It's working again

General discussion and support for the Peaberry SDR V2.

It's working again

Postby pilotcfii » Tue Feb 17, 2015 6:15 pm

Ok I am confused.......again.

I have been unable to get power out of my Peaberry on any band or any mode. I made the assumption that since Tx & Rx share circuitry, that the problem must be in Tx only circuitry. Using my trusty RS Multimeter I started checking voltages beginning at Q4 thru Q10 and eventually to Q7 & Q8. I saw what seemed like normal voltage changes between Rx & Tx modes. No confusion till I looked at the source of Q7 & Q8. They appeared to be working. They showed 0V during Rx and 47mV during Tx on Q8 and 51mV on Q7. That to me looks like I should be transmitting.

So once again I set up Tx for 14.150Mhz, FM, and into a dummy load with a QRP wattmeter in the middle. Now I get a power reading. 0.5W on 20m, but something less on 60/40/30. The sound comes from a webcam mic that is probably just picking up ambient sound from my office. Perhaps a better sound stimulus would provide better readings.

What is confusing is that I swear I have done this exact test before with no power out.
73
Dan Malcolm
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Re: It's working again

Postby AE9RB » Tue Feb 17, 2015 6:53 pm

Highly erratic test results are certainly confusing. Try using the spare BS170 from the kit to replace Q6.
73 David AE9RB
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Re: It's working again

Postby pilotcfii » Tue Feb 17, 2015 8:08 pm

Just to make sure I understand, I should replace Q5 (an NPN transistor) with a BS170 ( a FET)? Would I substitute gate for base, source for emitter & drain for collector?
Last edited by pilotcfii on Tue Feb 17, 2015 8:12 pm, edited 1 time in total.
73
Dan Malcolm
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pilotcfii
 
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Location: Alabama

Re: It's working again

Postby W4MMP » Tue Feb 17, 2015 8:12 pm

Dan,
I "think" that must have been a typo. It should be Q6, one of the three under the heat sink.
73
Ron / W4MMP
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Re: It's working again

Postby pilotcfii » Tue Feb 17, 2015 8:14 pm

Aha. Got it. That makes sense. I have several of those from an order to Mouser. Thanks.
73
Dan Malcolm
K4SHQ CFI/II
pilotcfii
 
Posts: 130
Joined: Sat Dec 07, 2013 6:52 pm
Location: Alabama

Re: It's working again

Postby AE9RB » Tue Feb 17, 2015 8:16 pm

W4MMP wrote: I "think" that must have been a typo. It should be Q6, one of the three under the heat sink.


Oops, yes, Q6.
73 David AE9RB
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Re: It's working again

Postby W4MMP » Tue Feb 17, 2015 8:18 pm

P.S.

While you are at it, may I suggest replacing all three? It will save you some time and trouble if one of the final Mosfets is shot.
73
Ron / W4MMP
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Re: It's working again

Postby pilotcfii » Wed Feb 18, 2015 1:27 am

Thanks Ron. May as well. putting the heatsink back is almost as hard as replacing the FET's, and I do have spares.

Addendum: Having second thought about the spares. Looking at Digikey there are several model and I am not sure I have the right one although the specs all look the same. In addition, I bought those through Amazon which is usually reliable but I don't know the supplier. They are not expensive but which ones should I have?
73
Dan Malcolm
K4SHQ CFI/II
pilotcfii
 
Posts: 130
Joined: Sat Dec 07, 2013 6:52 pm
Location: Alabama

Re: It's working again

Postby W4MMP » Wed Feb 18, 2015 3:24 am

Hi Dan,
Here is the Digikey part number I have used in the past: BS170-ND. They are guaranteed to be Fairchild Mosfets and have worked perfectly for me. There are variances even with the Fairchild produced Mosfets but nothing that needs to be particularly concerned with. I did match up three of them simply because I was curious and had the time. ( https://sites.google.com/site/g4zfqradi ... r-softrock ). However, I have never seen any from David regarding the matching of the PA Mosfets. This was based on discussions on the Softrock40 forum.
73
Ron / W4MMP
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Re: It's working again

Postby AE9RB » Wed Feb 18, 2015 3:48 am

All the experiments I've heard about from matching BS170s have yielded inconclusive results.
73 David AE9RB
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