[Amps] ALPHAs and momentary power outages

[Dick Green WC1M]

Yes, the 87A uses simple analog op-amp sensors to monitor the supply
voltages. The sensors can be hacked to fool the CPU into thinking all the
supply voltages are at nominal values, but there are quite a few of them and
it would take some major surgery. More problematic, you would be defeating a
significant part of the amp's self-protection capability. I wouldn't do that
with such an expensive amp. I guess you could add a circuit or
microprocessor to turn on the hacked sensor circuitry only if the main AC
voltage falls below a predetermined value, but that's even more complicated.

73, Dick WC1M

> -----Original Message-----
> From: jeremy-ca [mailto:km1h at jeremy.mv.com]
> Sent: Wednesday, July 18, 2007 1:30 PM
> To: Tom W8JI; wc1m at msn.com; 'Jim Brown'; amps at contesting.com
> Subject: Re: [Amps] ALPHAs and momentary power outages
> 
> I would think that the Alpha microcessor is pretty basic and looking
> for
> simple analog inputs.
> 
> Much like an automotive processor. I had a built up LT1/4L60E Corvette
> combo
> in a 38 Chevy coupe and the tranny began slipping. A rebuild was $1800.
> A
> little bit of monitoring with a DVM ascertained what voltages the
> processor
> was looking for to cause the shift solenoids to actuate.  Then it was
> simply
> a trip to the junkyard for a good non electronic 700R4 tranny and a
> couple
> of resistors across the old harness connector to fake out the processor
> and
> I was back in business for $250 with sharper shifting to boot.
> 
> Sometimes it pays to think out of the box.
> 
> Carl
> KM1H
> 
> 
> 
> ----- Original Message -----
> From: "Tom W8JI" <w8ji at w8ji.com>
> To: <wc1m at msn.com>; "'Jim Brown'" <jim at audiosystemsgroup.com>;
> <amps at contesting.com>
> Sent: Wednesday, July 18, 2007 1:02 PM
> Subject: Re: [Amps] ALPHAs and momentary power outages
> 
> 
> >> I'm glad someone was paying attention. It would be hard to
> >> reprogram the
> >> microprocessor, but it would be easy to patch the timer
> >> value on the fly, as
> >> needed. You just have to get the address(s) and meaning of
> >> the value(s) from
> >> Alpha.
> >
> > My bet is the timer has a reset line or line that monitors
> > power down. It may even just be when the power to the
> > microprocessor is removed, the CPU restarts.
> >
> > The simplest approach would be to fool the system into not
> > knowing the power ever went down. You could do that with a
> > battery and R/C timer, a large electrolytic and a few
> > diodes, or any other number of ways.
> >
> > Maintaining the entire power line and HV supply is probably
> > not even necessary. I would however restrict the hang time
> > to several seconds and no longer, and make sure the step
> > start recycled.
> >
> > 73 Tom
> >
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >