UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Reply
 
Thread Tools
Old 14th Sep 2019, 12:03 pm   #21
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

Thanks to you both. I only had a 0.47uF so that's what's in place of the 0.75uF.

The only thing is that having it in or out of circuit didn't appear to alter my rippling frame.

I did check the 2uF on the scan coils but it appears leak free.

I got a small improvement in positioning by removing the scan coils and bending the frame ones slightly.

Peter
peter_scott is offline   Reply With Quote
Old 14th Sep 2019, 12:19 pm   #22
wd40addict
Heptode
 
wd40addict's Avatar
 
Join Date: May 2009
Location: Stevenage, Herts. UK.
Posts: 717
Default Re: Yet Another Bush TV22

If you have one to hand try temporarily replacing the 2u electrolytic with a nonpolarised polyester or similar.

Also do add 0.22uf in parallel with your 0.47uf to get full benefit of hum reduction. Note the hum reduction caps should be rated at least 500VDC and preferably more.
wd40addict is online now   Reply With Quote
Old 14th Sep 2019, 12:42 pm   #23
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

I did look at the possibility of an electrolytic but saw that it would be reverse polarised on part of the cycle so I fitted a non polar 400 volt cap. I've now added a couple of 0.1 uF 1000v caps and I must confess that it does look much better.

I think you and David have just saved me from further fruitless going around the houses.

Very many thanks to you both.

Peter
peter_scott is offline   Reply With Quote
Old 14th Sep 2019, 12:44 pm   #24
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,757
Default Re: Yet Another Bush TV22

It's possible to restuff the 0.75mfd capacitor with RS components class X 300VAC 0.68uF and 0.068uF capacitors. Connected in parallel you've almost got the exact value.

DFWB.
FERNSEH is online now   Reply With Quote
Old 14th Sep 2019, 12:56 pm   #25
wd40addict
Heptode
 
wd40addict's Avatar
 
Join Date: May 2009
Location: Stevenage, Herts. UK.
Posts: 717
Default Re: Yet Another Bush TV22

This thread has the info on why the hum reduction cap has to be absolute minimum 465v DC rated.

https://www.vintage-radio.net/forum/...d.php?t=143583
wd40addict is online now   Reply With Quote
Old 14th Sep 2019, 1:38 pm   #26
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,757
Default Re: Yet Another Bush TV22

The DC rating of a 300VAC class X capacitor will be much higher.

DFWB.
FERNSEH is online now   Reply With Quote
Old 14th Sep 2019, 2:34 pm   #27
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

Just connecting my 1M scope probe on various parts of the frame oscillator I was surprised at the substantial increase in scan amplitude it produced. For example on the anode of V15b.

I also found that increasing the value of R53 from 220k up to 350k gave a similar scan amplitude increase and I think gave a benefit in the ratio of HT ripple to scan amplitude.

I'm still not out of the woods yet but it has been good to see where others have been with this.

I have pretty rubbish line linearity still. Probably not helped by me hand rewinding the linearity transformer.

If you ignore the aliasing brightness and just look at the scan ripple you can see my current state in this short video. Note the lethal collection of capacitors to the right of the screen.

Peter
Attached Thumbnails
Click image for larger version

Name:	TV22 frame op.jpg
Views:	35
Size:	52.3 KB
ID:	190159  
peter_scott is offline   Reply With Quote
Old 14th Sep 2019, 3:51 pm   #28
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,757
Default Re: Yet Another Bush TV22

Picture of the original 0.75mfd 250VAC capacitor.

DFWB.
Attached Thumbnails
Click image for larger version

Name:	BushTV220.75mfd.jpg
Views:	65
Size:	55.5 KB
ID:	190165  
FERNSEH is online now   Reply With Quote
Old 14th Sep 2019, 4:31 pm   #29
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

I have my original TCC just the same as yours.

Awaiting stuffing.

Peter
peter_scott is offline   Reply With Quote
Old 15th Sep 2019, 1:31 pm   #30
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

Quote:
Originally Posted by FERNSEH View Post
If the scan coils are wound on an iron core then it's possible the core could be magnetised. This condition has been experienced in the Pye LV20.
Thanks David, degaussing the scan coils has sorted the picture centring and with adding a little more capacitance to the linearity transformer I got some improvement in that department too.

I still need sort out the rippling frame.

Peter
Attached Thumbnails
Click image for larger version

Name:	P1040529 (Medium).jpg
Views:	64
Size:	83.9 KB
ID:	190229  
peter_scott is offline   Reply With Quote
Old 15th Sep 2019, 1:54 pm   #31
Argus25
Nonode
 
Argus25's Avatar
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,329
Default Re: Yet Another Bush TV22

Quote:
Originally Posted by FERNSEH View Post
The DC rating of a 300VAC class X capacitor will be much higher.

DFWB.
I would totally avoid any X class capacitor in any circuit where the uF value is important. Many continually lose capacitance over time.

Also if the job calls for a theoretical capacitor of around 500V, these days I simply fit a 1000V polyester or polypropylene part, because it allows for potential variation in manufacturing quality and tolerances and perhaps the more aggressive environmental conditions inside hot valve TV sets. This is also why I use the RS components silicone rubber insulated harsh environment wire in these sets.

Also modern capacitors are so much smaller, a 1000v part will probably be the same size as a 500V vintage capacitor. If space was an issue, obviously a 600V rated one would suffice. But in many ways it is better to know it will be definitely ok and you won't have to go back later to replace the same part.
Argus25 is offline   Reply With Quote
Old 15th Sep 2019, 4:27 pm   #32
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

Hi Hugo,

Can you recall your source?

