There is more to that board.
Make sure that the bypass caps near the ferrite beads where the 50v goes are
much better than the one u got from CCI put more caps 0.1/200v on that line
.
Also make small bridges of copper straps on the FET's from source to source
it will do you a much better ground plane for that board.
Baruch 4z4rb
4z4rb
Baruch Zilbershatz
Nitzanay-Oz 118
Nitzanay -Oz
42836
ISRAEL
phone: (+)972-052 8753838
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Dan Sawyer
Sent: Monday, January 17, 2011 7:00 AM
To: Amps
Subject: Re: [Amps] eb-104 bias question
Thank you for all for your replies. They uncovered an interesting series
of errors. I removed R6 and the result was the bias surged and wiped out
a MOSFET - unambiguous 'white flash'. Whoops.
The IC was installed backwards and the R6 in place; the result was a
voltage drop. The MOSFETs do draw a small current, hence the bias
circuit 'sort' of worked. I removed the old IC and reinserted a new one.
Now at least the bias circuits work, they support a constant voltage
with a small current draw.
This project has been a series of errors, mine. I hope I have worked
through them. I am looking for a way to go slow, 150s are too expensive
to use as fuses. :)
Dan
On 01/16/2011 04:31 PM, Tom Thompson wrote:
> Dan,
>
> The EB-104 uses an MC1723 voltage regulator. D5 is a 28 volt zener
> for the input of the regulator assuming you are obtaining the bias
> voltage from the 50 volt supply. I assume you have removed D5 and R6
> and are supplying 13.8 volts to pins 11 and 12 of the regulator. You
> should be able to adjust R5 for about 10 V at pin 3 of the regulator.
> With R1, R2, R3, and R4 adjusted so that no voltage appears on the
> wipers, apply 50 volts to the board. Adjust R1 through R4 while
> monitoring the current from the 50 volt supply. Adjust each pot for
> 250 ma additional current i.e. 250, 500, 750, and 1000 ma. The
> MRF150s should not draw any static current on their gates. If the
> voltage on pin 3 of the regulator is dropping as you adjust the pots,
> check the input to the regulator for stable voltage. If that is ok
> then you must be drawing current in the gate circuit so look there or
> check that the regulator is working properly.
>
> Hope this helps,
>
> Tom W0IVJ
>
> On 1/16/2011 2:17 PM, Dan Sawyer wrote:
>> All, I am building an eb-104. After several false starts, assembly
>> errors, the board is up and running at low power with two devices. The
>> current question is related to the bias circuit. I am using a 13.8 volt
>> supply and have the bias set to 6 volts. When the first device is
>> brought up to 200 ma the bias source drops to 5.8 volts. When the second
>> device is brought up the voltage drops even further. Needless to say
>> this would make balancing 4 devices difficult.
>>
>> Is there an update to the bias circuit?
>>
>> Does anyone have suggestions on how to debug the voltage regulator
>> circuit?
>>
>> Thanks, Dan
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>
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