Restoring Nylon parts (like the card guides in a PDP-8a chassis)

[Doug Ingraham]

A friend mentioned that there was a thread about the card guides in an 8a
or 8e chassis but I was unable to locate it so I am posting this as a new
thread as it has more relevance than just specifically those card guides.

Nylon is hygroscopic. Hygroscopic means it has the ability to absorbs
water.  As nylon ages it drys out.  When nylon dries out it shrinks and it
becomes brittle.  If a nylon part has not yet cracked or been damaged by UV
it can be restored to almost like new simply by boiling it in water for 15
to 20 minutes.  Boiling will force water back into the material and it will
expand and soften.

Do not use a pan with a ceramic type of non stick coating.  I almost ruined
a 10" skillet because it imparted a flavor to the coating which then
transferred to the food cooked in the skillet.  I don't know what effect
microwaves would have on the Nylon matrix so I suggest you just use
something like a Corning Ware ceramic glass pan on your range.

I was able to restore almost all the unbroken card guides on my 8a.  A
couple of them had taken on a permanent bend due to excessive shrinkage.
Some had broken pins.  A few of the pieces expanded too much and you could
plug them into the chassis but they bowed away from the edge because they
had lengthened beyond original length.  Waiting a few weeks allowed them to
dry out a little and shrink and restored them to original size.

Unfortunately there are no adhesives that will adhere to nylon long term so
it is not possible to repair broken nylon parts in a usable manner.  Nylon
while cheap and easy to injection mold was probably not the best choice for
card guides.  But then who would ever have expected these machines to still
be coveted 40 years after manufacture.

-- 
Doug Ingraham
PDP-8 SN 1175

Re: Restoring Nylon parts (like the card guides in a PDP-8a chassis)

[Paul Koning]

> On Mar 21, 2016, at 1:02 PM, Doug Ingraham  wrote:
> 
> A friend mentioned that there was a thread about the card guides in an 8a
> or 8e chassis but I was unable to locate it so I am posting this as a new
> thread as it has more relevance than just specifically those card guides.
> 
> Nylon is hygroscopic. Hygroscopic means it has the ability to absorbs
> water.  As nylon ages it drys out.  When nylon dries out it shrinks and it
> becomes brittle.  If a nylon part has not yet cracked or been damaged by UV
> it can be restored to almost like new simply by boiling it in water for 15
> to 20 minutes.  Boiling will force water back into the material and it will
> expand and soften.

Neat.

> ...
> Unfortunately there are no adhesives that will adhere to nylon long term so
> it is not possible to repair broken nylon parts in a usable manner.  

True.  But can you weld it (with a heat gun and nylon filler -- the way is 
routinely done with polyethylene)?

> Nylon
> while cheap and easy to injection mold was probably not the best choice for
> card guides.  But then who would ever have expected these machines to still
> be coveted 40 years after manufacture.

One possible consideration (apart from cheap and easy to manufacture) is that 
nylon is self-lubricating, a useful property for guides that have sliding 
contact with the card.

Some 3d printers (not the very cheapest but still moderately priced ones) will 
handle nylon.

paul

Free: DEC 19 Inch Rack and Kennedy Tri-Density 9-Track Drive in Exeter, NH, USA

[Marden P. Marshall]

I have a vintage DEC 19 inch rack with a Kennedy 9400 Tri-Density 9-Track tape 
drive located in Exeter, NH, USA that needs a good home.  If you’re interested 
I can send some photos, etc.

Thanks,

-Mardy

Re: Resistor/Fuse replacement (DEC H7104-D)

[Adrian Graham]

On 18/03/2016 02:11, "Josh Dersch"  wrote:

>> Onecall are education-only suppliers but the same part numbers work with
>> Farnell/Element14. Part# is 1692450.
>> 
> 
> Thanks!  Yes, that looks very similar except mine has a tolerance rating
> of 10%.  Vincent helpfully pointed me at:
> 
> http://www.digikey.com/product-detail/en/tt-electronics-irc/SPP2UL1R00JLF/989-
> 1272-1-ND/4215463
> 
> which look like they should do the job, and I ordered a handful just in
> case I ever need a few more.

Good news - mine worked so fingers crossed for yours too. I now have a
functioning PSU again though I've not tried it back in the chassis yet...

-- 
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?

