7027A - compatible with 6L6GC?

Ray Minich · Post by **Ray Minich** » 5 Mar 2004 5:24 pm

Can I use a pair of 7027A's (scarfed out of an old church organ) as pin/plug compatible in place of a pair of 6L6's? I'm getting conflicting information in my websearch

Thanks in advance and I promise this will be my last question for a while...

Jerry Erickson · Post by **Jerry Erickson** » 5 Mar 2004 9:24 pm

Ray,
Have you looked at any tube data charts on the 2 tubes? You need to find out how much filament current each tube(7027,6L6) draws, and also what the plate dissipation of each tube is. Knowing the bias current of each tube is also an important factor.
You might need to modify the bias circuit to be able to switch tubes.

Les Pierce · Post by **Les Pierce** » 5 Mar 2004 9:49 pm

Check out this site:

http://www.triodeel.com/7027.htm

Take care,

Les

Nicholas Dedring · Post by **Nicholas Dedring** » 6 Mar 2004 4:05 pm

I know Ampegs used the 7027s, which were ruggedized versions, heavier duty, of (I think) 6L6s. You might want to do some checking up... but they should work if that was what they subbed for. I know when 7027s were unavailable, 6L6s were listed as acceptable replacement, if i remember right. i've heard that the 7027s last a lot longer, the parts are all kind of overengineered... which is a good thing.

Blake Hawkins · Post by **Blake Hawkins** » 8 Mar 2004 4:28 am

Ray,
Electrically, the tubes are the same with the 7027A able to stand higher voltage than the 6L6GC. (Max plate voltage 600 on the 7027A and 500 on the 6L6GC.)
Heater voltage and current is the same for both.

However, you need to know how your amp is wired.
The 6L6GC does not use pin 1 or pin 6.
The 7027A duplicates Grid #2 on pin 1
and Grid #1 on pin 6.

This is not a problem if the amp has nothing connected to these pins.

But some amp manufacturers have the practice
employing unused pins on the tube socket as tie points for other circuit components.
Make sure your amp has no connections at pins 1 and 6 and your 7027A will work just fine.
My source for the information is the "RCA Receiving Tube Manual" Technical series RC-29.

Blake

Ray Minich · Post by **Ray Minich** » 9 Mar 2004 3:20 pm

My thanks to all for your advice and information. The 7027A info & pointers have been real handy in figuring out what to do with these tubes. Given some of the prices I'm seeing on some of the web pages for 6L6's, 7027's, 12AX7's and 12AT7's I think I should put these in a safe deposit box.

Thanks again.