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 Post subject: low power output on 30m
PostPosted: Mon Aug 05, 2019 1:37 pm 
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Joined: Sun Jun 30, 2019 2:07 pm
Posts: 3
I just completed the Hardrock-50 build (no QSK, no ATU) and it seems that I might have an issue with the 30m band. Latest board version and firmware.
I can't seem to find the serial number, but I do have my order invoice available.

Everything appears to be working great and I have been using the amplifier on all bands, however, the output power on 30m seems lower than it should be?

With 1.5W drive from my radio, I get full power output on all bands, except 30m (max power out around 20w with 5W drive). I haven't done any troubleshooting since I don't really know where to start. I have tested power output using both a 50 ohm dummy load or into my antenna - results were the same.


Drive Band PEP
1.5w 6m 44w
1.5w 10m 59w
1.5w 12m 62w
1.5w 15m 59w
1.5w 17m 55w
1.5w 20m 51w

1.5w 30m 8.8w
3.0w 30m 16w
5.0w 30m 20w

1.5w 40m 61w
1.5w 80m 54w
1.5w 160m 49w



I confirmed the output power using two different external SWR meters, so I believe the numbers are correct.

Thanks!


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PostPosted: Tue Aug 06, 2019 5:12 am 
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Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
Since everything else works OK the issue is probably with C5, C5, C31 or C33. On 30M, all of these caps should be switched into the circuit.

Remember that the relays are NOT set when you select a band but set the first time the amp is keyed after selecting a new band. So when testing the state of a relay, put the amp on PTT mode briefly key and unkey the amp after selecting a band to make sure that the relays are properly energizer/deenergized. I will refer to this as 'setting the relays'.

First select 40M and set the relays, you should see an open circuit to ground on the relay side of C5, C7, C31 and C33.

Next select 30M and set the relays, you should see a short to ground on the relay side of C5, C7, C31 and C33.

If one or more of these caps is not grounded, we've found the trouble.

Let us know how it goes.

73,
Jim WA2EUJ


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PostPosted: Tue Aug 06, 2019 11:54 am 
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Joined: Sun Jun 30, 2019 2:07 pm
Posts: 3
Hi Jim,

Thank you for the reply and instructions.

Unfortunately, I have a new problem, which may or may not be related. After operating FT8 on 20 meters with no issues for a couple hours (drive 2W, output about PEP 60W), the amplifier stopped producing any output power My radio indicated a Hi-SWR into the amplifier (>20), and the screen showed "SWR -.- and PEP 1.4" (also no output on my external SWR meter). Normally my SWR is < 1.5 on 20 meters (as read by my radio, about same SWR on the amplifier screen). This first happened yesterday and then I turned off the amplifier and today it was working this morning. However, the same problem happened again after operating an hour or so, and it is not putting out any output power. I can hear the relay click when I transmit. So it seems that I have some intermittment issue.

Best,
Jeff


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PostPosted: Wed Aug 07, 2019 11:10 am 
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Joined: Sun Jun 30, 2019 2:07 pm
Posts: 3
Hi Jim,

I tested C5, C7, C31, and C33 and they have the correct behavior - so I don't think anything is wrong with the relays. When I set the relay for 30M they are all short to ground. When the amplifier is off, they are open circuit and when I switched to 40M, they were also open circuit.

I followed these directions that I found in another posting:

It sounds like a C3 (I checked C5), C5 (I checked C7), C31, C33 issue. Those caps are located close to the MOSFETs right next to RLY12, RLY13, RLY14 and RLY15. The first thing to check is, with the power off, the relay side of C5, C7, C31 and C33 should show an open circuit to ground. If any are shorted to ground the associated relay has failed. The next thing to do is turn the amp on, select 30M, PTT, briefly key the amp by grounding the center pin of the PTT jack. This sets the relays for 30M. Now repeat the test, you should now see a short to ground on the relay side of C5, C7, C31 and C33.

However:

My amplifier was working again today, but then I then made a single contact on 30M and after using the amplifier for about 5 minutes, it stopped working again - got the High SWR reading and no output power, as described in my previous posting.

So I'm stuck again with this intermittment issue, any ideas?

Thanks,

Jeff, KM6LFY


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