18 Feb
2010
18 Feb
'10
8:50 a.m.
I've recently been restoring an H8/H17 system. Almost all of
the problems involved capacitors, including a bad electrolytic
in the H17 (diskette unit) power supply. I repaired the H17
supply using a dummy load but apparently the H17 was run with
the bad supply before I got it. I say this because some of the
tantalum caps on the logic boards of the Wangco model 82 diskette
drives popped and/or burned when correct power was supplied to
them. I've seen plenty of the "teardrop" tantalums pop, but I've
never seen one of the "black suppository" types (used on these
drives) go. I believe this was the result of bad ripple in the
supply.
Anyway, one of the Wangcos now runs perfectly and the other runs
fine for a while but fails after about an hour of applied power.
The difference between the two is that, on the flaky drive, a cap
in series with an inductor did a slow burn, resulting in the
inductor having a "nice brown toasty" appearance and a small split
in one side that some red resin leaked from. By the way, the only
way I know this is an inductor is that it is labeled "L5". It
looks like a large beige resistor with too many color stripes on it.
Inductors are a weak area in my electronics knowledge. How would
you know for sure that one has failed? Does it fail open?
Other info: When the drive fails, it can not read any data and,
when seeks are attempted on it, it sounds "funny", not the nice
sharp click it makes when operating correctly. The inductor does
not feel hot to the touch when the drive has failed. I'm out of
cool spray. Tonight I will try to apply an ice cube in a plastic
bag to it to see if that gets it out of failure mode.
Finally, assuming it is the problem, what do I need to replace it?
The stripes on it are:
Wide silver (covering one end)
Red
Yellow
Brown
Gold
Thanks,
Bill
18 Feb
18 Feb
9:04 a.m.
On 18 Feb 2010 at 11:50, Bill Sudbrink wrote:
Inductors are a weak area in my electronics knowledge.
How would you
know for sure that one has failed? Does it fail open?
They can fail open, or if toasted, can fail shorted. Regardless,
it's easy enough to replace one--and that's what I'd do anyway,
before goofing around much more.
You have a 240 uH 5% one, by the color codes.
--Chuck
9:15 a.m.
They can fail open, or if toasted, can fail shorted.
?Regardless,
it's easy enough to replace one--and that's what I'd do anyway,
before goofing around much more.
With a small choke of this value, internal shorts are almost never
fatal. The inductance may go down, due to one of the layers of
windings getting taken out of the circuit. A short that bypasses a
majority of the windings is extremely rare.
Still, a minor short can mess things up.
--
Will
9:53 a.m.
From: wh.sudbrink at verizon.net
To: cctalk at classiccmp.org
Subject: Deep fried inductor...
Date: Thu, 18 Feb 2010 11:50:23 -0500
---snip---
Inductors are a weak area in my electronics knowledge. How would
you know for sure that one has failed? Does it fail open?
Other info: When the drive fails, it can not read any data and,
when seeks are attempted on it, it sounds "funny", not the nice
sharp click it makes when operating correctly. The inductor does
not feel hot to the touch when the drive has failed. I'm out of
cool spray. Tonight I will try to apply an ice cube in a plastic
bag to it to see if that gets it out of failure mode.
Finally, assuming it is the problem, what do I need to replace it?
The stripes on it are:
Wide silver (covering one end)
Red
Yellow
Brown
Gold
Thanks,
Bill
Hi
The inductor is most likely a PS filter the analog paths. Although, I'd
measure it in a bridge before replacing it, it is most likely not the
problem you are seeing. As a filter, it is unlikely to cause too much
problems if short, as these circuits are often over designed there.
They rarely are temperature sensitive at the level you are seeing.
If it is not getting hot, it is unlikely to be effected by operation time.
It is more likely something failing in the stepper control. You might
also check to see if things are well lubricated ( no old grease ).
Dwight
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2:04 p.m.
On Thursday (02/18/2010 at 09:53AM -0800), dwight elvey wrote:
On the Siemens drives also used in the H89 and H17, there is an inductor
in series with the +12 to the spindle motor. It's a hash choke that keeps
the motor noise from going back into the +12 rail. When the grease in
the spindle motor gets old and sticky, the motor draws way too much current
at startup (if it ever does start spinning) and toasts this inductor.
It's an exciting failure on the H89, because the "Mission Impossible"
smoke comes out through the drive door and slowly flows down onto the
keyboard. Impressive image, horrible smell.
Chris
--
Chris Elmquist
Finally, assuming it is the problem, what do I need to replace it?
The stripes on it are:
Wide silver (covering one end)
Red
Yellow
Brown
Gold
Thanks,
Bill
Hi
The inductor is most likely a PS filter the analog paths. Although, I'd
measure it in a bridge before replacing it, it is most likely not the
problem you are seeing. As a filter, it is unlikely to cause too much
problems if short, as these circuits are often over designed there.
