17th Jan 2021, 7:42 pm | #41 |
Heptode
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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
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www.youtube.com/user/andyvalve100 Last edited by beery; 17th Jan 2021 at 7:43 pm. Reason: Added 8K2 suggestion |
17th Jan 2021, 9:42 pm | #42 |
Pentode
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Location: York, North Yorkshire, UK
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Re: My first telly TV22
Yes it has a PL81.
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17th Jan 2021, 9:46 pm | #43 |
Pentode
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Re: My first telly TV22
Yes I see the modification on the trader sheet makes sense now Thanks
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27th Jan 2021, 6:49 pm | #44 |
Pentode
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Re: My first telly TV22
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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6th Feb 2021, 7:14 pm | #45 |
Pentode
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Re: My first telly TV22
Lopt back in after some fiddly soldering. Let’s hope it’s a good un
Bit cleaner than it was |
18th Feb 2021, 11:19 am | #46 |
Pentode
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Re: My first telly TV22
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. |
18th Feb 2021, 11:54 am | #47 |
Pentode
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Re: My first telly TV22
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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18th Feb 2021, 2:44 pm | #48 |
Pentode
Join Date: Jan 2021
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Re: My first telly TV22
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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18th Feb 2021, 4:13 pm | #49 |
Pentode
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Re: My first telly TV22
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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18th Feb 2021, 7:20 pm | #50 |
Pentode
Join Date: Jan 2021
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Re: My first telly TV22
Found the fault
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18th Feb 2021, 7:23 pm | #51 |
Pentode
Join Date: Jan 2021
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Re: My first telly TV22
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. |
18th Feb 2021, 7:52 pm | #52 | |
Hexode
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Re: My first telly TV22
Quote:
Helder |
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18th Feb 2021, 8:18 pm | #53 |
Pentode
Join Date: Jan 2021
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Re: My first telly TV22
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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19th Feb 2021, 11:00 am | #54 |
Pentode
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Re: My first telly TV22
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 |
19th Feb 2021, 11:07 am | #55 |
Heptode
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Re: My first telly TV22
Well done - great feeling when you get that first light! Looks nice and bright too.
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Keith Yates - G3XGW VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm |
19th Feb 2021, 11:15 am | #56 |
Heptode
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Re: My first telly TV22
That's great!
Not far to go now Cheers Andy
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19th Feb 2021, 2:02 pm | #57 |
Pentode
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Re: My first telly TV22
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? |
19th Feb 2021, 2:02 pm | #58 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
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Re: My first telly TV22
Banding is a camera artifact
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19th Feb 2021, 2:06 pm | #59 |
Pentode
Join Date: Jan 2021
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Re: My first telly TV22
I guess I ought to refit the LOPT shield
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19th Feb 2021, 2:08 pm | #60 |
Heptode
Join Date: Jun 2006
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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. Cheers Andy
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