eHam Forums => Mods And Repairs => Topic started by: KJ6CFI on January 07, 2013, 02:13:24 PM

Title: Drake TR-7 transmit issues
Post by: KJ6CFI on January 07, 2013, 02:13:24 PM
I have a Drake TR-7 that will sometimes key up and transmit when you power up the rig by turning the power "on" with the AF gain control. There was no mic connected, the rig was set to the "PTT" mode (VOX was off). I then have to turn the rig on and off several times for it to stop transmitting. The only thing done to the rig when I got it was put the PA/Driver "brick" board back in. The previous owner told me this board has no issues, he was going to look into changing/upgrading the drivers and finals. The only other thing I did was try SSB with a Kenwood mic. I am thinking the problem might be a sticking transmit/receive (TR) relay. Any thoughts, help and advice would be greatly appreciated. 73. Denny Dollahon, KJ6CFI.

Title: RE: Drake TR-7 transmit issues
Post by: KE3WD on January 07, 2013, 02:39:40 PM
Well, the relay might be 'sticking' due to something in the relay driver circuitry. 

First thing that comes to mind would be an electrolytic filter cap that is letting ripple through until it gets a bit warmer. 


Title: RE: Drake TR-7 transmit issues
Post by: K8AC on January 07, 2013, 04:24:47 PM
You can chase your tail forever when shooting TR7 bugs, unless you do this:  Pull every board, one by one, clean the pins with DeOxit on a Q-tip, re-insert the boards.  Almost all intermittent TR7 problems will disappear when you do that.  The pins on the parent board that all the other boards plug into are not gold plated and oxidize quickly.  I suggest you do NOT pull the power supply board to the right of the PTO.  Just touching the pots on the top edge of that board will alter the BFO frequency in one or more modes, requiring an alignment.

73, Floyd - K8AC
TR7 owner