[tig] Rank MKIII Technical Problems
Sun Sep 28 21:36:30 BST 2003
Hello to all,
My name is Robert Houllahan. I have recently taken on the task of trying to
keep a MKIII alive and well at Cinelab in Fall River, Ma. I am a filmmaker
and S16 and 35 camera owner / operator. Before you think of me as a
blitherin' idjut, I have had a background in electronics I worked for
several years in the R&D dept at a firm which designed and built electronic
circuits, and amongst my duties there was the care and feeding of a
Scanning Electron Microscope.
When I came onto the scene at Cinelab the MKIII was, courtesy of Dave
Corbit, running but exhibiting 2 intermittent problems. The first to rear
it's ugly head was a breakdown in the raster on the CRT which looked like
vertical lines on the face of the tube. I was advised to look at the Field
Timebase card, and I replaced several pots on it to no avail.
In the meantime we worked out something with Chris Mann, and we moved his
IIIC to cinelab so there was a second machine there (not working) and I was
able to switch the Field Timebase card with a newer one (metaspeed) from
Chris's machine which solved the breakdown entirely.
The Second problem started to occur more frequently was the green channel
"blowing out", i.e. going to 100ire. I was able to bring this back down by
turning the PEC multi turn pot down and then bact to normal again, this
would hold for a while and then return to 100ire in the middle of a
transfer. I first tried switching PEC power supply boards and the problem
did no follow, I then tried moving some of the video amplifier boards (I
moved red channel boards to the green channel to see if the problem
followed) I knew enough to switch off the machine esp. when moving tube
control boards. I was beginning to suspect the PEC Preamp or collector on
the green channel when disaster struck.
I had moved the afterglow corrector cards from the other IIIC to follow the
chain of video. I turned on the machine and got a pop and the smell of
electronics burning. I felt really bad. Over the past few days Chris and I
traced back the fault to FS1 (EHT LBT power on the scan and tube power
board) R1 had cooked and on trying a number of things it was isolated to
the Line Timebase board which had a short and was taking the fuse down.
I have three different revs of the line timebase board, all of which are
dead this seems to be the problem with Chris's machine as well. I am going
to try to replace all of the Transistors on the original board on monday,
and I have already checked the "notorious" diode and found it to be good
(on the board which pops the fuse) the other 2 boards have been looked at
by Chris and he has not found the problem with them and hence has not been
able to get his machine back up. With this board being unreliable is there
either a newer rev board or some aftermarket replacement for this card
which would move us along to at least getting the machines running?
I thank anyone who reads this and certainly will thank anyone who replies.
Director / Cinematographer
lunarfilms at mindspring.com
401 499 6411
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