Star Tech Journal

February 1 996
CD
the others, then look at the collector. A good wave-
form there probably means picture tube problems,
but check for waveform at the CRT socket to be
sure. An open transistor will leave the collector
stuck at the video supply voltage, typically 100 to
200 V de. Also sometimes called video B+ by us
old timers, this supply should be clean. Any hash
on this video B+ line means a bad filter cap on the
supply. You will find each color gun driver transis-
tor has a load resistor, probably a 1 or 2 watt size
or so, between collector and video B+. Thus the
three resistors will have one end common ( con-
nected to the same trace). The common point is
the Video supply line. A washed out picture
that is hard to darken is probably due to bad
filtration here. The filter cap may be right on the
neck board or on the main board. Look for 10 ufd
or more, probably at 250V. Not sure which cap it
is and you're having trouble following the traces?
Use your scope to look at what is on the filter caps
around the board. With the exception of the verti-
cal output cap, you should expect to see smooth
DC on them. If you don't, the cap is probably bad.
STAR*TECH
4 Design Improvements to
the Industry Standard
The "Quick Release"
Ticket Dispenser
Improves serviceability
& reduces
maintenance
l
If the base of the driver has no signal, trace back-
wards through the circuitry by looking for wave-
forms at transistor leads and comparing to the other
two color circuits. My experience has been that
color woes are due to driver transistors first and
CRTs (picture tubes) a close second. H the prob-
lem is in the signal portion of the circuit, the
most likely culprit is the one closest (electri-
cally) to the input. Get yourself a CRT tester/
rejuvenator, even an older one, and use it. My old
and utterly basic Heathkit model works great. It is
simply amazing how many tubes can be saved and
how few cannot. A few hundred dollars may sound
like a lot for a piece of test gear, but save just a few
CRTs and it has paid for itself.
The neck board, that little PC board with the CRT
socket, is often silk screened with CRT pin identi-
fications. These are real helpful. K means cathode,
so KR or RK refers to the red gun cathode, KG is
green, your figure out blue. Filaments are labeled
F or H for heater. One side of the filament if often
... continued on page 12
Journal
"Quick Release" face plate
Dynamic, new design allows the
ticket dispenser to "quickly release"
from it's face plate on your cabinet
or ticket door, no tools needed.
Easily replace one dispenser with
another in just seconds. No tools
necessary! The new face plate
retrofits any existing Deltronic
Labs machine.
2
3
Bottom METAL ticket guide
The extended, durable ticket guide
prevents curled tickets from catching.
Foolproof braking system
Our impressive new braking system
eliminates brake slippage, allowing
foolproof, accurate dispensing.
Optical sensor dust cover
n Eliminates dust accumulation and
IUl.
increases accuracy of the ticket count.
Another quality product from De/tronic Labs ...
the ;ndu"'Y /eade, m ttoket _ . . , ,
Deltronic Labs, inc.
120 Liberty Lane, Chalfont, PA 18914 • 215-997-7753
FAX # 215-997-9506