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Any hope for that derelict HP-25?
11-12-2017, 05:46 PM (This post was last modified: 11-12-2017 05:47 PM by Benoit Maag.)
Post: #1
Any hope for that derelict HP-25?
Just bought on e-bay an as-is HP-25 with the intention to upgrade it with a Panamatik LP

Unfortunately, the machine was in a much worse condition that I expected (see slide 1)
After an hour with vinegar, Q-tips and an old toothbrush, I could get to a slightly cleaner board (slide 2), but there is still some blue corrosion I cannot reach, and some lines on the keyboard PCB are damaged and cut-off

Is there any hope to get it back to life?
Is it realistic to fix the broken PCB lines with conductive paint (like Bare Paint)?
Should all blue corrosion be removed? Any suggestion as to how to do that?
I damaged one of the feet - what is a good replacement? (eraser cut to size, caulk...)

Please help - Thank you


Attached File(s)
.pptx  HP-25 Repair v2 - compressed.pptx (Size: 244.04 KB / Downloads: 55)
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11-12-2017, 11:10 PM
Post: #2
RE: Any hope for that derelict HP-25?
(11-12-2017 05:46 PM)Benoit Maag Wrote:  Just bought on e-bay an as-is HP-25 with the intention to upgrade it with a Panamatik LP

Unfortunately, the machine was in a much worse condition that I expected (see slide 1)
After an hour with vinegar, Q-tips and an old toothbrush, I could get to a slightly cleaner board (slide 2), but there is still some blue corrosion I cannot reach, and some lines on the keyboard PCB are damaged and cut-off

Is there any hope to get it back to life?
Is it realistic to fix the broken PCB lines with conductive paint (like Bare Paint)?
Should all blue corrosion be removed? Any suggestion as to how to do that?
I damaged one of the feet - what is a good replacement? (eraser cut to size, caulk...)

Please help - Thank you

I fix electronic equipment all the time however I'm not in the business (or pastime) of restoring... I'm making the distinction because the approaches can be quite different. If that were my calculator I would remove all the corrosion as possible (I still see a lot), many times I use rubbing alcohol (+90%) and a toothbrush. Sometimes I use solvents but those are more aggressive... in any case, make sure that the plastic exterior parts don't get in contact with any alcohol or solvent of any type... make sure it stays in the PCB. You might need to do some scratching as well, I use a very small flat screwdriver for that (go easy to minimize collateral damage). To connect traces I just use wire-wrap (solid wire, 30 AWG if I remember well) and solder it in a clean part of the trace (before and after the cut), this part requires some skills, I use the soldering iron since I was a kid so it's kind of natural for me to chose this option.

My biggest concern would be the keyboard contacts, have you checked that part? I would evaluate that before starting if possible... you may use a DMM before breaking the rivets

My 2 cents... good luck with your project.
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11-13-2017, 03:53 AM
Post: #3
RE: Any hope for that derelict HP-25?
Dear acapde,

Thank you for the tips - really appreciate
I have not checked the keyboard contacts - good point - they do not look great...
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11-13-2017, 04:35 AM
Post: #4
RE: Any hope for that derelict HP-25?
Indeed, the keyboard is bad - some keys do not even click right
You mention about rivets -do you mean the small plastic dots? Do I need to break all of them to access the back of the keyboard PCB and the keys?
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11-13-2017, 05:08 AM
Post: #5
RE: Any hope for that derelict HP-25?
Those dots are the fabled Heat Stakes. Some one posted that he took the (long) time to shave them down to the size of the holes they go through and pried the board off past them. He said he was able to re-melt them and there was enough material to re-attach the board one time. I'm guessing he is gentle with his key-strokes.
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11-13-2017, 01:42 PM
Post: #6
RE: Any hope for that derelict HP-25?
(11-12-2017 05:46 PM)Benoit Maag Wrote:  Just bought on e-bay an as-is HP-25 with the intention to upgrade it with a Panamatik LP

Perfectly suitable for the LP. The broken keyboard lines can be repaired with small copper wires. The corrosion of the main board doesn't matter at all. But if the display is corroded internally you need a replacement.

Good luck
Bernhard

That's one small step for a man - one giant leap for mankind.
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11-15-2017, 06:29 AM
Post: #7
RE: Any hope for that derelict HP-25?
Den,
I do not think I will have the patience - so I will probably slice the post tops with a thin razor blade, clean-up the keys if I can and find a way to glue back the keyboard to its PCB

Bernhard,
Great news - can’t wait for the LP to become available - do you have a pre-order list?
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11-15-2017, 06:43 AM
Post: #8
RE: Any hope for that derelict HP-25?
Den,
I do not think I will have the patience - so I will probably slice the post tops with a thin razor blade, clean-up the keys if I can and find a way to glue back the keyboard to its PCB

Bernhard,
Great news - can’t wait for the LP to become available - do you have a pre-order list?
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11-15-2017, 07:33 AM
Post: #9
RE: Any hope for that derelict HP-25?
(11-15-2017 07:04 AM)Benoit Maag Wrote:  Bernhard,
Great news - can’t wait for the LP to become available - do you have a pre-order list?

There is no pre-order list. Nevertheless I will check all posts here. Please order by email (see thread "Woodstock Low Power") Thanks.

see also my keyboard fix at this thread:
http://www.hpmuseum.org/forum/thread-5936-page-2.html

Bernhard

That's one small step for a man - one giant leap for mankind.
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11-15-2017, 08:18 PM
Post: #10
RE: Any hope for that derelict HP-25?
Bernhard,

Just to confirm: do you need to cut all the post tops to separate the keyboard from its PCB, or just the ones that should show with a green arrow?
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11-15-2017, 11:11 PM
Post: #11
RE: Any hope for that derelict HP-25?
(11-15-2017 08:18 PM)Benoit Maag Wrote:  Bernhard,

Just to confirm: do you need to cut all the post tops to separate the keyboard from its PCB, or just the ones that should show with a green arrow?

To separate the keyboard from the PCB you have to cut all tops. I recommend to fix all of them with glue. I observed that the middle keys had a soft feeling after some time, therefore I added glue to all of them (also the not green marked) at a later time. This fixed the keyboard and key feeling durable. Be also careful not to glue them too tight together. I had another case were the two slider switches moved a little bit hard after fixing. A small amount of silicon grease at the slider contacts can be used.

Bernhard

That's one small step for a man - one giant leap for mankind.
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