Thursday, August 27, 2015

HP-21 Calculator

Picked up this HP-21 calculator at a yard sale.DSCF3670 DSCF3671 Plugged in and it doesn’t seem to work and the display is not refreshing quickly.DSCF3673 Power adapter is putting out what I think is the correct voltage more or less.DSCF3681 DSCF3682 DSCF3684 DSCF3687 Batteries looked ok, but are probably bad.DSCF3690 With the batteries out (something you’re not supposed to do) the calculator display is stable but pressing buttons does nothing.DSCF3694 Removed two rubber feet and the screws underneath.DSCF3695 Careful prying separated the halves. DSCF3698 DSCF3700 DSCF3703 DSCF3705 DSCF3707 The board interconnectors are pretty neat.DSCF3708 DSCF3711 So this is a problem (corroded and lifted trace)DSCF3714
And this as well…  DSCF3717 DSCF3718 More corrosion.DSCF3720 DSCF3721 DSCF3723 DSCF3724 DSCF3725 DSCF3727 DSCF3728 DSCF3731
So I’ll have to see about removing all of the corrosion and rebuilding the broken traces. I hope I won’t have to desolder any of the ICs but some of the corrosion runs underneath. Fun!

Monday, June 08, 2015

VESA Mount Keyboard Trays

Ran the CNC for the first time in the new shop and found that the keyboard was positioned perfectly to fill up with aluminum chips. I did a quick Google for VESA mounted keyboard trays was amazed at how much they cost. SDS has what looks to be a great product, but having bled money into the shop for the past few months, I needed to do this on the cheap. Of course VESA wall mounts are inexpensive, especially for smaller monitors. So I set about to make a mount that would go between the monitor and the monitor mount plate.DSCF3506 Some preliminary drilling for the VESA bolt pattern.DSCF3508 Looks OK.DSCF3518 This is a little thick for my small Diacro bending brake, but it was no problem at all.DSCF3526 Clamping the keyboard tray to the bent arm and match drilling holes. This keyboard tray was nothing more than a piece of already bent scrap waiting for this moment. DSCF3533 DSCF3537 I quickly realized that the main arm needed some stiffening as the leverage on the mount was too high. Some hardware store aluminum angle (my only expenditure, everything else was scrap and hardware on hand) made a world of difference.DSCF3538 DSCF3539 Kent made me this keyboard tray in a few minutes, of course he has a proper press brake and big shear. DSCF3540 It’s still a little bendy, But at this point that’s more the fault of the monitor arm. The small ones aren’t rated for too much weight so I need to remember not to hang on it anyway.DSCF3541 DSCF3546Ready to make chips!

Thursday, April 30, 2015

Synthrotek Ring Modulator Kit

As you can probably tell I’m getting into music-y/synth-y stuff. So I decided to build a ring modulator. I didn’t have the parts on hand so I impulse bought a kit from Synthrotek on Etsy (the kit was slightly less expensive on Etsy).
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Really easy to put together, just solder it up according to directions, took maybe 15 minutes total to put together in the project box. The box doesn’t come with the kit. This is what my voice sounds like modulated with a carrier wave at various frequencies between 100Hz and 400Hz.

Korg DS-8 Synthesizer Battery Replacement and Memory Recovery.

So I spotted this keyboard out of the corner of my eye at a yard sale. As soon as I saw it had a joystick I was intrigued. That it was $30 and said “needs work” on the tag cemented my desire to own it.DSC06416It’s a Korg DS-8. Pretty fancy for the late 1980’s. I did some reading at it became clear that it needed a new backup battery installed. The voices were all weird or missing and the LCD was displaying garbage characters. A factory reset restored one piano voice, but in order to load new patches (voices, instruments, whatever) I needed to replace the battery. I downloaded the user manual and the service manual.DSC06433DSC06426Joystick!DSC06385 You basically remove all the screws and the bottom comes off. It has to hang over the edge of the table so the joystick doesn’t get stressed.korg1 Korg.DSC06390 A soldered in CR2032 3V lithium battery.  DSC06395 DSC06396 FYI, you can’t solder tabs onto a lithium battery…these are spot welded. You can buy replacement batteries but I wanted to get it running ASAP.DSC06398 I used my Hakko desoldering tool to remove the old battery.DSC06404 While the desoldering tool was warm I removed the CR2032 coin cell holders from some dead PC motherboards I had laying around. Then I made some leads. DSC06408 DSC06409 DSC06412 Soldered in the holder. Now the next guy needing to replace the battery can just snap one in. You can buy the holders but why not recycle?
Coincidentally my friend Kent had the soldered in battery on his CNC mill motherboard (a 486 processor DOS based Centroid PC control…) fail this week, wiping his incredibly specific BIOS. I gave him one of the holders and he was back in business as well, although we did have to find out a bunch of detail about the hard drive, including the Landing Zone specification in order for the motherboard to see the drive.DSC06435The power cord was missing, I didn’t have an exact match so I made do with some large spade crimps that fit.DSC06442I had this USB MIDI cable on hand and tried to use it to upload some factory patches (Sysex files!) using both MidiOx and Bome’s SendSx. But it just wouldn’t work. I could play individual notes from the PC and I could retrieve data from the keyboard but it just wouldn’t work for sending data. Much Googling found some various forum threads that said that you need a better quality interface. DSC06437In what was my second ever Craigslist purchase, I found a nice guy selling an M-Audio MIDISport 2x2USB interface for about half of new price. A quick trip to town and I was in business. I forget which of the two programs I ended up using to upload the file, but it succeeded and I now have all the factory patches installed. DSC06429DSC06428Now if only I had some musical ability…