UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV 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 11th Jan 2021, 12:53 pm   #141
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 10,295
Default Re: Philips G8 G22K522

Might also be worth checking the line discriminator balance control if not already done so as that will affect the voltage at the reactance transistor.

Lawrence.
ms660 is offline   Reply With Quote
Old 11th Jan 2021, 8:25 pm   #142
19Seventy7
Octode
 
19Seventy7's Avatar
 
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,002
Default Re: Philips G8 G22K522

Quote:
Originally Posted by 1100 man View Post
As everything changed when you changed C498 (4mfd), I still think this is the cause of the oscillator running way too fast. After all, it was running at the correct frequency before C498 was changed, but there was a sync fault.

Look very carefully at the value on the new capacitor- is it really 4.7mfd? Not 0.47 or 47mfd? Is it actually connected? Check for lifted print or hairline cracks around its legs. Do you still have the original capacitor you could try?
Sorry all for the late reply, It's definitely 4.7uF but I do still have the original and have replaced it, which seemed to have made no difference. (Picture one is my replacement, Picture 2 is the original)

Quote:
The voltage on T4500's collector should be 17.8v, base 7.35v and emitter 6.9v
Testing this the collector was 17.83, the base was 7.190 and the emitter dropped from around 6.660 to around 6.450 (Written as seen on DMM)

Quote:
T4511 C 13.0, B -2.45 and E .014v
C is around 17.15V, B is 026V (not 2.6) and E is 027V (Again as seen on DMM)

Quote:
An important voltage is at TP47 - 7.35v - this is the control voltage to T500's base.
Tested this and it read around from anywhere between 7.000 to 7.060. It started off around the 7.060 mark and dropped down to 7.000 (Same as what was displayed on the DMM)

I'd do checks tracing backwards from the fault but I'd not be sure at which components to be looking at.

Quote:
Might also be worth checking the line discriminator balance control if not already done so as that will affect the voltage at the reactance transistor.
Where would this be or what would it look like? There's a few controls that I can see but they're for height, linearity and the likes.

Thanks
'77
Attached Thumbnails
Click image for larger version

Name:	Cap4.7uF.jpg
Views:	99
Size:	112.7 KB
ID:	224406   Click image for larger version

Name:	OrigCap4uF.jpg
Views:	93
Size:	108.0 KB
ID:	224407  
19Seventy7 is offline   Reply With Quote
Old 11th Jan 2021, 9:07 pm   #143
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 10,295
Default Re: Philips G8 G22K522

Quote:
Originally Posted by 19Seventy7 View Post
Where would this be or what would it look like? There's a few controls that I can see but they're for height, linearity and the likes.
I don't have a layout but it should be near to IC2001, the circuit ref. I'm looking at for the preset pot is 2177 (220 ohms) The preset pot sets the emitter voltage on the phase detector transistor inside IC2001 which is pin 1 the collector is pin 2 which is the output to the reactance stage.

There should be a procedure in the manual for setting the line frequency, if you follow that it should give an idea as to whether it's the oscillator or the voltage that controls the reactance stage.

Lawrence.
ms660 is offline   Reply With Quote
Old 12th Jan 2021, 12:12 pm   #144
Welsh Anorak
Dekatron
 
Welsh Anorak's Avatar
 
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 5,280
Default Re: Philips G8 G22K522

Those voltages look almost exactly right - you only need to go to one decimal place at most. Just check the adjustment slug hasn't fallen out of the coil - that frequency is so far out it has to be either that or a tuning component. There was no need for these oscillators to be crystal controlled, just to free run at approximately line frequency. Yours is galloping!
I'll get the manual out tonight and copy you the setting up procedure.
__________________
Glyn
www.gdelectronics.wales
Welsh Anorak is offline   Reply With Quote
Old 12th Jan 2021, 7:14 pm   #145
19Seventy7
Octode
 
19Seventy7's Avatar
 
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,002
Default Re: Philips G8 G22K522

Quote:
I don't have a layout but it should be near to IC2001, the circuit ref. I'm looking at for the preset pot is 2177 (220 ohms) The preset pot sets the emitter voltage on the phase detector transistor inside IC2001 which is pin 1 the collector is pin 2 which is the output to the reactance stage..
I think I might know the one actually, I noticed a control last night near the start of the yellow flylead from the central bottom PCB which would be board 2. I'll wait until I've got the setting up procedure from Welsh Anorak and take it from there.

Quote:
Those voltages look almost exactly right - you only need to go to one decimal place at most. Just check the adjustment slug hasn't fallen out of the coil - that frequency is so far out it has to be either that or a tuning component. There was no need for these oscillators to be crystal controlled, just to free run at approximately line frequency. Yours is galloping!
I'll get the manual out tonight and copy you the setting up procedure.
That's definitely a relief. I wasn't too sure about them. I'll check the coil and let you know. If it has fallen out, and I'd made adjustments would it still affect whats on screen? It does still adjust.

