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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Old Technics tuner, anyone ... ?
I thought I had the manuals for just about every common item Technics ever
produced, but not this one ... Anyone got a PDF of the schematic for a Technics ST-X990L. Particularly interested in the bit around the PSU The arfa.daily email address that this was posted from works, in case anyone can help TIA Arfa |
#2
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Old Technics tuner, anyone ... ?
I don't know specifically, but will check my service manuals on CD for this one.
Any particular problem you are addressing? I may also have service bullitens. Dan |
#3
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Old Technics tuner, anyone ... ?
wrote in message ... I don't know specifically, but will check my service manuals on CD for this one. Any particular problem you are addressing? I may also have service bullitens. Dan It has no 'proper' output. A bit of hum-y noise and that's it. Display is normal. Appears to tune normally, but I'm sure it isn't. Looks like a PSU problem or maybe a rail getting dragged down somewhere by a leaky rail decoupling cap as used to be common on all sorts of Pan gear back in the day. I picked one of the IF processor chips at random and looked up the data sheet on it to find the Vcc pin. The sheet claimed a Vcc of 14 volts, but there's actually only about 5 volts on the pin. I tried following the print back, but it rapidly starts jumping around the board on wire links and print 'splits'. It's really not worth spending the time on trying to trace where the rail comes from, and what decouplers are hanging across it, but it would of course be a very simple fix with the benefit of a schematic. If all else fails, I can get a download copy for $4.99 of the 'net, but cheapskate as I am ... d;-) Arfa |
#4
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Old Technics tuner, anyone ... ?
HIFIENGINE.COM has teh ST-x999l model. Close enough? Create an account for yourself and look in the manual section under Technics (Panasonic is also there, but does not have these).
Dan |
#5
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Old Technics tuner, anyone ... ?
"Arfa Daily" wrote in message ... wrote in message ... I don't know specifically, but will check my service manuals on CD for this one. Any particular problem you are addressing? I may also have service bullitens. Dan It has no 'proper' output. A bit of hum-y noise and that's it. Display is normal. Appears to tune normally, but I'm sure it isn't. Looks like a PSU problem or maybe a rail getting dragged down somewhere by a leaky rail decoupling cap as used to be common on all sorts of Pan gear back in the day. I picked one of the IF processor chips at random and looked up the data sheet on it to find the Vcc pin. The sheet claimed a Vcc of 14 volts, but there's actually only about 5 volts on the pin. I tried following the print back, but it rapidly starts jumping around the board on wire links and print 'splits'. It's really not worth spending the time on trying to trace where the rail comes from, and what decouplers are hanging across it, but it would of course be a very simple fix with the benefit of a schematic. If all else fails, I can get a download copy for $4.99 of the 'net, but cheapskate as I am ... d;-) Arfa Have you checked the power supply bulk capacitors for a high esr cap? Sure sounds like it could be an issue. |
#6
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Old Technics tuner, anyone ... ?
wrote in message ... HIFIENGINE.COM has teh ST-x999l model. Close enough? Create an account for yourself and look in the manual section under Technics (Panasonic is also there, but does not have these). Dan I've already got a HiFiEngine account. I'll go look. Thanks. In the meantime I have been sent a photo by Nigel. Haven't had a chance to have a close look at it yet to see if the voltages etc are readable Arfa |
#7
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Old Technics tuner, anyone ... ?
"Tom Miller" wrote in message ... "Arfa Daily" wrote in message ... wrote in message ... I don't know specifically, but will check my service manuals on CD for this one. Any particular problem you are addressing? I may also have service bullitens. Dan It has no 'proper' output. A bit of hum-y noise and that's it. Display is normal. Appears to tune normally, but I'm sure it isn't. Looks like a PSU problem or maybe a rail getting dragged down somewhere by a leaky rail decoupling cap as used to be common on all sorts of Pan gear back in the day. I picked one of the IF processor chips at random and looked up the data sheet on it to find the Vcc pin. The sheet claimed a Vcc of 14 volts, but there's actually only about 5 volts on the pin. I tried following the print back, but it rapidly starts jumping around the board on wire links and print 'splits'. It's really not worth spending the time on trying to trace where the rail comes from, and what decouplers are hanging across it, but it would of course be a very simple fix with the benefit of a schematic. If all else fails, I can get a download copy for $4.99 of the 'net, but cheapskate as I am ... d;-) Arfa Have you checked the power supply bulk capacitors for a high esr cap? Sure sounds like it could be an issue. First check, always. Nothing jumping out. Main rail off the reccy is there and looks about as ripple-free as you would expect pre the regulators ... Arfa |
#8
Posted to sci.electronics.repair
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Old Technics tuner, anyone ... ?
"Arfa Daily" wrote in message ... "Tom Miller" wrote in message ... "Arfa Daily" wrote in message ... wrote in message ... I don't know specifically, but will check my service manuals on CD for this one. Any particular problem you are addressing? I may also have service bullitens. Dan It has no 'proper' output. A bit of hum-y noise and that's it. Display is normal. Appears to tune normally, but I'm sure it isn't. Looks like a PSU problem or maybe a rail getting dragged down somewhere by a leaky rail decoupling cap as used to be common on all sorts of Pan gear back in the day. I picked one of the IF processor chips at random and looked up the data sheet on it to find the Vcc pin. The sheet claimed a Vcc of 14 volts, but there's actually only about 5 volts on the pin. I tried following the print back, but it rapidly starts jumping around the board on wire links and print 'splits'. It's really not worth spending the time on trying to trace where the rail comes from, and what decouplers are hanging across it, but it would of course be a very simple fix with the benefit of a schematic. If all else fails, I can get a download copy for $4.99 of the 'net, but cheapskate as I am ... d;-) Arfa Have you checked the power supply bulk capacitors for a high esr cap? Sure sounds like it could be an issue. First check, always. Nothing jumping out. Main rail off the reccy is there and looks about as ripple-free as you would expect pre the regulators ... Arfa Ok, yes. Knowing you, that was a dumb question. Good luck. |
#9
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Old Technics tuner, anyone ... ?
I'll still look on the CDs too. Just thought of the website.
Dan |
#10
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Old Technics tuner, anyone ... ?
First check, always. Nothing jumping out. Main rail off the reccy is there and looks about as ripple-free as you would expect pre the regulators ... Arfa Ok, yes. Knowing you, that was a dumb question. Good luck. Why thank you kind sir ! Very nice of you to say so :-) Arfa |
#11
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Old Technics tuner, anyone ... ?
wrote in message ... I'll still look on the CDs too. Just thought of the website. Dan Thanks Dan. Appreciate the effort. Arfa |
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