Re: Code listings for the I4004 or I4040

[Brent Hilpert]

On 2016-Mar-19, at 11:40 AM, Paul Birkel wrote:
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Brent
> Hilpert
> Sent: Friday, March 18, 2016 5:41 AM
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Code listings for the I4004 or I4040
> .
> 
> I had a failed 4201 chip (clock gen), it would be nice to come across a
> replacement, but solved the problem with a substitute made from 3 CMOS
> chips. 
> 
> -
> 
> Brent:  Could you share your CMOS circuit design for a 4201 substitute?
> THX!


Dwight's ebay solution may be preferable but otherwise:
http://www.cs.ubc.ca/~hilpert/tmp/timing4201.pdf

VCF Southeast + East details updated

[Evan Koblentz]

It's almost time for two awesome Vintage Computer Festival shows!

VCF Southeast is April 2-3. Details are here: 
http://vcfed.org/wp/festivals/vintag...val-southeast/.


VCF East is April 15-17 (now including Ted Nelson!). Details are here: 
http://vcfed.org/wp/festivals/vintag...festival-east/.

Anyone in the PNW Going to VCFwest this August?

[John Ball]

I'm trying to figure out a logistical nightmare to get a number of machines
down there before I commit to any reservations. I'm several hours East of
Vancouver Canada but there is several hundred pounds in Silicon Graphics
workstations, monitors and peripherals I planned to take. My car is far too
small and I am not fully licensed to rent a truck for the week. Best I can
hope is someone else with a large vehicle is going the same direction there
and back. Can totally help to pay some of the costs.

-John

Re: Restoring Nylon parts (like the card guides in a PDP-8a chassis)

[Jules Richardson]

On 03/21/2016 12:02 PM, Doug Ingraham wrote:

I was able to restore almost all the unbroken card guides on my 8a.  A
couple of them had taken on a permanent bend due to excessive shrinkage.
Some had broken pins.  A few of the pieces expanded too much and you could
plug them into the chassis but they bowed away from the edge because they
had lengthened beyond original length.  Waiting a few weeks allowed them to
dry out a little and shrink and restored them to original size.


Interesting... so boiling them can make them expand too much, leaving them 
for a few weeks will allow them to contract, but they "remember" their 
manufactured size, such that a few weeks after they they aren't trying to 
return to their shrunken, pre-boiled state?


cheers

Jules

Re: Restoring Nylon parts (like the card guides in a PDP-8a chassis)

[Chuck Guzis]

On 03/21/2016 04:25 PM, Jules Richardson wrote:


Interesting... so boiling them can make them expand too much, leaving
 them for a few weeks will allow them to contract, but they
"remember" their manufactured size, such that a few weeks after they
they aren't trying to return to their shrunken, pre-boiled state?


Interesting.  If water evaporation accounts for the dimensional 
instability, why not use something that doesn't evaporate quite as 
easily?  Say, ethylene glycol or a silicon oil?


--Chuck

Re: Restoring Nylon parts (like the card guides in a PDP-8a chassis)

[Mike Stein]

Interesting indeed; that explains why the two tiny nylon gears in almost every 
one of the small plotters based on the little Alps unit (Radio Shack, 
Commodore, Atari etc.) have split...

m

- Original Message - 
From: "Chuck Guzis" 
To: "General Discussion: On-Topic and Off-Topic Posts" 
Sent: Monday, March 21, 2016 7:37 PM
Subject: Re: Restoring Nylon parts (like the card guides in a PDP-8a chassis)


> On 03/21/2016 04:25 PM, Jules Richardson wrote:
> 
>> Interesting... so boiling them can make them expand too much, leaving
>>  them for a few weeks will allow them to contract, but they
>> "remember" their manufactured size, such that a few weeks after they
>> they aren't trying to return to their shrunken, pre-boiled state?
> 
> Interesting.  If water evaporation accounts for the dimensional 
> instability, why not use something that doesn't evaporate quite as 
> easily?  Say, ethylene glycol or a silicon oil?
> 
> --Chuck
>

Re: Resistor/Fuse replacement (DEC H7104-D)

[drlegendre .]

I don't quite get what makes this DigiKey part suitable for the role of a
fused resistor. I do see that it has specs for 'fusing behavior' but that
aside, I don't see that this series is marketed / sold as a "fusible
resistor".

One reason I question it, is the fact that the fusing ratings are only
plotted for like 40X or 50X expected current. Can the circuit under
protection be relied upon to produce those levels of current, even under
hard-fault conditions?

