Input transformer with only two leads??

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Input transformer with only two leads??

Postby Alistair » Mon Sep 09, 2013 3:30 pm

I'm in the middle of restoring some Rola 77mkIII units that as well as being 40 years old have had some modifications performed.

All of the connections as per the schematic to and from the input transformer have been cut- I presume at some point the unit was only used for playback. The input transformer has also been wired up to the HT I think... Not sure about this, it's pretty messy in there and I'm still tracing.

Anyway- the schematic shows dual primary and dual secondaries, but the input transformer only has two fly leads. How does this work? Is there an input and output lead referenced to chassis? I've never come across an input tx with less than 4 connection points before.

I have two units identical so I'm assuming that the transformer is original, but it could be a replacement and incorrect 60's ROla tx I guess.
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Re: Input transformer with only two leads??

Postby Wiz » Mon Sep 09, 2013 3:37 pm

What happens when you meter it out...?
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Re: Input transformer with only two leads??

Postby Junction » Mon Sep 09, 2013 6:45 pm

That can't be an input tranny, it must be a choke, in series with the HT supply. ;)
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Re: Input transformer with only two leads??

Postby Alistair » Mon Sep 09, 2013 7:44 pm

Obvious now you say it! I really need to get more used to valve amplifiers, a choke never occurred to me.
Makes sense why the input tx leads have been cut then. Someone has pinched it!

Anyone know what input tx was used in these? I'm guessing a standard rola input tx?
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Re: Input transformer with only two leads??

Postby rob » Tue Sep 10, 2013 9:45 pm

I might have a spare input transformer, email me.
But I am a bit concerned .... mistaking the choke for the input transformer .... I hope you'll keep one hand in your pocket when you turn it on.
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Re: Input transformer with only two leads??

Postby Alistair » Tue Sep 10, 2013 11:24 pm

Agreed. Feeling a bit silly. I saw three transformers, one was clearly output, one clearly monitor output so I assumed the last was input...
I was more confused when I found the code CH printed on the transformer and that appeared to be a Rola code used on output and line transformers... or just shorthand for choke!



I'll shoot you an email re: transformer.
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