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Old 27th January 2006, 10:36 PM   #1
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Default OP Transformer power rating guesstimate

Hi Guys,

I've been lucky enough to score a pair of Hammond '28185' OP transformers from a 50's Minshall organ.
Can't find any info on them.

Not sure if they're made by Hammond Transformers or Hammond Organs?

They were driven by 6L6's, so a conservative guess at the power rating would be around 15 Watts.

Can I confirm this by measuring the cross section area of the
transformer cores?

I'm probably going to use them to drive 6AQ5's, but having the octal sockets, I'm thinking of shelling out for some 6L6GC's...
just like to know how far I can push them, wouldn't like to fry them...

Cheers,
Pete McK
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Old 28th January 2006, 12:44 AM   #2
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Default Re: OP Transformer power rating guesstimate

Hi Pete,

Quote:
Originally posted by PeteMcK
They were driven by 6L6's, so a conservative guess at the power rating would be around 15 Watts.
Do you mean 6V6?

PP 6V6=15W, PP 6L6=30W (conservative)

Hmmmm, did Hammond Organ even use 6L6? I thought they were 6V6 fans. That could be a hint...

What's the primary impedance? 6V6 will be ~8K, 6L6 will be ~3 to 4K
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Old 28th January 2006, 01:34 AM   #3
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Hi Greg,

They were using 6L6's, but the early versions without extra letters had lower power ratings.

Haven't measured them yet...
might have a look for mfg/date code.

Have found references to a rule of thumb/ chart which gives approx pwr rating of transformer, but haven't been able to find an actual chart as yet...

cheers,
Pete McK
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Old 28th January 2006, 02:32 AM   #4
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Quote:
Originally posted by PeteMcK
Have found references to a rule of thumb/ chart which gives approx pwr rating of transformer, but haven't been able to find an actual chart as yet...
I am here to serve. I have a chart here

http://geek.scorpiorising.ca/windingtransformers.html


Quote:
...might have a look for mfg/date code.
Might not do any good. Hammond had a fire and lost pretty much all of their pre-1960 records

I have a pile of pre-1960 Hammonds (power trannies) I had to derive by hand.
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Old 28th January 2006, 02:48 AM   #5
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Default excellent...

just what I was looking for.

Much appreciated - I owe you a beer.
Cheers,
Pete McK
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