They rarely are temperature sensitive at the level you are seeing.
If it is not getting hot, it is unlikely to be effected by operation time.
It is more likely something failing in the stepper control. You might
also check to see if things are well lubricated ( no old grease ).
19 Feb
19 Feb
5:45 a.m.
Chris Elmquist wrote:
On the Siemens drives also used in the H89 and H17,
there is an inductor
in series with the +12 to the spindle motor. It's a hash choke that keeps
the motor noise from going back into the +12 rail. When the grease in
the spindle motor gets old and sticky, the motor draws way too much current
at startup (if it ever does start spinning) and toasts this inductor.
I don't have "real" schematics for the drive and I have not
had time yet to work out the whole circuit but what I do know
is that one side of the inductor is connected to +12. The
simple diagram would be:
+12----<inductor>---+---<tantalum cap>----ground
|
|
somewhere else
not yet traced
When the tantalum cap shorted, burned and popped, the inductor
was carrying +12 to ground. That's how it got "toasty".
The spindle motor seems to be nice and free. Judging by the
strobe sticker on the bottom of the flywheel, the disk RPMs
are spot on.
Interestingly, I could not reproduce the failure last night.
I went as far as putting a small piece of carpet on top of the
H17, blocking the vents. It got nice and warm, but no failure.
The last thing I did Wednesday night, two nights ago, before I
posted the first message, was to unsolder one of the leads on
the inductor so I could put an Ohm meter on it. It was not open
and, as others have suggested it should be, was almost a dead
short. I wonder if the desolder/solder heat has "fixed" it.
Bill
6:13 a.m.
On Fri, 19 Feb 2010 08:45:06 -0500, Bill Sudbrink wrote:
The last thing I did Wednesday night, two nights ago,
before I
posted the first message, was to unsolder one of the leads on
the inductor so I could put an Ohm meter on it. It was not open
and, as others have suggested it should be, was almost a dead
short. I wonder if the desolder/solder heat has "fixed" it.
That may have very well fixed it, I have found severely over heated
solder joints oxidise/chrystalize and simply reflowing the solder fixed the problem.
Back under my rock :)
The other Bob
12:49 p.m.
Chris Elmquist wrote:
OK, that's clearly a supply line filter.
WHat I would do to trace it is to remove the inductor (temporarily) and
then trace fro mthe +ve side of the capacitor to anything that might need
12V (spindle motor, stepper motor, head load solenoid, read amplifer).
See which of those go to the +e side of the capacito, and which go
directly to the 12V input.
On the Siemens drives also used in the H89 and
H17, there is an inductor
in series with the +12 to the spindle motor. It's a hash choke that keeps
the motor noise from going back into the +12 rail. When the grease in
the spindle motor gets old and sticky, the motor draws way too much current
at startup (if it ever does start spinning) and toasts this inductor.
I don't have "real" schematics for the drive and I have not
had time yet to work out the whole circuit but what I do know
is that one side of the inductor is connected to +12. The
simple diagram would be:
+12----<inductor>---+---<tantalum cap>----ground
|
|
somewhere else
not yet traced
When the tantalum cap shorted, burned and popped, the inductor
was carrying +12 to ground. That's how it got "toasty".
OK, so at least there's a reason why it overheated.
-tony
12:20 p.m.
On the Siemens drives also used in the H89 and H17,
there is an inductor
in series with the +12 to the spindle motor. It's a hash choke that keeps
the motor noise from going back into the +12 rail. When the grease in
the spindle motor gets old and sticky, the motor draws way too much current
at startup (if it ever does start spinning) and toasts this inductor.
If this is the Siemens drive used in the Z90, I have the schematics here
(io the Z90 hardware manuals). I can't see an 'L5' at all, but the drive
I have has a separate motor control PCB with a series choke (but a 10uH
one) in the supply line. It's easily posible that later drives put
everything on one PCB (as Tandon did).
-tony
3:22 p.m.
On Friday (02/19/2010 at 08:20PM +0000), Tony Duell wrote:
Right... I think the OP said his problem occurred on a Wang or somesuch
drive. Not a Siemens. I simply offered that on the Siemans, the choke
was there to filter the supply to the motor... presumably to keep
motor hash from getting back onto the 12V rail. My thinking was that
something similar was going on in the drive that he has... without me
knowing anything about the drive that he has obviously.
Chris
--
Chris Elmquist
On the Siemens
drives also used in the H89 and H17, there is an inductor
in series with the +12 to the spindle motor. It's a hash choke that keeps
the motor noise from going back into the +12 rail. When the grease in
the spindle motor gets old and sticky, the motor draws way too much current
at startup (if it ever does start spinning) and toasts this inductor.
If this is the Siemens drive used in the Z90, I have the schematics here
(io the Z90 hardware manuals). I can't see an 'L5' at all, but the drive
I have has a separate motor control PCB with a series choke (but a 10uH
one) in the supply line. It's easily posible that later drives put
everything on one PCB (as Tandon did).
