Re: k6100 chasis temperature?

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#
>
> __
> 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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Received on Mon Oct 24 19:41:06 2011