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IBM 5170 AT Problems

willmurray461

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Jun 11, 2018
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Boca Raton, FL
I just picked up two IBM 5170's, one being a type 1 motherboard, the other being type 3. I'm hoping to salvage the parts from both machines to make one functioning unit. All has been well except getting the hard drive to work again. On boot up it says "Error 1780 on Drive 0." When I use the AT advanced diagnostics disk and try to low level format the drive, I get "Error 1714: Drive not Ready." Some of the electrolytic capacitors on the board look suspicious. Could they be the problem; maybe a resistor? Also, the type 1 motherboard had a 80287-3 coprocessor installed, but I heard that the coprocessor on the AT is supposed to run at half of the CPU clock speed, which on a type 3 motherboard would be 4MHz. One of the pins was also not inserted correctly and was bent inwards; it doesn't look like this was a professional IBM job. Is this supposed to go with a type 1 board?
 

krebizfan

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IIRC, the 80287 ran at 2/3 the bus clock speed. The 80287-3 ran at 5 MHz which allows it to be paired with 8 MHz 80286. It should work with any IBM AT.
 

willmurray461

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To my knowledge, yes the jumper is selecting the second drive select option DS0/DS1, IDK. I just checked all of the electrolytic caps and they seem to be fine. I have noticed that on bootup the drive spins up but I never hear the head move. My guess is that the stepper motor might have seized up over the years and just needs to be started. However, there is no way to access it without de-lidding the hard drive, which I heard isn't the best idea.
 

willmurray461

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I have the twisted cable that came with the AT from the factory. I just accidentally put one of the electrolytic capacitors back in backwards, and there was a nice little explosion. Oh well, I guess no more testing for now until I get a replacement.
 

willmurray461

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It was on the part of the cable labeled "C" which is the end of the cable. I assumed this is where the C drive would be. The other, smaller cable is attached to J4 on the controller.
 

modem7

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Also, the type 1 motherboard had a 80287-3 coprocessor installed, but I heard that the coprocessor on the AT is supposed to run at half of the CPU clock speed, which on a type 3 motherboard would be 4MHz.
IIRC, the 80287 ran at 2/3 the bus clock speed. The 80287-3 ran at 5 MHz which allows it to be paired with 8 MHz 80286. It should work with any IBM AT.
Lots of IBM 5170 information at minuszerodegrees.net
The page covering the 80287 is at [here] - see the second and third lines of the 'Speed rating' section.
 

modem7

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Lots of IBM 5170 information at minuszerodegrees.net

Hard drive cabling (including termination) information at [here].

There can be other reasons for the 1780 error, e.g. hard drive controller accidentally in the 5170's 8-bit slot, e.g. hard drive controller's edge contacts need cleaning. See the list in the 1780 section of [here].
 

willmurray461

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Jun 11, 2018
Messages
285
Location
Boca Raton, FL
Yeah, I already checked pretty much everything on minuszerodegrees. I made sure the cabling and drive select jumpers were okay, but I never heard the drive move the head. It makes a single click-like sound on startup after the drive spins up, but nothing else. I guess when I get a replacement capacitor I can check with my other good controller card to make sure that the card isn't the problem. My guess is that there must be a broken trace or burned IC because I can't think of anything else. The board seems to have traces repaired before, meaning that it wouldn't be unreasonable to assume it might need repairs again.
 
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