Panasonic top-loader VCR Issues - Page 3 - Videokarma.org TV - Video

redk9258 · #31 02-21-2023, 07:26 PM

Oh and maybe those 47 uF 16v capacitors were from a crappy batch. Green corrosion sounds like electrolyte leakage to me.

vortalexfan · #32 02-22-2023, 01:11 AM

yeah unfortunately even after replacing almost 2 dozen failed electrolytics out of this VCR between the Audio, Servo, Slow/Still and Skew boards the VCR is still not wanting to play SP recorded tapes properly.

Plus the VCR has developed a new issue, where the video coming from the VCR when playing tape is just a garbled mess of white noise with the video's audio coming through clearly in the background (LP Mode specifically does this), where it will start off playing the tape at the wrong speed but then after about 2 seconds the screen goes blank and then starts playing at the correct speed, but the video is nothing but a garbled mess of white noise.

The weird thing is that after I had initially repaired the LP Playback speed issue, the VCR played the tape perfectly right away (there wasn't any delay in the speed selection like there is now) and the video playback was crystal clear (no garbled video output like its doing now.)

The weird thing is that the video started acting up when I went over the Audio and Servo Boards a second time and replaced the rest of the bad caps I missed the first time I went over those boards.

That was when I then decided to go over the Skew Board and the Slow/Still boards as well to see if those would make any difference with the playback speed detection issue, and that's when I figured out that unplugging and plugging back in all of the plugs on the Audio board for some reason corrected the video issue initially.

But then when I recapped the Slow/Still Board and the Skew Board and plugged those back in and tested the VCR that's when the garbled video issue showed up and unplugging and plugging back in the cables from the Audio Board didn't fix the problem this time around.

That's why I was saying that replacing the capacitors on some of the boards in this VCR was somehow making the tape playback issues worse and not better, (because while I was able to fix the LP mode playback issue, the SP mode playback issue was still not fixed and the video playback quality went from crystal clear, to nothing discernable in no time flat.)

And I'm not sure what's going on with this VCR and why all of the sudden when I replaced about 2 dozen nearly dead leaky capacitors that the VCR is no closer to being repaired than it was when I first discovered it had a playback speed issue.

redk9258 · #33 02-22-2023, 05:15 AM

Maybe the video heads are clogged? I believe there are different ones for different speeds. Try cleaning with alcohol on a folded piece of paper. Do not use any up / down motion. Just rotate the drum while holding the paper against the drum.

vortalexfan · #34 02-22-2023, 11:45 AM

Quote:

Originally Posted by redk9258

Maybe the video heads are clogged? I believe there are different ones for different speeds. Try cleaning with alcohol on a folded piece of paper. Do not use any up / down motion. Just rotate the drum while holding the paper against the drum.

I didn't think about that, and actually I did try cleaning the heads, but I used cotton swabs which I realize now was a no-no I'll try and and go back over the heads with paper and alcohol.

vortalexfan · #35 02-22-2023, 08:57 PM

OK, so now I've replaced so far 42 capacitors in this VCR all of them of which had the green corrosion on the capacitor wire leads (the corrosion was on either one or both legs of the capacitors, but thankfully it wasn't bad enough to of eaten through the circuit board yet.)

I removed the Luminance and Chromanance board and replaced at least 2 dozen caps on that board alone (all of them had the green corrosion as well), and so far it seems that 99% of the capacitors I've replaced in this VCR were 47uF 16v capacitors with the other 1% being other values.

redk9258 · #36 02-24-2023, 05:06 AM

Did you get the picture back?

vortalexfan · #37 02-24-2023, 05:18 PM

Quote:

Originally Posted by redk9258

Did you get the picture back?

Yes the video came back, but only for a little bit, as soon as I hit the pause button and then hit it again to un-pause the movie the video started messing up again, so I'm not sure what's going on, although if I had to guess I probably need to replace all of the electrolytics on the audio board and the Servo board and not just the ones that had the green corrosion on them that I already replaced...

redk9258 · #38 02-25-2023, 01:46 PM

Maybe the head is clogged again?

vortalexfan · #39 03-01-2023, 11:49 PM

Quote:

Originally Posted by redk9258

Maybe the head is clogged again?

I let the VCR sit for a couple of days and the video is working again, but unfortunately the SP Playback mode still isn't functioning, LP and SLP mode is functioning properly but SP isn't.

