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7591A in 5E3?


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3/28/2003 8:18 PM
Howard Parks
7591A in 5E3?
A while back somebody asked about using 7591A's in a 5E3, and Bruce responded but I've lost the post. Seems to me it was a rather simple mod... can you post that again, Bruce?  
Thanks,
 
3/29/2003 3:21 PM
quayhog

I built a 5E3 circuit in an old Ampeg Reverbojet carcass. It had the original transformers but little else that was useable.  
I used the 5E3 circuit but when I got the the 7591 part I used Ampeg circuit values.  
 
The best schematics for ampeg are found at:  
http://home.rochester.rr.com/piazza/index.html  
 
7591's will burn up a small 5E3 OP transformer so I suggest you get a new tranny capable of 45watts at 6.6k primary load.  
 
Btw, the amp sounds great. I gave it to my nephew and he uses it all the time.
 
3/29/2003 7:07 PM
Bruce /Mission Amps

quote:
"7591's will burn up a small 5E3 OP transformer so I suggest you get a new tranny capable of 45watts at 6.6k primary load."
 
I'd say be carefull but I'm not so sure about burning up a 5E3 ot.  
The OT in a 7591A Reverberocket is not much bigger then a real tweed deluxe OT and I doubt the AMPEG OT is anywhere near a 45 watts rating.  
I've used reissue SF Deluxe Reverb OTs (6k6ohm@20watts)as replacement OTs in several AMPEG amps using 7591As and none have returned.  
I think as long as the idle current is reasonable, you should not have a failure.  
 
Bruce
 
3/29/2003 11:59 PM
Howard Parks

Thanks,  
Is this plug and play, or is there some rewiring necessary? I bought my kit early last year (I think it's the NSF output trannie?), I'm using a zener, and a 10 watt 270 ohm resistor.  
Howard
 
3/30/2003 12:08 AM
Bruce /Mission Amps

Yes, you could use that NSC OT but, no, you have to rewire both the tubes sockets, save the plate and the filament leads, for 7591As.  
Best to use Sovtek 6L6WXTs or nos 5881s with no zener.  
They are plug and play.  
 
Bruce
 

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