You may have read of the advice to use a variac for first powering up an old valve unit that has been in storage for years - may I please pass on the London Sound approach that does not require any equipment?
This was first devised over thirty years ago, and has been passed on to many valve hi-fi enthusiasts with many tales of success. It applies to all valve units that have not been used for two years or more.
Start by checking the mains plug and ensure that it is earthed. Do not skip this check, I did recently and suffered a very painful electric shock! Also in the case of amplifiers ensure that loudspeakers are attached or very serious damage may result. Assuming that the equipment looks ok - no mould, mice or dampness etc - and the correct fuses are in place, turn on for thirty seconds.
Switch off, and go and make yourself a coffee.
About five minutes later, turn on for a minute, and see if it's showing signs of life.
Go off to find a bottle of whisky to pour in your coffee.
After another five minute gap, turn on for five minutes, and see if it still seems to work.
Five minutes is long enough to explore and play - but stick to this limit.
As you've finished the coffee, make another - and this time remember the whisky!
After another five minute gap, try the unit for ten minutes. Switch off for a further five minutes, then try for fifteen minutes. Allow a further five minutes, then run it for thirty minutes. After the final thirty minute run, switch off until the following day.
The whisky and coffee are optional, but the time limits are not.
However, if you don't want the whisky, send the bottle to me!
The explanation is quite straightforward.
When first switched on after a very long time, various components will draw excessive current. Electrolytic capacitors are not the only culprits - anything that can absorb moisture over a while will have done so, and may malfunction.
I am unsure about this, but I also think that the getter in a valve unused for many years, (the chemical which is supposed to absorb air that has penetrated the valve in microscopic quantities), needs the heat of operation to perform its duties.
Obviously, abandon the process if there's a big puff of smoke and a loud bang!
However, the short intervals should allow circuits to function, but not over heat badly, (we hope!). The final switch-off overnight after thirty minutes is as important as the other parts of the process, as even during the thirty minutes test, some parts of the circuitry may be still overheating due to electrolytics being unhappy, or moisture still evaporating.
I always apply this procedure with all old valve hi-fi units repaired here at London Sound, and as a result, even with equipment stored unused over many years, after the above procedure, and an overhaul, I always am able to guarantee repaired equipment for twelve months!
So, from my regular professional use of this method, I can assure readers that it actually works - it gives good components the best chance of remaining in service, so minimising the work of the repairer!
One further tip, only for the technically minded with good electrical skills - if you are really worried, put a mains light bulb in series with the feed, (be careful with insulation!), and if the bulb lights brightly, assume there may be a short circuit in the unit's power supply.
Choose your bulb carefully, to draw enough but not too much current, and you should see it varying in brightness during warm-up, as though a testmeter in series - but with the added bonus of short circuit protection!
As a final caution - be aware of the potential for catastrophe, and if unsure, do not take chances. I own a wireless purchased, new, by my grandfather, in 1932, which I recently part restored. The operating h.t. voltage virtually doubled when I replaced the original metal rectifier. After about half an hour's operation, I noticed a strange sound, and was trying to work out what it was for a few minutes. When I realised what it was - I cut the power and left the room! It was a completely sealed original electrolytic capacitor, which was boiling! Literally! If I hadn't noticed this, it would have exploded - with bits of the metal can flying across the room, accompanied by boiling electrolyte! If that had happened, I would not be writing this now!
I hope, dear reader, you found the above of interest, and that you take note! Obviously if the unit does not function, we will be happy to advise on repairs, (take the repairs link to find out how) or ring us on 020.8868.9222.
Alternatively, email me at:-
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