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K7DYY go boom!




 
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W9BHI
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« on: August 02, 2018, 06:25:22 PM »

I bought this K7DYY 80/160 last week from a less than honest ham on QTH.
He said it was working perfectly.
I guess you can't trust anybody's word anymore these days.
When I received it, it would only do 900 or so watts PEP and was flat topping.
It is supposed to do at least 1400 watts PEP.
Looks like the 500 volt rated silver mica caps in the 80 meter output filter can't take that kind of power if the audio is too hot or the SWR is too high.
I talked to Bruce and decided to send it to him for repair and a health check.
He now uses 1000 volt srface mount SM caps in the new units.
I Just wanted to show the results.
Don W9BHI



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n1ps
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« Reply #1 on: August 02, 2018, 08:53:39 PM »


When I received it, it would only do 900 or so watts PEP and was flat topping.
It is supposed to do at least 1400 watts PEP.
Looks like the 500 volt rated silver mica caps in the 80 meter output filter can't take that kind of power if the audio is too hot or the SWR is too high.

Sorry to read of your troubles.  I gather from others and my own experimenting with this TX that it should be limited to 200-225 watts carrier.  Also the TX must only see 50 ohms.  Dont push the limits on this TX.   There is no metering so you have no idea of drain currents on those finals (unless a newer model has this feature).

When operated in a safe range the DYY TX does pretty well. 

My .02...worth just that perhaps.... Shocked
Peter


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KD6VXI
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« Reply #2 on: August 03, 2018, 12:24:07 AM »

Everything I've seen about the DYY boxes points to them being like a motorcycle.  You'll eat sh!t at least once!

However!  Bruce seems more than fair, fixes them and it seems also looks to failure modes to ensure new updates!

As PS said.  50 ohms!!!  That TX, like the new ldmos amps, needs an auto tuna.

(and what's with the new ldmos amps that have to have a tuna, but the mfg demo videos show them working full power into a shorted load!)!

Once you get that TX sorted out, you'll love it.  W6OM recently let his Bauer 707 go to a friend of mine.  He's running a DYY now.  His sig dropped about 6 dB, but other than the s meter, you'd never know.

--Shane
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W9BHI
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« Reply #3 on: August 03, 2018, 12:55:44 PM »

Sent an email to Bruce and he responded in less than 10 minutes.
How's that for service?
I shipped the rig to him today for a full checkout and repair.
The caps in the 80 meter LPF will be upgraded to heavier duty parts.

Don W9BHI
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W9BHI
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« Reply #4 on: August 21, 2018, 10:43:17 AM »

Got the rig back from Bruce yesterday and it is working FB, full power out now.
Had it on 3885 this morning running 290 watts of carrier and seeing 1200 watts PEP on the Array Solutions wattmeter.
Running 98 percent negative and 130 percent positive modulation on the REA mod monitor and got several great audio reports.
I would like to know if there is anybody out there with a 40/80 K7DYY rig that they would
like to trade for a 80/160 unit.
The 40/80 would suit my needs better.
I know it's a long shot but I thought I would ask.

Don W9BHI
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steve_qix
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« Reply #5 on: August 21, 2018, 05:33:38 PM »

That's great!  Nice to have the rig back for sure.

The propagation should be getting longer, and regular QSOs to your part of the world should be come commonplace on 80 meters :-)  Looking forward to talking with all of you folks during the later afternoon/early evening.

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KD6VXI
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« Reply #6 on: August 31, 2018, 05:11:56 AM »

There where 3 K7DYY on the air on west coast ami this week.

And talks of a 4th coming online.

They are getting popular......

--Shane
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W9BHI
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« Reply #7 on: August 31, 2018, 06:14:34 PM »

I have been switching between my Gates BC1-G and the K7DYY on 80 meters and nobody can tell the difference between the two.
Of course I use the same audio equipment (Symetrix 6200 and an Inovonics 222) to feed audio to both units.
Definitly an amazing little performer.

Don W9BHI
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