Quote:
Originally Posted by thejazzageuk
I'd be grateful for any advice as to how long I should safely leave it powered for in order to give faulty components a chance to get warm.
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I would keep doing it for a minute or two a number of times with a five minute break in between to see whether the hum level that you're hearing reduces due to the smoothers recovering and whether there's any slight warming of any of these electrolytic capacitors in the smoothing section.
With regards to the hum, you need to determine whether it's HT smoothing related or whether it's being picked up by the wiring that you're 'patching' your audio source (Garrard deck) in to the unit with. So remove all audio input wiring for the first test to see if it removes the hum, if it doesn't, proceed with the intermittent powering up and see if it lessens and let us know the results. If there's still a lot of hum, then one or more of the smoothing electrolytics has lost capacitance and will need replacing. Some would advise replacing them all regardless, but you could tack an appropriately rated separate electrolytic across each one to diagnose the faulty one - if you're not sure about any of this, then ask for advice.
It's normal for the HT to be low with the lamp limiting the input current. Volume may be low due to the lower HT and also that it would probably normally go through another pre-amp stage in the radio tuner head.