Re: 1502 TDR project - using bench supply


On 12/12/2019 11:59 AM, Mark Pilant wrote:
Hi Tom.
Got around to testing the 1502 using a bench supply.  As you suggested,
when hooked up, the 1502 power supply started operating as expected.  All
the voltages appeared to be to spec.  Although still no trace on the CRT.
I guess there may be some issues with the TekWiki suggested modification
of a 2200uf cap in parallel with a 270 10W resistor.
So now I need to figure out what to do.  I'm thinking of possibly using
a 12V 2A "wall wart" supply connected to the banana plugs instead of the
nor mal AC power cord.  The main problem is how to actually connect it
all up.
There is room on the rear panel for one of the ubiquitous coaxial power
connectors, but I'm a little reluctant to drill a hole for it.  I could
terminate the power card in the supply in a female banana jack attached
to some sort of "paddle" to make it easier to connect / disconnect; but
it would be "a bit" ugly :-)
Any other ideas out there?
Yes. First see Paul's reply. It's good for building a
battery pack AND for the cap/resistor mod AND for
mounting a jack for a 12V supply. NO internal mods
to the 1502.

Another way (but Paul's is better in my opinion) is
what I did years ago with a method a little different
than Paul's: two plates, connected by a threaded
rod and held apart by nuts on the rod. The distance between
the plates is adjusted so they exactly fit the depth of
of the battery compartment, then the nuts are tightened.
The inner plate has the dual banana plug and the outer
plate has the jack for the wall wart supply. There's
tons of room between the plates for the cap and resistor.

Inside Outside
Plate Plate

The = signs are the threaded rod, the {} are the nuts.
Ignore the periods - they are there to make the spacing
appear correctly for those with different font settings.


- Mark  N1VQW

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