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Old 3rd Feb 2017, 11:46 am   #120
thejazzageuk
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Join Date: Feb 2014
Location: Carmarthen, Wales, UK.
Posts: 238
Default Restore beau decca amplifier

I've now got a bit of free time and would like to complete the restoration of my beau decca amp.

I've been following guidance from Techman- at the end of the previous post he advised:

So to sum up - remove mains filter capacitors, remove rectifier, power up full mains and check heaters. Switch off, replace rectifier and connect a speaker and power up via a 100 watt lamp in series with mains input, with a DVM set to highest DC voltage range (600 volts?) clipped between first smoother after the rectifier and chassis to monitor the HT. Leave to warm up until you see some HT. Switch off and increase bulb wattage to let HT rise a little more and hopefully hear some low hum from speaker - or better, music, if you've connected an audio source. DON'T run for any length of time when doing this. Switch off and check for any slight warming of smoothing cans etc. Note HT voltage each time. Once you know it's capable of working you can start replacing components that need to be replaced. Note: running this up with the lamps will help re-form the smoothing electrolytics - no need to replace these unless they prove to be bad.

When you come to replace capacitors, those you list for replacement are correct, but I would also advise replacing the small decoupling electrolytic C36, as this is likely to be unreliable.'


I've now linked the amp up to a speaker and to my garrard record deck (see photo) and am using a lamp limiter. When I switch on, lamp glows medium to low bright and HT voltage rises to around 175V. After about 20 secs, sound comes from the speaker, but is low volume and accompanied by lots of hum. After about 60 secs HT has risen to 185V and seems steady at this. After 2 mins I switch off. No components appear to be warm. 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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Last edited by Station X; 3rd Feb 2017 at 11:57 am. Reason: Threads merged.
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