'VERY' loud buzz [resolved]

[El Tel]

Hi Paul

I thought I'd also check the resistors on the Speedball small board, the 237 ohm 1/8 watt resistor on the good side of the board is reading 237 ohms as expected but the other 237 ohm on the side of the board where there's no volts at OA is reading 0 ohms, do you think this could be why there's no reading at OA ?

Obviously I'm going to have to change it, but i can only find 240R 1/8 watt here in the UK, are these OK?

 

[Paul Birkeland]

I wouldn't change that resistor necessarily. 

Your meter has a setting where it will beep when touching the leads together.  Get it setup to do this, then start touching pairs of leads on each transistor on that side of the board, then you may run into a pair of leads that's shorted out. 

It's pretty rare for a resistor to short to 0 ohms,  so I'd be looking for an external issue causing this problem.

 

[El Tel]

Hi Paul

I've done the tests on the transistors on the bad side of the pcb and yes they both have continuity, and buzz on the multimeter.

Can you let me know if these are the ones that I need to order as I'm in the UK.

https://www.digikey.co.uk/en/products/detail/central-semiconductor-corp/PN2907A-PBFREE/4806938?_gl=1*1sf5dg5*_up*MQ..*_gs*MQ..&gclid=Cj0KCQiAgdC6BhCgARIsAPWNWH0i2a-r8WVvCzaFxJjLPlQQksmUUl4V6LA11_TE-SxLiJjdtscIm2oaAmRAEALw_wcB&gclsrc=aw.ds

https://www.digikey.co.uk/en/products/detail/good-ark-semiconductor/MJE350/24613252?_gl=1*b0yvy7*_up*MQ..*_gs*MQ..&gclid=Cj0KCQiAgdC6BhCgARIsAPWNWH0i2a-r8WVvCzaFxJjLPlQQksmUUl4V6LA11_TE-SxLiJjdtscIm2oaAmRAEALw_wcB&gclsrc=aw.ds

Many Thanks

Terry

 

[Paul Birkeland]

Those will work.

 

[El Tel]

Hi Paul

A quick update, it's all OK again, all reading measure as they should again.
Turned out that replacement of the two Transistors and the 237 ohm resistor seemed to do the trick.

Thank you everyone

Ps - I learnt a little along the way too, so all in all what's not to like