I need to fix an igniter box, I suspect it might be the high voltage
rectifier, what modern equivelent could I use for the rectifier diodes?
The box is a rotax type NB 25/3, 24 volts in, 2kv out, 12 joules.
It's a simple circuit comprising of a trembler mechanism, induction coil,
rectifier, choke, reservoir cap, discharge gap.
When I apply 24v, the trembler buzzes as normal but no high voltage. Any
ideas?

Ted wrote:
I need to fix an igniter box, I suspect it might be the high voltage
rectifier, what modern equivelent could I use for the rectifier diodes?
The box is a rotax type NB 25/3, 24 volts in, 2kv out, 12 joules.
It's a simple circuit comprising of a trembler mechanism, induction coil,
rectifier, choke, reservoir cap, discharge gap.
When I apply 24v, the trembler buzzes as normal but no high voltage. Any
ideas?





A microwave oven diode would probably do the trick.

Is this for a manned aircraft? If so then I'd hesitate to make any sort
of substitutions even if they're likely to work fine. There's a lot of
regulations surrounding that, and for good reason.

"James Sweet" wrote in message
news:QWhVh.3551$BS2.54@trndny01...
A microwave oven diode would probably do the trick.

Is this for a manned aircraft? If so then I'd hesitate to

It's for ground use only.
The microwave diode is a good idea, what is the rating for these?
Any other suggestions of common faults with igniter boxes, I'm only guessing
it's the rectifier, haven't made any checks yet.

Ted wrote:
"James Sweet" wrote in message
news:QWhVh.3551$BS2.54@trndny01...

A microwave oven diode would probably do the trick.

Is this for a manned aircraft? If so then I'd hesitate to


It's for ground use only.
The microwave diode is a good idea, what is the rating for these?
Any other suggestions of common faults with igniter boxes, I'm only guessing
it's the rectifier, haven't made any checks yet.




A common rating is 12KV 500mA, I've never worked on one of these boxes
but I'd start by checking for bad solder joints and then check any
generic semiconductors, it sounds like a pretty simple device. If you
happen to be near Seattle I'd be happy to take a look at it just to dig
into something I've never seen before.

"Ted" wrote:

}I need to fix an igniter box, I suspect it might be the high voltage
}rectifier, what modern equivelent could I use for the rectifier diodes?
}The box is a rotax type NB 25/3, 24 volts in, 2kv out, 12 joules.
}It's a simple circuit comprising of a trembler mechanism, induction coil...

The simplest test would be to check the primary & secondary of the induction
coil for continuity. Have you?

Stan.

"Stan" wrote in message
news:stanleyh-1804070021390001@dialup- The simplest test would be to check
the primary & secondary of the induction
coil for continuity. Have you?

The primary is .5ohm, the secondary+ diode is 6M.
I removed the high voltage cap and is measures zero ohms.

Ted wrote:
"Stan" wrote in message
news:stanleyh-1804070021390001@dialup- The simplest test would be to check
the primary & secondary of the induction

coil for continuity. Have you?


The primary is .5ohm, the secondary+ diode is 6M.
I removed the high voltage cap and is measures zero ohms.




Sounds like that's your problem then. The cap should measure open circuit.

On Apr 18, 10:50 pm, James Sweet wrote:

Sounds like that's your problem then. The cap should measure open circuit.

Amen to that except: If it is an electrolytic cap, resistance will be
in the megohms after it stabilizes, but *not* 0. If it is a film cap,
then resistance should be as near-infinite as matters, but again
*after* it stabilizes. I am also assuming it wants to be an AC-rated
cap as well? If so, please be sure to replace it with a similarly
rated cap.

One last thing, if this is an electrolytic cap, make sure it doesn't
bite you. Discharge it before handling it.

Peter Wieck
Wyncote, PA

In message .com,
" writes
One last thing, if this is an electrolytic cap, make sure it doesn't
bite you. Discharge it before handling it.
Discharge any caps that are used in high voltage/energy circuits, they
don't need to be electrolytic to carry a nasty amount of charge.

Peter Wieck
Wyncote, PA


--
Clint Sharp