Noisy pots on A60 - what to do?

Discussion in 'Hi-Fi Stereo Systems & Separates' started by endure, Apr 17, 2016.

  1. endure

    endure
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    Hi folks. This is my first post so make allowances please :)

    I'm resurrecting a system that's been sitting doing nothing for the past 20 years. The amp is a Cambridge A60 and the speakers are Rogers Compact Monitors.

    I was quite surprised that it actually worked when I plugged it in but it's all OK from the fact that the controls on the A60 are noisy. If I alter the volume/balance/treble/bass knobs I get crackles and hiss while they're turning.

    Is there any fix for this please? Will they just sort themselves out with a bit of use? I'd rather not open the amp up if possible.

    Thanks.
     
  2. andy1249

    andy1249
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    You can try exercising them about 20 or 30 times across the full range.
    This might break up any crud on the tracks and get them working again.

    If that doesnt fix them you have no other choice but to open it up.

    Depending on the pot type, you may be able to try contact cleaner on them.
    Obviously if they are the enclosed type , this wont be possible.

    If you cant clean them or the cleaning doesnt work, you need to get a part number or descriptor code off the pots, buy new ones , and replace them.
     
  3. endure

    endure
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    OK thanks Andy. I'll give that a go.
     
  4. RugbyAl

    RugbyAl
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    Hi, I had a similar problem with a 20 yr old amp of mine. I took the lid off and sprayed some contact cleaned into the pot the best I could. I did find however that 20-30 turns wasn't enough - I ended up doing nearly 200 cycles on the volume pot.
    Don't be tempted to switch the amp on with the cover off, the capacitors can contain substantial electrical charges...
     
  5. Stinger69

    Stinger69
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    It's worth noting that pure contact cleaner without inbuilt lubricant can cause the pot's travel to feel a bit rough. The tracks on these pots usually have some lubricant on them that can be cleaned off by the cleaner.
     
  6. 12harry

    12harry
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    Just come across this post - sorry if you aren't looking for answers . . . but endure hasn't come back saying it's FIXED.

    I suspect the amp was OK when is was put aside, otherwise you'd remember never to use it again.... and it would have been dumped.
    So, I wonder if the "noise" is not down to track-noise itself I caused by loose particles of track - although the bonding agent may be deteriorating, which would give rise to this and no "cleaning" will fix it IMHO.
    The other possibility is that there are DC currents going through the pots, due to electrolytics that have started to leak ( electrical ). ...these may "Reform" or could be replaced. Usually fining replacements pots is not easy as manufacturers change designs and if they are mounted onto the pcb there is risk to the circuitry too.
    Note that these capacitors can be physically quite small - but other than plastic caps ( which should be OK over 20-years), any electrolytic is suspect...almost as soon as they leave the factory - it's a marvel of modern manufacture they are so good.
    The warning about voltages . . . may be Safe Warning, but ONLY if this is a valve amplifier will "high voltages" be available on supply capacitors - provided the mains-plug is removed, the PSU should not be trying to kill you - but then there's the old maxim... if you don't know what you are doing - Stop.

    Hope that helps. Let us know if the pots are OK
    If it's only when you adjust them . . . then maybe leave well alone and banish Amp. to the Den, where the level can be set by the input-source.
     

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