Author Topic: R27 receiver  (Read 14743 times)

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Offline Lazarus

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Re: R27 receiver
« Reply #30 on: June 28, 2013, 09:23:57 PM »
it makes no sense to me, the red trace on the top looks like just a dirtier version of the green trace on the bottom, plus both scope pics look almost identical, i'm lost bro there should be alot more difference in the two signals, and all of em say 5.xxMhz, it makes no sense, looks like the VFO is all thats working in these pics,

Offline The Radio Shop

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Re: R27 receiver
« Reply #31 on: June 28, 2013, 09:35:05 PM »
it makes no sense to me, the red trace on the top looks like just a dirtier version of the green trace on the bottom, plus both scope pics look almost identical, i'm lost bro there should be alot more difference in the two signals, and all of em say 5.xxMhz, it makes no sense, looks like the VFO is all thats working in these pics,

BINGO!

The scopes counter is reading 5 MHz from bother oscilators. There is very little difference in the two signals.
Now remember. I disconnected the 2 oscilators from the mixer and from each other.  I am not sure if this is causing the oscilators to run away or what is going on.  But, My guess is there is something wrong with the 31.4 MHz oscilator circuit.
Buddy kc4umo

Offline The Radio Shop

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Re: R27 receiver
« Reply #32 on: July 01, 2013, 10:20:06 AM »
So checked the tubes and dont think the problem is with them. My tube tester says 40% but installed 2 new 12AT7 in the unit and does the same thing. No difference.  I now have 3 units here with this problem.
Buddy kc4umo

Offline The Radio Shop

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Re: R27 receiver
« Reply #33 on: July 06, 2013, 09:40:55 AM »
Got my new 12AT7's in. Going to try and get back on this today.
Buddy kc4umo

Offline The Radio Shop

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Re: R27 receiver
« Reply #34 on: March 14, 2014, 09:05:34 AM »
Cleaned the sockets and no change. So decided to drag out the Sencore CS61 scope and take a few measurments.  Seems that the Tek scope loaded the signal paths down.  But the Sencore did the job. What I did was probe the output of bother oscilators, the 5 MHz and the 31 MHz where they combined. All I could see was the 5 MHz side as noted in below screen shots.
Buddy kc4umo

Offline The Radio Shop

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Re: R27 receiver
« Reply #35 on: March 14, 2014, 09:06:39 AM »
After replacing R11 a 47K I now see 31 MHz
Buddy kc4umo