temp substitution, 45 for a 2A3 ?

[gadget73]

I came into a radio that runs a pair of 2A3 tubes, but unfortunately they are missing. I have some 45's around though. Can I temporarily sub a 45 for the 2A3 for testing ? I don't have a schematic yet for this thing, so I'm not really sure how the amp biases things yet. I just don't want to buy tubes for this unless I'm going to keep it and I know its fixable.

 

[GordonW]

Probably not a good idea.

The 2A3 is roughly like two 45s in one envelope, wired in parallel inside.

A 45 probably isn't going to handle the power properly. Likely will red-plate.

Now... if you had FOUR 45s... if you could find a way to jumper them in parallel (two 45s for each 2A3), then that would work for testing, no question...

Regards,
Gordon.

 

[gadget73]

I actually may have 4 45's but I dont have any 4 pin sockets. Well, I can ring out the transformers and such to see if its got signs of life in it without any tubes I guess. Its for a Scott Allwave 15 that I picked up sinfully cheap. I just don't want to pop for a pair of 2A3's unless I've decided to keep the thing. Maybe I can look at the AW12 schematics to see how different the amp is. The AW12 ran a pair of 45's. Maybe I can temporarily modify things to drop power down to levels that a 45 would survive under.

 

[battradio]

If the 2A3's are cathode biased you will be ok for a short time to see if it works , the 45 draw 1/2 current and will bias them self higher than tham 2A3's . It will be half power but ok to use .

 

[Gary Kaufman]

The E.H. Scott Alwave 15 is a pretty special radio - if the cost of a pair of 2A3's is a consideration perhaps it would be best to pass the radio along. A buyer would be much happier with the radio untested and original. In any sort of nice shape this is probably well over a $1K radio. It is also not an easy radio to work on.

 

[radiostar]

It'll be big pitty to make any modifications on a jewel like Scott Alwave 15 ... Better wait some time and find 2A3s ...


Good luck!

 

[analog addict]

Now on the other hand....

I was just given some 2A3's and told to stuff them in my 45 SE amp. Thought I'd try with some cheaper Sovteks first, and they sound great. Guess this works as long as your PT has the omph to handle the extra filament current.....:thmbsp:

 

[gadget73]

I really don't want to modify the thing, but I would like to see if the basic circuitry has life in it before investing at least 100 bucks for a pair of tubes. I'd hate to fork over the money for a pair of 2A3's only to find that some impossible to replace item is dead, leaving me with a pair of tubes that I have no use for. Its not that I don't have 100 bucks to put towards a worthwhile project, but I don't have 100 bucks to throw around just for S&G. If this thing is fixable, I will fix it and it'll be right. More than once I've gotten myself into projects only to find that after pumping a lot of money and time into them, I'd run into a brick wall because some part failed and it wasn't something I could get a replacement for. I'm trying to get smarter about this stuff as I get older.