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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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NAD 7020e has its signals crossed
NAD 7020e receiver just failed most strangely. If only one source is connected to the appropriate input (such as CD),
the signal can be heard on both channels at about 1/2 volume when tape monitor or video is selected. Tuner is also audible regardless of which input is selected. I've disassembled it and cleaned contacts etc to no avail. There's no visible damage under illuminated magnifier. tia in advance for help Nigel |
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Nigel,
The switching in this receiver is purely mechanical, and all before the the volume control, so what you are getting is really odd. I would have to guess at a cracked circuit board, or some blown ground foils, unless the switch latching mechanism has failed and allowing multiple sources to be selected, or there is major corrosion in this unit creating unwanted signal paths. Regards, Tim Schwartz Bristol Electronics Nigel Burnett wrote: NAD 7020e receiver just failed most strangely. If only one source is connected to the appropriate input (such as CD), the signal can be heard on both channels at about 1/2 volume when tape monitor or video is selected. Tuner is also audible regardless of which input is selected. I've disassembled it and cleaned contacts etc to no avail. There's no visible damage under illuminated magnifier. tia in advance for help Nigel |
#3
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On Sat, 28 Aug 2004 13:29:29 GMT, Nigel Burnett
wrote: NAD 7020e receiver just failed most strangely. If only one source is connected to the appropriate input (such as CD), the signal can be heard on both channels at about 1/2 volume when tape monitor or video is selected. Tuner is also audible regardless of which input is selected. I've disassembled it and cleaned contacts etc to no avail. There's no visible damage under illuminated magnifier. tia in advance for help Nigel If you want to end that kind of noise, you should add a grounding plug to unused inputs. When I had the audiovirus back in an earlier lifetime, I used to use old RCA plugs cut off a cable, strip the wires and twist them together. I actually soldered them. I forget if some people used some special value resistor soldered onto the wires instead of just twisting them. I'm not sure what the deal is with your tuner, I'd think the tuner circuits would be turned off if it isn't selected. Damn noisy otherwise |
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On Sat, 28 Aug 2004 14:17:31 GMT, Tim Schwartz wrote:
Nigel, The switching in this receiver is purely mechanical, and all before the the volume control, so what you are getting is really odd. I would have to guess at a cracked circuit board, or some blown ground foils, unless the switch latching mechanism has failed and allowing multiple sources to be selected, or there is major corrosion in this unit creating unwanted signal paths. Hi Tim, It is odd. I've ohmed out the signal paths and switches and everything seems ok. Disassembling the switches looks like a mechanical nightmare given that 5 ganged xwitches need 6 contacts each desoldered. Phew. It does appear that the Tape Monitor is the problem as any signal (even built in tuner) comes through at 1/2 vol. A signal applied to either left or right CD input can be heard on both channels when tape monitor is pressed. The unit hasn't moved for a year so cracked traces seem almost impossible. No corrosion or anything visible. It could be internal to one of the switches I guess. I'm really stumped esp with no schematic. *sigh*, Nigel Burnett wrote: NAD 7020e receiver just failed most strangely. If only one source is connected to the appropriate input (such as CD), the signal can be heard on both channels at about 1/2 volume when tape monitor or video is selected. Tuner is also audible regardless of which input is selected. I've disassembled it and cleaned contacts etc to no avail. There's no visible damage under illuminated magnifier. |
#5
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Nigel,
What happens if nothing is connected to the tape in/out jacks? After that, try one pair of RCA cables looping from the tape out to the tape in, but no equipment hooked up to the receiver. Regards, Tim Schwartz Bristol Electronics Nigel Burnett wrote: On Sat, 28 Aug 2004 14:17:31 GMT, Tim Schwartz wrote: Nigel, The switching in this receiver is purely mechanical, and all before the the volume control, so what you are getting is really odd. I would have to guess at a cracked circuit board, or some blown ground foils, unless the switch latching mechanism has failed and allowing multiple sources to be selected, or there is major corrosion in this unit creating unwanted signal paths. Hi Tim, It is odd. I've ohmed out the signal paths and switches and everything seems ok. Disassembling the switches looks like a mechanical nightmare given that 5 ganged xwitches need 6 contacts each desoldered. Phew. It does appear that the Tape Monitor is the problem as any signal (even built in tuner) comes through at 1/2 vol. A signal applied to either left or right CD input can be heard on both channels when tape monitor is pressed. The unit hasn't moved for a year so cracked traces seem almost impossible. No corrosion or anything visible. It could be internal to one of the switches I guess. I'm really stumped esp with no schematic. *sigh*, Nigel Burnett wrote: NAD 7020e receiver just failed most strangely. If only one source is connected to the appropriate input (such as CD), the signal can be heard on both channels at about 1/2 volume when tape monitor or video is selected. Tuner is also audible regardless of which input is selected. I've disassembled it and cleaned contacts etc to no avail. There's no visible damage under illuminated magnifier. |
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