Hello,
I'm looking for the schematic of this medical instrument or even only
the schematic of its power supply board (HP 43100).
The switching mosfet is arcing between drain and source until a
resistor fuses on the 220V AC line (usually a couple of zeners around
the mosfet driver BJT go short too). I checked the snubber part of the
circuit and it tests ok. The schematic would tell me if arcing
interrupted one or more hidden traces around the mosfet circuit.
D-S arcing sounds like no current recirculation, doesn't it?
Thanks in advance

Francesco

On Feb 17, 8:09 am, wrote:
Hello,
I'm looking for the schematic of this medical instrument or even only
the schematic of its power supply board (HP 43100).
The switching mosfet is arcing between drain and source until a
resistor fuses on the 220V AC line (usually a couple of zeners around
the mosfet driver BJT go short too). I checked the snubber part of the
circuit and it tests ok. The schematic would tell me if arcing
interrupted one or more hidden traces around the mosfet circuit.
D-S arcing sounds like no current recirculation, doesn't it?
Thanks in advance

Francesco

A common failure on that supply is high esr capacitors. Beyond that,
you cannot get any component level information on it.
You won't get the schematic, it was board level replacement repair and
HP never released them.

On 17 Feb, 14:33, " wrote:
On Feb 17, 8:09 am, wrote:

Hello,
I'm looking for the schematic of this medical instrument or even only
the schematic of its power supply board (HP 43100).
The switching mosfet is arcing between drain and source until a
resistor fuses on the 220V AC line (usually a couple of zeners around
the mosfet driver BJT go short too). I checked the snubber part of the
circuit and it tests ok. The schematic would tell me if arcing
interrupted one or more hidden traces around the mosfet circuit.
D-S arcing sounds like no current recirculation, doesn't it?
Thanks in advance

Francesco

A common failure on that supply is high esr capacitors. Beyond that,
you cannot get any component level information on it.
You won't get the schematic, it was board level replacement repair and
HP never released them.

Thanks for info, I failed to mention that I also checked ESR of all
electrolitics. The big ones are well below 0.5 ohm and the tiny axial
33 uF ones are below 2 ohm. It doesn't seem an ESR problem,
unfortunately. But I'll recheck all just in case.

Francesco

On 17 Feb 2007 05:09:49 -0800, put finger
to keyboard and composed:

Hello,
I'm looking for the schematic of this medical instrument or even only
the schematic of its power supply board (HP 43100).
The switching mosfet is arcing between drain and source until a
resistor fuses on the 220V AC line (usually a couple of zeners around
the mosfet driver BJT go short too). I checked the snubber part of the
circuit and it tests ok.

I'd replace the relevant components anyway. I recently repaired a
timing light where a faulty HV (pulse rated?) ceramic cap tested OK
out of circuit but behaved as if it was OC in-circuit.

The schematic would tell me if arcing
interrupted one or more hidden traces around the mosfet circuit.
D-S arcing sounds like no current recirculation, doesn't it?
Thanks in advance

Francesco

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

This is a medicial lifesaving device to be used to restart a stopped
heart.

As a retired biomed engineer I would not attempt a repair with no
documentation available.

Way too much lialibility involved and you want them to work everytime
100 percent.

Board replacement is probably best.

Hugh
And yes I have had them used on me once. Still glad it worked.