Can disks be copied using only one RL02 drive?

[Tony Duell]

> The other option I can think of, is that you could change the unit number 
> on one of your RL02's, either by snapping fingers off the ready 
> indicator, or (probably a better idea) sticking small plastic rods or 
> similar into the holes where the fingers go in the ready lamp for the 
> 2nd RL02, and use that.
> 
> A little bit of googling or "ask-Tony" :) should help you figure out 
> exactly how to trick the drive into being another unit number.

>From what I remember, and you need to the RL printset to check (I will 
dig mine out if you're serious about wanting to do this), the RL's 
'ready' lampholder has 4 internal switch contacts, which are 
opened/closed by the shape of the top and bottom edges of the 2 side pegs 
on the lamp cap. In the RL, only 2 of the contacts are used, as a binary 
encoding of the unit number.Oh yes, there's a fifth cotnact that detects 
there is a cap in place (and disables the drive if not).

I wouldn't mess about with the lamp cpas themsleves, since any 
modifications are not easily reversed. What I would to is remove the 
front panel from the drive, remocve the switch/indicator PCB from that 
and do the changes there.

Now, what I can't remember (as I said, I'll check the prints if you're 
serieous), is whether a closed contact is a '1' or a '0'. If it's the 
former, then the kludge is easy. Just solder a wire across the 
least-significant contact, and your drive 0 becomes drive 1. If it's the 
latter, then either cut the trace ot the least significant contact (so it 
appears open to the rest of the electronics), or remove the lamp cap, and 
solder a jumper across the 'cap present' contact, and across the most 
siginificant drive number conact.

Doing it that way has the advantage that it'll be easy to undo the mods 
when you want to put the PDP8/a back together.

-tony