Thanks for help, much appreciated
'77
19Seventy7 is offline   Reply With Quote
Old 13th Jan 2021, 10:11 am   #146
Welsh Anorak
Dekatron
 
Welsh Anorak's Avatar
 
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 5,280
Default Re: Philips G8 G22K522

Here's what the manual says:-

Tune the receiver to a transmission and adjust the controls for a normal picture. Connect a voltmeter between TP9 and chassis and adjust R2177 for a reading of 6.4 volts. Reconnect the meter to TP8 and adjust L4501 for a reading of 6.9 volts.

The two test points and R2177 are at the rear of the IF panel by the audio output transistor T225. You'll notice a 10uF capacitor C2170 nearby. Although it's a good quality component, it's possible this is faulty.
__________________
Glyn
www.gdelectronics.wales
Welsh Anorak is offline   Reply With Quote
Old 21st Jan 2021, 2:50 pm   #147
19Seventy7
Octode
 
19Seventy7's Avatar
 
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,002
Default Re: Philips G8 G22K522

Sorry for the late reply, just haven't had to chance really to do the set.

I've just done the adjustments, TP9 and R2177 was reading around 7.2 volts at first and is now at 6.4.

TP8 and L4501 were at something stupid like 2 volts, and the coil was almost hard over to the anticlockwise. It's now almost hard over clockwise at 6.6V but we've a MUCH better picture, and the line-whistle isn't making my ears bleed anymore.

The picture isn't stable with this, as it still scrolls left to right, but it's not slanted like it used to be. As you can see in the photo too, there's also a greeny-yellow/purpley-blue variation that overlays the main image and flies from right to left, and of course, no colour, but one step at a time.

I'm starting to think this set's been the victim of a twiddler.

Thanks all for the help, I really appreciate it
'77
Attached Thumbnails
Click image for larger version

Name:	G8TCF.jpg
Views:	138
Size:	86.5 KB
ID:	225083  
19Seventy7 is offline   Reply With Quote
Old 21st Jan 2021, 6:17 pm   #148
19Seventy7
Octode
 
19Seventy7's Avatar
 
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,002
Default Re: Philips G8 G22K522

Weird discovery, I turned the set on again to see how it'd perform from cold, and there was loss of sync again, adjusting L4501 sort of brought it back to how it was before, with the scrolling, but I noticed if I take my coil adjusting tool out, it loses sync again, but there's not the 4 pictures this time so it's still somewhat of an improvement

Edit: My fault, I realised it's a metal tool, using a plastic one sorted this out. It still scrolls side to side but much slower.

'77

Last edited by 19Seventy7; 21st Jan 2021 at 6:29 pm.
19Seventy7 is offline   Reply With Quote
Old 22nd Jan 2021, 11:01 am   #149
Welsh Anorak
Dekatron
 
Welsh Anorak's Avatar
 
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 5,280
Default Re: Philips G8 G22K522

You're losing sync, which does point to the Taa IC or an associated component.
I'm a bit concerned about excessive width and height - cleck the +205v rail. If that's OK you'll need to balance the BU205s.
The lack of colour is possibly just the reference oscillator off lock as I think you can see unlocked colour in the display.
__________________
Glyn
www.gdelectronics.wales
Welsh Anorak is offline   Reply With Quote
Old 23rd Jan 2021, 2:41 pm   #150
19Seventy7
Octode
 
19Seventy7's Avatar
 
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,002
Default Re: Philips G8 G22K522

I’m hoping it’s not the IC... I’ll check the other components later on when I’m home, along with the 205V rail. I think it’s running at around 200V, but I’ll check again. If that’s okay, how do I balance the BU205s? Is that the coil next to the green tuning caps which I think was mentioned earlier on in this thread?

I’m not entirely sure if it’d be the cause, or part of it, the colour control seems to just spin, so I’m not sure what condition the pot itself is in, there’s no difference if the control is at the maximum or minimum.

Thanks
‘77
19Seventy7 is offline   Reply With Quote
Old 23rd Jan 2021, 5:58 pm   #151
Horris
Hexode
 
Horris's Avatar
 
Join Date: Nov 2006
Location: Colchester, Essex, UK.
Posts: 300
Default Re: Philips G8 G22K522

Been working on a G8 this afternoon with no line sync. It turned out to be c4520 on the timebase panel. It decouples the emitter of T500. It is 16mfd.

Dave
Horris is offline   Reply With Quote
Old 23rd Jan 2021, 8:25 pm   #152
19Seventy7
Octode
 
19Seventy7's Avatar
 
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,002
Default Re: Philips G8 G22K522

Thanks for the heads up, Iíll give it a check in a bit and let you know.

