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GDMike

HRD (Horizon Ramdisk) 2018

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Super! I can't wait to check it all out!! I can't thank you enough Barry ! I'll keep you posted.

I'm, um, not Barry. Just a guy who spent way too much time troubleshooting broken HRD+ units.

 

Sent from my Pixel 2 XL using Tapatalk

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ooops....I really was expecting Barry to respond with that same info as he had posted earlier..BUT Im super excited for the response Mr Wiley! well see if the RAMDRIVE will live again!

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Oh, I have this and was told that it's not for this drive, that this drive is actually a 1000.

It is the right schematic. The HRD+ is a HRD with a lot of Frankensteining. You'd be better off following this document and correcting the wiring to match it. It's a pain in the arse but there's a reason that the HRD+ was built using the PCB.

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Yes I did this previously, and found, as in my previous comments, the three stacked 138s do not work as this schematic describes. BUT they work as wired in the photo, unlike this schematic. This is the reason for the post, and in previous comments explained not to use this schematic, and Someone named Barry had replied that the card was an early board 1000 and is different from the 2000 and 3000 layouts as this schematic was. But yeah I started off using this months ago and got nowhere. Now I'm able to turn the card on/off as I rewired it back the way received it originally. The reason for changing it was that the card was intermittent and I was told by Gary Opa that the problem AT that time was related to the 3 stack so I rewired it as these instructions. But it was worse, the card never responded. Thanks

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There's a lot more that needs to be rewired (thinking specifically of the 259 stack, but the 138s and the 254s are going to be wrong too), and there's probably a cut trace that needs to be restored between the fingers and the rest of the card.

 

Seriously, please take it from one who fixed a HRD that matched no known wiring diagram into a stable HRD+ testbed that I used for prototyping OSHPark boards to eliminate stacking and bring it up to a minimum of 2 meg. Make it look like the instructions; there's a reason they switched from HRD wiring to HRD+. Treat it like a fresh build with all the parts present and you're just touching up bad solder joints and flywires icon_smile.gif

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Hmm. I understand. But I did my best to follow these. I replaced the 3 stack and I replaced the 259 two stack with new parts, I wired as schematic and I never got a data light after loading cru >1000. So I reverted. Now I can turn the card on/off. I just now don't know why the ram won't allow writes. This is where I'm stuck.

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Look very, very carefully at the underside of the board near the card interface for cut traces. Use a multimeter if you want to be certain.

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Not seeing any- i also ohm'd them out JUST to make sure! Do you want a photo of the 138 stack and the 259 stack?

Edited by GDMike

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Hmmm. Offhand I'd start with some desoldering wick and refresh every single solder joint on the card. After 40 years you're going to have at least five bad ones. Those flying wires look pretty marginal too. Might as well treat this as a restoration project rather than a break/fix.

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Yep, that's the board that's covered by the HRD+ doc I put up. If you've got a TL866, you can pull each chip except for the soldered stacks and do a logic test for everything except the '245s I think.

 

What I ended up doing was desoldering everything except the RAM, replacing all the DIP sockets with machined sockets, and swapping the dead '154 with a small circuit board that incorporated a SMD CMOS '154 (the DIP is only NOS AFAIK).

 

That was the first iteration. When I return from this deployment, I'll visit the ex, grab the board, and send photos. All of my stack replacements and RAM plugin are available on OSHPark.

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No, unfortunately I can't test those. But I will swap out all that I can, caps, resistors v regulator, diodes etc..

post-63012-0-80466600-1541068162_thumb.jpg

post-63012-0-50710800-1541068201_thumb.jpg

post-63012-0-71656900-1541068238_thumb.jpg

post-63012-0-83955900-1541068281_thumb.jpg

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I have plenty of new-manufactured 154s. Rochester Electronics still produces them on demand, and I bought about 1,500 of them (the minimum order) a couple of years ago. Mine are the .300 width chips, not the wider, .600 style.

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I have plenty of new-manufactured 154s. Rochester Electronics still produces them on demand, and I bought about 1,500 of them (the minimum order) a couple of years ago. Mine are the .300 width chips, not the wider, .600 style.

There's a really neat way to take the 154s out of the equation entirely. Basically what you do is get a couple of the right size SRAMs, wire the 154 chip select from the 259 stack into the CE of each SRAM, and run the synthesized address lines in. I'll post schematics when I return from this deployment.
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With everything out, what are the chances of making a larger drive? Could I use this board in achieving that?

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With everything out, what are the chances of making a larger drive? Could I use this board in achieving that?

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