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#1
03-11-2012, 03:22 PM
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Quote:
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." 
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#2
03-12-2012, 07:18 PM
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Thanks for the kind words. I grew up dragging home old TV sets and back then they were all tube models so I have a soft spot for them. Among them was what I now know was a Dumont RA-109 and a CTC-5. Anyway, another VK member asked if it would be possible to get video and audio modulation with a programmable frequency. I did hook up my VA62 set for 45.75 MHz to my RCA 721TS set to channel 1 and got both video and audio. There are only a dozen or so unused locations in the EPROM, so don't hold your breath.
Dave
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#3
03-12-2012, 08:32 PM
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It doesn't look like the signal rolls off too bad yet at 21Mhz, and probably not even worth messing with it considering the variable output level. Could they have used another PLL as a programable bandpass filter, or would it more likely be a simple high pass op-amp stage on the output?
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#4
03-12-2012, 09:36 PM
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A quick look at trying to change the 45.75 MHz to be programmable finds that its not controlled by the PLL. It has a separate fixed source. I will investigate Brian's origiinal request for replacing the programmable cable function (chan 2-73 with +/- 9.75 MHz offset) with a programmable frequency.
No clue here about the passband of the analog amps that might cause a low frequency attenuation. Dave
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#5
03-13-2012, 01:15 PM
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I loaned my photocopies of the service manual to a fellow collector (Tom K.) and he scanned the schematic and parts list. This is 100 megabytes of material.
I'll be happy to share it, but I don't want to post anything that size permanently on my website. If you're interested, let me know and I'll figure out a way to get the files to you, either by temporarily posting on my website for download, or by mailing you a CD. He also provided a scan of the (22-megabyte) operations manual, but I gather that some people already have that. Anyway, same deal there -- let me know if interested. Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html To send me email, kindly go to http://antiqueradio.org/contact.htm .
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#7
03-16-2012, 07:09 PM
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Boy that is one congested piece of test gear.
 From what I gather, it sounds like the output level was factory programed to a flat response at the various RF/IF frequencies for each individual VA-62. So any variation at lower IF frequencies is likely coincidental and would need to be programed out via Eprom. Are you guys pursuing these units to use as an IF marker generator; to be used along with another sweep generator? Or are you planning to use the Sencore multiburst modulation method of IF alignment? I'm curious just how well the Sencore multiburst alignment method caught on with repair techs? For my hobby use I think I'll prefer to stick with the old tried and true scope method of actually seeing the IF response curve on a scope. I can however see the practicality of the burst method for a busy repair shop. Last edited by Kevin Kuehn; 03-16-2012 at 11:44 PM. Reason: spelling
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#8
01-01-2013, 11:08 AM
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Quote:
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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