OT? Apple Stylewriter problems (PS progress)

From: Mark Tapley <mtapley_at_swri.edu>
Date: Thu Jan 24 10:30:28 2002

>From: ard_at_p850ug1.demon.co.uk (Tony Duell)

>Do these tap into the plastic of the case, or into brass inserts, or what?

They go into pre-drilled cylindrical studs that extend from the back of the
case (the side that doesn't plug into the wall) toward the front. There
were matching
cylindrical recess barrels from the front that extended toward the back and
had holes in their circular bottoms large enough for the screw threads to
pass through. Those barrels were what melted.

>Are they machine screws, self-stripping screws (OK, self-tapping screws
>:-))? If they're machine screws, they're likely to be metric sizes....

Self-stripping :-) which is what I'll therefore replace them with.

>Ignoring the ceramics (likely to be for RFI suppression), it would appear
>you're describing this circuit :
>
>
>o-----)|| +---------------+------------o +ve output
> )||(------>|----+ |
> )||( | =====
> )||(--o\o-------)----+ -----
> )||( | | |
> )||(------>|----+ +----------+-------------o -ve output
>o-----)||
>
>A very standard PSU circuit using a 'bi-phase' full wave rectifier.

I think that's it. Why did I see a small voltage when I tested it *after*
the fuse blew? The - side doesn't connect to *anything* - I'd think it'd
float right up to the voltage of the positive side (charging through my VOM
meter, if no other way). Or is there some effective resistance through the
electrolytic?

>Is there room to insert a normal fuseholder (maybe a 20mm one), then you
>could use a fuse without pigtails...

Hm. Maybe. I actually have a small fuseholder (one of the few parts I have
in my box). I'll see whether I can make it fit. It would mount in among
caps and diodes with not much room to spare on a small circuit board,
though, so I may be stuck with a pigtail version.
                                                        - Mark
Received on Thu Jan 24 2002 - 10:30:28 GMT