19th Feb 2021, 2:17 pm | #61 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
Thanks Andy
I will check those points |
19th Feb 2021, 2:40 pm | #62 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
|
Re: My first telly TV22
|
19th Feb 2021, 2:43 pm | #63 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
Just checking my notes , and R37 the brightness pot measured 1.5 Meg and should be 50k so looks like I may have a duff pot
|
19th Feb 2021, 2:49 pm | #64 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
|
Re: My first telly TV22
It's easy to open the top cap on those pots (with a small suction cup or a piece of blu tak) so you can check whether you have a broken track or a bad/dirty contact between the winding and the top/down contacts). I had this problem in my pot and fixed it by cleaning and retightening one of the contact holders, which was isolated from the winding.
|
19th Feb 2021, 2:52 pm | #65 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
Hi Helder
When I got the set the width control was set to max so I was expecting to find some issue here, in fact it is working somewhere in the middle of its range. There was an O/C resistor in the line output stage so maybe this is what caused the sets decline. |
19th Feb 2021, 2:58 pm | #66 | |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
|
Re: My first telly TV22
Quote:
|
|
19th Feb 2021, 3:02 pm | #67 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
It was an 8k in the feed to the screen of the line output valve PL81 , listed as a mod on later sets
|
19th Feb 2021, 3:04 pm | #68 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
The resistor you mentioned measured 890k v 820k on the trader sheet
|
19th Feb 2021, 3:22 pm | #69 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
|
Re: My first telly TV22
|
19th Feb 2021, 3:57 pm | #70 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
So measured A1 voltage , that’s the one from the metrosil right?
Getting about 205 v , so a bit low. I checked the brightness pot and the track was OC right at one end. Managed to fix it for now by wedging a bit of foil under the end contact Now the brightness is working I can get a better focus by twiddling with the Ion trap magnet but ends up being rather a dim picture. Not sure how sharp/bright it should be Maybe the tube needs to run in a bit Any way low A1 voltage may be the culprit? |
19th Feb 2021, 3:59 pm | #71 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
Latest screen taken in the dark
Gently glowing valves |
19th Feb 2021, 4:17 pm | #72 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,987
|
Re: My first telly TV22
Well done, looks good
__________________
Stephen _________"It`s only an old telly" ___ |
19th Feb 2021, 4:21 pm | #73 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
Just reading on the forum and note that ion trap should be adjusted for max brightness right? - in which case my last adjustment may not have been the best thing to do.
|
19th Feb 2021, 4:23 pm | #74 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,987
|
Re: My first telly TV22
Its easy to reset, best to work with a low brightness to start with so you can see it increase easily as you adjust.
__________________
Stephen _________"It`s only an old telly" ___ |
19th Feb 2021, 4:25 pm | #75 | |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
|
Re: My first telly TV22
Quote:
|
|
19th Feb 2021, 4:28 pm | #76 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
to chassis
|
19th Feb 2021, 4:39 pm | #77 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
|
Re: My first telly TV22
|
19th Feb 2021, 4:40 pm | #78 |
Pentode
Join Date: Jan 2021
Location: York, North Yorkshire, UK
Posts: 155
|
Re: My first telly TV22
Im using a DMM
Any suggestion why I would be getting a low voltage - where should I be measuring from Chassis or HT? Cheers |
19th Feb 2021, 4:57 pm | #79 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
|
Re: My first telly TV22
From chassis is fine. The value should be stable, an according to several posts on the forum it should be between 200-300V when measured with a DMM. I get 250V on mine, and it's fine (tried a replacement metrosil, and got the exact same value). I guess it will depend on the exact impedance of your DMM/scale. The value quoted in the service sheet (300V with respect to chassis) is for an electrostatic voltmeter. The Bush fault sheet quotes 210V with respect to HT, so basically the same thing.
|
19th Feb 2021, 5:42 pm | #80 |
Heptode
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 988
|
Re: My first telly TV22
Hi Travellingwave,
the clue as to whether you are loading the A1 supply significantly when you measure it is to see if the raster dims a lot when you take the measurement. Have you replaced the A1 decoupling capacitor? It is 0.1uF 500V and is hard to spot as it is underneath the tag board that is below the chassis. If you have replaced it then metrosil if probably faulty, which is quite a common problem with these sets. The circuit I have attached will replace the metrosil. Cheers Andy
__________________
www.youtube.com/user/andyvalve100 |