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Old 17th Jan 2021, 7:42 pm   #41
beery
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Default Re: My first telly TV22

Hi Travellingwave,
it looks like you have a TV22U or a TV22P, or simply a very late version of the TV22 (just before the TV22A was released) hence the 8K resistor. The set should also have a miniature PL81 for the line output instead of an octal PL38, can you confirm?
Trader sheet 1091 mentions this under 'Modifications'.
That resistor looks to be at least 10W, an 8K2 replacement would be fine.

Cheers
Andy

Last edited by beery; 17th Jan 2021 at 7:43 pm. Reason: Added 8K2 suggestion
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Old 17th Jan 2021, 9:42 pm   #42
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Yes it has a PL81.
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Old 17th Jan 2021, 9:46 pm   #43
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Yes I see the modification on the trader sheet makes sense now Thanks
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Old 27th Jan 2021, 6:49 pm   #44
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Progress has been a bit slow due to work. Have done all waxies on main deck and moved my attention to main smoothing can. I had a go at reforming it , leakage seemed a bit high so have restuffed it. Opened it by filling away the lip holding the lid on.
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Old 6th Feb 2021, 7:14 pm   #45
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Lopt back in after some fiddly soldering. Let’s hope it’s a good un
Bit cleaner than it was
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Old 18th Feb 2021, 11:19 am   #46
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I finally got all the recapping done

Applied power for first time - bit of smoke from some of the power resistors - heaters working, a bit of hum from the speaker.

I measured the HT at anode of V1 and only seeing about 50vdc

At this point I noticed that one of the rectifier valve anodes was starting to glow red hot so killed the power. I think it’s the boost diode side but need to double check , it’s the side indicated in the photo.
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Old 18th Feb 2021, 11:54 am   #47
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After tracing the anode connections visually in the PZ30 Im pretty sure its the main rectifier that's glowing which ties in with the low HT , so somethings dragging it down. If Im right the schematic on the trader sheet is wrong as it has v10a as being the boost diode.
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Old 18th Feb 2021, 2:44 pm   #48
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I guess most likely suspect is line output stage. I checked control grid voltage of the line output valve and have negative voltage here. I’m going to double check my work after replacing LOPt in case I made an error
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Old 18th Feb 2021, 4:13 pm   #49
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Ive Isolated the HT rectifier and smoothing caps from the rest of the set - and I'm getting full HT now with a happy rectifier valve - so I will gradually reconnect stages to see where the fault lies. Before doing this I had disconnected the line output stage - I think by disconnected the HT feed to C32 - this did not cure the fault so it may not be the line output after all.
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Old 18th Feb 2021, 7:20 pm   #50
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Found the fault
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Old 18th Feb 2021, 7:23 pm   #51
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Made a schoolboy error restuffing the main smoothing bomb , surprised it didn’t go bang
Got line output and EHT judging by EHT rectifier valve lit and sound of corona from the tube anode. No raster yet will try with a signal tommorrow.
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Old 18th Feb 2021, 7:52 pm   #52
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Default Re: My first telly TV22

Quote:
Originally Posted by Travellingwave View Post
Made a schoolboy error restuffing the main smoothing bomb , surprised it didn’t go bang
Got line output and EHT judging by EHT rectifier valve lit and sound of corona from the tube anode. No raster yet will try with a signal tommorrow.
Looks promising! Could you hear the line whistle?
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Old 18th Feb 2021, 8:18 pm   #53
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Not really but my hearing might not be up to it. Def working getting EHT though sounds like an ioniser going.
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Old 19th Feb 2021, 11:00 am   #54
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Got a raster - the black band is an artifact from camera
Grounded cathode of crt via a resistor , initially nothing but a quick tweak on ion trap got it going
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Old 19th Feb 2021, 11:07 am   #55
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Default Re: My first telly TV22

Well done - great feeling when you get that first light! Looks nice and bright too.
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Old 19th Feb 2021, 11:15 am   #56
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Default Re: My first telly TV22

That's great!
Not far to go now

Cheers
Andy
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Old 19th Feb 2021, 2:02 pm   #57
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Hooked up the hedgehog - as far as I could see the tv was tuned to band 4 . Got a tone straight away and after a bit of fiddling I got a test card

Picture is a bit out of focus and adjusting the focus lever doesn’t seem to make much difference

Also I only get a picture with brightness turned right up to max , below that nothing , and contrast has to be fully clockwise too.

I haven’t changed any resistors yet and I know a few are out of whack so that may be the next thing

Any suggestions?
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Old 19th Feb 2021, 2:02 pm   #58
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Banding is a camera artifact
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Old 19th Feb 2021, 2:06 pm   #59
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I guess I ought to refit the LOPT shield
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Old 19th Feb 2021, 2:08 pm   #60
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Default Re: My first telly TV22

Check the CRT A1 (g2) voltage with a digital meter. It should be about 300Vdc. An AVO would load the supply too much to measure.

I also once had a TV22 with a broken wire wound track in the brightness control, which gave me nothing or an overloaded CRT depending on which half of the break the wiper was on.


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Andy
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