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 Post subject: Tubes UY85 and UCL82
PostPosted: Oct Thu 17, 2019 4:05 am 
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Joined: Oct Thu 17, 2019 3:40 am
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I am reviving and old amplifier from an old english record player Bush RP60. This amp is based on just 2 tubes; the UY85 for half wave rectification of voltage and then the UCL82 does the rest. The architecture taps off the turntable drive motor to get power for the both tube heaters, I think it was 50v. My problem is the motor is burned out and I am using a more modern turntable. These valves seem to have different requirements for the heater namely 50V max for the UCL82 and only 38V max for the UY85. I can use a transformer to supply what the old motor supplied but my worry is finding a common voltage that will be enough for the UCL82 but not too much for the UY85. Any suggestions will be appreciated.


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 Post subject: Re: Tubes UY85 and UCL82
PostPosted: Oct Thu 17, 2019 4:56 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 37561
Location: Livermore, CA
Both tubes have 100 ma filaments. They may have been operated in series? In series they will operate on 88 volts. The rest of line voltage can be dropped by a resistor or other method.

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 Post subject: Re: Tubes UY85 and UCL82
PostPosted: Oct Fri 18, 2019 5:05 am 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3248
Location: Lexington, KY USA
If you are running off a 120V line, a silicon diode might work with the two tubes in series.

Else use a series capacitor. The capacitor value has to take into account the AC line voltage and frequency.

For 120V operation, a second diode might be used to make a voltage doubler B+ supply.

Ted


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 Post subject: Re: Tubes UY85 and UCL82
PostPosted: Oct Sat 26, 2019 6:07 pm 
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Location: Spain - 28110 - Algete
You can see the original sch:

https://www.radiomuseum.org/r/bush_rp60.html


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 Post subject: Re: Tubes UY85 and UCL82
PostPosted: Oct Sun 27, 2019 5:07 pm 
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For parallel operation you'll need two separate power sources. Not very practical.

For series operation(original configuration), a 1N4007 can be added to string and operate directly from 120v line. Tubes add to 88v & that's just about exactly result when 120v is fed through a rectifier.

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 Post subject: Re: Tubes UY85 and UCL82
PostPosted: Oct Mon 28, 2019 12:08 pm 
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Joined: Jan Mon 18, 2010 2:13 am
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Location: Dayton Ohio
You could replace the UCL82 (50BM8) with an ECL82 (6BM8) and power its filament with a 6.3 volt power transformer.
Eliminate the UY85 with a 1N4007.

Just a thought.

-Steve

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