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boardjunkie boardjunkie is offline
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Default Fostex G16/24 again

I repaired a G24 for a local studio about 4-5 months back and its down
again with the same problem. The issue is the high current switch for
the take up side reel motor (2SD1047). The one I pulled out was not
shorted, but really leaky. So this makes the third time the same
problem has cropped up.

Anyone else seen this problem? Possible that the motor's on the way
out and pulling too much current? I'm thinking of subbing a little
higher current part for that d1047, but that just may be a band-aid
fix. I didn't check the driver x-istor in front of the 1047for
leakage, just for shorts. Seems like if that was causing a problem it
would've lasted a few days, not a few months.
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Scott Dorsey Scott Dorsey is offline
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Default Fostex G16/24 again

boardjunkie wrote:
I repaired a G24 for a local studio about 4-5 months back and its down
again with the same problem. The issue is the high current switch for
the take up side reel motor (2SD1047). The one I pulled out was not
shorted, but really leaky. So this makes the third time the same
problem has cropped up.

Anyone else seen this problem? Possible that the motor's on the way
out and pulling too much current? I'm thinking of subbing a little
higher current part for that d1047, but that just may be a band-aid
fix. I didn't check the driver x-istor in front of the 1047for
leakage, just for shorts. Seems like if that was causing a problem it
would've lasted a few days, not a few months.


Could be, I would also lubricate the motor and do a tension adjustment.

I would also make sure that the 2SD1047s that you are getting are
actually good, and they aren't cheap knockoffs. There are a LOT of
semiconductors these days that do not meet original specs.

I'd try both a higher current and a higher voltage part and see how it
goes. I'd also look at the base waveform on a scope and see that it
looks reasonable. I'd also check it in fast forward; it's possible
something is going wrong only in fast forward mode which is why it takes
so long to crop up.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Gareth Magennis Gareth Magennis is offline
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Default Fostex G16/24 again


"boardjunkie" wrote in message
...
I repaired a G24 for a local studio about 4-5 months back and its down
again with the same problem. The issue is the high current switch for
the take up side reel motor (2SD1047). The one I pulled out was not
shorted, but really leaky. So this makes the third time the same
problem has cropped up.

Anyone else seen this problem? Possible that the motor's on the way
out and pulling too much current? I'm thinking of subbing a little
higher current part for that d1047, but that just may be a band-aid
fix. I didn't check the driver x-istor in front of the 1047for
leakage, just for shorts. Seems like if that was causing a problem it
would've lasted a few days, not a few months.



For this kind of switching application you may as well use the highest rated
(current AND voltage) equivalent device you can find in that package, it
will probably not cost that much more.
The same can be said for things like rectifier diodes / bridges, higher
voltage/temnperature electrolytics, where they have been found to be
vulnerable.



Gareth.


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Scott Dorsey Scott Dorsey is offline
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Default Fostex G16/24 again

In article ,
Gareth Magennis wrote:

"boardjunkie" wrote in message
...
I repaired a G24 for a local studio about 4-5 months back and its down
again with the same problem. The issue is the high current switch for
the take up side reel motor (2SD1047). The one I pulled out was not
shorted, but really leaky. So this makes the third time the same
problem has cropped up.

Anyone else seen this problem? Possible that the motor's on the way
out and pulling too much current? I'm thinking of subbing a little
higher current part for that d1047, but that just may be a band-aid
fix. I didn't check the driver x-istor in front of the 1047for
leakage, just for shorts. Seems like if that was causing a problem it
would've lasted a few days, not a few months.



For this kind of switching application you may as well use the highest rated
(current AND voltage) equivalent device you can find in that package, it
will probably not cost that much more.


2N5683 maybe?

The same can be said for things like rectifier diodes / bridges, higher
voltage/temnperature electrolytics, where they have been found to be
vulnerable.


I pretty much only keep 1N4007 diodes in the bins these days, along with
a couple schottky and high speed types. The difference in price between
a 1N4004 and a 1N4007 is a penny and a half. I'm cheap, but not THAT cheap.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Gareth Magennis Gareth Magennis is offline
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Default Fostex G16/24 again



I pretty much only keep 1N4007 diodes in the bins these days, along with
a couple schottky and high speed types. The difference in price between
a 1N4004 and a 1N4007 is a penny and a half. I'm cheap, but not THAT
cheap.
--scott

--



And, 4A 50 volt bridge rectifier - £1.17. 4A 1000 volt bridge rectifier,
same package, £1.20. Makes you wonder.



