Narco com 810

jangiolini · Post by **jangiolini** » Mon Jan 03, 2011 4:35 pm

Hi Happy New Year! I have just found the fault on my Narco radio which tripped the circuit breaker! It was the diode on the +12 volt line into the on/off switch had gone short circuit!! The diode marking is SES 131 9328 but this number doesnt come up in any of the books. There is another diode 1n4005 on the switched side of the switch? Has anyone come across this before and if so what did they substitute it with? Anyone have a schematic diagram for this radio?
Lots of questions but I am hopeful that someone has had this before.
Thanks.
John.

jangiolini · Post by **jangiolini** » Thu Jan 27, 2011 10:12 am

Hi an update to this conundrum! I had a chat with various bods and eventually it was decided that 16 volt 5 watt zener diode from the switch to earth would do the job! This located and installed would appear to be working fine. Will keep you updated!
John.

Kevin Stewart · Post by **Kevin Stewart** » Thu Feb 03, 2011 10:15 pm

Hi John,

Whilst I cannot find a data sheet for the short circuit diode I would suggest that the diode was an over-voltage protection device. It is possible that the diode 'just failed' but it might be possible that there was an over-voltage event that killed it. I would make a few measurements of your supply voltage with the alternator running. If you have other equipment that has 'gone faulty' then I would be most suspicious of a regulator fault.

I think that the diode that you have fitted sounds reasonable as an over-voltage protection device.

Kevin

jangiolini · Post by **jangiolini** » Fri Feb 04, 2011 4:38 pm

Hi Kevin thanks for the reply and I have checked the output with alternator running and it would appear to be high as in that it is around 16 volts so I have purchased a new regulator which I will fit at the weekend. So far nothing else has failed but I am not happy with the protection so I plan to install some form of crowbar setup. That should dump to earth if it goes high again and protect everything.
John.

Kevin Stewart · Post by **Kevin Stewart** » Fri Feb 04, 2011 5:18 pm

Yes, 16V is about 2V too high. I would not bother with a crowbar circuit, my experience is that they are more trouble than they are worth. Most voltage sensitive equipment will have its own internal over-voltage zener designed to blow a fuse or trip a breaker.

Does your engine have a separate regulator or is it built into the alternator?

Kevin

jangiolini · Post by **jangiolini** » Sat Feb 05, 2011 9:16 am

Its a separate regulator VRG3627 Very costly!!!!! £11 delivered from wood auto.
John.