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[Amps] Capacitor and Alpha 374 question

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Subject: [Amps] Capacitor and Alpha 374 question
From: "Jim Thomson" <>
Date: Sun, 21 Aug 2016 09:51:02 -0700
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Date: Fri, 19 Aug 2016 13:05:20 -0400
From: Ted <>
Subject: [Amps] Capacitor and Alpha 374 question

     I have a three tube Alpha 374, it has an oil-filled capacitor rated 
at 40pf/5KV.  After running awhile in cw an AC hum occurs on my signal.  
I am thinking that after heating up this old oil-filled capacitor may be 
going bad and breaking down.  It seems impossible to find another such 
oil-filled capacitor so I bought a capacitor replacement kit from "Tube 
Meister."  The add says it is for Alpha/76/78/374.  I do have two other 
Alpha 374A amplifiers and the replacement kits are great.

     My question is since there are just two leads from the oil-filled 
capacitor can I just simply connect the 6 210pf/450 volt capacitors in 
series and run the leads to where the oil-filled capacitor connected?  
Am I missing some important step here?  I'd rather not blow the 374 up!  
Perhaps even someone might suggest where one finds an oil-filled 
40pf/5kv capacitor?

     Thanks for any help/suggestions.



##  The original 374  used a single oil cap.   The 374A  used   6 x  180 uf @  
450 vdc
This is the manual for the 374A   Any string of lytics will be wired to the 
same + /-  as the oem
oil cap.   Use a single 100 K  @  3 watt  MOF  across each lytic...which is 
your eq /  bleeder. 
You can buy the  100 K  eq resistors from AG^K, who matched them, but your kit 
probably came with them. 

##  When wiring in your string of lytics, make sure the polarity is correct !!  
 There is no polarity on the oem oil cap. 
Dont mess with oil caps, they went the way of the do-do bird..and weigh too 
much, cost too much etc.  

Jim  VE7RF   
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