1.44MB HD7 media change wiring w/Epson 340

Update your old 720k to a 1.44 drive etc.
PacificState
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1.44MB HD7 media change wiring w/Epson 340

Post by PacificState »

I just installed a HD7 1.44MB upgrade kit into my STE with an Epson 340 floppy drive and I'm trying to understand the media change wiring.

Having pulled the shield off the drive, it appears to have a slightly different PCB revision to the one shown in https://blog.troed.se/2017/01/20/the-ta ... i-mystery/. That said, my multimeter indicates:

- The second pin from the edge of the drive->PCB connector toggles between 5V (no disc/1.44MB disc inserted) and 0V (720KB disc inserted)

- Pin 2 of the floppy connector sits at ~4.5V irregardless of whether a 720KB or 1.44MB disc is installed or the drive is jumpered to use an internal or external HD select signal

- The (unnconnected) drive select via on the HD7 board sits at 5V

I had thought that only the drive ribbon cable pin (connected to the HD detect sensor) would toggle, and then pull up the input to the HD7 board - is that not the case? I'd like to understand the behavior before connecting everything up - thanks!
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exxos
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by exxos »

The HD select wire is 5V when 1.44 is inserted and 0V when 720K is inserted. I think troed routed it via the floppy cable somehow, but i've never even had one of those drives to even figure it all out. Other than troed, I think he is the only person who attempted it.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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PacificState
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by PacificState »

Thanks! What should the pin/via on the HD7 PCB, though? It seemed weird it was at 5V - should it be 0V and pulled up by the drive?
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exxos
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by exxos »

There is a pull up on the HD7 board. If there wasn't, it wouldn't likely ever get a logic high and never work with 1.44 floppies.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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PacificState
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by PacificState »

Got it! I'll connect it to the switch.

One thing - with the line floating and the E6 jumper connected, I seem to get a consistent error formatting 1.44MB floppies at around the 60% mark. I have cleaned the drive, but no joy. Is it possible that a.) I have a DMA problem (there's a socketed Motorola part and the 'bad' DMA chip, b.) that I need to switch out the 1k resistors by the 1772, or c.) both?
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by exxos »

Well it could be many things. Check out the fixes for the STE. But with the drive being old, it could just not be reliable.

I really wouldn't use GEM to format anyway. Use something better like FCOPY or something. It will give you more information on track errors for starters.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by troed »

Just so that we're clear on the workings. HD mods work "backwards" from how Atari implemented it*, sort of. We use the fact that the drive signals whether it has an HD or DD disk inserted, and route that signal to the HD mod PCB. The floppy cable isn't involved - you just wire the pin you found to the HD mod.

I thought I had documented another board revision as well, found on an Epson 349 .. let me see. Hmm. Not more than having a photo ...

epson349.jpg
epson349.jpg (119.74 KiB) Viewed 2358 times

/Troed

*) TOS 2.06 doesn't make use of any HD signals at all but just tests whether it's able to make some sense out of the drive when using either mode. To do this, Mega STE and TT have a PAL that can be poked from software to change the speed of the floppy IC.
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by frank.lukas »

EPSON HD Modul Mod ...

epson.jpg
epson.jpg (418.96 KiB) Viewed 2342 times
PacificState
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by PacificState »

Thank-you all! I guess I was trying to understand the pull-up behaviour before I shorted anything out - it sounds like there are pull-ups both on the HD7 and pin-2 of the floppy connector, and I can wire them both to the detect switch which will then pull them down to 0V when a 720KB disk is inserted.

As for the formatting failure - these floppies have been used before and, after inspection, there's a physical 'band' on at least one of them - I have new disks on the way to try.

I just wish that my existing 720KB drive was also made by Epson, then it'd be easy to swap the front panel and button over - if anyone has a broken drive they'd like to sell, PM me!
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frank.lukas
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Re: 1.44MB HD7 media change wiring w/Epson 340

Post by frank.lukas »

PacificState wrote: Wed Dec 01, 2021 3:32 pm As for the formatting failure ...
WD1772 is a 8Mhz DD Controller. 16Mhz does not work reliably and not permanently. I use Atari AJAX Controller and have no problems at all.
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