Gareth.




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boardjunkie boardjunkie is offline
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Default Fostex G16/24 again

On Feb 6, 2:51*pm, (Scott Dorsey) wrote:
boardjunkie wrote:
I repaired a G24 for a local studio about 4-5 months back and its down
again with the same problem. The issue is the high current switch for
the take up side reel motor (2SD1047). The one I pulled out was not
shorted, but really leaky. So this makes the third time the same
problem has cropped up.


Anyone else seen this problem? Possible that the motor's on the way
out and pulling too much current? I'm thinking of subbing a little
higher current part for that d1047, but that just may be a band-aid
fix. I didn't check the driver x-istor in front of the 1047for
leakage, just for shorts. Seems like if that was causing a problem it
would've lasted a few days, not a few months.


Could be, I would also lubricate the motor and do a tension adjustment.

I would also make sure that the 2SD1047s that you are getting are
actually good, and they aren't cheap knockoffs. *There are a LOT of
semiconductors these days that do not meet original specs.

I'd try both a higher current and a higher voltage part and see how it
goes. *I'd also look at the base waveform on a scope and see that it
looks reasonable. *I'd also check it in fast forward; it's possible
something is going wrong only in fast forward mode which is why it takes
so long to crop up.
--scott
--
"C'est un Nagra. *C'est suisse, et tres, tres precis."


The plot thickens......
I went over to take care of the problem (temporarily) with just a
replacement d1047. Put it all back together and the motor didn't fire
off. So after that I take the reg pcb back with me to check everything
out.....both motor switching circuits are fine. Pwr supply for the
motors is ok since the other motor operates.
What should I look to next...tension sensor or the motor itself? I'm
not up on how this machine's hows and whys since its just a favor and
not my day job.
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Scott Dorsey Scott Dorsey is offline
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Default Fostex G16/24 again

boardjunkie wrote:
The plot thickens......
I went over to take care of the problem (temporarily) with just a
replacement d1047. Put it all back together and the motor didn't fire
off. So after that I take the reg pcb back with me to check everything
out.....both motor switching circuits are fine. Pwr supply for the
motors is ok since the other motor operates.
What should I look to next...tension sensor or the motor itself? I'm
not up on how this machine's hows and whys since its just a favor and
not my day job.


Look at the voltage on the motor... if there is voltage on the motor
and it isn't turning, you have a motor problem.

Also check continuity on the motor.

Tension sensor could be an issue, but if you have been blowing
drive transistors, I'd be more suspicious of something on the other
end of the circuit. You'll know for sure by looking at the waveform on
the motor.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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Default Fostex G16/24 again

On Feb 13, 9:02*pm, (Scott Dorsey) wrote:
boardjunkie wrote:
The plot thickens......
I went over to take care of the problem (temporarily) with just a
replacement d1047. Put it all back together and the motor didn't fire
off. So after that I take the reg pcb back with me to check everything
out.....both motor switching circuits are fine. Pwr supply for the
motors is ok since the other motor operates.
What should I look to next...tension sensor or the motor itself? I'm
not up on how this machine's hows and whys since its just a favor and
not my day job.


Look at the voltage on the motor... if there is voltage on the motor
and it isn't turning, you have a motor problem.

Also check continuity on the motor.

Tension sensor could be an issue, but if you have been blowing
drive transistors, I'd be more suspicious of something on the other
end of the circuit. *You'll know for sure by looking at the waveform on
the motor.
--scott

--
"C'est un Nagra. *C'est suisse, et tres, tres precis."


Call off the hounds

Turns out I was chasing the wrong motor circuit....it was the other
motor driver. The service manual I have sucks. A lot of it doesn't
agree with the machine, but they have the motor outputs labeled
opposite on the schematic! Thanks Fostex for wasting about 2 hrs of my
time...I was all the way back into the control circuitry for nothing.
Took 30 seconds to find/fix the problem after disregarding the
documentation and tracing it out manually.
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