In a message dated 2/23/99 2:46:09 AM Eastern Standard Time, jrr@flippers.com
writes:
<< Later circuits for that unit (The Ampliphone series) added a back emf
diode across the input/output of the two voltage regulators, there was
also a 15 ohm (or so) 5 watt resistor addded in series with the input to
the regulators to reduce the input voltage a bit. This should save
yours...The diode goes in with the band to the positive side of the
circuit, a 1N4005 was used (I STILL don't think they are fast enough) by
Atari in this mod...perhaps someone with one of those units in hand can
confirm the resistor value (I always seem to be at home when these
questions appear)
>>
These are 50 ohm 5 watt resistors that are in each regulator curcuit.
They were NOT on the early Amplifone HV boards (this one is really early, out
of a Quantum, Amplifone serial #505, Quantum #396). I was told that they were
only there to lower transient voltages in Star Wars during the death star
blowout, but I think having them on any Amplifone HV board is a good idea, now
that I've gone through so many regs. I'm going to install them (I'm going with
50 ohm 10w ones) on this Amplifone HV board now. I did add the diode to each
reg (CR5 and CR6, its a 1N4001), the real early Amplifone HV's do NOT have
these either.
I'm starting to think of the early Amplifone boards like the first year a
new model of a car, it took a while to make some changes to improve the
design. I don't think this info pertains to very many people (there are VERY
few of these early AMP. HV's around). However anybody with one (these boards
are blue, and the dead givaway is that there are no 50 ohm resistors in front
of the 7824/7924) should definately make the mods.
I've been getting ALOT of e-mails from people who have had similar
problems on their Amplifone HV boards, so when this whole thing is fixed, I'm
going to put together a Amplifone HV refernece guide. I have to applaud Joe W
for laying the groundwork for this. Jess, would you want to post this thing on
the Arcive when it's through?? Also, if Gregg is here, would you want to add
this to the Vector Faq??
BTW, and pardon my mouth, but does anybody know what the hell the MCI
does on the Amplifone HV board???
Michael Kelley
Received on Tue Feb 23 10:51:43 1999
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