Hello,
this set is an RA-6 chassis.Im fairlysure I have a video drive problem.Blue is bright /retrace.Turning down screen has liesettle effect.Switched red for blue crt boards,now it is red .which should confirm tubes and neck boards are ok.Have schematic,and will check for drive from video processor.
Ever had this before?
Thanks marv
Excellent Diagnosis!!! The problem is the video driver on the crt board, it is another common problem, and the diagnosis you did is how i isolate between the crt or the video driver. it generally is not the jungle on the main board. try changing the video driver ic. that will probably fix your problem.
Hi, zapdf,
Thanks for that fast reply, Loooks like someone else had tried this as I can see that one is soldered in, that does not mean it is good , of corse, today I will install a new Ic and cross my fingers.
I will let you know how it goes,
Thanks Again,
ps, lots of experiene with Rca projos, if I can help, unfortunately older models.....
just replaced tda611, no change. went into service mode, adjusted blue drive and cut, no effect.
looks like i must go deeper? into the chassis.
any hints from what ,info is here? checked components on crt board,exept caps,maybe i should esr them,but set is fairly new.
Marv
You could have a problem with the focus block, the g2 may be too low, Try switching the g2 leads from the red to the blue and see if the problem follows.
Interesting, will try that and let you know, thanks for the help.
I have acess to some used parts for this set.
Marv
zapdt,
I switched the leads on the HV block, I think this is what you meant,Still same,Blue is bright.
I may have misunderstood, perhaps there is a problem with the focus/screen control?
otherwise I have not yet checked for the 2.5v from the video processor.
yes i was checking to see if the screen voltage was too low, not focus, low screen voltage will cause bright tube. you need an oscilloscope to continue. Need to check the video drive waveform going to the blue crt. If you have a staircase generator. (i am assuming you are a tech) that would help. I will look at the schematic today to get more ideas.
yes, I am /was a tech, was in the repair business 10 years ago,im from Canada.
havent used the scope in years, but might be next step to check for video drive, as alot of components that would cause this have been eliminated,
Not sure if I told you, original problem was power supply, which , after repair got set running.
My "instinct" tells me, suface mount component or chip is bad.
Really appreciate your help here.
Well i still think you could have a problem with the neck module, but by comparing the green scope pattern to the blue with a staircase, you should see the same pattern exactly. because it is a black and white image, (same should be true for any black and white image) if the pattern is the same, we still have trouble with the neck module, if not it should be fairly simple, it just goes to the jungle. that is where the blue drive is split off. Try to scope this first if you can.
Set the scope to DC to check for a dc bias offset. I am not sure if there is a pass cap that would neutralize this effect, but at Least you will have a truly accurate picture of the waveform.
We have a Winner!!
kept thinking that you were not convinced that the neck board might be bad!! It WAS!!
very happy,with your help, scrounged a replacement from friend, it was hurting a little.
Slapped it in and, Bingo. Some adjustments and set looks fine!!
Want to diagnose old board, chip was good.
Again,thank you for the much needed help!!!!!
Marv
If you are wanting to troubleshoot that board, i would be checking for problems with the g2 trace on that board. or any components associated with the g2 i believe that is where you will find your fault.
The symptoms remind me of shorted guns.G2 is for sure what I will lookk for on that board.
hey just for grins, what is that set you have on your profile?looks fairly old
been hanging on to a 1949 rca, needs vertical tube, and some caps. ha, museum peice, but think it will go in rec room to have conversation peice.
Do you work for a repair shop?
Marv,thanks again.
what is that set you have on your profile?looks fairly old - just somthing i found on the internet.
Do you work for a repair shop? -
yes, my day is consumed with repair. Of all kinds. I am the senior tech here, i support the techs on the road. and tackle what they can't fix in the home. I feel like we(techs) are a dyeing bread.
I don't mean to hijack this thread as it seems like you've taken care of your issue, but I have been looking for a replacement contrast screen for this set for some time now. Sony has discontinued it and its' replacement and I have not had any luck trying to find one. The part number for the original replacement is 4-081-065-01 and I believe the replacement for that part number is 9-910-999-35. Any help would be greatly appreciated. Happy Holidays.
Regards,
Hawkes