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previous: Rob Just picked up a Harmony H430 amp, ... -- 8/14/1999 3:59 PM View Thread

Re: 6973=6CZ5?

8/15/1999 4:54 AM
Bruce
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Re: 6973=6CZ5?
Yes, the odd 6973 is the reverb driver tube.  
 
I think I found the H430 schematic in my old copy of Jack Darr's amp book.  
 
If Steve A. will help me.... hint...I can scan a copy (with some minor mods to make it sound a little more hip) and email it to you or him.  
 
Even for a decent DIY'r, it's an "unusual" amp design and circuit board layout that produces some serious head scratching.  
 
It takes some concentration to reverse engineer it so try and get a copy of the schem.  
 
 
 
I just refurbed one for a customer last week and the retail price of the two 6973s was over $50.00 so, while he wasn't looking, I rewired the sockets for EL84s and they worked just fine too.  
 
But since I had three NOS 6973, and he wanted to keep it mostly original, I redid it and installed the 6973s.  
 
Dont waste too much time on this tube issue and just rewire the sockets to take a different but similar pentode tube.  
 
Also carefully remove the cheap cardboard box cover that houses the reverb springs and clean the RCA jacks and plugs.  
 
This is a source of weird reverb problems on a few of these old timers.  
 
 
 
Bruce  
 
Bruce  
 

 
Replies:
Rob Thanks to Graywater and Bruce for h... -- 8/15/1999 8:28 PM