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Got a HP 19C
11-18-2016, 11:57 AM (This post was last modified: 11-25-2016 08:10 PM by david sanz.)
Post: #1
Got a HP 19C
My first HP vintage calculator.

I'm so excited.

Excelent cosmetic condition, except for a curious detail. Made in USA. Probably non-working

I am surprised by the quality of the leather poach, which is also in excellent condition.

I am aware of the issues with AC powering

Battery pack was fairly corroeded, but not a Fukushima-grade disaster. Oddly enough, there are two "+" keys and no "x" key. So somebody must have been playing with this before. The two screws visible in the battery compartment seem to be disimilar, another sign of previous manipulation. Whoever did it, it was very carefully done, no scratches or any other external damage.

edit: some pictures of the machine

https://postimg.org/gallery/1jr2o4weo/46ebbe60/
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11-18-2016, 12:23 PM
Post: #2
RE: Got a HP 19C
(11-18-2016 11:57 AM)david sanz Wrote:  My first HP vintage calculator.

I'm so excited.

Excelent cosmetic condition, except for a curious detail. Made in USA. Probably non-working

I am surprised by the quality of the leather poach, which is also in excellent condition.

I am aware of the issues with AC powering

Battery pack was fairly corroeded, but not a Fukushima-grade disaster. Oddly enough, there are two "+" keys and no "x" key. So somebody must have been playing with this before. The two screws visible in the battery compartment seem to be disimilar, another sign of previous manipulation. Whoever did it, it was very carefully done, no scratches or any other external damage.

Congratulations! Enjoy your "new" calculator!

Though the pouch being shipped with such a calculator was no real leather but some kind of soft plastic although many sellers on TAS claim such pouches are leather. That could be a sign of no idea but I don't know.
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11-18-2016, 08:53 PM
Post: #3
RE: Got a HP 19C
You are right, the pouch is not leather. It is a soft material. Still much better and more elaborated than casio and texas instruments poaches.
Predictably and regretably the machine does not work properly. New batteries installed. Upon powering up, the display stays dead, but the printer goes mad working non stop. Nothing is printed though, do not know if it is due to the printing head or to overdated thermal paper.

Sorry about my terrible English.
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11-18-2016, 09:39 PM
Post: #4
RE: Got a HP 19C
(11-18-2016 08:53 PM)david sanz Wrote:  ......
Upon powering up, the display stays dead, but the printer goes mad working non stop. Nothing is printed though ......

It would have nothing to do with the paper or the print head, even if the head was defective.

You might consider the power supplied to the calculator. There have been previous posts (can't identify them) about that behavior being related to the internal power of the 19C as not sufficient.

i.e. corroded battery terminals, internal connectors (the gold finger things) tarnished, etc. There is a connection but the amount of current able to flow is seriously diminished.

I have a 19C with the same problem, internally cleaning all contact points bypassed the problem. Taking a 19C apart is easy, putting it back together is tedious. Aligning the multiple rows of "finger pins" without bending them is bothersome. As I recall, there was a row basically at the top of the keyboard which is difficult align and reach.

Should you be mechanically inclined you might consider a product like Deoxit and clean the battery contacts and internal connections of the calculator. Doing so might restore its operation, you may still have problems with individual keypresses.

Just a thought.
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11-22-2016, 09:21 PM (This post was last modified: 11-23-2016 03:33 PM by david sanz.)
Post: #5
RE: Got a HP 19C
Thank you for the sugestions.
Did I say it did not look like an absolute disaster? Well, it turns out it is. Just opened the calculator, to find four broken «golden fingers» ( it was not me, belive me). Plus some white stuff on the coil at the bottom of the PCB and blue stuff in the nearby big resistor.

edit:

link to image of catastrophic area
https://postimg.org/image/krtvyzo83/
broken fingers can be seen on the left
I think blue dirt comes in fact from damaged capacitor (in green)
From what I have learnt reading around here, I expected to have to do some cleaning and replace some faulty capacitors.
But.... removing the PCB is more chalenging than I thought, so for the time being I will left the machine as it is. Do not want to scratch or break something.

Actually, putting the two halves of the machine back together is tricky, but easier than I thought. The trick is to align carefully the bottom edge of the machine, and then snap it close.
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11-23-2016, 12:20 AM
Post: #6
RE: Got a HP 19C
(11-22-2016 09:21 PM)david sanz Wrote:  Thank you for the sugestions.
Did I say it did not look like an absolute disaster? Well, it turns out it is. Just opened the calculator, to find four broken «golden fingers» ( it was not me, belive me). Plus some white stuff on the coil at the bottom of the PCB and blue stuff in the nearby big resistor.

Perhaps not Smile

If the chips are ok, then the other problems could be repaired if you feel confident enough. The circuit board can be carefully cleaned. The "stuff" might just be the cause of the improper operation - perhaps upsetting the power supply circuit. Fiddly, but coils can be rewound if corroded, simple components like resistors can be replaced and possibly someone in this forum may have extra fingers from an old unserviceable calculator or know of something else that will do the job. If any of this works, it will be a cheap fix.

I don't think it would be wise to apply any more power to the calculator until it has been cleaned up.

cheers

Tony
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05-20-2017, 01:47 PM (This post was last modified: 05-20-2017 04:14 PM by PANAMATIK.)
Post: #7
RE: Got a HP 19C
(11-22-2016 09:21 PM)david sanz Wrote:  Did I say it did not look like an absolute disaster? Well, it turns out it is. Just opened the calculator, to find four broken «golden fingers» ( it was not me, belive me). Plus some white stuff on the coil at the bottom of the PCB and blue stuff in the nearby big resistor.

The four broken fingers are not broken, they had to be cut to follow the slanted PCB leveling. All HP-19Cs have four smaller fingers at this part of the connector.

Your PCB looks very clean compared to my HP-19C machine, which I just restored. I measured all capacitors and resistors and they were still working. The transistors are prone to fail. You can replace them by any standard TO-92 NPN type like 2N3904, 2N3704 to get the power supply running.

Bernhard

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