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dhe

This old Horizon #2

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Recently I was able to get my first old horizon online with a TI.

 

My second old horizon has ended up, being as problematic as the first.

When I pulled it out of the pbox, I noticed some slight 'fuzz' on the positive side of one battery. Didn't look like anything.

  a)  Pulled all the batteries NiMH and cleaned the terminals with alchohol.

  b)  Replaced batteries with new AAA NiCads.

  c)  RamDisk wouldn't hold the memory chips when power pulled. 

 

I took the card out and had a look, it looks like even thought only one battery had started to fuzz, it looks like it damaged all the positive connections on all three battery holders. It also looks all the coating on the battery holders got turned to rust.

 

  The is an R9 (470 ohm) , and it looks like two diodes (1N4) that also got fuzzed, almost like it wicked....

 

  I'm guessing newark or ebay are my friend?

 

  I'm inclined to not try to reproduce the diodes and just put in a single resister?

 

ex1.jpg

ex2.jpg

res.jpg

toh2.jpg

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I did some checking... Amazon has AAA solder tail holders for $6.00 - newark has them .26.

 

My bad holders are I think held in with hot glue. Bud in his build guide recommends 5 minute cement - I think I can just pull the old ones off.

 

What's the modern best practice for attaching the holders to the board.

 

PS... bad had to fix a number of boards where people had used superglue and it ate through the solder mask and the traces, so I know that's out...

 

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The diodes are definitely required for the battery recharge circuit--they are what lets power through to the batteries to charge them one the one hand, and what lets the power flow to the memory chips on the other. When power is off, they block power flow to anything except the memory. . .

 

On battery holders, I personally use the ones that have solder pins on the bottom and solder them in. I'm not sure the oldest boards support that mode though. . .this type doesn't need anything else to hold them in place though. I've bought from this seller before. They are pretty reliable.

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Does anyone have the original horizon build manual, so I can figure out the diode parts?

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11 minutes ago, dhe said:

Does anyone have the original horizon build manual, so I can figure out the diode parts?

Here you go. . .these are for the original release. If yours is an HRD+, let me know, as I have those docs too. Your serial number makes me think it isn't a + though, as most of those had serial numbers in the 1000 range. . .

Horizon Ramdisk.pdf HRD Reference Manual - Booklet.pdf HRD 256K Expansion .pdf HRD 256K Expansion Project.pdf

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I suspect the diodes will be 1N914 (possibly 1N4148) or 1N34A (if it is one of these, please replace with a Russian D9K though, as most 1N34As for sale do not meet spec, but the D9K subs do).

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Ksarul,

 Thank you so much for the manuals... Not sure what happened to my manual, I have the one for the 3000, but of course, that doesn't help in this case.

 I've found the battery holders on newarc, I was able to save all the old parts, I think with some fresh solder and they should be fine.

 

  I've order some double sided tape, once I get no holders in, I will try to reassemble.

 

image.png.ec893b051b6b49d5f3f434da4682160f.png

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With the help of a gooseneck LED lamp and 10X magnifying glasses, I managed to ID the diode that was in series with another like model.

On one side was printed 1N4 and on the other !$*... err.. 148.

So, I have a winner, a 1N4148 Switching Diode.

 

Interesting pricing model (1) for $4.99 or (100) for $4.29...

 

 

image.thumb.png.f4f2144e9e546a0b8712fc6d54718667.png

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Cost per item is almost always a lot better when buying in bulk. I think I spent $25-$30 a few years ago to buy an entire reel of 5,000 of these. . .

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