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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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24th Sep 2020, 8:31 am | #1 |
Tetrode
Join Date: Jan 2020
Location: Ilkley, West Yorkshire, UK.
Posts: 92
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Sony amp (F411R). Loss of sound at low volumes on power on
Can anyone point me in the right direction here? I have quite an old Sony amp (F411R) and often (but not alway) when I power it on I get sound from only the left channel and occasionally no sound at all from either. Turning up the volume instantaneously restores the sound and then turning it back down again it continues fine.
I've done all the obvious things, de-ox'ed the volume pot (and all the other ones), checked solder connections on the output, etc. But it still does it and I don't know where to look next. Once it starts working it is perfect. If I don't touch the volume control then the sound doesn't come back on the faulty channel - so it's not just a warming-up problem. Any ideas? |
24th Sep 2020, 9:02 am | #2 |
Nonode
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 2,038
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Re: Loss of sound at low volumes on power on
Faults like you describe are frequently due to oxidised switch contacts or poor connections to speakers or ancilliary gear. Turning up the wick is often enough to break through the oxide and resore normal operation until next time.
Selector switches, pots, phono connections, speaker fuses/relays and speaker terminals are all under suspicion.
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Andy G1HBE. |
24th Sep 2020, 9:52 am | #3 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Sony amp (F411R). Loss of sound at low volumes on power on
I agree that poor contacts somewhere are likely to be the cause. The protection relay would be a prime suspect although it's not usually very easy to clean the contacts and replacement is often the best option for long term reliability. The manual doesn't say anything about the relay's spec but markings on the relay itself might help. By the way, the service manual can be downloaded for free from Hi-Fi Engine if you don't already have a copy. An amp that's worthy of some TLC in my view.
Alan |
24th Sep 2020, 11:56 am | #4 |
Heptode
Join Date: Jul 2014
Location: Boston, Lincolnshire, UK.
Posts: 995
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Re: Sony amp (F411R). Loss of sound at low volumes on power on
Another possibility with Sony's of that age would be any rotary remote slide switches it might have - the contacts are in the slide portion of the switches, and they are inaccessible for cleaning without removal from the pcb. I've had issues on slides for source selection or speaker selection, in different Sony's.
Alan |
25th Sep 2020, 6:16 pm | #5 |
Tetrode
Join Date: Jan 2020
Location: Ilkley, West Yorkshire, UK.
Posts: 92
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Re: Sony amp (F411R). Loss of sound at low volumes on power on
Thanks for those suggestions. I have cleaned all the rotary switches but haven't check the protection relays. When I power on I can hear the relays click so I had assumed they were ok but maybe worth a look.
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25th Sep 2020, 6:42 pm | #6 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Sony amp (F411R). Loss of sound at low volumes on power on
There's only one relay. The clicking's good but there could still be a problem with the contacts for the intermittent right channel. Have a look at the schematic.
Alan |