Star Tech Journal

Diode/Coil Tester Modification
Daniel Zavaro
S.F. Music & Games
San Francisco, California
Refer to the article, .. Build Your Own Test
Equipment Project" published in the
January, 1989 issue of STAR,tTECH
Journal by Jean-Guy Hardy. This project
is a great idea! Now, I won't have to
desolder those diodes from the pinball
machine coils to test them any more.
FINDINGS
After building the project, though, I took a
flipper coil (FL21-400/33-1300) to test. In
the 1300 section, the reading was perfect: 1
LED on and 1 LED off. In the 400 section,
however, both LEDs on the tester remained
off. After verifying that the diodes and flipper
coil were good, I did a little thinking.
MODIFICATION
The voltage drop, because of the low supply
current, was not sufficient to light the for-
ward-biased LED. I then modified a few
values in the tester and was then able to
successfully test flipper coils.
NOTE
Due to the high current nature of this modi-
fied tester, this test needs to be completed
quickly. That is to say that the test is now a
"Touch & Go" type of procedure (as opposed
to clipping the leads onto the coil under test).
A couple seconds is all that is needed any-
way to get a good/bad reading on the tester
LEDs. Thanks Jean-Guy Hardy for a good
tool that will fmd a permanent place in my
travel box!
T'Shooting Hi Tron
Power Supplies
Bill Schelb
Palisades Amusements
Las Vegas, Nevada
PROBLEM
Hi Tron power supplies not restarting after
being turned off.
SOLUTION
Capacitor Cl0 (220 mfd/25v) and resistor
RS (33 ohms/2w) go bad. Replace Cl0, and
also RS, when it looks like the capacitor is
either golden brown in color, or like it has
blown up (or undue pressure has deformed
the component).
NOTE
I have been able to fix 90%-95% of all Hi
Trans by replacing these components. Tack
this article up on your workbench!