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Re: I could use a hand locating hardware bits and pieces and/or technical documentation for repair.

Newsgroups	comp.sys.3b1
Date	2015-12-19 09:19 -0800
References	<11f11849-2c2c-433a-ad2f-555403129d14@googlegroups.com> <slrnn79ivu.nhp.BPdnicholsBP@Katana.d-and-d.com>
Message-ID	<ad5cc3ed-254f-416b-8c23-94023aae288e@googlegroups.com> (permalink)
Subject	Re: I could use a hand locating hardware bits and pieces and/or technical documentation for repair.
From	Peter Schmidt <peterhschmidt@gmail.com>
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I bought an MFM drive, a Seagate ST-4096, for $79 off eBay in 2009 to replace the one in my 3B1.  Searching eBay now for "MFM hard drive" yields lots of options.

Do you have the floppies to reinstall it?

Good luck!

On Friday, December 18, 2015 at 10:17:10 PM UTC-5, DoN. Nichols wrote:
> On 2015-12-19, Chris Smith <protheus@byteorder.net> wrote:
> > Hey everybody,
> 
> > I've had a 3B1 since the mid 90s, which I love, but recently it had to
> > move out of the house for a while due to space constraints.  This was
> > bad news since apparently the storage area we were using became a nest
> > for a small animal.  Now, well, I've cleaned the system and popped the
> > case apart again to double check everything.  It's mostly fine
> > (thankfully), but...
> 
> > I believe the keyboard is not functioning properly.  This is not a
> > surpise since it was full of some liquid the origin of which I don't
> > really want to know.  It's clean now but corroded in spots.  I've
> > removed and discarded the metal shielding around the outside of the
> > keyboard and the (now very musty) cardboard insulating panel between the
> > keyboard and shielding. 
> 
> 	Have you washed it?  Clean tap water can't do much damage to it
> compared to what the "unspecified liquid" has already done.  I did this
> with a different keyboard which suffered from "unidentified liquid"
> damage from a squirrel who was resident in the house.  Luckily, I
> discovered it rather quickly, so the wash and let dry worked well that
> time.  
> 	Strip the case open.
> 
> 	Turn on warm to hot water in the shower.  (Hot will be better,
> but warm easier to control things by hand.)
> 
> 	Rinse it for quite a while, ending with water as hot as you can
> manage, then shake it, and stand it on end for a day or two to let it
> dry thoroughly.
> 
> 	You probably have some of that liquid under the chips, which is
> why you want to rinse it quite a wile and then let it dry.  (Rapid
> drying could be done with a vacuum chamber, but most houses don't have
> that. :-)
> 
> >                          Caps lock light flashes when the system comes
> > on, but I can't get the keyboard to do anything, even though the
> > switches do seem to be making contact from what I can see with a
> > multimeter.  If you pull the cable and re-insert it, you can get some
> > characters to show up on the screen, but they keyboard itself isn't
> > doing much.
> 
> 	Yes -- the rinse and dry should help greatly.	
> 
> > Nothing obviously wrong with it upon inspection except some corrosion
> > and the switches are a little stiff.
> 
> 	Operate the keys while the water is flowing, which may help to
> free them up, too.
> 
> >                                       I've tried to clean any dust of
> > corrosion that seemed to be located between traces or wires just in
> > case.  I strongly suspect I may need to rebuild all or part of the
> > keyboard.  I'm willing to try that if I must, but I'm not really sure
> > where to start.  I don't know the electrical specifications even, and
> > I'd much rather if somebody could tell me what they are than have to
> > prod the machine to figure it out.  In fact, if anyone has a keyboard
> > schematic, I'd love to see it.
> 
> 	A couple of days ago there was a request for schematics of the
> power supply, and I mentioned that the power supply and the video board
> in the monitor assembly were purchased in rather than built as part of
> the computer, and the vendors did not supply the schematics.  I *think*
> that they keyboard may be the same.
> 
> 	I note that there is someone on eBay selling a copy of the
> _Technical Reference Manual_ (_TRM_) (Service Manual) -- for an
> astounding $600.00.  (I think that I paid something like $60.00 for mine
> way back when.)  But the article to which I was replying had the URL for
> downloading the whole _TRM_ for free.  IIRC, all the schematics are
> single page, not foldouts, so that should print fairly well.
> 
> 	Can you back up about a week in this newsgroup and check for the
> URL?  I never noted it down, because I have the printed manual, but it
> would be worth your while to download and print out.
> 
> 	O.K.  A quick check of the _TRM_ shows no schematics for the
> keyboard -- nor for the mouse, both of which are also purchased in
> products like the power supply and the video card (which came with the
> CRT itself, I believe.)
> 
