Re: Starwars and Amplifone Issue

----- Original Message -----
From: John Robertson <pinball@telus.net>
Date: Thursday, March 25, 2010 11:33 am
Subject: Re: VECTOR: Starwars and Amplifone Issue
To: vectorlist@vectorlist.org

> pj pj wrote:
> >
> >
> > ----- Original Message -----
> > From: David Fish <dfish_1@comcast.net>
> > Date: Thursday, March 25, 2010 2:36 am
> > Subject: RE: VECTOR: Starwars and Amplifone Issue
> > To: vectorlist@vectorlist.org
> >
> > > Just for fun, try unplugging the degaussing coil.
> > >
> > >
> > >
> > > Dave
> > >
> > >
> > >
> > > From: owner-vectorlist@vectorlist.org
> > > [mailto:owner-vectorlist@vectorlist.org] On Behalf Of PJ
> > > Sent: Thursday, March 25, 2010 2:44 AM
> > > To: vectorlist@vectorlist.org
> > > Subject: Re: VECTOR: Starwars and Amplifone Issue
> > >
> > >
> > >
> > >
> > >
> > > ----- Original Message -----
> > >
> > > From: Chris Loggans <mailto:cloggans@yahoo.com>
> > >
> > > To: pj1@shaw.ca
> > >
> > > Sent: Wednesday, March 24, 2010 3:55 PM
> > >
> > > Subject: Re: VECTOR: Starwars and Amplifone Issue
> > >
> > >
> > >
> > >
> > > PJ,
> > >
> > >
> > >
> > > I have seen this problem
> before.
> > > I know you have stated that the
> > > output looks correct on the scope, but I would try replacing Q7
> > > and Q8 in
> > > the Bipolar output section of the AVG board (page 14B in the
> > > schematics).
> > >
> > >
> > >
> > > Thanks,
> > >
> > > -Chris
> > >
> > >
> > >
> > > I replaced these transistors, as well as replacing the two 0.1uF
> > > caps by the
> > > MPSu57s on the deflection board to no avail. I even tried
> > > to bridge the
> > > current sense resistors with ceramic capacitors to see if it
> > > made any
> > > difference with no luck.
> > >
> > >
> > >
> > > So just to recap, the work done on the game to date:
> > >
> > > -replaced all the 1N914 diodes and transistors on the deflection
> > > board,except for the four 6A main rectifiers, the video output
> > > transistors, and
> > > zener CR5.
> > >
> > > -replaced all electrolytic capacitors on the deflection board
> > > and HV board,
> > > including the 4700uF power supply filter caps.
> > >
> > > -replaced the BU406D, the regulators, diodes, 50ohm resistors,
> > > and HV
> > > transformer. The high voltage setup procedure completed.
> > >
> > > -removed all brown jumpers on the deflection and HV boards.
> > >
> > > -replaced the pots on the deflection board
> > >
> > > -replaced the fuses on the deflection board
> > >
> > > -repaired the fuse block and wiring on the power transformer
> block.> >
> > > -recapped the ARII and added sense mods.
> > >
> > > -added additional heavy leads between grounds on ARII, logic
> > > boards and
> > > deflection board.
> > >
> > > -replaced both 15v regulators and filter capacitors on the AVG
> > >
> > > -replaced Q7 and Q8 on the AVG.
> > >
> > >
> > >
> > > and still no luck...
> > >
> > >
> >
> > Did that last night by removing the three toed posistor ...no
> joy.
> >
> >
> > I did solve the video brightness problem however. I re-
> jigged the
> > video amps with the resistor values from the WG's circuit, and
> alas,
> > the brightness is all good. Fireballs, the green scaled
> text, and the
> > sheild level changes still can slightly defocus the beam, but
> they
> > don't grow so overly bright as to preclude any ability to clip
> the
> > transistors into full saturation.
> >
> > Now if I could only solve the deflection issue: Here's
> more
> > information after throwing a couple of hours at the thing.
> >
> > I left it going for about 45 minutes while I probed with a
> scope.
> > After some time warming up, I noticed that the issue isn't as
> obvious
> > as when its cold. I also noticed that the higher the
> levels are setup
> > off the AVG, the more square the characters
> become. On that, I ran
> > the self test when I was setting up the cutoffs and drives
> after
> > "WG"izing the video amps, and on the Linear/binary and linear
> scaling
> > test, the edges of the shrinking square become slightly jagged
> at
> > about 3/4" to the tune of about say 1/32", and progressively
> more
> > jagged when the square is less than 3/16" to the tune of about
> 1/8".
> > When it becomes nearly a dot, the jagged edges are larger than
> the dot
> > itself.
> >
> > Since I likely have a high frequency response issue in the
> deflection
> > system, it could be I'm chasing something that isn't in the
> AVG. I
> > also noticed that there is a lot of old heatsink compound
> between the
> > heatsink and the deflection pcb substrate. Could this
> have become
> > conductive?
> >
> What is your girlfriend saying? Live with it? (ducking)
>
> I suggest stepping back for a little while and let it percolate
> for a
> while in your mind. I don't think the grease is conductive, in
> any case
> you do have an insulator between the transistor and the heat
> sink, don't
> you?
>
> John :-#)#
>

The WAF (woman acceptance factor) on this one is still quite low.
It keeps me away from TV(evil), and the computer (ha!), so it has some WAF.

I'm going to sweep each amplifier to see where the reponse is at, as well as throw a step function at it that I can vary the rise-time. Something is ringing (the response is underdampened at a certain critical draw rate), which is what I saw on the scale test screen, and when I look for it, on the controller test box as well. At this point I'm even suspecting the twisted pairs they used in the harness. Remember that the deflection signals can contain harmonics of significant energies at higher frequencies, given the arbitrary waveforms encountered here: sawtooth, sinusoidal, step, pulse and any combination thereof.

The diodes came in today, along with a fresh set of op-amps, which I'll throw in to see what happens.

I expected pulling the bypass resistors on the HV's DC supply would show up as something either in brightness or size, but suprisingly, no artifacts materialized or disappeared.

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Received on Thu Mar 25 17:59:44 2010