Ugly soldering (HP 67 internal)

[n1msr]

I have made a complete mess of attempting to solder wires back on to the HP 67 board after replacing a gummy wheel. Unfortunately during the disassembly several wires detached from the board(s). Careless, I know.

Look at the before and after pics, and after you have recovered from the shock of this act of vandalism - are there any general hints about how best to get these tiny joints tidied up? I have what I think is a narrow pointed soldering iron tip, but clearly my soldering technique is completely lacking. I am reluctant to try again for fear of doing further damage.

Thanks.

[Maximilian Hohmann]

(11-07-2016 09:59 PM)n1msr Wrote:  I am reluctant to try again for fear of doing further damage.

On the picture it does not look sooo horribly bad. But can't you just practice your skills outside that calculator a little before the next attempt?

[Harald]

(11-07-2016 10:16 PM)Maximilian Hohmann Wrote:  

(11-07-2016 09:59 PM)n1msr Wrote:  I am reluctant to try again for fear of doing further damage.

On the picture it does not look sooo horribly bad. But can't you just practice your skills outside that calculator a little before the next attempt?

I agree, you haven't done any serious damage. So you should practice your soldering a bit and then have another go. Where are you based? Maybe there is someone near you who would be happy to help.

One thing I don't get though is, could you not simply plug the wires back in? I think there are sockets in the pcb.

[Mark Hardman]

(11-07-2016 09:59 PM)n1msr Wrote:  [A]re there any general hints about how best to get these tiny joints tidied up?

Might I suggest watching Dave Jones' "EEVblog Soldering Tutorials" on YouTube? They are worth the time. An added bonus is hearing Dave drop the B.S. bomb in his wonderful Austrailian accent.

https://www.youtube.com/watch?v=J5Sb21qbpEQ

Mark Hardman

[TASP]

A trick from sparky school:

you can get some 8, 10, 12, 14 gauge solid copper wire (or whatever you think appropriate) and wrap a length tightly around the end of your soldering iron, and then have a short length protrude beyond the existing tip.

You can take wire nippers, grinding wheel, whatever, to make the new tip pointy, or flat or angled, whatever.

You now have a custom modified soldering iron. The new wire will take a bit more time to heat up, and the increased length and surface area serve to lower the effective wattage of your iron somewhat too.

Grab any dead/unused electronics in the house and practice your technique and fine tune your new soldering iron.

Then when things seem to click, you can go back to your HP67 again.

[damaltor]

These are plug-in joints - no soldering required...

[n1msr]

Thank you to all who responded to my posted problem with my soldering issue on an HP-67.

The connectors are plug-in joints, as rightly highlighted by damaltor.

One of the connectors has gone - I must have lost it in the fight with the board and the soldering iron. Can I get replacements as a generally available component from an electronics stickist? What is the proper name for these things, i.e. do I need a more precise description than plug-in joint?

Thank you again.

[jebem]

(11-12-2016 01:47 PM)n1msr Wrote:  Can I get replacements as a generally available component from an electronics stickist? What is the proper name for these things, i.e. do I need a more precise description than plug-in joint?

Hi,
I don't think you can find spare parts anymore for these vintage machines, except if you get additional machines for spares.

There are a couple of options, but the obvious would be to install terminals on the board and solder the wires to the terminals.
For example, a "machine pin solder tail" IC socket could be used. It can easily be cut to the number of pins required.

See here.

[teenix]

(11-12-2016 01:47 PM)n1msr Wrote:  The connectors are plug-in joints, as rightly highlighted by damaltor.

One of the connectors has gone - I must have lost it in the fight with the board and the soldering iron.

Please be aware that handling the board incorrectly may cause static damage to the IC components which may not be repairable. Always handle the board by the edges. Any wires connected to a circuit board requires extra careful handling or you risk damaging other connections, especially on older boards.

If the connector has totally gone due to the soldering attempt, you might need to check where it came from and make sure the circuit board tracks have not peeled away from the board because of excess applied heat.

If that looks ok, then you may be able to replace the connector with the IC socket connector mentioned by damaltor.

To do this, the hole where the original connector came from must be free from excess solder so that the new pin can be inserted. You can get "solder wick" from hobby suppliers which will help clean things up. If you do not think it is possible to clean up without damaging the board with excess heat then don't do it or your problems will get worse.

You can break one of the mentioned socket pins out of the plastic housing. They are a press fit, so can be pushed out. Insert it into the hole where the original connector cam from and solder that to the board from underneath. Then solder the wire to the top of the connector.

As already mentioned, practice a bit. Vero board available from hobby suppliers where you get the IC socket from would be cheap and good to practice on.

If it is not possible to reinsert a connector, then you could have it professionally repaired but obviously, at a cost.

As a "dodgy" fix, you could also look under the board and see where the connector was originally soldered, and solder the wire end to that spot. This method should work, but is a bit messy and may require the wire be lengthened, and may cause problems fitting back into the calculator casing

An easy solder method is first to make sure the solder tip is clean and free from excess solder. (A little bit is good) A tip size 3-5mm should suffice.

Pre tin the wire end before soldering to the board.

Don't put new solder onto the solder iron tip then move the tip to the wire end or the solder flux will burn away beforehand. The solder needs its internal flux to help combine it with the wire.

Having said that, it is good to have a "little" bit of solder on the iron tip to help with heat transfer to the wire or circuit board.

Hold the soldering iron on the bare wire end and a few seconds later push the new solder to where the solder tip meets the wire. The solder will melt around the wire (if it is clean) with the help of the flux. Don't take too long though. As soon as the solder "takes" pull the iron away and perhaps blow on the wire to cool it in case the insulation gets a bit hot.

Pre tin the top of the connector in the same way - only just enough heat heat though.

Now hold the wire end, pointing vertically down, onto the connector.

Put the solder iron tip (still with a little bit of solder on it) to where the wire rests against the connector and the two will melt together. Once this happens pull the soldering iron away and again blow on it to cool quickly.

Hopefully all fixed :-)

cheers

Tony

[n1msr]

I thought I ought to mention the conclusion to this thread, which I was surprised to see is from 2016. I didn't realise it was so long ago! Anyway...

After having the 67 in "bits" since 2016, I found The Calculator Store in late 2023 and through them Ignacio in Valencia. He put together my HP-67 (I had done the gummy wheel repair already) and so my original 1978 machine was back working in late 2023.

In passing, Ignacio recommended Tony's (teenix.org) boards. I bought one and it has given this 67 a new lease of life and interest for me. I had another non-working 67, which Ignacio fixed, although the card reader is not working properly (thr motor is OK). I have a teenix board in this now. The only real deficiency with this 67 is two cracked key springs. But I would need a donor calculator to even attempt this.

I also had a 65 that never worked, and Ignacio repaired this. It's CPU board was dead so you can probably guess that this is where another teenix board saved the day. The LED was fixed by Ignacio and is bright. I had to clean a couple of seemingly "dead" keys (reference Tony Nixon's Classic Notes) and this 65 is now fully working. It led me to discover some of the 65 quirks, and made me realise why some (many?) of the 67 features came about!

So all good now. I really would like a 29C. I sold a very nice one on eBay in 2012 when I had a big clear out of calculators that I simply wasn't using. IMHO the 29C is a beautiful machine and more so because it is compact. They are rather expensive for fully working ones, so perhaps when I have saved up my pennies...

Thanks for all your advice/comments. I am amazed at how quickly some replies appear in this forum!

Mark.