[AMRadio] Help with Baur 707 transitter

[Mel Farrer via AMRadio]

Hello Don,
I have a 707 also and converted it up to 75 meters.  L5 is just a RFC choke.  The adjustment is just a peaking coil, the cap on the cold side of the coil is just a bypass.  Since you don't know the condition of the existing coil whether the slug has been changed to brass or ferrite, I would resonate it with a cap.  If you have a scope and can look at the final grid current on 1600, you should be able to put the coil on max and observe the grid current.  Adding a 100 pf or so should allow you to see if the grid current moves higher.  Put the scope on the final grid and make sure the waveform is a clean sine wave for 1600 KHz.  Also, start at the osc current and make sure you are starting off with rated reading.  I found that most of the 707s modified for SW had considerable changes in the RF components to get the drive up.  Take a picture of the RF chain and the final tank configuration.  I hope they left all of the HP components in place and just bypassed them...  Keep in touch.
Mel, K6KBE

      From: Don Moore <wa5ffk at juno.com>
 To: 3890_AM at yahoogroups.com; amradio at mailman.qth.net 
Cc: amradio at qth.net 
 Sent: Sunday, December 28, 2014 12:18 PM
 Subject: [AMRadio] Help with Baur 707 transitter
   
Hello fellows,I really need someones help.  I am currently in central america in the country of Honduras working on a Bauer 707 transmitter for a Christian Radio Station.  The 707 was converted and was on 3.250 khz.  I am now putting it back on 1600 KHZ  
The  coil which links the 6ac7 drive to the final is a slug tinned ceramic  coil with about 1/2 inch diameter.  I need to know how many turns should be on this coil.In the manual all it gives me  the coil number It is a Miller 43A224CB1.  I need to know how many turns.  This coil is L5 of the schematic. I didn't bring my frequency counter do have a scope here but very limited on test equipment.Any ideas or help sure would be appreciated.  Don MooreW5FFK
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