Subject: Re: DEC part number for RL02 unit number plugs ?

From: [email-masked] (Frank R. Borger)
Date: Tue, 31 Jan 1995 16:37:43 GMT

In article <[email-masked]> [email-masked] (PDP11 Hacker .....) writes:

>In article <[email-masked]>, [email-masked]
>(Richard Seymour) writes...
>> it's 12-12691-00   (for unit zero... break pins for other numbers)

>Not on an RL-drive. There are 2 pins that encode what number it is, and the
>shape of the top and bottom edges of these pins is what matters. There is no
>easy way of converting one plug into another.

	Well, kinda. I've converted a couple of '2' plugs to '0' plugs
	just by cutting some plastic off with a moto-tool, but doing the
	inverse requires adding some material, a harder thing to do.

	FWIW, here is the coding.

	Look at the back of the plug.
	It looks something like this           --------
                                               |______|  top pin

                          Bit 0 coding ------> -      -  <- bit 2 coding
                                              | |    | |                   
                                              | |    | |                    
                       plug inserted coding-> |_|    |_| <- bit 1 coding

	Viewed from the side, each         _________
	pin looks something like this      _________\__
                                           ------------
                                           _____/

	If the plastic extends almost to the end of the pin, it actuates
	a switch when the plug is inserted, and that data bit is read as
	a '1'. If it is trimmed back, it is short, it reads a 0.

	Bit 2 coding goes nowhere on the RL02.

	The drive won't function unless the plug is in, similar to
	the operation of similar CDC and Ampex drives.

	Hope this helps

---

From: [email-masked]
Date: 8 Feb 95 16:19:29 AEST

In article <[email-masked]>, [email-masked] (J Lothian) writes:
> PDP11 Hacker ..... ([email-masked]) wrote:
> : In article <[email-masked]>, [email-masked] (Richard Seymour) writes...
> : > it's 12-12691-00   (for unit zero... break pins for other numbers)
> 
> : Not on an RL-drive. There are 2 pins that encode what number it is, and the
> : shape of the top and bottom edges of these pins is what matters. There is no
> : easy way of converting one plug into another.
> 
> A nail-file, he said darkly, works wonders...
> 
> James

Oh, the memories!  Many Many moons ago, I bought an Twin Tub 11/23 that had been
run as drives 2  3 for an identical system.  Unit nos 0 and 1 long gone, no 
terminator either.

A kindly DEC FS gave me a part used kit of unit nos. and Terminator, missing 
Unit no 0.  I borrowed a unit no 0 and carefully checked the differences.
Application of a hobby type high speed drill with used dental diamond drill
to a spare unit no 3 made the drive respond to unit 0.  More fine grinding
on the face and a black permanent marker create a zero on the front.

Andy.

PS.  Stupid question.  I missed the orignal message.  Is he after unit nos?