Re: SB2 #118 Update


You know, a picture's worth 1000 words, or approximately one awshit.

I did have to replace the IRF510, but only to the other side of the PCB.
That's what I get for building past midnight...

I'll tweak it at the office and see what it looks like on the SA.
I did see the my power meter peaking up to around 4W just
playing around a bit.

Where's the best place to check the modulation with a scope?
At the gate of the IRF510 or the antenna?

Thanks for your patience!


On 2/18/2019 8:06 PM, Steven Weber wrote:

It’s kind of hard to cook those fets. If it’s not shorted, it’s probably good.

It would take a pretty good static spike to cook the gate.


Do you have 12V on the tab?

Your not seeing any current increase with the bias pot?

You sure the voltage is making it to the gate?


Take  a close look at T1 and T2 and make sure their installed correctly.

Transpose the ends of the windings and it doesn’t work anymore.


Just going down the check list. This is when having a ‘Scope saves a lot of time.



The diodes were good.  5.1V supply was good.

I think I cooked my IRF510 somewhere along the line.
No shorts. 
Power out with the modulation pot at it's highest is 5-10 mW.
Bias pot doesn't make any difference to the output despite raising
the gate voltage.  I did start fully CCW.

I think I'm getting a pretty good signal to the gate, but not much
is happening at the output.

I'll replace the IRF510 and try again.


On 2/17/2019 8:41 AM, ajparent1/kb1gmx wrote:

Check to be sure you didn't put the zener diode (d1) in backward.

FYI the crystal for the 5351 will age and move in frequency with time
so retest in a month or two. 




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