Bill Beard BB100 valves

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Moss23
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Bill Beard BB100 valves

Post by Moss23 » Thu Jun 25, 2015 6:37 am

Hi all,

I have been asked to repair a BB100 with a dead channel Before I start however it's obvious someone has installed the wrong valves in the preamp section. Instead of 4 ECC81s and 2 ECC82s there is only one ECC81 and the rest are ECC82s. There are no labels on the amp itself to indicate what the valves should be. Can anyone help with information about what goes where?

Thanks,

Moss

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andrew Ivimey
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Re: Bill Beard BB100 valves

Post by andrew Ivimey » Sat Jul 04, 2015 10:07 pm

Sorry no one has replied so I'll add my two pence. I used to have a BB100. It was smashing but needed regular servicing largely because of the biasing arrangements of each el84 having an LED which showed when balance was no longer acceptable. This could happen every six months, which I consider a poor design criterion no matter how exactly old Bill chose his design to operate. Getting under the bonnet to see the bits and bobs in situ and working was very difficult particularly without damaging the peculiar screws that held the base plate on. Damaged screws meant a serious lecture from Bill's engineer. Any other fiddling could produce and unwillingness to service. So, there was only one bloke in London who used to work with Bill who would do a service. Can't remember his name but he lived down near Fulham - that doesn't help at all but perhaps it is interesting. I only met the chap once and we got talking and very quickly got into transmitter valve amps. He'd bread boarded a particularly dangerous looking SE amp with VT4Cs driving electrostatic panels, all in the living room of a small flat - with pets and small child - oh well. But he was good at what he did, was interesting and friendly and I would conclude that Bill Beard amps are excellent quality if fussy. I'd be surprised if you could find schematics though perhaps by now a good hard internet search could yield a few nuggets - good luck!
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.

Moss23
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Re: Bill Beard BB100 valves

Post by Moss23 » Sun Jul 05, 2015 4:26 am

Thanks for the reply! I'm in Australia so a long way from any British people with experience of these amps. I did manage to repair it without a manual, it helped that it's really two separate mono amps only sharing a common power transformer. That made comparing the two channels a useful strategy. The fault was easy to find - a shorted rectifier diode in one channel power supply. Replacing it fixed the problem. The blown mains fuse was an entirely inappropriate 6 amp fast blow which I replaced with a 3.15 amp slow blow. That amp has a very high switch-on surge due to the huge power transformer and enormous filter caps on both HT supplies and the heater supply. The HT rectifier diodes are quite stressed when it's switched on. It's not really good design but had lasted a long time. I managed to work out the preamp valves too - it used ECC81 valves with unusually large plates which was confusing but a bit of time with an AVO valve tester soon sorted that out. Anyway it's gone back to its owner who is very happy. My back has recovered too!

Cheers,
Moss

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Paul Barker
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Re: Bill Beard BB100 valves

Post by Paul Barker » Sun Jul 05, 2015 9:10 am

Nice to hear a conclusion to the story. Sorry I had no knowledge at all to contribute.
I can do it right or I can do it now, but I can't do it right now.

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pre65
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Re: Bill Beard BB100 valves

Post by pre65 » Sun Jul 05, 2015 9:59 am

I'd think a switch on surge limiter (thermistor) would be a good idea, I use them on all my amps.
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Moss23
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Re: Bill Beard BB100 valves

Post by Moss23 » Mon Jul 06, 2015 10:16 am

Thanks for the replies! I had thought of installing a thermistor but I wanted to keep the amp original and avoid installing something that would get very hot. There's not much room where the mains connector comes in. I used thermionic rectifiers in my own amp with a choke input filter to avoid that problem.

Moss

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Paul Barker
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Re: Bill Beard BB100 valves

Post by Paul Barker » Mon Jul 06, 2015 6:30 pm

Moss23 wrote: I used thermionic rectifiers in my own amp with a choke input filter to avoid that problem.

Moss
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I can do it right or I can do it now, but I can't do it right now.

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