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Followed the schematic and got the DPDT switch installed.
What a pain in the a**!! Its really tight in there. I cut loose the cable straps and got the switch installed. Looks like everything is working as described. I did note that when a signal did not occur, toggling the switch brought it out - like Dave noted. Now, I got to spend some time learning how to use this to align vintage TVs. Carl
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CW 1950 Zenith Porthole - "Lincoln" |
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Nice work Carl, I'm glad the installation went well! I must have checked my RF/IF switch wiring four times just to be sure I had the wiring right since I did'nt want to mistakenly send the -15VDC to the +15VDC, and vice versa, to the wrong RF/IF amplifier power inputs. I also found it a bit tough to fit the new DPDT level switch in the panel but I think its the right placement. I find that I forget which RF-IF SIGNAL switch positions can can work with the DPDT in the RF or the IF position so I may tape a copy of the list on my VA62 for reference. Good to hear that toggling the new RF/IF switch persuades your VA62 PLL to lock in the same as mine.
Dave |
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wow that one's cool, i have the sencore va-48 its not as modern as that one is.
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Very nice mod that Dave developed.
Makes those old Sencore VA62's very useful on vintage TVs. Anyone have suggestions on the best way to learn the fine points about aligning IF in TVs? I watched bandersen's video and I guess just jump on a TV and experiment. Too bad we don't have hands on instructional classes anymore. Might be a consideration at a future ETV Convention or Radio swap meet. Carl
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CW 1950 Zenith Porthole - "Lincoln" |
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Some more info on the modification
For anyone interested in the modification that allows the Sencore VA62 to be used to generate TV video/audio modulated IF for any frequency from 15.75MHz to 35.25MHz as well as the original 45.75 MHz, attached is a document describing the installation, whats modified, and its new capabilities for the EPROM plus RF-IF switch modification. I can supply the EPROM for $5.00 and USPS first class flat rate shipping is about $6.25 IIRC. Or I can send you a .HEX file if you want to burn you own EPROM. YOU WILL have to install an RF-IF manual level switch to get the IF level output for the 15.75MHz to 35.25MHz range (on channel 42).
Dave |
Audiokarma |
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Sencore VA62 vs VA62A
I have been asked whether there are any differences between the Sencor VA62 and the VA62A. I have always thought they were functionally identical. Can anyone shed any light on this subject?
Thanks, |
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Quote:
Carl
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CW 1950 Zenith Porthole - "Lincoln" |
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Thanks Carl,
That's why I never noticed the difference between the two boxes. I'll pass that info along. Quote:
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Has anyone used a modified VA-62 to align a vintage TV?
Carl
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CW 1950 Zenith Porthole - "Lincoln" |
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I just picked up a VA-62 this week. I'll send you a PM concerning the chip.
Thanks, Phil |
Audiokarma |
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chip modification offer
Dave,
Are you still offering the modified chip? Thanks Phil |
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Yes, did you get the PM I sent?
Dave |
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Just got it.
Thank you |
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Just snagged a VA62A on eBay for $42.50 from a seller within 20 miles of me. Claimed to be working, and the only thing that looks wrong in the auction pics is that somebody busted off the ground pin on the power cord. Once I get the thing onto the bench, I'll be wanting one of the hacked EPROMs for my unit, as well. Will PM you soon to make arrangements...
Thanks for all the great info on these units! Particular thanks to Phil for hosting all those manual scans! Just grabbed the full set... Last edited by N2IXK; 09-28-2012 at 02:03 PM. |
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Got the unit on the bench over the weekend, and everything seems to work just fine. All the patterns display properly, RF frequencies all nice and stable on a counter, and all the drive signals look good on a scope. Replaced the line cord, and swapped the 3 front panel RCA jacks (30 Hz Servo drive, Video out, and 3.58 MHz drive) for BNCs. Why would they even use RCA phono jacks on this kind of equipment? BNCs are much more rugged with stuff being plugged/unplugged all the time.
How many different accessory units were made for this thing? I know of the NTSC pattern generator and the VCR test unit. Any others? |
Audiokarma |
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