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previous: drewl okay students, today we have a Hart... -- 1131591912 View Thread

Re: Hartke overheating

11/10/2005 1:43 AM
Enzo
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Re: Hartke overheating
Bipolars or MOSFETs? They made it both ways.  
 
I am an authorized Hartke repair center, and I can't say that I have found that to be a common problem.  
 
By all means dial down the bias current. Underbiased just means ther will be some xover distortion, but it won't hurt it.  
 
I just had a large QSC something or other through here that was heating up and shutting down when used. The idle current was about twice what it should have been. Set the bias back wher it belonged, burned it in for a couple hours to be sure, problem solved.  
 
Your Hartke could be that simple.  
 
On the bipolar model output module, there should be two twiddles. On my drawing the numbers are VR301,302. The 1k pot is the bias. The 470 ohm one is for DC offset at the output - set that without load.  
 
Monitor mains current as you tweak. If it rises, turn it the other way.  
 
The spec is 2.5mv across a PAIR of ballast resistors. That is, emitter to emitter across the outputs. The ballasts are .47/5w on my print.

 
Replies:
woodyc Hey Enzo, I own a r... -- 11/10/2005 10:40 AM