Re: jobs from hell


 

Reducing the incandescent lamp voltage has a huge effect on life which
is inversely proportional to the 16th power of the voltage. Most
(all?) of the 7000 mainframes have adjustable lamp voltage and I just
leave it set to minimum.

On Wed, 17 Jul 2013 15:48:13 +1000, Don Black
<donald_black@bigpond.com> wrote:

I wonder if reducing the lamp voltage slightly to increase their life
would be worthwhile? Perhaps a silicon diode in series with their supply
would give about 0.7 volts drop and improve life (a diode would give a
constant drop however many lamps were lit where a resistor would depend
on load).

Don Black.

On 17-Jul-13 3:38 PM, David wrote:

On Tue, 16 Jul 2013 17:50:00 -0600, David DiGiacomo
<daviddigiacomo@gmail.com <mailto:daviddigiacomo%40gmail.com>> wrote:

Was it the pushbutton switches which they kept in later plug-ins or
the relays? I imagine those relays were expensive which would be
another reason to get rid of them.
I'm not sure what you are saying, but the white relays were used in
the 7A13 for a long time after the 7A12 was gone.
The 7A13 "pull for x10 Vc" function would require another x10 switched
input attenuator to implement without relays.

I am just suggesting that Tektronix made more effort to stop using the
relays than to stop using the pushbuttons. I remember seeing a price
list somewhere showing that Tektronix was OEMing the relays for a
price in the $50 range until alternative products became available.
After a certain time, it seems like the 7A13 was the only product
using them.

Also, there are lots of other plugins (and mainframes) where changing
the lamps is no fun at all. Soldering incandescent lamps just seems
like a bad idea.
I think the only problem is easy access which as has been pointed out,
is a major problem in many cases. My 7A12 needs new bulbs installed.

The on flakey pushbutton switch that I need to repair is on my 7T11A.

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