View Full Version : JVC videosphere


Aquat
05-14-2017, 03:05 PM
High I resently purchased a JVC Video sphere and am confused as to why I can't use it due to it displaying 4 images overlapped onto each other I've tried hooking it up to dish commodore Vic and my n64 and nothing seems to make a image it's Al just overlapping images and I have adjusted every adjucment on the thing is this an internal problem?

benman94
05-14-2017, 04:05 PM
Moved to the appropriate sub-forum.

Findm-Keepm
05-14-2017, 09:20 PM
High I resently purchased a JVC Video sphere and am confused as to why I can't use it due to it displaying 4 images overlapped onto each other I've tried hooking it up to dish commodore Vic and my n64 and nothing seems to make a image it's Al just overlapping images and I have adjusted every adjucment on the thing is this an internal problem?

Um, model? Sams doesn't list a videosphere. You want help, you gotta give us some meat....

Board policy:

http://www.videokarma.org/showpost.php?p=3152065&postcount=1

Electronic M
05-15-2017, 09:19 AM
It sounds like a horizontal or vertical hold or osc. issus depending on whether the images are side by side or stacked....If it is hold the correct hold control will get it down to one image, but if the osc. is far enough off freq that the hold cannot compensate then parts replacement will be necessary.

WISCOJIM
05-15-2017, 09:51 AM
Um, model? Sams doesn't list a videosphere. You want help, you gotta give us some meat....That wasn't a very friendly response to a newbie.

Besides, how hard is it for you to Google "videosphere model number" to get the answer?

JVC 3240/3241 is in Sams 1472-2.

Tom (Electronic M) is on the right track.

.

zeno
05-15-2017, 11:51 AM
Sounds like horz osc is way off. Try the horz hold control.
Turn it slowly while watching the pix.
If not that probably needs deeper work.

73 Zeno:smoke:
LFOD !

Findm-Keepm
05-15-2017, 05:28 PM
There's a mod - you change C401 and C402 to a polystyrene/styroflex cap (originals are polyester/mylar film with a crappy TC...). Replace with 4700pF, 160V polystyrene, hard to find anymore. eBay would be the best bet. The old mylars (in the AFC circuit) would change value independent of each other and cause horizontal hold/frequency issues, usually double the H-osc freq.

I've used 4700 pf NP0 100V ceramics in a pinch - they are about 30 cents each and just as stable.

There's also an AGC mod, if I can find my photo-stat copy from the 80s - it's also a cap change from mylar to something more stable IIRC.

From my notes, also the 470uF/25V cap off the yoke (yoke return cap) will cause non-linearity issues. The only other note is about the Hfe on the vertical transistors - make sure any replacements have the correct Hfe code on the transistor, as linearity issues also erupt with the wrong Hfe group.