Always trying to learn..

On Mon, Mar 21, 2016 at 2:53 PM, Adrian Graham  wrote:

> On 18/03/2016 02:11, "Josh Dersch"  wrote:
>
> >> Onecall are education-only suppliers but the same part numbers work with
> >> Farnell/Element14. Part# is 1692450.
> >>
> >
> > Thanks!  Yes, that looks very similar except mine has a tolerance rating
> > of 10%.  Vincent helpfully pointed me at:
> >
> >
> http://www.digikey.com/product-detail/en/tt-electronics-irc/SPP2UL1R00JLF/989-
> > 1272-1-ND/4215463
> >
> > which look like they should do the job, and I ordered a handful just in
> > case I ever need a few more.
>
> Good news - mine worked so fingers crossed for yours too. I now have a
> functioning PSU again though I've not tried it back in the chassis yet...
>
> --
> Adrian/Witchy
> Binary Dinosaurs creator/curator
> Www.binarydinosaurs.co.uk - the UK's biggest private home computer
> collection?
>
>
>

Re: Resistor/Fuse replacement (DEC H7104-D)

[dwight]

Maybe a real fuse in series with a real resistor.
Dwight



From: cctalk  on behalf of drlegendre . 

Sent: Monday, March 21, 2016 6:50 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Resistor/Fuse replacement (DEC H7104-D)

I don't quite get what makes this DigiKey part suitable for the role of a
fused resistor. I do see that it has specs for 'fusing behavior' but that
aside, I don't see that this series is marketed / sold as a "fusible
resistor".

One reason I question it, is the fact that the fusing ratings are only
plotted for like 40X or 50X expected current. Can the circuit under
protection be relied upon to produce those levels of current, even under
hard-fault conditions?

Always trying to learn..

On Mon, Mar 21, 2016 at 2:53 PM, Adrian Graham  wrote:

> On 18/03/2016 02:11, "Josh Dersch"  wrote:
>
> >> Onecall are education-only suppliers but the same part numbers work with
> >> Farnell/Element14. Part# is 1692450.
> >>
> >
> > Thanks!  Yes, that looks very similar except mine has a tolerance rating
> > of 10%.  Vincent helpfully pointed me at:
> >
> >
> http://www.digikey.com/product-detail/en/tt-electronics-irc/SPP2UL1R00JLF/989-
> > 1272-1-ND/4215463
> >
> > which look like they should do the job, and I ordered a handful just in
> > case I ever need a few more.
>
> Good news - mine worked so fingers crossed for yours too. I now have a
> functioning PSU again though I've not tried it back in the chassis yet...
>
> --
> Adrian/Witchy
> Binary Dinosaurs creator/curator
> Www.binarydinosaurs.co.uk - the UK's biggest private home computer
> collection?
>
>
>

Andy Grove passed away last night

[Curious Marc]

>From the CHM:

"Dear all,

The museum is remembering Andy S. Grove, who passed away last night. Please 
read David C. Brock’s timely blog post this evening, 
http://www.computerhistory.org/atchm/remembering-andy-s-grove/

Best,
Kirsten Tashev

Vice-President, Collections & Exhibitions

Computer History Museum"



I met him during my time at Intel, he attended a couple important meetings 
(acquisitions discussions, company wide technical strategic planning meetings, 
quarterly meetings). But already in not so good health and not saying much. We 
sure listened when he spoke up. I remember in particular once when Intel had a 
really bad quarter because we raised the price of Flash, after misjudging 
worldwide inventory. We consequently lost a large part of the market to Samsung 
– which probably never returned. Most CEOs would have fired the VP, but instead 
he took the mike and congratulated him for having had the guts to raise prices. 
We all applauded, but I distinctly remember I wasn't quite sure why... Bless 
his soul, he brought a company back from the brink of extinction selling RAM at 
negative margins, to industry dominance in microprocessors with 65% gross 
margins. That is excessively difficult to do. 



Marc

Re: Resistor/Fuse replacement (DEC H7104-D)

[Josh Dersch]

On 3/21/16 12:53 PM, Adrian Graham wrote:

On 18/03/2016 02:11, "Josh Dersch"  wrote:


Onecall are education-only suppliers but the same part numbers work with
Farnell/Element14. Part# is 1692450.


