Re: Anybody done John's Raster Hack for Ampliphone?

Hi Greg (et all),

Sounds like something here is wrong...what do you mean about "I clipped a 3
(5?) Watt carbon resistor's leads and soldered one to each of those two
wires"? I don't recall adding any resistors to either the Focus or Screen
lines. As I recall the Focus wire goes directly to the socket pin #1, and
the Screen line goes to the terminal on the tube socket that originally
connected to the wiper of the Screen Potentiometer that was mounted on the
neck board (removed now).

My question is about the heater lines. Did you hook them up to the correct
pins on the tube? There needs to be a 1 ohm 1 watt resistor in series to
reduce the inrush current to the tube (lengthens the filament life). You
should get 6.3VAC across the pins on the back of the neckboard on the
filaments pins to the tube socket. Check there. If not present do a
continuity test with the neckboard unplugged (power off!) - you should see
something like 1 to 20 ohms I expect. It should not be an open circuit.

Next check the same circuit with the neckboard plugged in, the resistance
should be much lower as you have added the picture tube heater in parallel...

John :-#)#

At 12:13 AM 04/08/2002 -0500, Gregg Woodcock wrote:

>OK, here's an update. I have confirmed a working power supply and game
>board (fires up a W-G monitor). I metered the heater and it is still good.
>Before I began the operation, I had heater glow. After removing the 2 wires
>from the HV controls, I have no heater glow and no 6.3VAC on the brown
>twisted pair to the tube. Something is kiling the heater and that is the
>problem. Is it something in my procedure below? Also, I forgot a couple of
>things last time so here's the correct summary:
>
> > I put in an IT (1:1) and wired up the 4600 chassis.
> > I kept the 4600 yoke and pulled the green RGB PCB.
>I grounded the chassis to game/earth ground.
> > I put replaced the original secondary anode connection to the tube with
>the
> > one from the 4600.
> > I ripped off the 2 wires going to the socket which were connected to the
> > focus and screen controls on Amplifone.
> > I clipped a 3 (5?) Watt carbon resistor's leads and soldered one to each
>of
> > those 2 wires.
> > I pushed the "screen" wire into the 4600's "G2" pin.
> > I pushed the "focus" wire into the 4600's (unlabeled) focus pin (the
>offset
> > pin).
> > I fired her up but could not see heater and got no picture.
> >
> > The only thing that concerns me about my approach is that inside the neck
> > socket of the amplifone is a 10K resistor in series with the focus wire.
>If
> > I am reading (into) John's notes correctly, he soldered onto the other end
> > of this resistor, removing it from the circuit, right? This may or may
>not
> > be OK with the extra resistance but the worst case is that I should at
>least
> > get a very blurry picture, right? The other thing that concerns me is
> > John's notes allude to eliminating the neck board altogether which I don't
> > see as possible because the only screen control available is on the neck
> > board, right? How would one control the brightness?
>
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Received on Sat Aug 3 22:56:14 2002