Vectorlist Archives: RE: k6100 chasis temperature?

From: Mendel Pearl <mypearl_at_dds.nl>
Date: Tue Oct 25 2011 - 04:03:11 EDT

Yes, I always replaced the old paste with new. The old one has always dried
to a crumble and for sure will limit heat transfer...

That -10 degrees will probably translate to an even bigger temperature drop
on the transistor die itself.

- Mendel

From: owner-vectorlist@vectorlist.org
[mailto:owner-vectorlist@vectorlist.org] On Behalf Of Ed Lawless
Sent: dinsdag 25 oktober 2011 4:18
To: vectorlist@vectorlist.org
Subject: Re: VECTOR: k6100 chasis temperature?

I have found that with my 6100s when I rebuild the output transistors (TO3s)
I use CPU heat sink past like arctic silver; or a CPU paste that is very
good at heat transfer. I have not measured in the cabinet but on the bench
with an ambient air temp around 72F 40-45% humidity; I am finding these
output transistors running around 115-120F. Before rebuild they are
running around 125-130F for me; it may be my obsessive compulsiveness
kicking in here but 10 degrees is 10 degrees. Anyone else doing this?
Take care,
Ed

On Mon, Oct 24, 2011 at 7:40 PM, Mendel Pearl <mypearl@dds.nl> wrote:

Good one, I will do a retest to see the dfference!

Thanks

- Mendel

On 25-10-2011 1:16, Ken Sumrall wrote:

It's important to remember when using IR thermometers, that the emissivity
of
the material being measured matters. Most things have an emissivity of
about
0.95, but bare metal is much lower, and can cause inaccurate readings.

A simple solution is to put a piece of masking tape on the metal object to
be
measured, assuming it's not so hot it will burn the tape.

I'll dig out the manual for my old Wahl. It's an older analog meter version
of this:

http://www.palmerwahl.com/product_home.php?cat=3
<http://www.palmerwahl.com/product_home.php?cat=3&catl=11&line=31&itm=46>
&catl=11&line=31&itm=46#

__
Ken

On 10/24/11 15:54, Mendel Pearl wrote:

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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