Thanks!  Yes, that looks very similar except mine has a tolerance rating
of 10%.  Vincent helpfully pointed me at:

http://www.digikey.com/product-detail/en/tt-electronics-irc/SPP2UL1R00JLF/989-
1272-1-ND/4215463

which look like they should do the job, and I ordered a handful just in
case I ever need a few more.

Good news - mine worked so fingers crossed for yours too. I now have a
functioning PSU again though I've not tried it back in the chassis yet...

Nice!  My replacements arrived today and unfortunately I did not have 
such good luck.  No smoke or fire, but now I get nothing at all out of 
the supply.  The whine is gone, but there's nothing output at all.  The 
fuse/resistor didn't blow (it's still got continuity across it) and the 
transistor I replaced is still fine, but there must be something else in 
the supply that's causing issues...


Blargh.  I hate working on power supplies.

- Josh

Re: Resistor/Fuse replacement (DEC H7104-D)

[Chuck Guzis]

On 03/21/2016 07:34 PM, dwight wrote:

Maybe a real fuse in series with a real resistor.


I'd asked that, but reconsidered in that fusible resistors all seem to 
have a strong positive temperature coefficient and then a point at which 
they will fuse.


IOW, the things degrade gradually before going ka-pow; something not 
realized with a resistor+fuse combination.


See, for example:

http://www.vishay.com/docs/28737/nfr25.pdf

--Chuck

Re: Baydel Unibus disk systems

[Mike Ross]

On Sat, Mar 19, 2016 at 9:41 PM, Christian Corti
 wrote:
> On Fri, 18 Mar 2016, Mike Ross wrote:
>>
>> I just have the controller board; I don't have any of the hard drives
>> left. All I remember is the disk was an 8" and the interface is a
>> single 40-pin cable; so not SMD and not SCSI. Far too early for IDE or
>> ATA. Any suggestions for what the interface might have been and what
>> disks might have been used? What hard disks were around in late 70s /
>> early 80s that used a single 40-pin connector??
>
>
> My guess is that it's not a controller board but just the interface to the
> controller found in the external enclosure, probably with the hard drive.
> The interface would implement things like NPR and BR and the like, so there
> wouldn't be enough board space to implement a complete hard drive
> controller, especially if the board dates from that era. IMO it's something
> like a RX211 board for hard drives.

Well you were right on the money! I found a manual for the thing. More
precisely I found I had a manual for the QBus version of the thing
squirreled away.

Baydel called the entire Qbus subsystem the 'Baydel D405' - and Google
returns precisely zero relevant hits for that search! I don't know
what they called the Unibus version. The host interface (Unibus or
Qbus) was indeed only half the system. Bayel referred to it as the
'I-board' (for 'interface'); it talked via the 40 pin connector to the
'P-board' (for 'personality') mounted in the drive chassis; the
P-board did indeed implement the drive controller functions. The drive
was a Pertec D8000 20MB Winchester; the drive chassis could contain
one of these (which all my systems did) or two of these (which needed
a special handler for the OS) or one 20MB hard disk plus one Shugart
8" floppy - which emulated an RX02.

That all rings bells with what I had.

Doesn't help much as the chances of me finding such a subsystem are
tending to zero I suspect. But mystery solved!

Thanks

Mike

http://www.corestore.org
'No greater love hath a man than he lay down his life for his brother.
Not for millions, not for glory, not for fame.
For one person, in the dark, where no one will ever know or see.'

multinet 4.1 PAK

[william degnan]

Anyone have the multinet 4.1 PAK checksum and install key info?  I need to
re-install my PAK and I don't have *doh!* the checksum value.  I thought I
did but...nope.

--- Product ID  Rating - -- Version --
Product  Producer  Units Avail  Activ  Version DateExpires
MULTINET TGV   200   F  0  0.0 31-JUL-1997 (none)

A-10098-116512
issued by TGV

thanks
Bill

-- 
@ BillDeg:
Web: vintagecomputer.net
Twitter: @billdeg 
Youtube: @billdeg 
Unauthorized Bio 

Request for TU58 tapes (DECtape II)

[malcolm]

I've just finished a restoration of a TU58 drive.  I'm looking for a small
quantity of TU58 tapes (perhaps 2 tapes?) to use with it.

 

Ideally I'm looking for tapes that have been run through a drive recently
and known to be not shedding oxide.

 

If anyone has some that they are prepared to part with, please let me know.
I'm happy to pay for the tapes plus shipping.

 

Thanks - Malcolm.