Help with HP-97 Soldering Question



#8

I'm a software guy who is trying to learn electronic repair. I've had some small success lately thanks in part to the kind help and advice I've received here. I find that I could use some advice now, and I hope someone here can help.

I have a question about soldering a wire on to the electric motor of the card reader I just obtained. I fixed the "gummy wheel" using instructions found in the articles forum. It all went very well up until after I had reassembled the card reader housing and reattached the card reader PCB. I then noticed that the hot lead to the motor had broken off at the motor housing. The article had warned me to take note of the colors and positions of the various wires, so I wasn't suprised that one had broken off. So I started to plan how I would solder this lead back on. There's a picture below that shows the situation. The leads are connected to the terminals on the motor via two "wings" that also allow a cap to be soldered across them. Looking at the ground lead, which is still attached, I see that the end of each wire is connected between the very end of the "wing" which appears to be rolled up around it. (I hope the picture makes this clear.) In the picture, I have pried the wing on the positive side away from the bundle. We are looking more or less straight down on the end of the motor. The broken off end of the positive lead is still pinched between the two sides of the end of the "wing." I don't think I can open this terminal part of the wing:





So what I propose to do is to pinch the end of the positive lead (already stripped as can be seen in the picture) between the sides of the "wing I have opened up. Istead of the very end of the wing, the wire will sit in the "v" we are looking down into in the picture. I will then solder it in place.

My questions are these:

  1. Is this likely to work? Will I be changing the electrical characteristics of the terminal in a way that would be harmful? (My guess is "no," but I'm a paranoid amatuer. Or maybe that's an amateur paranoid. 8)
  2. How hot should I set my temperature controlled iron to perform this soldering? The PCB is on the other side of he housing, with presumably a large heat sink of a motor, and the plastic frame between it and the soldering tip. I'm using standard 60/40 rosin core solder.
  3. Any other tips or suggestions?

Thanks in advance for any advice you can offer.


#9

Quote:
So what I propose to do is to pinch the end of the positive lead (already stripped as can be seen in the picture) between the sides of the "wing I have opened up. Istead of the very end of the wing, the wire will sit in the "v" we are looking down into in the picture. I will then solder it in place.

Don't do that, as it will certainly fail and probably even break something. Put a little bit of solder on the lead, heat up the soldered area below the left (in the picture) leg of the condensor, put the lead in place, wait 2 seconds.

Quote:
Is this likely to work? Will I be changing the electrical characteristics of the terminal in a way that would be harmful? (My guess is "no," but I'm a paranoid amatuer. Or maybe that's an amateur paranoid. 8)

This will work :)
Quote:
How hot should I set my temperature controlled iron to perform this soldering? The PCB is on the other side of he housing, with presumably a large heat sink of a motor, and the plastic frame between it and the soldering tip. I'm using standard 60/40 rosin core solder.

I prefer to solder at highest temperature, but 350 degrees C should be fine. Just take care to work fast enough to not melt any plastics or roast any other part.
Quote:
Any other tips or suggestions?

Nah, this should work well :)
You should consider purchasing some good solder (colophonium core plus parts of silver - or if you can get your hands on it, some good Pb stuff) plus good iron - you might want to check ebay for some used equipment (Weller Magnastat or PACE)

#10

Quote:
Put a little bit of solder on the lead, heat up the soldered area below the left (in the picture) leg of the condensor, put the lead in place, wait 2 seconds.

Thanks for the advice!

Let me restate what I think you said to check if I understand. First, tin the stripped end of the red lead. Second, heat the solder pad where the condensor attaches to the positive side of the bridge, wait until heated, apply the tinned lead, wait two seconds then withdraw the iron.

Did I get that right?

Thanks again!

#11

Thanks for your help, Frank! I just finished my first HP-97 card reader "gummy wheel" repair. It was a complete success, partly thanks to your advice!

Regards,
Howard.


#12

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#13

Yes, I recalled you earlier advice on this, Don. Thanks. I've adopted it in my work. I used a setting of 600F in this case, which worked great.


#14

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#15

I wasn't complaining, Don. 8)

Just saying that I took your advice and it has worked out well for me.

As to the 9816, I was finally able, with Jon Johmston's (of hpmuseum.net) help to get TELEDIK.EXE to work on my old P75. I had to install and boot real MS-DOS before the low-level access to the floppy controller TELEDISK uses succeeded in reading the SS/DD disks I had. But I also proved I could write SS/DD images to one side of a DS/DD dik. That means I can use all the great 9816 software Jon has up on his site. So I'm sitting pretty in the 9816 department.

Loading real MS-DOS also made the NI drivers for my AT-TNT GPIB board work. It almost worked under DOSEMU, but that software doesn't do DMA, other than for the SB emulation. The "TNT" board is a high-speed GPIB card, and it needs DMA to make that work on the PC side. I'm sure I could get a slower HP-IB card to work under Linux/DOSEMU, but not this particular card. The Linux GPIB project drivers are supposed to work with this ISA card on a 2.4 or 2.6 kernel, but I haven't taken the trouble to build the custom kernel yet. I'm not hugely motivated because I'd also have to write a file system driver for Amigo and/or [CS]S80 to talk to any of the various HP-IB drives I have. As usual, data transfer, particularly software transfer is my main interest. There just aren't any extant drivers with source for these old drives, at least as far as I'm aware. I do know HP maintained drivers for use in HP-UX for many of these devices, but I'm sure they have long since stopped doing that.

Regards,

Howard


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