> > All that said, does anyone happen to know if there are still keyboards
> > for these things floating around somewhere?
> 
> 	Keep your eyes on eBay.  Right now they have some software and
> the _TRM_.  but no hardware.  You'll likely need to buy a whole computer
> to get the keyboard, unless you are really lucky.  (Note that there may
> be some offered on eBay by someone who does not know that it is for the
> 3B1/7300/Unix-PC, so if you can get a model number off a label on the
> bottom of the keyboard, you *might* find it that way.
> 
> 	Also -- depending on where you are -- you *might* find them at
> hamfests (electronics flea markets held by radio amateur organizations),
> more common in the summertime -- and I don't know how may are in your
> area (wherever that is).  There are about six or so every summer not too
> far from Washington DC which I regularly attend -- fewer than there used
> to be.
> 
> >                                              Also, does anyone have
> > document describing the protocol that should be spoken to the keyboard
> > port?
> 
> 	I don't.  I do know that it is common for keyboards to send one
> code when the key is pressed, and a different one when it is released,
> which is how it knows to repeat when you hold down a keycap.  At a
> guess, exclusive of the function keys and the like, I would expect the
> plain ASCII code when the key is pressed, and perhaps the same but with
> the parity bit set when released -- but I've never checked what these
> keyboards do.  And holding down the shift key probably does change the
> codes sent by the other keys -- but tells the software in the system to
> modify it appropriately.
> 
> 	Really old keyboards, such as the one for the Texas Instruments
> Silent 700 printer actually sent the proper codes for the various mixes
> of keypresses -- but that was before things were set up for keyboards at
> the end of a skinny cable. :-)
> 
> >        I might not mind building a converter.  I'd be very tempted to
> > buy a spare keyboard at this point, even if the original can be
> > recovered.
> 
> 	Note that there were at least two versions of the keyboard.  One
> has the tactile modifications of the index finger home keys (F and J) as
> vertical grooves to the left of the letter, and the other has similar
> grooves under the letters.  IIRC, one had a better feel than the other,
> but you first want something which *works*.
> 
> > On another, similar note, the hard drive (which I pulled from a pile
> > of parts and installed into the system in '95 when I got the machine)
> > has finally given out.  Not a bad run for a disk, at any rate, and who
> > knows how old and well-used it was before I put it into service, but
> > it's a lot harder to find these than it used to be.  What does everyone
> > else do for that problem?  Is there a good source for these drives?  A
> > piece of modern replacement hardware?  There has been some talk (and
> > apparently some success) about emulating the old Shugart interface with
> > a CPLD, though the price may be a bit high on such a device.
> 
> 	The emulation would be a trick with modern drives.  (Hmm ...
> perhaps easier using something like an Arduino and thumb drives. :-)
> 
> 	The old MFM drives sent a raw signal from the read head, and
> depended on logic in the computer (the WD101 or for modified systems the
> WD-2010 chip) to convert that into bytes for transfer to memory.  You
> first have to tell the drive which cylinder you want to step to and
> which head within the cylinder.
> 
> 	Todays drives (IDE, SCSI and the like) accept a request for a
> specific sector number (counting from zero at the beginning) and figures
> out internally what cylinder and head to look for) and then spews out
> the sector's contents as a sequence of bytes.  I think that translating
> between the two would require another controller chip like the WD-1010,
> and a smart board (Arduino, Raspberry PI, or other) to ask the modern
> drive for the data and make it look like the old MFM drive.  Not a
> trivial task.
> 
> 	A pity that there was only one SCSI interface board (a
> prototype) ever made for the 3B1.  Someone who was a regular here had
> that prototype board and drivers after the company he worked for gave it
> up as a product.
> 
> > Anyway, if anyone has recommendations on how to proceed here, I'd love
> > to hear them.
> 
> 	You have my suggestions -- starting with the taking it into the
> shower with you and giving it a good bath.
> 
> 	Once you get it working (or find another), then comes the trick
> of observing it on a 'scope to try to figure out the encoding.  If you
> do find it -- please post it for future reference.
> 
> 	Good Luck,
> 		DoN.
> 
> -- 
>                   Remove oil spill source from e-mail
> Email: <BPdnicholsBP@d-and-d.com> | (KV4PH) Voice (all times): (703) 938-4564
>    (too) near Washington D.C.     | http://www.d-and-d.com/dnichols/DoN.html
>            --- Black Holes are where God is dividing by zero ---
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