[Hammarlund] AADE Digital display for SP-600 WORKS!

[Eugene Hertz]

I have a special version of the DFD-hamm. I found a source of VFD (vacuum florescent displays) that are pin for pin compatible with the LCDs that neil uses.  He bought a few and made me one. Now my DFD is BEAUTIFUL! blue VFD. Easily seen in darkness. There were one or two small mods he had to make to get it to work (something about noise from the onboard dc-dc converter).

I highly recommend asking him about this option.  If I can I will try to post a picture of the unit tonight.

Next project for me is to use nixies!

Eugene


>-----Original Message-----
>From: Philip Atchley [mailto:beaconeer at sbcglobal.net]
>Sent: Tuesday, August 30, 2005 12:20 PM
>To: hammarlund at mailman.qth.net
>Subject: [Hammarlund] AADE Digital display for SP-600 WORKS!
>
>Hi All, 
> 
>Well, after a number of hours of working on it, I got this little 
>critter to work properly. As I mentioned in an earlier Email, I'd tried 
>tapping the LO at both the grid and the plate connection., Finally I 
>made a "gimmick capacitor" off the lead going to the FCU switch, to feed 
>my Source Follower "Isolation amplifier", but STILL had problems. Last 
>night I even put a small pot on the BNC connector input of the unit so I 
>could adjust the level. 
> 
>This confirmed ONE thing. I had plenty of signal, at least on the low 
>bands. That because if I turned it up all the way it would read a 900kc 
>tuned frequency as over 2MC (apparently the 2nd harmonic of the LO). 
>Turning it down about halfway and the three lower bands worked PERFECTLY! 
> 
>HOWEVER, the readings were still very erratic on the three higher bands. 
> I could often make it read anything I wanted from the "real" frequency 
>to about +/- 15-20kc. Not what I would call a stable circuit. 
> 
>THEN, this morning I removed the "tweak" jumper from the display board 
>and things settled down to a nice steady reading of exactly what it 
>should be!! That "tweak" jumper activates two small, 25turn pots that 
>allow you to "tweak" the unit to allow for Xtal Filter errors and a 
>second LO Xtal that is off frequency. 
> 
>NOW, it reads correctly, but is about 200Hz off on BOTH the low and high 
>bands, this probably due to a drifted Xtal filter. I CAN LIVE WITH 
>200CPS ERROR! 
> 
>So far it appears to be working exactly as it should, with no 
>instabilities, but time will tell. 
> 
>One other thing I noticed is that it no longer reads up to 53MC (it's 
>specked to 40MC). I 'might' be able to get it to read higher by 
>adjusting the input pot, but I'm going to leave well enough alone ;-) 
> 
> 
>73 de Phil KO6BB 
>My DXing tools (RECEIVERS), all fully overhauled: 
> Hammarlund SP-600 R-274C/FRR, 18 tubes (Circa 1952) 
> National NC-60 Special, 5 tubes (Circa 1960) 
> Heathkit Mohican (Circa 1962) 
> Icom IC-751 Digital Transceiver (Circa 1986) 
> Grundig S350 Digital Portable (Circa 2004) 
> 
>THE BEACONEER'S LAIR: http://www.geocities.com/ko6bb/ 
>QSL GALLERY: http://photobucket.com/albums/y123/KO6BB/ 
>Merced, Central California, 37.3N 120.48W CM97sh 
> 
>****************************************************** 
> 
> 
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