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Epson HX-20, $10 at the flea market

The light board is made by ACS (Adaptive Communications Systems), just as the RealVoice is. I get the impression that there's s'pozed to be a template or templates that go over the top of the lights and allow the user to select various menu choices using some kinda (magnetic?), (capacitive?) pointer, with the LEDs as visual feedback. The blinkenlights mode is prolly as you said, some kinda diagnostic routine. That's my best guess anyways.

--T
 
I've decided not to try to make another null modem cable for this thing, but simply adapt the serial port to a standard DB9 and use the storebought null cable. I broke down and spent a whopping $17.24 on parts >gasp!< from mouser. I love those guys. They never try to screw me on shipping and never had any problem with receiving or returning. parts included a snap-in battery holder for the power 'upgrade.'
 
Quick update: I got all my parts from Mouser but the AA batteries didn't fit so I just used the dustbuster batteries that I have. So I have a few spare parts for a future project. The batteries are new so they oughtta last a good long while.

I must have done something wrong about the serial cable, cause it didn't work. It was my 2nd attempt and I've been out of practice for a while so I'll try again while I still have parts. Are there any proprietary parts lurking around out there that I can just pick up? Certain part numbers for different cables? maybe some kind of cash register cable?? It has the DIN style connectors like old cash registers, is why I am asking.
 
Just a follow-up as I work with this computer.

Hints for making a replacement battery cheaply:

Get a cordless drill battery, mine came from a Craftsman. Open it up and you got a lot of sub-C cells, the same cells that the Epson uses. Get four of them out and arrange them the way they're arranged in the Epson. Mine were presoldered all around and all I had to do was disconnect two solder points. Take the wire off your old battery and attach it to the + and - of the drill cells. I crimped mine and it works fine. If the drill cells don't fit perfect, that's okay, you can take out the foam pad on the inside. It'll make a little more room. Mine were still a little tight but that helped to keep the the connection to the batteries tight.

I have charged mine once and I haven't had to recharge yet, and it's been used off and on for six days.
 
Hi Nathan,

congrats on your find! An HX-20 for $10??? Unbelievable...

I just got an HX-20 off eBay -- for triple the price!
It's actually relabeled Taylor-Hobson, with a sticker covering the original label. Weird.

There's also an additional ROM in the spare socket containing an "RTH Terminal Emulator" which you can call up from the menu. I have no idea how to work the thing, all it does is show a title screen and plays an irritating (and endless!) glissando over the beeper. I assume RTH is the acronym for Rank-Taylor-Hobson, since they were apparently part of the Rank Corp. at some time. Anybody know anything about this? Is it possibly a customised unit for the company?

Btw, mine still had its original NiCd's, and they are *dead*, lasting just 5 minutes or so. I'm a bit apprehensive about replacing them with NiMH since they'd require a much higher charging current than the 200mA the HX-20 uses, otherwise charging times would be unbearable. If I replace the original 1100mAh NiCd's with 2400mAh ones, does it make sense to roughly double the charging time to ca. 16 hours, or is there a nonlinear relationship?

Thanks for any info!

--Roland
 
I have a charger here that is switchable between NiCad or NiMH, and the only difference is the amount of time before it kicks down to trickle voltage at the same current (400mA for C-cells); 8 hours for NiMH vs 5 hours for NiCad, FWIW.
The replacement Sub-C NiCad cells that I'm using (Eveready No. CH1.2T) have charging info printed on them:

Capacity: 1.2 amp hours
Charge: 14 hours at 120mA max
Fast Charge: 4 hours at 400mA max

The H00AAA charger for the HX-20 outputs 6v. @ 600mA, although the computer can prolly run on a lot less (I'm not sure where you're getting the 200mA from). The recommended charge time is 8 hours with the original charger & batts.

--T
 
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Hi Terry,

the label at the bottom of my HX-20 says:
Rating: DC 4.8V, 400mA
Charge input: DC 6V, 200mA
Charge time: 8 hours

So I assume 200mA is the charging current, since the HX-20 doesn't actually monitor the charge. The manual gripes about using anything other than the original H00AU adaptor, but how's it supposed to differ from any universal adaptor as long as it outputs 6V and at least 200mA?

--Roland
 
Oh, I see now. I have used the 'wrong' chargers before, with no harm done. The H00AAA charger has the tip reversed from most others, but there is a diode in that part of the circuit to prevent damage if a reversed-polarity charger is used. If you're building your own battery packs tho, be very careful of plugging in the battery backwards, as that part of the circuit has no such protection. I killed an HX-20 once by accidently doing that.

--T
 
Hi Terry,

I've got those adaptors with reversable tip plugs, so no prob there. I took a closer look at the area around the power connector; as you point out, the + pin of the battery is in series with a diode for protection, and also a fat 2W 3.9 ohm (?) resistor, presumably in case the battery shorts. Incidentally, the diode in mine appears to have been sloppily replaced; looks like someone didn't check the tip polarity. :)

Thanks for the warning about the battery polarity. Fortunately the HX-20 board is clearly marked, which I can't say for some of the others I've seen.

--Roland
 
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