Ed Henciak wrote:
>
> While on the subject of Amplifones, has anyone tried using TO3 versions of
> 78 and 7924s in place of the TO220 ones? They source .5A more and might
> perform better under heavy 'death star explosions'. Also, Mouser sells a
> 7824/7924 from NJR which sources more current? Would these help the
> Amplifone more/ make it more reliable.
I've only rarely seen the regulators fail. The primary problem seems to
stem with the HV unit.
There is some input protection that would be a good idea to limit the
levels to the amps. Does everyone have that or would it be a usefull
addition on my site?
> I was over Mike's last night with him tinkering with the Amplifone...it
> really wasn't making a hissing sound...it actually sounded more like you
> were pissing in a bucket (for lack of better terms)...it was kind of loud!
That Sizzling sound is NOT good. It usually means a HV leak somewheres.
Turn off all the room lights and take a look to see if you can see the
arcing.
> The absolute highest the HV rose to was 9 KV.
How did you measure this? WIth a proper HV probe or extrapolation?
> I checked out pin 3 on the
> 555 and there was a square wave (initially), but my scope sucks and I
> cannot really read the frequency very well (I got it for $15 at a thrift
> store, and it works in XY mode so I cannot complain). Now, there is no
> square wave which leads me to believe the 24V sources are dead. There is
The 555 should be running regardless of the HV system, it will turn on
at about 4 Volts...did you measure the B+ across the 555?
> no LED comming on anymore on the HV board. John, we did exactly what you
> explained last night. However, I think shotgun replacing parts on this board
> isn't necessary (i.e. replacing all transistors). If the 555 isn't
> producing the square wave, then it is a
> safe bet that the board isn't producing 24V (or getting voltage from the
> deflection board), or the overvoltage circuitry SCR is stuck on somehow,
> right? If it is producing a square wave, then every time Q1s base gets a
> high pulse, Q2 should be shut off...etc.
>
> The basic building blocks of the HV booard are real easy to understand
> now that I have a good set of schematics. I'm just curious to hear
> other people's experience with these monitors after upgrading them with
> Wintron flybacks. Oh, and one more thing, does anyone know what the hell
> that big, red MC1 thing is?
The red thing is some sort of resonator...maybe...
We do now have the flyback testor kit in. It's something like $27US plus
postage. Enough advertising...
>
> Sorry to ramble ...
> Ed
We'll get this fixed!
John :-#)#
-- John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) mailto:jrr_at_flippers.com, web page http://www.flippers.com "Old pinballers never die, they just flip out."Received on Sat Sep 5 11:37:11 1998
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