Re: k6100 chasis temperature?

Coincidentally I took temperatures of the TO3 transistor casings after I
restored the 6100 of my Space Duel. None of them should run hotter than
60C 140F.
This translates to a chassis that is warm to the touch, not so hot you'd
have to remove your hand again not to get burned.

I took these measurements with a cheap IR temp meter after the 6100 was
running for an hour inside a cabinet.

If it runs very hot, you will likely that only one half of the power
output transistor(s) get hot, positive or negative. You should be able
to pinpoint the hotter transistor by touching them.

A cause could be a DC offset in the wg6100 due to a defect. This might
not be noticeable on screen because it is possible to compensate for
this with the X and Y center pots on the game board, so everything seems OK.

Another cause could be a bad contact in one of the power resistor sockets.

A giveaway of such problems is increasingly unstable vector positioning
the farther from the CRT center the vector is drawn. On a good 6100, all
vectors should have no visible jitter and should sit absolutely still.

Also, it is interesting to note that these kind of problems will blow
the LV regulator. This in inherent to the design. The base current for
the DC power supply output transistors is supplied by the small 500 mA,
signal transistor Q100 / Q101. Since the HfE of the original Q102 and
103 is 25 at best (verified on my Tek 575 transistor curve tracer), a
(peak) current of 12.5 amps in the deflection coils would destroy the
small signal drivers.

To make original design bullet proof, I just put in a 2 amps, 100+ volts
BD237/238 in place for the MPSA06/57drive pair, and upgrade R102 and
R103 to a half watt. This way these will not blow by excessive drive of
the amplifier. When the power transistors will short however, these will
probably also blow before the fuse opens.

The LV2000 prevents itself from blowing up for even better protection.
The added regulation in normal operation is unnecessary since we have an
amplifier that rejects power supply ripple good enough for very stable
display.

- Mendel

On 24-10-2011 22:30, David Shoemaker wrote:
> Burning in one of the monitors I fixed I noticed that the main part of
> the chasis is getting hot to the touch.
>
> What is the normal temperature range for these?

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Received on Mon Oct 24 18:54:43 2011