|[AMRadio] Help with Baur 707 transitter|
Mel Farrer via AMRadio
amradio at mailman.qth.net
Sun Dec 28 17:48:25 EST 2014
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.
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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