[Amps] DEAD Alpha 91B

[Michael Tope]

Jim Brown wrote:

>On Mon, 18 May 2009 12:33:19 -0300, Thomas Carlsson wrote:
>
>  
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>>The Alpha 91b is a great amplifier
>>    
>>
>
>Mike,
>
>While you're in there, you might want to check to see if this model 
>is running a 120V fan between one side of 240V and ground. As you 
>know, that's a no-no, and generates problems with magnetic fields. 
>Alpha does that with some of their older amps. Ten Tec solved that 
>design problem correctly by running their 120V fan off of half of 
>the primary of the power transformer. 
>
>73,
>
>Jim K9YC
>
>
>  
>
Hi Jim,

Per the schematic, it looks like the blower is run from the between one 
side of the 240V input and the center tap on the transformer primary. 
One of the units I have here (I have two in my workshop) has a 
supplemental muffin fan bolted over the air intake port (the other unit 
only has the blower).  I don't think the muffin fan is shown on the 
schematic, so I will have to trace the wiring to see if it is wired 
correctly (this fan was probably added by the previous owner). 

73, Mike W4EF.................