50 ohms between the primary and secondary of the transformer with it still in circuit - I have read that they often fail with secondary to primary shorts - if I measure in circuit I presume there should be no resistance here? Looks like lopt is going to have to come out |
24th Feb 2021, 3:30 pm | #174 | |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
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Re: My first telly TV22
Quote:
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24th Feb 2021, 3:34 pm | #175 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
Well got it out and definately short between primary and secondary - well 30 ohms so near as damn it.
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24th Feb 2021, 3:43 pm | #176 |
Heptode
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 988
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Re: My first telly TV22
How rusty are the laminations?
This can effect the line output transformer enough to cause problems with a self oscillating stage. A good ECL80 is more important than a good PL81. Note that once the transformer has failed such as to prevent oscillation, then the PL81 will be biased fully on and this will quickly kill the valve and further damage the transformer. If you are very lucky then the fault is something simple like failure of one of the two 2uF capacitors, such as the one on the scan coils. If you find the top deck valves glowing brightly, but some of the rf valves cold, then one of the heater decoupling capacitors on the RF deck has gone short, you can just snip one end as a temporary fix. For some reason this fault sometimes also stops the line time base working. Have to stop there for the school run! Cheers Andy
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24th Feb 2021, 5:23 pm | #177 | |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
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Re: My first telly TV22
Quote:
Anyway, I hope you can get it rewound fast and get the set back up and running. It sure looks great in your room. Helder |
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24th Feb 2021, 6:21 pm | #178 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
Thanks Helder , should have followed your advise more closely.
Any way since it was a very clear primary/secondary short at least I’m not wondering if it’s the LOPt or some other fault. I have started to carefully dismantle the transformer. I’m inclined to have a go at rewinding it myself , unless people really feel this is a daft idea. I see others have managed it. I am taking very careful notes and pictures as I go so the process can be reversed as closely as possible. Might even start a little side project in the form of an automatic coil winder I guess life would be boring if stuff just worked!! |
24th Feb 2021, 6:25 pm | #179 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
Inner coil and laminations removed
The laminations have suffered some corrosion and swelling at one end. Good smell of white spirit so Helder right it does get in. As I unwind it will get a better idea how well the spirit has impregnated the paper. |
24th Feb 2021, 7:42 pm | #180 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
Have ordered some double insulated 0.25 mm enabled wire, and some polyester transformer tape, 60 microns thick.
Have also ordered a 4 axis CNC shield for arduino , for next to nout, so a coil winder is def on the cards. |