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Power supply?

T

Terry Yager

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May 1, 2003
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Saginaw, MI, USA 48601
I'm looking at an old Columbia VP that doesn't want to boot, although the Monitor program runs just fine. I checked the power going to the floppy drives and the 5v is ok, but the 12v pin only reads 11.5v. Is that enough power to spin-up properly, or should I be looking hard at the power supply? Any input would be appreciated.

--T
 
I'm no EE but that seems within tolerance.

Was that with the PS loaded or unloaded?

If you think it's low then disconnect one of the drives and see if that helps. . .

Best of luck!

E
 
11.5V is definately within the 12V specs. Can you give more detail on the symptoms your having? Does the drive not spin at all? Have you tried all the basic things like reseating connectors, IC's, etc?

It's not like I don't already spend 8 hours a day troubleshooting but I like to help where I can.

Cheers,

Vince
 
Yup, tried all the usual incantations, including waving the dead chicken at it, no joy. The drive spins, but doesn't read, no activity light, nothing. Swapped drive with known good one, cleaned heads etc. Oh yeah, the head does seek track 0 if I manually move it before power-up. This thing was working perfectly when put into storage several years ago, but don't work now.

--T
 
I'll just throw out some of the usual suspects, though I'm sure you've already checked'em... but for the purpose of being redundant.... :)

-sure the cables are plugged in properly, not reversed on the board?
-sure your boot disk is in drive A, not B (cable on in reverse order)?
-sure you have bootable media (tried different copies, and that machine boots to dos or cp/m, right? tried both?)
-sure the drive cable is good?
-sure the bios is set to boot from floppy?
-sure your onboard memory is ok? if you have an expansion card, pull it and try booting.
-check all the other cards... not too familiar with this particular machine, but a bad video card (or not seated propery) will cause a no boot error (though on newer machines you'd get a 2 beep error). and if the machine has sat a long time, sometimes the card edges get corroded a bit and need cleaned for a good connection.
-checked the power supply? The 11.5 volts is a tad low, you might try using a bench supply on the drive, and as Erik mentioned, remove everything getting power from the supply except what is absolutely necessary and try it.

anyway, like I said, I'm sure you've already done these things, this is just usually my troubleshooting list I use for disk problems, at least the things I can think of at the moment :)
 
Tim Wellman said:
I'll just throw out some of the usual suspects, though I'm sure you've already checked'em... but for the purpose of being redundant.... :)

-sure the cables are plugged in properly, not reversed on the board?
Click to expand...
The VP's drive cable can't be reversed without completly disassembling the machine to get to the connector on the mainboard, which I did do in order to try a different cable.
-sure your boot disk is in drive A, not B (cable on in reverse order)?
Click to expand...
Unlike the IBM, the Columbia uses the device select jumpers to select the drive number (what a concept!). It doesn't have a twist in the cable, so both connectors are wired the same.
-sure you have bootable media (tried different copies, and that machine boots to dos or cp/m, right? tried both?)
Click to expand...
Tried several different bootdisks (including CP/M-86). Checked all disks in another machine, all bootable.
-sure the drive cable is good?
Click to expand...
See above.
-sure the bios is set to boot from floppy?
Click to expand...
It's a PC/XT compatible, no setup in the BIOS.
-sure your onboard memory is ok? if you have an expansion card, pull it and try booting.
Click to expand...
The Columbia has an in-built System Monitor program (Software Front Panel) which can be used to thoroughly check the memory. There is only one expansion slot, and nothing was installed in it.
-check all the other cards... not too familiar with this particular machine, but a bad video card (or not seated propery) will cause a no boot error (though on newer machines you'd get a 2 beep error). and if the machine has sat a long time, sometimes the card edges get corroded a bit and need cleaned for a good connection.
Click to expand...
The video is built-in on the mainboard.
-checked the power supply? The 11.5 volts is a tad low, you might try using a bench supply on the drive, and as Erik mentioned, remove everything getting power from the supply except what is absolutely necessary and try it.
Click to expand...
The power supply is proprietary, so it can't be swapped-out with a normal ps. I did jack-in the drive to another ps, still no boot.
anyway, like I said, I'm sure you've already done these things, this is just usually my troubleshooting list I use for disk problems, at least the things I can think of at the moment :)
Click to expand...

Also tried swapping a known-good drive, still no luck. Etc, etc, etc...

--T
 
I still think 11.5V is within specs. Believe it or not, it could probably function at 10V. My guess is that the track seek function of the controller is not functioning. From what I understand that you're saying, it will read track 0 if you manually move the head there ahead of power up. Don't suppose you have schematics that could help locate the stepper motor function do you?

So far you have eliminated, drive, disks, and power supply (you did say you tried an alternate source for power, right?)

If the pinout of the drive matches a PC drive then you want to check pin 18 (step direction) that controls the direction of the stepper motor or pin 20 (step pulse) with a scope. If you don't have an oscilliscope than maybe a volt meter than can measure the pulse freq of pin 20.

Vince
 
I don't know if it is relevant, by the hardware monitor on my Athlon PC motherboard constantly reports the 12V to be 11.5V etc. I checked yesterday, and all the voltages were slightly below the nominal values. Maybe this is completely different from how a 1970's computer should work?
 
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