Toshiba TVs

[Radio Fixer]

Well C807 measured OK. But R15 - R17 chain measured over 1M. Shunted this with a small (dont have many low W res) with 470K and the set switches on again.

As its working do you think I should go as is or should I open the R15 - R17 chain by removing one of these resistors? Even with my smallest iron, not that small, so tempting to leave it as is.

Thanks again Gary

[Mark Hennessy]

That's a result

Don't worry about leaving the 100k resistors in circuit (what's left of them!). The current supplied by them is not critical, providing it meets a certain minimum value.

Regarding your 470k, it's fine to leave it in place, but do be aware that it might end up suffering the same fate eventually.

In my experience, carbon film resistors fail quickest, metal film are better, and metal oxide are the best.

This subject comes up now and again - here's one of my old posts on the subject: http://golbornevintageradio.co.uk/forum/...8#pid46468

If carbon film is all you have, copying what the manufacturer did (putting several in series) might be worth considering, assuming it's physically possible, etc...

[Radio Fixer]

Its a metal film Mark so should be OK.  Well if it happens again I know how to fix it now (and the other one eventually)   

Thanks Gary

[CambridgeWorks]

Not that I am into mending any tv sets! Just an observation on my part, I hope you don't mind?
Where I used to work, one particular model of air traffic control receiver had a custom built mains smps. We had to replace the start up resistor with one rated for sufficiently high enough voltage rating. It was also stood off the pcb using ptfe sleeving, to assist ventilation. I was involved in trialing this with our qa department. The electrolytic capacitor in the start up circuit was replaced at the same time, along with 3 other capacitors.
Rob

[Murphyv310]

Hi
As Mark says there will be no issue leaving the 470k in circuit with the 3x 100k although I'd remove the old resistors. I'd also fit the correct values and use decent quality resistors suitably voltage rated and metal film or oxide. If you can use through hole resistors suitably mounted all the better.

[Radio Fixer]

Well Rob thanks for your thoughts. The original resistors 3 X 100K are SMD and must have very low wattage and not much voltage rating but I will check the rating of my thin film to be sure.

Yes! Trevor, thanks, I would normally remove at least one of the SMD resistors but as Mark says they are not going to cause any prob and its hard to see how they could go short as a final failure mode. But will check out getting hold of the correct value / voltage, always better to do a "proper job" (Frank Murphy).

Gary