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The BA-3 as preamp build guide
The BA-3 as preamp build guide
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Old 16th March 2018, 05:50 PM   #911
Hikari1 is offline Hikari1  United States
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Quote:
Originally Posted by Manolo47 View Post
Its between the interface between the output mosfet and the heatsink...
The mosfet also has a heatsink...
Thanks
I think you mean between the metal tab on the misfit and the heatsink.

The answer is yes if anything will or can accidentally touch the heatsink like the top of the case, etc.

I would isolate the mosfets from the heatsink because there is a big resistor down on the board awfully close.
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Old 19th March 2018, 10:35 AM   #912
GumGum9000 is offline GumGum9000  Germany
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Which resistor values do I need to change to decrease the gain?
And are Takman Metal Film resitors ok for this build?
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Old 19th March 2018, 10:45 PM   #913
Todd Mills is offline Todd Mills  Canada
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Default Preamp finished

Finally got around to finishing the chassis and hooking the mechanicals up. I will work on the power supply next and wire everything up. I will cross my fingers and hope all is well. May need help setting bias.
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Old 20th March 2018, 12:14 AM   #914
vdi_nenna is offline vdi_nenna  United States
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The BA-3 as preamp build guide Send a message via Yahoo to vdi_nenna
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Old 20th March 2018, 07:00 PM   #915
Manolo47 is offline Manolo47  Puerto Rico
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Default Antek Transformer to power supply

Would appreciate your help. I gather that I would have to connect both primary red wires to AC positive input and the 2 primary blk wires to AC neutral.
The Purple wire is for what? I assume chassis ground?

And about the secondary wires, 2 are green and two blue... One pair of blue/greens extend longer than the other pair, is this indicative of how to connect them?

How do I connect these to my PS board inputs. Inputs are labeled as S1/S2 pairs. Thanks in advance.
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Old 20th March 2018, 09:51 PM   #916
Manolo47 is offline Manolo47  Puerto Rico
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Looking into this further, I gather that one pair of blue/green wires that come out from the transformer further back but together, belong to one winding and the other pair of blue/green that come out at a different position belong to the other winding. So, I should connect the blue wire from one winding to the green wire of the other winding.... And the primary connection as described in my previous post. Is this so? Thanks.
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Old 20th March 2018, 09:59 PM   #917
Manolo47 is offline Manolo47  Puerto Rico
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Furthermore, the blue/green connected together from different windings should be center tap, and the other 2 blue green should be 20 v each...
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Old 20th March 2018, 10:32 PM   #918
6L6 is offline 6L6  United States
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The BA-3 as preamp build guide
Are you building this for US mains or European mains??

And the answer to your secondary question is “maybe”, what’s your PSU? I’m sorry if I didn’t see that info earlier...
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Old 21st March 2018, 01:28 AM   #919
Manolo47 is offline Manolo47  Puerto Rico
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120v mains. Power supply is dual PS from twisted pear audio... Supposedly I have to connect two center outputs together to get +24 and - 24v according to them.
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Old 21st March 2018, 03:56 PM   #920
Manolo47 is offline Manolo47  Puerto Rico
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Did this connection to check voltages across primaries (120V) and secondaries.
Fuse WAS a 1 amp fast Blow, It blew immediately. No loads on secondaries...I was checking for voltages, is this what went wrong --i.e., no loads.

I guess 1 amp fuse was sufficient. Thanks guys.
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