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THE AM BULLETIN BOARD => Technical Forum => Topic started by: n8yhy on June 25, 2005, 02:58:37 PM

Title: Heathkit DX-100 HELP
Post by: n8yhy on June 25, 2005, 02:58:37 PM
I finally got my DX-100 up and running a few days ago and made my first contact with it on 75M phone..The rig was playing great and had great forward modulations, Towards the end of my QSO it started backward modulating so i ended my qso quickly..I took the rig apart and began looking things over..When i first turned the rig on i noticed that the 12BY7A Driver Tube by the Mic Plug began to glowing a Nice Blue and after a few moments the plates in the tube began to glow red,This happens with the rig turned on Idling not being used. I measured the voltage on Pin 8 of the 12BY7A and it was up around 405 volts which i believe is way to high.I plugged the mic in and there does'nt seem to be any audio now but there does seem to be some type of osculating going on when i turn the audio gain up..Its like its pulsating..Any one ever had or heard of this problem? I did check a few of the componets around the 12BY7A socked like the caps and resistors and they seem to be fine..Please if any one knows any thing about this type of problem please Email me at and let me know your thoughts as i would love to get the DX-100 back on the air...thanks chris N8YHY

Title: Heathkit DX-100 HELP
Post by: Ed - N3LHB on June 30, 2005, 11:08:51 PM
Check the 560 ohm cathode resistor on the 12by7, I found that mine went way out of limits causing the 12by7 to glow a very nice orange.... If that doesn't help, let me know, there are some other common problems in the dixie 100...

Title: Modify It
Post by: WA1HZK on July 15, 2005, 12:48:54 PM

While it's open, replace the Coupling cap from the driver plate to the final grids. Cheapo part & when it shorts it kinda overdrives the finals -POOF_.

Title: Heathkit DX-100 HELP
Post by: wa2zdy on July 15, 2005, 06:29:14 PM
Wow, outstanding work on that DX100 driven rock crusher!  If you can't have a BC rig in the shack, that thing is just as impressive.
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