Subject: 8250 LP Double disk drive for the commodore 64

From: "Lance S" <[email-masked]>
Date: Thu Jul 3 18:26:00 2003

The drive on http://www.zimmers.net/cbmpics/deieee3.html is what I'm looking 
for.
I've had a chat to my dad who's said that the technician said it could be 
one of 2 things.

1. The head moves & is attached to a wire. A connection in the wire could be 
faulty.
He said that fixing the wire was niot an option for some reason or other but 
I guess we could replace the head. Can I replace the head with one from a 
different model? If so, which are compatible?

2. There are 3 main chips on the mainboard which seemed to be running hot. 
The guy replaced 2 but didn't have one to replace the 3rd.

I have been chatting with another guy who has said that the 8250 drive is 
functionally the same as the 8250 LP so if anyone reading this has either 
for sale please let me know.

Lance.

----Original Message Follows----
From: Ethan Dicks <[email-masked]>
Reply-To: [email-masked]
To: [email-masked]
Subject: Re: Fwd: Re: Fwd: Re: 8250 LP Double disk drive for the  commodore  
64
Date: Wed, 2 Jul 2003 20:03:41 -0700 (PDT)

--- Lance S <[email-masked]> wrote:
 > Ethan, I'll find out the part that the technician thought was suspect.
 > If I haven't explained myself clearly enough, the 8250 LP is a double
 > disk drive that connects to a commodore 64.
 >
 > Thanks,
 > Lance.

Looks like this:

   http://www.zimmers.net/cbmpics/deieee3.html

Right?

We are all talking about the same thing, but the drive by itself
hooks to a PET.  Your father must have a cartridge for his C-64
that provides an IEEE-488 port.

One possibility is if you can't find an 8250LP is to get a regular
8250 (using the same connection).  Dunno if an SFD-1001 would work
or not... the DOS is not the same, so if your father's application
depends on certain features of the drive itself, it might or might
not be a reasonable substitute.

There was a discussion about 8250LP repair on the CBM-Hackers list
last year.  This article is interesting:

http://www.softwolves.pp.se/misc/arkiv/cbm-hackers/6/6731.html

It suggests that the "fragile" part is a 6530 - a part made by
Commodore that was always customized for its particular application.
I've seen them on the KIM-1, in many Commodore disk drives and a
few other places.  Apparently some drives (perhaps the DOS 3.0 ones)
used a daughter card in the 6530 socket with a 6532 (which is generic)
and an external ROM.

Dunno what's wrong with your father's drive, but if you can get in
front of it, turn it on and watch for flashing lights.  In many cases,
that can narrow down the problem to a few chips.  If it doesn't flash
at all (i.e., it acts totally dead), that helps, too.  Likewise if you
can power it on, "talk to it" (read the error channel), but not read
or write drives.

Depending on the fault, it might actually be easier to fix than replace.
Most "technicians" these days only know how to swap out entire boards
or entire boxes.  If it _is_ a 6530, that's kind of a problem... It's
theoretically possible to fabricate a replacement, but I'm not sure
the CBM community knows enough about that particular model to describe
a functional replacement.  A 4040?  Sure.  Maybe even an old-fashioned
8250.  Not positive about the 8250LP.

Cheers,

-ethan

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---

From: [email-masked] (Tony Duell)
Date: Thu Jul 3 19:30:00 2003

> different model? If so, which are compatible?

Err... This worries me. How can he not know if the head connections are 
open-circuit (they are not hard to test!). Why can't the cable be 
replaced (I've resoldered connections inside drive head assemblies many 
times). It's a lot easier to replace the cable (if that's the problem) 
than to replace the head, since if you do the latter you'll need the 
right alignment disk to set it up. 

> The guy replaced 2 but didn't have one to replace the 3rd.

They do. In fact my 8250LP has factory-fitted heatsinks on some of the ICs...

I hate to say this, but that 'technician' sounds to be terminally 
clueless. I fail to see how he can't tell whether it's a fault on the 
mainboard or an open-circuit head connection on one of the drives (First 
question : does one drive work correctly and the other fail, or what?). 
Has he done any meaningful tests at all?

-tony

---

From: [email-masked]
Date: Thu Jul 3 20:07:01 2003

<snip>
> right alignment disk to set it up.
<snip>

I remember on my first 1541 that the drive head and cable were moulded
together (cheap b*st**ds) -- replacement was the only solution there.

I sent my drive to a factory authorized tech who wanted >$150 to repair
the drive, and new drives were about $200 and dropping.  I took a wild
guess at the cable broken from the multiple head travels, and ordered one
($30~) from Grapevine in NY.  I replaced the head, did a quick alignment
and it is still working to this day, 25 years later.  I bought a second
drive and it now has the same problem, and I don't have another head to
replace that one, until I find a junk 1541 with a good head.

They should have been built with a film ribbon like the printers use on
print heads rather than small gauge stranded wire.  Another blatant effort
by Commode-door to make things cheaper.

Gary Hildebrand
St. Joseph, MO

---

From: "Patrick Rigney" <[email-masked]>
Date: Thu Jul 3 21:40:00 2003

> by Commode-door to make things cheaper.

Gary, I may be wrong (and I'm sure a lot of folks will chime in if I am),
but it seems to me that most of the drives I look at, even modern ones, have
that thin-wire construction connecting head to board.  I don't think that's
unusual, and C*dore probably didn't get much choice from their vendor, or at
least see a need to choose a vendor that could supply something different
from what may have been the norm. --Patrick

---

From: Vintage Computer Festival <[email-masked]>
Date: Fri Jul 4 00:14:00 2003

> and it is still working to this day, 25 years later.  I bought a second
                                       ^^^^^^^^

That can't be right.  The Commodore 64 is only 20 years old this year.

-- 

Sellam Ismail                                        Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger                http://www.vintage.org

 * Old computing resources for business and academia at www.VintageTech.com *

---

From: Ethan Dicks <[email-masked]>
Date: Fri Jul 4 01:52:00 2003

--- Vintage Computer Festival <[email-masked]> wrote:
> > the drive, and new drives were about $200 and dropping...
> > I replaced the head, did a quick alignment and it is still working to
> > this day, 25 years later.  I bought a second
>             ^^^^^^^^
> 

I had my hands on one in April of 1982, serial number 2007.  My first
job was programming it for the company that received it as a pre-release
development system.  According to "The Secret Timeline" at
http://www.floodgap.com/retrobits/ckb/secret/timeline.html
The C-64 was announced in January, 1982.  So... it was 20 last year,
but still not 25.

-ethan

---

From: [email-masked] (Tony Duell)
Date: Fri Jul 4 16:12:59 2003

> that thin-wire construction connecting head to board.  I don't think that's

My experience is that 3.5" drives tend to use tapewire, as do some 
half-height 5.25" ones. 8" drives, full-height 5.25" and other 
half-height 5.25" use conventional screened cables.

-tony