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#1
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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. |
#2
Posted to rec.audio.pro
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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." |
#3
Posted to rec.audio.pro
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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. |
#4
Posted to rec.audio.pro
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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." |
#5
Posted to rec.audio.pro
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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. |
#6
Posted to rec.audio.pro
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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. |
#7
Posted to rec.audio.pro
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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." |
#8
Posted to rec.audio.pro
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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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