Thanks
Ď77
19Seventy7 is offline   Reply With Quote
Old 24th Jan 2021, 12:47 am   #153
19Seventy7
Octode
 
19Seventy7's Avatar
 
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,002
Default Re: Philips G8 G22K522

Had a check, C4520 in mine was a 33uF cap, I checked the capacitor and it seemed way out of value, so I've ordered some. Hopefully this cures the sync fault, we'll soon find out.

Quote:
It is 16mfd.
As I say, mine was 33uF, so I checked my circuit diagram I have which also said 33uF. Just wondering why they'd be different in our sets? Could it be the VCR modification?

Quote:
cleck the +205v rail.
checked the 205V rail, it's at 191V on the dot. This isn't too low is it? I know some people run them at 195V but it seems to be working just fine at 191V. Not an issue to raise it to 195V if need be.

Thanks for the help
'77
19Seventy7 is offline   Reply With Quote
Old 24th Jan 2021, 5:03 pm   #154
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 5,980
Default Re: Philips G8 G22K522

When I was at Philips, we used to set the HT to 200V....not official but we got fed up with changing line output transistors and transformers.
__________________
On Spike Milligan's headstone......I told you I was ill...
Sideband is offline   Reply With Quote
Old 24th Jan 2021, 5:31 pm   #155
neil29
Heptode
 
neil29's Avatar
 
Join Date: Dec 2004
Location: Newport, Gwent, UK.
Posts: 799
Default Re: Philips G8 G22K522

I've set several of my A823's to around 190-195v whether it makes a difference or not because on occasion the pot has become intermittent and it has shot up to 220-ish volts.

Cheers
Neil.
neil29 is offline   Reply With Quote
Old 24th Jan 2021, 9:46 pm   #156
19Seventy7
Octode
 
19Seventy7's Avatar
 
Join Date: Jun 2018
Location: Essex, UK.
Posts: 1,002
Default Re: Philips G8 G22K522

Quote:
Originally Posted by Sideband View Post
When I was at Philips, we used to set the HT to 200V....not official but we got fed up with changing line output transistors and transformers.
Iíve seen people say 200V too and, as i say, Iíve seen some say 195V too. Itís working fine (well...) at 190V and Iíd have thought itíd be even easier for the set at 190V. Should I raise it or leave be? Iím surprised that even a 5V difference improves reliability so much.

Quote:
I've set several of my A823's to around 190-195v whether it makes a difference or not because on occasion the pot has become intermittent and it has shot up to 220-ish volts
Whats the likelihood of that happening with a G8 pot? Iíve cleaned the track so hopefully there shouldnít be a fault there, but the actual pot itself? In the threads Iíve read Iíve not seen that mentioned on the G8, but as Iíve no prior experience on G8s (or any other set really) I donít know what does and doesnít go wrong.

Thanks
Ď77
19Seventy7 is offline   Reply With Quote
Old 24th Jan 2021, 9:55 pm   #157
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 5,980
Default Re: Philips G8 G22K522

If the HT goes too high, the power supply tends to 'hunt' giving you a pulsing picture. If you check the setup details there is a 'course' and 'fine' adjustment. I really don't remember the sequence now but I seem to recall that you set the HT pot to 210V then adjust the other so that the picture hunts and then back off the HT pot to 205V....something like that anyway.
__________________
On Spike Milligan's headstone......I told you I was ill...
Sideband is offline   Reply With Quote
Old 24th Jan 2021, 11:27 pm   #158
rambo1152
Nonode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 2,541
Default Re: Philips G8 G22K522

I don't recall a fine adjustment, just a set HT and an overvoltage protection pot.

The pulsating was the overvoltage protection kicking in.

To set the latter empirically, we would set the HT correctly on a meter, then set the overvoltage pot until the picture pulsated, then back it off a bit.
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 25th Jan 2021, 10:20 am   #159
Welsh Anorak
Dekatron
 
Welsh Anorak's Avatar
 
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 5,280
Default Re: Philips G8 G22K522

To answer your question, the balance coil is indeed on the small sub-panel. However the core will be stuck, so it needs to be soaked to free it off. Once you get the sync sorted out then you can adjust this - it's fine for the moment.
As said, around 200v is fine. It's quite well stabilised, but not up to later standards so as long as it hovers around 200v then it's OK. Graham's method of setting up the overrvolts is the one we all used.
__________________
Glyn
www.gdelectronics.wales
Welsh Anorak is offline   Reply With Quote
Old 25th Jan 2021, 11:34 am   #160
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 8,360
Default Re: Philips G8 G22K522

There is a page on sorting out the stuck core, the information was originally in Television magazine from 1985.
https://www.radios-tv.co.uk/vintage-...tor-balancing/
__________________
Frank
Nuvistor is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 4:38 am.


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 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.