US Billiards Quasar Maintenance 2017
06/06/2017 - Northwest Pinball and Arcade Show (2017)
After a few hours of run time during setup the game lost all sync and wouldn't adjust
back into lock. I brought some spare Philips KT-3 parts the following day and swapped
in a replacement line frame sync daughter PCB that fixed it. I'd always had a problem
with this chassis where the vertical sync would not lock until the chassis warmed up
and alas the replacement sync PCB exacerbated this problem and eventually the vertical
sync would not stay locked even when warm (it could be tweaked to lock, but would lose
lock after a few minutes). The game was out for the remainder of the show :(
06/11/2017 - Philips KT-3 test rig, video input
The Philips KT-3 chassis uses the same type of video input connector as the
Hantarex MTC-90 (but with a different pinout) so I was able to reuse MTC-90 connectors
that I'd kept from previous MTC-90 to MTC-900 conversions to make up a video input cable
for my test harness.
11/11/2017 - Philips KT-3 test rig, power supply
The Philips KT-3 chassis runs off an isolated 220VAC supply. I had a spare power
supply from a Zaccaria Scramble along with a power input cable made up from connectors
recovered from some scrapped KT-3 chassis.
12/11/2017 - Philips KT-3 test rig, yoke
I had no spare Philips KT-3 CRT to dedicate to a test bench CRT so the plan was
to determine how close the Philips A51-572X CRT was to any of the other CRT's I already
had available. The neck pinout was compatible with the A51-211X CRT I was using for
testing MTC-90/MTC-900 FB monitor chassis according to the BK 467 CRT adaptor
guide (both using adaptor CR-25 with 6.3V heater voltage), so this was the first
one to try out.
The next step was to measure the yoke resistances of both the original A51-572X and
the A51-211X to see how close they were to each other:
A51-572X |
A51-211X |
Green - Yellow |
12.0 Ohms |
Virtical |
15.2 Ohms |
Red - Black |
2.5 Ohms |
Horizontal |
2.2 Ohms |
The horizontal winding looked pretty close but the vertical was further off. I decided
to give it a try anyway and hope the chassis was forgiving.
The yoke cable was made up from a KT-3 yoke recovered from a necked CRT and a Hantarex
yoke connector recovered from a scrapped MTC-900 chassis, ready to try when I had a known
good KT-3 chassis to use.
16/11/2017 - Quasar PCB testing
On the bench the chassis didn't exhibit any of the vertical sync lock problems
seen in the cabinet. There was a wide range of vertical sync pot range that locked
sync versus in the cab where it was very sensitive. I suspected that the Quasar main
PCB might be the problem so I pulled that out of the cab and ran both the PCB and
monitor chassis on the bench together but still saw no problems with the vertical
sync. I verified the sync output from the Quasar main PCB with a scope against another
Quasar main PCB and saw no differences in appearance. As far as I could tell both
chassis and game PCB were working fine on the bench together :|
26/11/2017 - Line frame sync pot replacement
During the show the repeated pot tweaking had bent the adjustment pots and caused
them to become lose. I found some higher quality ceramic ones with matching pinout
off eBay and replaced both pots on the line frame sync board. I measured and made a note
of the current pot in-circuit resistance settings and set the new pots to match after
installation so that little re-adjustment would be needed.
05/12/2017 - Philips KT-3 and A51-211X CRT
With the chassis now confirmed working OK with the original A51-572X CRT it was time
to try the chassis on the MTC-90/MTC-900 FB A51-211X test CRT. I was expecting the
geometry to be mismatched due to the differences in yoke resistances and as expected
it was over-scanned. Other settings for brightness, focus etc were also mismatched. I
didn't attempt to correct any of these settings because they would mismatch the A51-572X
CRT in the cabinet. As it was, the picture was good enough for most common fault
diagnosis.
14/01/2018 - Reassembly
I wasn't sure what I was going to see with the game PCB and KT-3 monitor chassis
installed back in the cabinet. The vertical sync problem had existed ever since
I'd owned the game and had not cleared up with a cap kit or replacement sync board.
On power on the monitor came up without any issues and was still working properly
after an hour. It remained a mystery…
prswan@gmail.com