Mode Zero

The pulser circuit on my Mattel has stopped pulsing and I found that one of these tantalum capacitors has failed - tested as open circuit.
I just need to be sure of the value. It's brown and black bands with a white dot. So is that 0.1uf? The band that indicates the voltage rating is a tan colour but can't find a value for it. Any ideas? Looks more grey in the photo.

Thanks for any help,
Carl

Phil_G wrote: 22 Apr 2018, 00:32 How are you testing it Carl, with a multimeter a capacitor should test open circuit....
Brown black with a white dot is 1uF
Never exceed a tants max voltage, they catch fire! I'd suggest 16v if its a 9v battery.
Cheers
Phil

Thanks Phil for the info. My brain was working backwards last night

One capacitor shows open and the other a resistance. I did another test by applying a voltage to each and then checked the voltage stored. The one that shows as open gave a voltage reading on the multimeter and the one with a resistance doesn't give a voltage reading and guess this second capacitor is the faulty one.

So it looks as tough we've found the culprit. Hopefully replacing the two capacitors will bring the pulser circuit back to life

Thanks again Phil,

Carl

Just ordered a small pack of 1uf 16v tantalum capacitors.

That colour coding was a blast from the past.

A while back I purchased a cheap component tester that can be used to check a variety of components such as resistors, transistors and yes you've guessed it capacitors. It may be worth considering purchasing one if you plan on more renovations.

A quick search on Ebay should result in a wide choice to suit depth of pocket.

Ade

Thanks for your help so far I say so far as the pulser circuit still isn't pulsing. I checked the caps I put in are good to eliminate them. There are two npn transistors in the circuit, so took those out and have found one of them had failed also

They are 2SC537E and are unavailable. Looking up online for an equivalent returns NTE289A, but can't get these in the UK. Anyone suggest an alternative? Or anyone have either in your stash that you'd be willing to sell me? Or even have a board taken out of a converted transmitter - I do remember someone did a conversion but that's lost on the previous forum.

Thanks again,
Carl

TUP TUN DUG DUS

When Elektor was in its heyday they came up with a term for general purpose, non-critical applications -
TUP - transistor, universal, PNP
TUN - transistor, universal, NPN
DUG - diode, universal, germanium
DUS - diode, universal, silicon

What you need Carl is a couple of TUN's - 2N3904, BC107/108/109/184, ZTX300, and many, many more alternatives. You dont need an exact equivalent for a simple pulser.

Thanks Phil, I was hoping one of you electronics geniuses would say that. I have some BC108s and will give them a go.

Carl

Thanks Phil, that's another vintage transmitter back in action You might remember you gave assistance for the receiver for this very set.

That was a very useful pdf you provided. I remember Elektor as a lad. My father must have purchased that mag as he was an electronics man and had a tv repair business in the days when you had them repaired.

Carl

exuprider wrote: 25 Apr 2018, 18:39 he was an electronics man and had a tv repair business in the days when you had them repaired.

Carl

You still do!!
www.rons-television-services.co.uk

Ron.

Sorry Ron, I forgot you repair tvs. It explains why you turn out such cracking transmitters.

Carl