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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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5th Dec 2021, 3:20 pm | #1 |
Diode
Join Date: Feb 2021
Location: Stajerska, Maribor, Slovenia,
Posts: 5
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Sony mhc-2700
Hello,
I have a mini hi-fi system SONY MHC-2700 from 1993. It served me well all the time, so I decided to try to extend its lifespan. I replaced rubber things like belts and pinch rollers (cassette deck), etc. A big problem is the tuner (ST-H3700), which does not make sound in stereo mode. If you press the MONO button, then the sound appears, but of course mono. I’ve checked all the electrolytic capacitors that could be worn out due to age, but the ESR70 says none are critical. I suspect it could be a defective tuner chip (LA1851N). The next problem is the brightness of fluorescent displays on all components. So I checked the voltages coming from the amplifier (TA-H2700) - this serves as a power supply to the other components - which are all, I think, within tolerance limits. Could the cause of poor luminosity be the age or wear of the gas in the fluorescent displays? I would be very grateful for any hint. |
5th Dec 2021, 4:18 pm | #2 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,970
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Re: Sony mhc-2700
Some vacuum fluorescent displays do go dim as they age. This particularly affects equipment which keeps the VFD powered up during standby (so as to show a clock, for example.)
Some mini systems can only be switched between mono and stereo using the remote control. Have you tried that? |
5th Dec 2021, 7:17 pm | #3 | |
Hexode
Join Date: Dec 2020
Location: Raunds, Northamptonshire, UK.
Posts: 359
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Re: Sony mhc-2700
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5th Dec 2021, 7:43 pm | #4 |
Nonode
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 2,820
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Re: Sony mhc-2700
Those displays just look like they are suffering from old age! If they were uniformly dim then it'd be a power supply issue, but those just look like old worn phosphor to me. As to the FM stereo fault, I also have a Sony tuner that suffers the same! Never did find out what was causing it, it wasn't poor signal in my case, as I tried one of those iPod FM transmitters right next to it, which does do FM stereo, but it still refused to pick it up in stereo. That particular unit does mute the audio on FM unless it's receiving a stereo transmission, or you press the mono button. Someone did suggest trying the 10.7mHz filters, as they can cause it, but i couldn't find any suitable to try it.
Regards, Lloyd |