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.

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.

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.

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.

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.