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 11th Feb 2019, 2:27 pm   #1
its ur aerial
Triode
 
its ur aerial's Avatar
 
Join Date: May 2009
Location: Ryde, Isle of Wight, UK.
Posts: 39
Default Thorn 8500 19in with Mechanical Tuner

It`s probably almost 38 years since I last looked at a 19 inch Thorn 8500, but I have been asked for some advice on one, its dead except for the CRT Heaters, no HT on the line O/P Transistor and the regulator on the audio out put/ Power supply PCB appears correct.
Can any one jog my memory with a possible cause.
No circuit diagram to hand at the moment.
All comments appreciated.
__________________
Life is not Hollywood, life is Cricklewood.
its ur aerial is offline   Reply With Quote
Old 11th Feb 2019, 5:21 pm   #2
slidertogrid
Heptode
 
Join Date: Apr 2005
Location: Peterborough, Cambridgeshire, UK.
Posts: 848
Default Re: Thorn 8500 19in with Mechanical Tuner

Hi Its a few years since I worked on one regularly. Have you checked the Mains dropper ? I can't remember if the cut out cuts the mains to the whole set or if it interrupts just the supply to the line stage. I don't have a circuit to hand and I can't find one on line. The other thing I would check is for dry joints or O/C print on the power panel they used to get a bit cooked after a few years.
Rich.
slidertogrid is offline   Reply With Quote
Old 11th Feb 2019, 5:29 pm   #3
jayceebee
Hexode
 
jayceebee's Avatar
 
Join Date: Jun 2007
Location: Durham, County Durham, UK.
Posts: 335
Default Re: Thorn 8500 19in with Mechanical Tuner

First checks I would make would be on the anode of the thyristor W703, no volts here would point to either X701 which is the thermistor mounted on the large mains filter choke below the PSU or W704 on the PSU itself being o/c. If you have volts on W703 anode check to see if the 25V rail is present on the PSU test point. No 25V rail was often caused by a dry joint on R704.

John.
jayceebee is online now   Reply With Quote
Old 12th Feb 2019, 8:58 am   #4
its ur aerial
Triode
 
its ur aerial's Avatar
 
Join Date: May 2009
Location: Ryde, Isle of Wight, UK.
Posts: 39
Default Re: Thorn 8500 19in with Mechanical Tuner

A big thanks for the informed replies, it all now starts to ring bell`s, the X701 thermistor, W704 and the DJ`s on R704.
I will relay the info to the person who asked me.
I never stop being amazed, at the amount of information and knowledge people have on this Forum.
Thanks again.
PS. I have found a TV Mag article of 1976 that includes a circuit diagram.
__________________
Life is not Hollywood, life is Cricklewood.
its ur aerial is offline   Reply With Quote
Old 14th Feb 2019, 10:20 am   #5
its ur aerial
Triode
 
its ur aerial's Avatar
 
Join Date: May 2009
Location: Ryde, Isle of Wight, UK.
Posts: 39
Default Re: Thorn 8500 19in with Mechanical Tuner

All sorted, W704 was O/C.
It was repaired for some one who is trying to get a collection together for a small TV Museum.
A big thanks to the members who replied.
__________________
Life is not Hollywood, life is Cricklewood.
its ur aerial is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 8:54 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 - 2018, Paul Stenning.