"I replaced the one in my set with a 0.68uF 1kV rated polypropylene type."

Peter
peter_scott is offline   Reply With Quote
Old 15th Sep 2019, 10:01 pm   #33
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

Checking the effect on the HT ripple the 0.74uF makes a substantial reduction but curiously it makes virtually no difference to the ripple on the frame.

Peter
peter_scott is offline   Reply With Quote
Old 15th Sep 2019, 10:48 pm   #34
Argus25
Nonode
 
Argus25's Avatar
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,329
Default Re: Yet Another Bush TV22

Quote:
Originally Posted by peter_scott View Post
Hi Hugo,

Can you recall your source?

"I replaced the one in my set with a 0.68uF 1kV rated polypropylene type."

Peter
Good question, it has been some years since I restored my TV22. I generally get parts from RS, Farnell(Element 14) or ebay.

A quick search on the RS site shows a perfectly satisfactory part for the task, cheap enough too, 850V is fine:

https://au.rs-online.com/web/p/polyp...itors/6842232/


I think this must have been the actual 1000V part I used from Element 14:

https://au.element14.com/cornell-dub...citor%200.68uF

I also replaced the electrolytic yoke capacitor with a non-electrolytic as shown in the photo. Also you can see the wiring leading to the yoke is the RS silicone rubber type and I put some white fiberglass sleeving over it as well. Its darn hot inside these TV's. Especially when you run them here with a 30 DegC ambient temperature !
Attached Thumbnails
Click image for larger version

Name:	tv22.jpg
Views:	57
Size:	76.8 KB
ID:	190263  

Last edited by Argus25; 15th Sep 2019 at 11:01 pm.
Argus25 is offline   Reply With Quote
Old 15th Sep 2019, 11:10 pm   #35
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

Thanks Hugo, those look good.

Peter
peter_scott is offline   Reply With Quote
Old 16th Sep 2019, 7:43 am   #36
beery
Heptode
 
beery's Avatar
 
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 686
Default Re: Yet Another Bush TV22

Hi Peter,
looks good so far.

Now I know from its circuit position, C63 should not effect the frame timebase, it is worth checking anyway as I usually find it to be low in value, which is a supprise as the dual canned C61 and C62 are usually fine.
I do have a spare for C61/C62 and a linearity coil, but won't be able to get to them before Christmass.

Another thing you could try is replacing the PZ30, just in case it is a bit leaky.
I have had field hum from ECL80 valves, you have swapped them, with each other or did you try a spare? I have known two valves to have similar problems if they have been well used (I know this is unlikley though).

Cheers
Andy
beery is offline   Reply With Quote
Old 16th Sep 2019, 9:04 am   #37
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

Thanks for those suggestions Andy. You are quite right about R63 mine reads 45 ohms instead of the 38 ohms intended and I did parallel it up to give 35 ohms but didn't see any change in the frame ripple. I also tried messing with C60 and it definitely makes a very significant reduction in the HT ripple at the frame timebase. The thing I can't understand is that I don't see any significant change in the frame ripple regardless of whether the HT ripple is reduced or not! Perhaps that does point to heater "crosstalk" even with grounded cathodes.

I have a lot of ECL80s and lots are duds that I should discard but I'll try again for a good swap. I haven't tried swapping the PZ30 but I will do.

Thanks,

Peter
peter_scott is offline   Reply With Quote
Old 16th Sep 2019, 9:44 am   #38
beery
Heptode
 
beery's Avatar
 
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 686
Default Re: Yet Another Bush TV22

Quote:
Originally Posted by peter_scott View Post
Thanks for those suggestions Andy. You are quite right about R63
Hi Peter,
I meant C63 (although R63 was a good thing to check). C63 is the metal canned 16uF electrolytic located on the underside of the chassis, near the front. If it is leaky it could be dragging the HT down and increasing the ripple.

Yes, ECL80s seem to multiply. I've got thousands of valves, but most are used Mullard TV types. Every time I need an MOV, Mazda, Cossor or Brimar, I have to get my wallet out...

Cheers
Andy
beery is offline   Reply With Quote
Old 16th Sep 2019, 10:07 am   #39
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,757
Default Re: Yet Another Bush TV22

Hi Peter,
How did you degauss the scanning coils? I remember the method used to degauss the Pye LV20 scan coils was to apply the rather brutish method of hitting the coils with a burst of HT. Bangs and sparks but it solved the problem. An alternative method is to use a fully charged capacitor.
Sound on vision and vision on sound is often caused by the RF deck HT supply decoupling capacitor having gone low capacity. The 16mfd capacitor is located on the main chassis near the five pin socket.

DFWB.
FERNSEH is online now   Reply With Quote
Old 16th Sep 2019, 10:36 am   #40
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,149
Default Re: Yet Another Bush TV22

Hi Andy, Oops, sorry Andy. Can't read! Yes, I had renewed all three C61,62,63. The ripple on C63 is huge so I also replaced all screen decouplers in RF deck and C8 and 17.

I just tried 6 different ECL80s this morning. Four were low emission and two usable but without exception they all displayed the frame ripple.

Just tried swapping the PZ30 but still no change.

Thanks,

Peter

Last edited by peter_scott; 16th Sep 2019 at 10:46 am.
peter_scott is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 11:07 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.