Re: Wicked intermittant Amplifone (Ampliphone) issue

pj pj wrote:
> ----- Original Message -----
> From: Cinelabs Info <cinelabs.info@gmail.com>
> Date: Wednesday, May 11, 2011 9:29 am
> Subject: Re: VECTOR: Wicked intermittant Amplifone (Ampliphone) issue
> To: vectorlist@vectorlist.org
>
> > P.S. To answer your other question, after a few hours under
> > normal operating
> > conditions, it's normal for the flyback core to be warm. Unless
> > by "warm",
> > you mean it was glowing orange.
> >
> >
> >
> > On Wed, May 11, 2011 at 11:24 AM, Cinelabs Info
> > <cinelabs.info@gmail.com>wrote:
> > > The most common cause of the symptom your described is the
> > screen and/or
> > > focus wires fraying, oxidizing or breaking underneath their
> > boots on the
> > > focus assembly.
> > >
> > > For starters, I'd pull back the boots, cut, strip and *TIN*
> > the focus and
> > > screen connections, then re-terminate them on the focus
> > assembly. I would do
> > > this, even if the "look" good. Ensure there are no sharp
> > points left after
> > > your final cut.
> > >
> > > You might do one wire at a time, just to ensure they don't
> > accidentally get
> > > swapped.
> > >
> > > Also check the connection to the flyback, but this is usually
> > ok, as it was
> > > re-terminated during the most recent installation of the
> > flyback itself.
> > >
> > > After that, you would need to supply voltage readings (i.e.
> > anode, screen
> > > and focus) for further diagnosis.
> > >
> > > I don't think I caught your name, or you forgot to sign your
> > post. What's
> > > you name again?
> > >
> > > Thanks,
> > > -Mark
> > >
> > > On Wed, May 11, 2011 at 12:39 AM, pj pj
> > <pj1@shaw.ca> wrote:
> > >
> > >> Hi All,
> > >>
> > >> I have an interesting one that makes you go "OH $%#&".
> > >>
> > >> Having been awhile , I flashed up my starwars and after a few
> > hours of
> > >> running normally, I glanced at the screen, and found a super
> > bright,>> swollen, out of focus and light greenish game display,
> > with the game
> > >> running.
> > >>
> > >> Since the tube had a deflection loss sometime in the past,
> > there already
> > >> was a small burn spot, but now its' a lot worse
> > (<1/4"). I installed a
> > >> Cinelabs transformer in the past to replace a dead/red, which
> > I checked
> > >> almost right after I powered the game off, and found the
> > ferrite core warm.
> > >>
> > >> Cautiously restarting the game with the screen down, I slowly
> > brought the
> > >> control up with a cross hatch, and it did the same behaviour
> > again, with the
> > >> brightness up.
> > >>
> > >> I'm wondering if I have a bad rectifier in the transformer, a bad
> > >> focus/screen resistor block (connections are fine), or a tube
> > with an
> > >> intermittent H-K short. The 24V regulators are fine and
> > have mil-spec metal
> > >> power resistors replacing (as in Andre's rebuild) the
> > regulator bypass ones
> > >> now mounted to the main heatsink and the board was fully rebuilt.
> > >>
> > >
> > >
> >
>
> I was thinking warm like not lukewarm but warm like uncomfortably core
> being heated by some inductive heating issue oversaturation warm.
> I'll tear into the drive waveform this weekend and snap a pix.
>
> JR suggested running the heater off an isolation transformer, so I'll
> try that at the same time using a separate adjustable supply that I
> can ease the filament voltage up a bit to see if that will trigger the
> event (I had such an issue back with a G07 on a really bad tube).
>
> The 3 focus block connections were redone when I overhauled the board,
> wrapping the leads around the terminals. I used Ag/Sn/Cu solder I use
> for high power RF joints on these specifically since I felt it
> couldn't hurt.
>
> I'm wondering has anyone ever seen what a heater/cathode or heater to
> grid short would on an Amp look like? One thing that came to mind was
> that when it did this, the deflection sensitivity was much higher,
> which likely meant that the HV during the episode was probably way low.
The last monitor I had through here with a heater to cathode short was a
Vectorbeam Space War. The symptom was the picture got very fuzzy and
bloomed a bit. I was unable to fix it with a transformer, had to dig out
another 19" B&W tube from my reserve stock. I do recommend picking up
any 19" colour or B&W TVs that were made in North America to harvest the
tubes...

John :-#)#

-- 
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                 www.flippers.com 
"Old pinballers never die, they just flip out"
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