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View Full Version : Atari 520 STFM Floppy Drive Problem



SonicMonkey
December 25th, 2010, 07:37 PM
Hey guys.
I got an Atari 520 STFM a while ago and I think it might be broken. When I put a floppy in the built-in drive, it just makes a grinding noise and it can't be read from the desktop icon. I can't write to a disk either. I think this might be a motherboard issue because I swapped out the original drive for a spare and it does the exact same thing.
Has anybody else come upon a problem like this and found a solution? If not, then I would at least like some help troubleshooting the problem and possibly fixing it from there. This is such a cool old computer and I'd love to be able to do some stuff with it.
Thanks,
Dan.

Chuck(G)
December 25th, 2010, 08:03 PM
Fortunately, the ST floppy controller is pretty simple--a WD1772 chip and a 7406 inverter for the control signals. If you're certain it's not the drive or the media, I'd start by replacing the 7406 (usually situated near the WD1772--a continuity check from one of the WD1772 output pins (DIR, STEP, WD, WGATE, etc.) to the suspect 7406 will ensure you're pulling the right tooth...

SonicMonkey
December 27th, 2010, 09:35 PM
Thanks for the input. I think I know what you mean and it sounds simple enough. If it is the inverter, where can I get a replacement? I did a quick search on Google and couldn't find any.

Chuck(G)
December 27th, 2010, 10:14 PM
The 7406 (or 74LS06; in this application it doesn't matter) is one of the more common TTL ICs.

Try searching for SN7406 on eBay, for example. Or 74LS06.

It's much harder finding WD1772 FDCs, so cross your fingers.

Since I don't know your location, I can't tell you where it will be the cheapest.

SonicMonkey
December 28th, 2010, 05:35 PM
Ebay's got one that'll only cost me about $5. I live in Canada but it's in the US. Looks about right to me, but I'll give you the link so you can make sure it's the exact thing I need.
http://cgi.ebay.ca/SN7406-HEX-INVERTER-OPEN-COLLECTOR-OUTPUTS-lot-3-/300419084609?pt=LH_DefaultDomain_0&hash=item45f25f7141
Thanks again!