RK611 schematics

[Tony Duell]

> 
> I have done some measurements while running XXDP ZR6A??.???.
> Although I cannot explain some signals I got the controller working!
>  =
> 
> First, the S/R flip flop E46 (UB5) gets the reset pulse on pin 1.

OK...

> On the output (pin 5) is a 'continuous' pulse train, and I also see pulses

Hang on, there can't be. Assuming there's not a continuous stream of 
reset pulses too, E46 can't be setting and resetting.

What instrument are you using to check these signals? Do you know it's 
got the right thresholds for TTL logic? What are you using as the ground 
reference?

> on the SET input (pin 4). So going a bit more back on the signals,
> I checked the 4-input NAND E5 ... although all 4 inputs (xxx COMBINED ERROR=
>  L)
> are continuous "1", I see lots of pulses on the output pin 8 ...?

Again, impossible unless eirhter E5 is malfunctioning, or you're not 
actually seeing what's at that point. I hate to say this, but I suspect 
the instrument and/or its use.

> Perhaps I have missed something, but as the 4 inputs are "combined" error
> signals, I decided to remove the flat cable from M7904 to the bulkhead.
> Don't ask me how that idea came up.

I would love to know which of those signals was actually to blame. I've 
traced ech of them back onto the other boards, but the logic quickly 
becomes complicated, and I don't want to go too deeply into an irrelevant 
area...


> To my surprise, the diagnostic test ran without reporting any error!
>  =

Sounds like noise pickuop on the cable or something. Looking at RG6 
COMBINED ERROR L, for example, it's a combination of bits read back from 
the drive status shift registess on sheet RG6. The input to that lot 
comes from the drive cable receicers on sheet DR8, so noise there could 
well cause problems.

> Time to connect one RK07 drive with termination on the OUT channel.
> The .DIR DM0:  command still reports the same error, but "something"
> happens when I enter the .INIT DM0: command.  Then I get an error as
> I previously reported.  I removed the rear cover, to see the head movement.=
> 
> On .INIT the head moves fast to the centre, and then back to cylinder 0
> I tried .FORMAT DM0:  Again, the 11/34 seems to be hung, but that is
> *NOT* the case: I see the head make small steps (hardly visible) ...

If you fold out the logic cage in the RK07, you should see a 00 01 10 
pattern on the head select LEDs and a binary count on the cylinder LEDs.

> it is no hung on the 11/34, the drive is formatting the cartridge!
> Finally I get the RT11 prompt, but also a message that the formatting is
> aborted due to too many bad blocks.

Right. I'd be interested to know if, perhaps, one surface is completely 
bad and you have head, head switch, or something like that, problems.

I've not got the diagnostics, but I wonder if one of those programs could 
tell you that sort of thing. 

> But is was working, so I tried .DIR DM0: ... no error now, the drive report=
> s
> 0 files and some 56??? block free!  Next I copied a small program to the
> RK07. The I entered .RUN DM0:HELLO, and I get "Hello world" on the
> terminal! When I try to copy a big file to DM0 I get an output error,
> but that makes sense.
>  =
> 
> I have a few more RK07 cartridges, but I will first run the other diagnosti=
> cs
> that use the RK07 drive.  I must thank Tony. Without his replies I probably=
> 
> would have done nothing for a few weeks. Because he put some of his time in=
> 
> helping I felt obligated to keep going ...
>  =

Thank you for that. I was fairly close to leaving this list due to the 
amount of flamage I seem to receive, but I'll stay while I'm still 
managing to help people to keep these fine old machines going.

-tony