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Tandon tm-502 mfm hard drive

Klyball

Klyball

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Feb 15, 2014
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Surrey, BC
Can and how do heads go bad, i have a drive with bad heads i believe. I have 2 tm-502's 1 good and 1 bad and would like to get the data from the bad one. I'm thinking of trying a head swap but would like to confirm that this is the only solution. i have placed the logic board from the bad drive in the good drive and it runs fine, the bad drive gives a good index pulse and track 0 logic is ok. if i probe the read data line on good drive i see a nice wave form but on the bad drive just a logic high. As far as i can figure is has to be bad heads. if the drive was blank with no format would it show no wave form?
 
Usually the discs lose particles after a while and these particles scratch and ruin the discs first, so under normal circumstances the disc goes bad before the head. A head can be damaged by physical force, e.g. dropping the drive or other measures of inducing shock. Not saying that heads can't go bad, but it is statistically unlikely compared to the actual discs. You could try a head swap, but opening the drives would expose them to dust and mean certain death for both of them pretty soon, so be sure to recover all data instantly and say goodbye to both of them.
 
Since you're going to perform open heart surgery you might be better of moving the platters to the good drive rather than moving the heads. The platters won't need alignment like the heads will after you transfer them.
 
I assume you are using the original controller the drive was formatted and used with? Remember if you use a different model of controller than what it was formatted with, it will usually appear blank.

Do you have any history on this drive? Do you know when it went bad and what conditions it was subject to?

Although possible, it doesn't seem likely that a head would just go bad by itself. Usually that sort of thing is due to a head crash. Either an impact causes the head to hit the platters, or debris on the platter hits the head and it crashes back in to the platter. Either way usually the platter itself is damaged and beyond recovery. You may not always hear screeching or other noises after things settle down.

If you have a working TM-502, it probably is not worth tearing it apart.
 
Klyball said:
if i probe the read data line on good drive i see a nice wave form but on the bad drive just a logic high. As far as i can figure is has to be bad heads.
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Seems improbable that all four heads have failed. You did that probe four times, each time with a different head selected ?

Klyball said:
if the drive was blank with no format would it show no wave form?
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Even if the drive came straight from the factory, I would expect magnetic flux transitions on the tracks due to testing by the OEM.

Stone said:
Since you're going to perform open heart surgery you might be better of moving the platters to the good drive rather than moving the heads. The platters won't need alignment like the heads will after you transfer them.
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I think it unlikely that Tandon would anticipate a need to transfer platters between their drives, and thus perform a radial head alignment to a standard of theirs on every TM502 produced.
 
Ok i probed the drive selecting the 4 heads and got a signal on 2 of the 4 heads. i made semi clean room and popped the cover to visually exam the drive ,the top platter is clean with no scratches or any visible damage and popped it back on. Are the heads labeled top down 0,1,2,3 so for sure head 0 is gone bad .
I wounder if the flex cable is maybe damaged
 
Klyball said:
Are the heads labeled top down 0,1,2,3
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There is no international standard. It comes down to the engineers. Some engineers, knowing that head 0 sits on a very important track (cylinder 0, head 0), may have chosen for head 0 to be one that is underneath a platter (i.e. a contaminant in the head chamber is more likely to settle on the top of a platter rather than underneath it). Maybe some engineers tossed a coin.
 
Klyball said:
Ok i probed the drive selecting the 4 heads and got a signal on 2 of the 4 heads. i made semi clean room and popped the cover to visually exam the drive ,the top platter is clean with no scratches or any visible damage and popped it back on. Are the heads labeled top down 0,1,2,3 so for sure head 0 is gone bad .
I wounder if the flex cable is maybe damaged
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Just a thought, did you try testing for a signal when the heads were positioned over something besides track zero? If that returned a signal on all heads, that would indicate only track zero on the first platter is dead, and in that case your best bet for retrieving data would be leaving things as is.

If not, that still probably means the platter is damaged.

From a few I have looked at (not Tandons) usually the bottom platter is 0 and 1 (no idea which side is which though) because they use the same parts for drives with one, two, three, or sometimes four platters and they just stack them from the bottom up. No guarantees of course.
 
Just a thought, did you try testing for a signal when the heads were positioned over something besides track zero?
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tested all heads in different position with stepper unplugged and still 2 good 2 bad, from the logic diagram its head 0 and 2 that have no signal
 
I assume you are using the original controller the drive was formatted and used with? Remember if you use a different model of controller than what it was formatted with, it will usually appear blank.
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All bets are off for data recovery once you do head and platter swaps. You're better off running a new low-level format and starting over due to alignment issues.
 
I'm leaning towards the connections where the flex cable turns to tiny wires that go to the heads there is a pinch point and a ground wire runs loosely around the tiny connections .
i would really like to try and save the data.
 
Klyball said:
I'm leaning towards the connections where the flex cable turns to tiny wires that go to the heads there is a pinch point and a ground wire runs loosely around the tiny connections .
i would really like to try and save the data.
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I've never heard of those sort of things going bad (unless someone was pulling on them, doh!). Are you talking about inside the sealed part with the platters? If they did go bad like that then heavily used drives would have just dropped dead for no apparent reason.
 
SomeGuy said:
I've never heard of those sort of things going bad (unless someone was pulling on them, doh!). Are you talking about inside the sealed part with the platters? If they did go bad like that then heavily used drives would have just dropped dead for no apparent reason.
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I read somewhere these drives are famous for dying ,some one had a huge stack of dead ones . This could be a design flaw that caused their early demise, just speculating at this point.
Time to get out the magnifying glass
 
That was me. I was visiting one of those long-gone Silicon Valley surplus places. I spied a pile of Tandon FH hard drives stacked up in a corner. I asked "how much?". "Five bucks" was the answer. "I'll take one" says I. "No--you don't understand. It's five bucks for the pile--and you have to take the whole pile." So I did. I got a few of them working. But only a few. They were really awful and didn't last.

Jugi was never famous for producing reliable stuff. Just consider the JTS drives. Made in India. Need I say more?

Same place also had a pile VIC-20s. Same deal--a few bucks buys the pile. I didn't need a VIC-20, or more like 20 of them.
 
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