Re: Digital VX40B - Multia?

On 3/30/24 13:19, John Klos wrote:
>>> In the same place we found a Mac Quadra we also found a Digital
>>> VX40B-F2 system. I have taken photos and will upload them someplace
>>> soon. I believe this machine will also run NetBSD.
>>
>> Several people have asked about the Multia, and offline I am
>> conversing about other gear that could go to a museum. Much
>> appreciated!
>> The capacitor I noticed and other views are here:
>> https://chaos.social/@jspath55/112179795399182319
> 
> That capacitor is precisely cut on purpose to give it an exact value. 
> That's done with resistors, too, for certain applications.

   Whoa, no.  That is an "arc gap" capacitor, which is a capacitor that 
has an integral spark gap that shunts high-voltage spikes to ground, 
usually on signals that leave a board and are expected to have long 
wires.  (Note that it's right next to an external connector)

   The capacitance is fixed and is not affected by the cut, and the 
dimensions of the cut determine the breakdown voltage, not the capacitance.

   To be clear, this is an ESD protection component, manufactured this 
way on purpose, it is not damaged, and it is not a precision component 
in any way.

   (Disclaimer [or is it a "claimer"?]: I am a design engineer who has 
designed these components into commercial products, though not for DEC.)

            -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA