color adustments do only one at time (sony pvm-8220)

"NN" bravely wrote to "All" (17 Oct 05 18:51:05) --- on the heady topic of "color adustments do only one at time (sony = pvm-8220)"

NN> From: "NN" NN> Xref: core-easynews sci.electronics.repair:345546

NN> I got this sony pvm-8220 from a thrift shop and it was only black and NN> white when setup. There are two set of RGB adjustments in the back NN> that is easily accessible. But any adjustments results in either a NN> red, blue or green picture. (red and white, or blue and white and NN> etc.) Neither the tint or color knobs have any affects either while NN> the others work. I don,t know if this is a simple issue or complex NN> enough to end up in a thrift shop. That would be a start for me.

Could be a bad video processor IC. The lack of colour might mean the colour info or reference isn't being demodulated. Maybe a bad crystal. Perhaps someone played with the screws in the little cans. It might be a tuner afc problem. Might be a bad contact for the colour control on the main board, etc. More things can cause a loss of colour. It will require good signal tracing and diagnostic skills. Are you savvy?

A*s*i*m*o*v

... The first rule of intelligent tinkering is to save all the parts.

You shouldn't have touched those adjustments, they are irrelevent to your problem. Did you mark them so you can return them to their original settings?

Look around the chroma processing circuitry. However, unless you are familiar with the operation of chroma processing circuitry, you won't get anywhere. You could check for dry joints, but that's about it I'm afraid. Don't be tempted to start fiddling with settings, there is a fault which needs repairing, and misaligning settings in the hope of sorting it out will add to your problems.

If it's any help, I've known the crystals and trimmers in the chroma circuit go bad in certain Sonys.

Dave

The common problem causing no color for this model is the varicap in the color circuit. They go bad all the time. You can adjust it and the color will come back but it will drift out again. It is located at the lower right of the board when viewing it from the front. It is available from Sony parts and costs under $5.00. Chuck

This sounds like a solution I can afford. I will have to readjust the color boxes I moved around. You don,t know how to get to sony parts online? I find sony stuff really hard to find on the web besides regular consumer stuff at the store.

You can probably order it online from sony.com, I know Pioneer works that way, for parts that is, not whole units.

Don't ask for a varicap though, that is an entirely different device. The part is a 'variable capacitor'.

Dave

Thanks Dave. I must be going senile. Chuck

Here is the Sony part no. for the trimmer cap. 1-141-245-00

That makes three of us! I mean two of us...

:-)

Dave

Thanks to both Chuck and Dave. I have soldering and take apart skills and no tv knowledge beside safety issues with CRT and capacitors. The part number is perfect for me to do the job.

David

The order went smoothly with your help (actually step by step directions) and the total was less than 6 dollars!

Now I would have never found the part because I tried to find it my way by using their model number option and got no results.

The best of luck with the repair. If it fails, at least you haven't spent a large amount of money on it! With the absence of proper test equipment and service manuals, you'll have to play around with the new variable capacitor to get the right setting. TBH, it's good enough except perhaps for a commercial outfit / dealer with strict procedures ;-) You'll know when you get it right.

If it still doesn't work, then you are left with the problem of what to do next. You could try replacing the crystal, but there'll come a time when buying parts on the offchance they'll cure the fault will cease to be cost effective. I think the new part will fix the problem though as it was a common falure.

Dave

I can always leave it alone as a black and white if all else fails. It is interesting to note that everything else works great and even the blue screen works. No wonder it was at the thrift shop.

David

Does it have a scart socket or RGB inputs on the back? If so, you can input an RGB signal and you'll get colour. ie, a satellite or terrestrial digital TV decoder with an RGB output can be connected to your TV and you'll get a colour picture as RGB does not use the chroma decoder circuitry in the TV.

Dave

All it has is two BNC (I use a rca adapter) in and out with a rf switch for 75ohms and some other input labeled tally.

I got my part but I don,t know if it is covered by one of the external control knobs or where to look. The tv is put together like sony always does, modular boards all around.

The part is green, is that a standard to look for ? all they usually green?

Thanks Again

David

to make clear, the rf switch is part of the monitor, not being used by me since I input from a vcr video out.