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Old 12th Aug 2020, 5:29 pm   #1
vinrads
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Default Rock Ola amp restoration.

This one I named the pond find because it looked like it had been in a pond , I have refurbished many of these this one has got to be up there with the worst, total strip painted chassis new valve bases ,etc note! the original brown capacitors I do check them but haven't found a faulty one yet , The smoothing's are sometimes faulty , the bass/balance/ treble controls were all duff, and replaced , the chap I do them for will do the printing . a great deal of satisfaction is to be had ,when I look at a before and after . Mick.
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Old 12th Aug 2020, 8:27 pm   #2
The General
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Default Re: Rock Ola amp restoration.

Very nice job Mick. I'm impressed. It's good to see work like that. I'm guessing an Empress?
The 6973s are a bit pricey these days as the audiophools like them, do you use actual 6973s or substitute 6CZ5s instead?
Mark.
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Old 12th Aug 2020, 10:28 pm   #3
vinrads
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Default Re: Rock Ola amp restoration.

Hi Mark you are correct it is an Empress, up to now we are using Russian made 6973's they seem ok The problem one is the 6cy7 which are pricey , it is used in the avc cct , no one is making them, my friend brought me a German amp, a copy of the Empress ,they used an ECL82 I managed to draw the cct , and have incorporated it as a trial in this amp , now on the lookout for a pair of thimistors otherwise the stage is working ok . Mick.
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Old 13th Aug 2020, 9:27 am   #4
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Default Re: Rock Ola amp restoration.

That's a great job, I bet a few hours went into that!
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Old 13th Aug 2020, 10:05 am   #5
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Default Re: Rock Ola amp restoration.

Yes he's clearly put some real time & skill into that one.
The 6CY7 is an odd valve, one high gain triode plus one power triode in the same valve.
Mick, I'm sure you're aware, but it may help someone else; one thing to be aware of with Russian 6973 is that some are actually rebranded 6CZ5. The characteristics are identical but the 6CZ5s have the screen grid on pin 1 whereas 6973s have the screen on pins 1+8, meaning the valve base may need a small rewire depending on which pin the amp manufacturer originally used.
6EM5 is also a good substitute for 6973 but the heater current is higher & the screen grid is also only connected to pin 1.
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