Re: 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&catl=**
>> 11&line=31&itm=46#<http://www.palmerwahl.com/product_home.php?cat=3&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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>> chris@westnet.com
>>
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Received on Mon Oct 24 22:18:05 2011