18 Feb
18 Feb
12:21 p.m.
I've recently been restoring an H8/H17 system. Almost all of
the problems involved capacitors, including a bad electrolytic
in the H17 (diskette unit) power supply. I repaired the H17
supply using a dummy load but apparently the H17 was run with
the bad supply before I got it. I say this because some of the
tantalum caps on the logic boards of the Wangco model 82 diskette
drives popped and/or burned when correct power was supplied to
them. I've seen plenty of the "teardrop" tantalums pop, but I've
never seen one of the "black suppository" types (used on these
drives) go. I believe this was the result of bad ripple in the
supply.
Anyway, one of the Wangcos now runs perfectly and the other runs
fine for a while but fails after about an hour of applied power.
The difference between the two is that, on the flaky drive, a cap
in series with an inductor did a slow burn, resulting in the
inductor having a "nice brown toasty" appearance and a small split
in one side that some red resin leaked from. By the way, the only
way I know this is an inductor is that it is labeled "L5". It
looks like a large beige resistor with too many color stripes on it.
Inductors are a weak area in my electronics knowledge. How would
you know for sure that one has failed? Does it fail open?
Other info: When the drive fails, it can not read any data and,
when seeks are attempted on it, it sounds "funny", not the nice
sharp click it makes when operating correctly. The inductor does
not feel hot to the touch when the drive has failed. I'm out of
cool spray. Tonight I will try to apply an ice cube in a plastic
bag to it to see if that gets it out of failure mode.
Finally, assuming it is the problem, what do I need to replace it?
The stripes on it are:
Wide silver (covering one end)
Red
Yellow
Brown
Gold
Thanks,
Bill
12:22 p.m.
I've recently been restoring an H8/H17 system. Almost all of
the problems involved capacitors, including a bad electrolytic
in the H17 (diskette unit) power supply. I repaired the H17
supply using a dummy load but apparently the H17 was run with
the bad supply before I got it. I say this because some of the
tantalum caps on the logic boards of the Wangco model 82 diskette
drives popped and/or burned when correct power was supplied to
them. I've seen plenty of the "teardrop" tantalums pop, but I've
never seen one of the "black suppository" types (used on these
drives) go. I believe this was the result of bad ripple in the
supply.
Possibly. Or jsut old age.
Anyway, one of the Wangcos now runs perfectly and the other runs
fine for a while but fails after about an hour of applied power.
The difference between the two is that, on the flaky drive, a cap
in series with an inductor did a slow burn, resulting in the
inductor having a "nice brown toasty" appearance and a small split
in one side that some red resin leaked from. By the way, the only
way I know this is an inductor is that it is labeled "L5". It
looks like a large beige resistor with too many color stripes on it.
Inductors are a weak area in my electronics knowledge. How would
you know for sure that one has failed? Does it fail open?
I';ve never sene an inductor that failes and then works again. Most of
the time they fail by burning out (after all, they're jsut a coil of wire
on a suitable core), and then they test open. A good one will test as a
dead short on most ohmmeters.
Sometimes you get shorted turns. A DC test (e.g. an Ohmmeter) will not
show this up. The only way is to meastue the inductance and/or the
losses. But that's a rare failure mode for small inductors. I'd not worry
about it. Just see if it's open or not.
Other info: When the drive fails, it can not read any data and,
when seeks are attempted on it, it sounds "funny", not the nice
sharp click it makes when operating correctly. The inductor does
not feel hot to the touch when the drive has failed. I'm out of
cool spray. Tonight I will try to apply an ice cube in a plastic
bag to it to see if that gets it out of failure mode.
I think you have some other fault here.
The inductors on floppy disk drives are normally there for one of 2
purposes. Either as part of an LC resonant circuit in the read filter, or
as filtering on the power line to a critcial piece of the circuitry. The
fromer is a very low power applicaiton, and it's dificult to see how the
inductor could burn out without other components failing spectaculuarly.
A power line filter inductor can overheat if the load draws too much
current. In this case of course, the inductor is damaged because of a
fault elsewhere, and simply replacing the inductor will simply cause the
new one to overheat.
My guess, thougm, given the intermittany nature of the fault and the fact
taht the head positioner is misbehaving, is that you have a problem
elsewhere.
Do you have scheamtics of the drive? If so, where is L5 in the circuit?
Finally, assuming it is the problem, what do I need to replace it?
The stripes on it are:
Wide silver (covering one end)
Red
Yellow
Brown
Gold
Normally you read the colour bands using the obvious code and this gives
the value in micorhenries. So you have a 240uH inductor.
-tony
5372
days inactive
5373
days old
11 comments
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ard＠p850ug1.demon.co.uk -
caveguy＠sbcglobal.net -
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