Peaberry On the Air, mostly.

General discussion and support for the Peaberry SDR V2.

Re: Peaberry On the Air, mostly.

Postby camqrp » Tue Jan 06, 2015 12:37 am

What"s the resistance reading across R44? I get about 500 ohms...
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Re: Peaberry On the Air, mostly.

Postby W4MMP » Tue Jan 06, 2015 1:03 am

camqrp wrote:What"s the resistance reading across R44? I get about 500 ohms...


I get the schematic value of 22.1K. Lift one end of R45. This will remove the PA FETS from the circuit and check it again.
73
Ron / W4MMP
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Re: Peaberry On the Air, mostly.

Postby camqrp » Wed Jan 07, 2015 6:32 am

OK, same result here. What are the voltages on the base of Q5?
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Re: Peaberry On the Air, mostly.

Postby W4MMP » Wed Jan 07, 2015 2:49 pm

base of Q5 - Receive 0.02v, Transmit 0.6v
collector of Q5 - Receive 0v, Transmit 1.68v
However, are you saying that you lifted one side of R45 and the resistance across R44 came back to the 22K?
73
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Re: Peaberry On the Air, mostly.

Postby camqrp » Thu Jan 08, 2015 6:32 am

Ron -

(Typed while doing Happy Dance) Finally, all is well in Peaberry Land! I replaced the final BS170s and problem solved.

Over the last few days while I wasn't measuring voltages in the Peaberry I was building a new keyer kit from the Four State club. It makes beautiful CW but wouldn't key a rig properly. Whenever I plugged it into a rig, the rig went key down and stayed there. The keyer uses BS170s for its keying switch and for unknown reasons, in the off state the DS resistance was only about 1500 ohms, enough to key all of the rigs I tried it on. I replaced the BS170 and all was well. Which made me think I could have a similar problem with the Peaberry's finals, so I put in a different pair and that solved the problem. The fact that I was getting good power out with the originals kept me looking elsewhere for the problem.

Thanks for your help along the way!

Cam
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Re: Peaberry On the Air, mostly.

Postby W4MMP » Thu Jan 08, 2015 10:53 am

Hi Cam,

I'm really glad you found the problem. Honestly (believe or not) I was going to suggest looking at and/or replacing the PA FETs. You had mentioned that the resistance across R44 was approx. 500 ohm. Examining the resistor values leading from R44 to the ground point of either of Q7 or Q8 (R45,R39,R43), the values add up to 444.21 ohm. This indicates one of the PA FETS is shorted. This is why I asked if lifting R45 restored the resistance reading to 22K.

Happy PBing :D
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