Can anyone tell me what this component is?

[kingchops]

I'm in the process of trying to restore an Altair 8800 BT. The system powers on but nothing more. On the CPU board I noticed that this component was installed next to the CPU chip. I've never seen this on any other Altair B CPU boards so I removed it. Can anyone tell me what it is?

My guess would be some sort of temperature sensor, but it's only a guess.

 

[Dwight Elvey]

This is no a temperature compensator.
It is a trim capacitor.
It is used in place of one of the capacitors
attached to the crystal.
These are used for two purposes.
One is as a fine tune of frequency.
If one pulls the frequency too far off,
it may not oscillate.
The other purpose is to reduce the Q of the
crystal.
Normally the high Q is a good thing. It makes
for a nice stable frequency.
There is a problem if the Q is too high and
that is that it may take too long come up to amplitude
during power on reset.
But off tuning, the reduced Q allows it to start
full amplitude faster.
Dwight

 

[kingchops]

Dwight,

Thanks, this makes sense, one end was attached to the crystal. I needed to remove it in any case to get the CPU off of the board. The CPU had a couple of cracked pins and I've replaced it with a newer cpu. I'll clean up the area it was attached to and I can easily replace it if need be.

 

[Chuck(G)]

The trimmer was mostly used on early motherboards when a CGA was being used with composite output to "tweak" the colors.