Sencore VA-62
 

I took a gamble and picked up one of these in unknown condition for about $50.

http://farm8.staticflickr.com/7063/6...cc22488f_b.jpg

I crossed my fingers and powered it up. It actually seems to work properly :banana:
I don't have any manuals, but I think I can figure out the basics. All the RF-IF modes seem to work. It would be so, so nice if the programmable IF could go down to 21 MHz, but it bottoms out at 35.

I haven't tried the Ringing Test or Drive Signals yet. I think I'll need a manual for that.

Below are the test patterns on my Panansonic Tau TV. I suspect the flaws are in the TV and not the Sencore. Can anyone clue me in on what the 'Chroma Bar Sweep' is for ?

Crosshatch and Dots
http://farm8.staticflickr.com/7156/6...cd2ba78a_m.jpg http://farm8.staticflickr.com/7028/6...7272d0bc_m.jpg

Multi-burst Bar Sweep and Staircase
http://farm8.staticflickr.com/7067/6...d8aeb8f3_m.jpg http://farm8.staticflickr.com/7030/6...b6a542d9_m.jpg

Color Bars and Chroma Bar Sweep
http://farm8.staticflickr.com/7173/6...05c00a9e_m.jpg http://farm8.staticflickr.com/7057/6...664b6674_m.jpg

Bob-

The chroma bar sweep is for alignment/bandpass testing and adjustment if I remember right. I have a VA-48, the predecessor to your unit, and I bought a manual for it from Sencore about 10-15 years ago. Some Photofact manuals perhaps in the 1980s had scope pictures of the chroma bar signal in various circuits. I think you got a bargain!

Nice looking patterns. I wonder how they manage the RF programing on this. Is it new enough to be micro controlled, or more likely some custom analog chip set? I'd have to get right inside and look things over.

Thanks for the info. I've read these are tricky to service so I'm really glad it's working :yes:

I will be soon as I need to clean some dirty controls. I'll let you know what I find.

Early 80s technology at it's finest. The chips are date-marked late 1983 / early1984 There's an 8035 microcontroller at it's heart. I assume the RF is done with a programmable PLL.

http://farm8.staticflickr.com/7044/6...e67f7cff_z.jpg http://farm8.staticflickr.com/7017/6...a91ccc51_z.jpg

http://farm8.staticflickr.com/7029/6...efd688c2_b.jpg

Wow! That was obviously an expensive piece back in the early 80's. I bet with a little program hack and a new eprom burnt, one could have that thing singing down in the 20Mc band. But don't ask me how. I always though some of their 60-70's gear was made sort of on the cheap, but this thing looks first class, fiberglass pcb's and all.

It might be easier than that. Assuming this uses a PLL, there should be a hi-speed digital divider in the feedback loop. Something like ÷ 256.

Perhaps that could be tweaked to ÷128, so it would put out a frequency 1/2 of what the display shows. 22 MHz instead of 44 MHz for example. Then add a range switch so it could do 17.5 - 25 Mhz or 35 - 50MHz. :scratch2:

You're probably onto something there. The schematic should reveal if it's divide by 256.

Unfortunately, I don't have manuals other than the quick start guide I found tucked inside. Anyone out there have a schematic ?

I paid around $1.5K for one of these back in 1986. I never had a minutes trouble with mine. I sold mine with the manual included.

I have the bound 100-page operations manual and a photocopy of the monstrous service manual. Someone let me borrow his service manual to photocopy onto 11x17 pages. The original has a number of super-sized pages that cleverly unfold to about the size of a card table. I brought it to Kinko's to copy on their big fat machines and it was still a bit of a trial. Not something I could readily scan on our dinky home printer.

The operations manual is interesting, although the basic VA62A functions are pretty evident if you look at the front panel.

Phil Nelson

I wonder if you contacted Sencore ... maybe they have a Tech Bulletin for altering the IF frequency?

Carl

Perhaps. I also found a few places that sell the user and service info.

Bob,

I'll do some digging - my Dad had two, sold one, and likely kept the manuals. I fixed his several times, first the meter would act funky, then the power supply couldn't be monitored. Turns out there are some protection diodes across the input of the meter - I got the replacements from Mouser and fixed the metering problem.

Sadly, Dad passed away December 30th, and won't be needing his VA62 or the manuals...

Brian

I'm sorry to hear about your dad and thanks for the offer. bharris kindly emailed me a pdf copy of the Operation and Application manual, but I could still use the schematics and service info. Looks like I can get them from Tucker: http://www.etestmanuals.com/Search.aspx?Mfg=SEN