I am trying to restore a 1986 Sharp 3" TV, model 3LS36, with a vertical problem. Upon first powering on, the picture rolls vertically, even with the vertical hold control fully clockwise. As it plays, the rolling slows and eventually stops after 12 to 20 minutes. I have no schematic. Howard W. Sams didn't print one for this model. Can anyone offer any help?

You probably don't need a schematic if you can identify the vertical section. Get a can of Freez Spray ('Component Cooler') from RS. With the TV warmed up and not rolling, hit each electrolytic cap in the V section individually and see which one(s) set it to rolling when cooled. With about 99% certainty, you'll find the problem that way.

Just HOPE & PRAY that its just a bad cap & NOT that infamous "Jungle" IC chip fixing to die...Those l'il guys DO have excellent pictures on 'em...I have all versions except for the silver one, & MOST of mine work.

That should be a bad electrolytic cap between the IC and the vertical output. If you do need the schematic for it and can't find a Sharp version, you can look for an RCA PVM-035 manual. Same TV but with a different style case.

Charles

Is that RCA schematic in Sams? I looked under that model number but didn't find it.

Let me know if you have a Sams number; I can download it using my library subscription. My website has an article about this TV and it would be nice to include a schematic.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Thanks fgor all the input!
Yes, there is a Sams publication. I copied this from the online Sams index:
Item #
142414 PHOTOCOPY RCA PVM035 $25.00 OEM Service

The online index is https://www.samswebsite.com/photofact/pf_search.asp

I'll keep checking daily. Good luck Phil.

I don't think I have a Sams, but I might have an RCA factory manual. My friend's TV shop in LA was an authorized RCA dealer in the 80s, and had a subscription to all the manuals and supplements. But don't hold me to it, because I may not have a chance to check on that for awhile.

Charles

No luck over 2 evenings in checking caps and using the rest of my can of FreezeIt. I also went the other way and used a heat gun. No effect on the vertical circuit.
I also did some research on the RCA PVM-035. It is similar, but more closely a relative of the Sharp 5LS36. Similar chassis, but different. No Sams on it either.
I'm uncomfortable running it at this level of disassembly too, so I have the front attached to the bottom again. I've been quite thorough with the freeze and heat. I don't think it's a thermal problem. I'm definitely leaning toward component failure.

I think that set has one of those inline IC chips for the vertical outputs, and I've seen those go intermittent a lot, but they act more like a cracked solder connection (popping in & out of full sweep) ; not so much just gradually shrinking or slowly changing as the set warms up. But they're cheap, so it might be a good shot to try it. I don't remember which version it would be, but it might be LA7838, or if not, LA78(and two more digits) .

Charles

I think that set has one of those inline IC chips for the vertical outputs, and I've seen those go intermittent a lot, but they act more like a cracked solder connection (popping in & out of full sweep) ; not so much just gradually shrinking or slowly changing as the set warms up. But they're cheap, so it might be a good shot to try it. I don't remember which version it would be, but it might be LA7838, or if not, LA78(and two more digits) .

Charles

I thought the Vertical chips for these were unobtainable?

The Vertical Output IC tends to affect deflection, and rolling is more of an oscillator malfunction. Since the oscillator and vertical drive pulse are generated in the jungle IC, I am leaning toward that conclusion. I wish there were a way to drive the vertical with the equivalent of the old B&K Television Analyst, but I would be afraid to try it on this set. It would sure be a good way to divide the circuit though.

I thought the Vertical chips for these were unobtainable?


I don't remember it being hard-to-get... But maybe time has gotten away from me, since now I can't remember the last time I repaired one. Probably the mid-90s :sigh: . But I think those output ICs are still out there. Mitsubishi used a funny one (AN5553 or something like that odd number), which was a tough one to get in the early 2000s. But I blamed it on so many of them blowing, and the demand. The nice thing is that the most expensive one I remember, was about $3 from the traveling salesman. Most (like LA7838 and AN5521), were about $1.25.

I've seen them cause a vertical hop or jump, which can look like a roll. It's not a loss of v-sync, as if the oscillator is acting up. It's a feedback from the output that kicks the oscillator out of whack as it tries to correct the hop.

Charles

Now THAT is what I needed. I got off the set for a few days to clear my head. You talking about it taking a "hop or jump" gets me to thinking. Right now, I'm not sure. I interpret it as a roll because it appeared to slow with the vertical hold control fully clockwise, but now, I'm not sure. I did scope the vertical pulse at the yoke, and the frequency disply indicated 59.97 Hz on my Sencore SC-61, which tends to be accurate, but I'll check and be sure it's a roll later this evening.

Thanks Charles