Sima SVS4 video selector

[The Robman]

Let me christen this new forum already. I have a Sima SVS4 video selector that has started acting up. The symptom is that the picture will roll on certain programs. The funny thing is that it's not random. When I play back certain shows (on my ReplayTV) it will always start scrolling at the same spot in the show. It tends to happen more often with cartoons than with regular shows. Does anyone have any idea which might be causing this?

I've opened up the unit hoping to see some burned out capacitors that I could easily replace but there's nothing like that visible.

One of my online friends was kind enough to give me his Sima that he wasn't using anymore, and while this unit doesn't have the scolling problem, the colors in the picture aren't exactly right. The overall color level is lower than it should be and the tint is wrong for certain colors, for example, red shows up as pink, etc.

I'm more than happy to dive in and replace parts as needed, I just need some idea of what to be looking for to decide which ones to try replacing.

Any ideas?

Additional info:
Sima's web site is: http://www.simacorp.com/

I couldn't find a page there on the SVS-4, but there is one for the more recent SVS-4D
Here's the SVS-4D's user manual and spec sheet.

Here are some consumer reviews from AudioReview.com

[zaphod7501]

I almost suggested some things when you mentioned this problem in another post but you probably have electrolytic capacitors failing. They rarely pop up and "tell" you they're bad and trying to pick out 1 or 2 bad ones is usually futile in a case like this ; and if some are failing then all of the similar types are probably failing too.. If there are a relatively small number of them then I'd change them all. (using Mouser and Digi-Key cost is low) Neatness counts , especially in a mass changeover. Flux remover a must. If there's a lot of them then I would change them one value at a time. (1uf , 3.3uf etc.)

If there are controls on the board then they may have become noisy and a good contact cleaner (I prefer "Cramolin" red) might help. Without a scope and reference data I would mark carefully the original positions when moving the controls.

The failure of electrolytics usually only affects Luminance , sync , filtering , and power supplies but rarely color circuits (capacitor values too small to use electrolytics) because mylar and ceramic capacitors almost never change value. However many "color" problems are actually a low luminance problem. The classic "it looks all red" complaint is usually low luminance.

I had an old garage door opener that I thought I would have to replace. After changing 15 capacitors and resoldering the plug-in connectors it now works much better than it did brand new.

Edit (already): values from 1uf to 10uf tend to be coupling capacitors in the video range. 22uf to 100uf can be coupling , decoupling , or filtering. 100uf and up tend to be power supply filtering. Less than 1uf are high frequency filtering or possibly color related. For various reasons all ranges could produce your symptoms.

[The Robman]

... you probably have electrolytic capacitors failing. They rarely pop up and "tell" you they're bad.

Actually, they do sometimes. I've had a DVD player (Raite AV715) and a cable box (Viewmaster VM4000+) go bad on me, and when I opened them both up, it was obvious that most of the capacitors where bad as they'd all spilled their guts everywhere.

In the case of the Raite, I knew of an online forum dedicated to this player (because it's hackable) so I checked the archives and many people had reported the same problem and there were fixes posted. I replaced all the parts mentioned in the fixes and the player was brought back to life.

For the cable box, I just replaced the parts without looking for advice and it was brought back to life also.

The Sima sure has alot of capacitors onboard, so to replace all of them will take some effort, but I might give it a whirl.

Thanks for the advice Steve.

[zaphod7501]

Surface mount capacitors may show the oil leakage around their base while through hole types might not. One test of surface mount leakage is to touch a soldering iron to one of the leads , if it smokes and gives off a strong odor then it's leaking. The leaking capacitor might not have any direct effect but the oil can short out other connections and components so clean up with a mild solvent is critical. A strong solvent can actually damage the capacitors further.

Mass capacitor changing isn't too hard with a nice desoldering station but while I could justify the $600+ purchase most people could not. With vacuum desoldering , hot air jet and micro tip soldering , mine has paid for itself many times over. Too bad you're not closer to Peoria but I doubt that I'm on your commuting route.

[The Robman]

Actually, the leaking ones that I was describing are the "cylindrical can" thru-hole type.

I just did a quick inventory of the cylindrical capacitors in this thing and here's the breakdown:

capacitance/voltage = count
1u 50v = 6
2.2u 50v = 1
10u 25v = 52
47u 16v = 4
100u 16v = 15
470u 16v = 5
470u 25v = 2
2200u 16v = 4

Do any prime suspects stand out in that list?

On the underside of the PCB there's a few surface mount components, mostly transistors and capacitors.

Too bad you're not closer to Peoria but I doubt that I'm on your commuting route.

Hey, if you're up for taking a look at it yourself, I'd be more than happy to mail it to you.

[zaphod7501]

That's a lot of 10uf caps, guess what the most likely suspects are?
I'd be more than happy to take a look at it (this is the slow season) but there are several things to do first, some of which you may have done already. Since you have a repeatable problem with it acting up at certain spots on certain shows you should be able to do most of the following things.

Try it on another TV.
Try all the inputs, all the outputs.
Try S-video , try composite , try combinations since the manual indicated that it will convert composite to S-Video (composite in, S-vid out, etc).
Swap wall (power supply) adapters.
Check cold (just after plugging in power) versus hot (after having power on for hours) I know my A/V switches are on 24/7 even when devices are off.
Try some different cables (a poor ground shield on a video cable can do odd things).

The more detailed the information , the fewer parts to examine. Even if it happens on all inputs and all outputs that puts the problem after the video switch and before the output splitter or in the power supply buss eliminating all 4 input processing circuits and the 2 output circuits. While it might be practical for you to change the few 1uf and 2.2uf caps; without a scope and a reference video signal there would be no way to pin the problem down to a small group of parts and changing that many capacitors without desoldering equipment is likely to leave the board looking like a minefield.