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Title: And Another Valiant Mod Post by: n1ps on April 26, 2020, 07:55:58 PM Over parts of the winter I rebuilt my Valiant. I decided to go the RC route as far as a driver and went with a FET driver. At first I tried just 2 FETS to drive the 6DQ5s,which replaced the 6146 mod tubes, but ended up with 4 FETs on a small heat sink. Have had nice reports on the audio (just a D104). I use it most every day with no failures.
The design is basically by Frank WA1GFZ (see previous similar posts by Tom K1JJ). Frank also was a great help and offered many suggestions along the way. The FET is the common FQA11N90 that I used for my Class E transmitter. I also discussed with Steve WA1QIX who helped out too with suggestions (I used a couple of his design ideas too). In the end it would have been easier to go with all tube drivers. But I thought this would be fun and worth a try. I get 130% positive peaks with a Heising reactor. The OPT is standard wiring. Here is a link to the Youtube video I posted. A SSB nutcase (last week) panned the project of course :'( (see the comments section)....but that is OK.....you have to have thick skin on YT. https://www.youtube.com/watch?v=DO7wHg8HmjI&t=33s Here is the schematic (at bottom of the page). https://wordpress.com/view/fibrdesign.com Its on my commercial website....just scroll past the business stuff. Cheers.... Peter Title: Re: And Another Valiant Mod Post by: n1ps on April 27, 2020, 05:38:10 PM Attached is the schematic. Meant to put it up here this AM.
Peter Title: Re: And Another Valiant Mod Post by: WBear2GCR on April 28, 2020, 05:40:38 PM wondering what voltage do the screens of the 6DQ5 sit at, keyed, no modulation?? Also what is a the keydown quiescent current for same? Given the 1N4007s in the drive line I'm expecting very very class B? Title: Re: And Another Valiant Mod Post by: n1ps on April 28, 2020, 07:25:39 PM 1. I dont recall.
2. 40ma I believe 3. Correct. Your rack work looked good....meant to comment....but alas a wasted mind is a terrible thing.... ;D Cheers.... ps Title: Re: And Another Valiant Mod Post by: WBear2GCR on April 29, 2020, 11:30:59 AM 1. I dont recall. 2. 40ma I believe 3. Correct. Your rack work looked good....meant to comment....but alas a wasted mind is a terrible thing.... ;D Cheers.... ps gotta check the curves on the tube (not the book, but how it is actually run), but 40ma seems too high for Class B... otoh, doesn't make any difference since it works fine. |