The AM Forum

  It's heeere !

http://smallwonderlabs.com/RH_Blurb.htm   

  The VFO add-on for the Retro 75 is in stock and shipping. Now you can fill the mystery holes at the rear of the Retro 75 with a useful add-on. The VFO tracks the RX tuning to allow more mobility within the operating range. Check it out at Dave's website . Hope there is room in your home-brew case for one of these , Jack  ;) (W9GT)

  Now, if only we can get the news on the 40M version. ;D

Built and installed mine.  Got to do the alignment real fast otherwise you might trash the mod transformer.  Mine started smoking but seems OK after it cooled off. 

Tested it and it works quite well with a real VFO now.  Transmit carrier seems a little taller compared to the crystals.

    I run my Retro off a 1 amp current limited supply. For those that hook theirs to a bigger supply, or a big battery, I suggest a 1 amp inline fuse. I'd rather pop a fuse instead of burning up the rig in case of a high current internal fault.

    The issue here is that while tuning the VFO up, there may be moments with no drive, and the RF power fet driver may turn on. Here we have 12v feeding a saturated fet and the only real impedance in between is the ~ 0.3 ohm winding of the modulation transformer.

    This reminds me of keying a tube final with no excitation, and no protective bias.. i.e. the plate meter hits the peg. Once the VFO board is tuned up (two RF transformers to peak), there are no more lack of RF drive concerns.

   I understand that the VFO kit instructions have already been edited to tune the VFO board before connecting it to Rf chain.

Jim
WD5JKO

I read Dave's new instructions. Either way, one needs to do this alignment very fast. My suggestion would be to do the alignment disconnected from the Retro.  1.25 or 1.5 amp fuse should be the max for the rig as it pulls about 0.7amps when transmitting. The mod transformer can smoke up at 1 amp.  The mod transformer should have a dedicated fuse.

 The alignment instruction I received (On April 04 2011) directed to remove U8 . I was able to take my time with alignment and noticed no heating problems whatsoever.

Built and installed my "Helper" Saturday night, works like a dream, what a great idea for a fun little rig.

The kit build is very straightforward, and if you've already built the Retro 75, you'll find the Retro Helper a real breeze, took me about 2 hours, and that was being extra fussy about lead dress, solder connection quality, etc. The Helper board installs on the rear panel of the Retro 75 enclosure, using predrilled holes, and requires just 4 leads for connection to the Retro 75 main board. You can find the Retro 75 and the Retro Helper at the Small Wonder Labs website www.smallwonderlabs.com.

(http://www.w1ujr.net/Bruce's%20Bench%202011/DSCN0427_small.jpg) (http://www.w1ujr.net/Bruce's%20Bench%202011/DSCN0428_small.jpg)

(http://www.w1ujr.net/Bruce's%20Bench%202011/DSCN0432_small.jpg) (http://www.w1ujr.net/Bruce's%20Bench%202011/DSCN0431_small.jpg)

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EEEEEEEEEEeeeeeeeeeeeeeeee!

Seems we can't delete our own posts any longer, so had to settle for that when I duped my post.

Thanks for the heads up Bruce. You should be able to delete your own posts now.