I have a feeling that the Audio and the Servo Boards both need to be completely recapped, not just having a few capacitors swapped out here and there.

vortalexfan · #40 03-09-2023, 01:06 AM

UPDATE: I finally got the speed issues resolved, I ended up replacing almost every single cap on the Servo and Audio boards in the PV-1750 except for one of the higher value caps and several super low value caps (less than 10uF in value, such as 4.7. 3.3 and .1 and .33 and .22 uF electrolytics, mainly because I didn't have access to those values of caps in the voltage I needed.)

But now I'm having issues with the video playback again, where the video is nothing but a garbled mess but the audio is fine.
And yes I already checked the video heads and that wasn't what was wrong with it, it acts almost like when a TV has an analog station (from an RF Modulator or DTV Converter Box) tuned in but its off frequency (referring to a TV with a knob tuner on it that you had to fine tune the signal, or a varactor tuner that has the station tuned in just enough so that the audio comes in loud and clear but the video is snowy and bouncy.)

Its making me think possibly something is up with the RF Modulator portion of the VCR (the UHF/VHF I/O section of the VCR that has the Channel 3/4 switch), because otherwise I don't know what else could be causing the video playback issues I'm having, I haven't tried to see what it does using the RCA Video outputs on the back of the VCR to see what that does, but unfortunately I don't have any CRT TVs that have built in A/V jacks.

vortalexfan · #41 03-10-2023, 03:29 PM

I did try operating it with the RCA Output jacks and the video outputted onto the screen is the same, but I did notice that when I dinked around with the RF Modulator's channel 3/channel 4 switch on the back of the vcr the picture cleared up a little bit but then it went back to being a garbled mess.

Is the Video signal outputted to the TV screen controlled by the same circtuitry regardless of if its being put out through the RF Modulator or if its being put out through the RCA outputs? Or are the RCA Outputs and the RF Modulator Video outputs separate circuits in the VCR?

I'm so close to getting this VCR going, and the only thing holding me back right now is the video output signal right now.

redk9258 · #42 03-10-2023, 03:45 PM

Maybe it's a cold solder joint or crappy connection somewhere. By moving that switch you are causing vibration. I'd poke around with a wooden chopstick or something.

I would think that the composite signal is sent to the RF modulator.

vortalexfan · #43 03-10-2023, 06:16 PM

Quote:

Originally Posted by redk9258

Maybe it's a cold solder joint or crappy connection somewhere. By moving that switch you are causing vibration. I'd poke around with a wooden chopstick or something.

I would think that the composite signal is sent to the RF modulator.

I'm not sure what's going on with it, I know that if I take the audio board and the servo board and the Chroma/Luma boards off the VCR fiddle with the wire cable connections and then put the VCR back together the video will go back to normal but then if I do a Forward or Reverse Search then the video goes bonkers again for no apparent reason, and I'm not sure what's going on with it and why it does that. I have a screen cap of what it looks like when the video is going beserk.

The Video when its working properly gives a rock solid still image (pause) and the picture during playback is really clear and probably the best picture I have seen on an old 4-head VCR.

Also apparently the SP mode is only mostly fixed because while it puts out a picture and audio that is normal sounding and looking you can still kind of hear a little bit of a "drag" in the speech but just barely and then there are lines that go across the screen periodically, its acting almost like the video is paused and you're doing a frame search, but its actually playing and has audio.

If any of this makes any sense to you.

vortalexfan · #44 03-10-2023, 06:24 PM

As for the PV-1650 I'm waiting for the play idler tire to get rebuilt by Gary over at the Voice of Music Enthusiasts, because its one of those Idler Tire assemblies that you had to replace the whole assembly or get it rebuilt because the rubber tire portion of it was permanently affixed to the metal shaft, and the rubber was petrified on it so it wasn't allowing it to grip the take-up reel drum so it could play a tape, so I sent it off to Gary to have it rebuilt so that hopefully I can get that VCR checked out for functionality as well, and maybe see if I can get a remote located for it.

The rebuilt idler is supposed to be done and mailed back to me by the 21st of March.

vortalexfan · #45 03-12-2023, 11:51 AM

OK, well a little update on the PV-1750 VCR, I tried it out again today and it worked just fine today, and the speeds were working as they should.

But there now seems to be a video issue for sure, but I'm not sure what's causing it or why its doing it, because its kind of random.

I was playing an old tape in it just now and it was playing perfectly but then I heard what sounded like the video heads (the head that spins around in the VCR) revving up a little bit and then slowing down back to the normal speed after awhile, and when it did this the video being outputted by the vcr lost horizontal sync (the horizontal hold went crazy) but then when the video head went back to normal speed the picture went back to normal but with a slightly off center picture that would bounce back and forth between the right and left hand side of the screen before finally going back to normal.

I know I've heard about capacitors going bad on the board that controls the video head rotation/speed but I'm not sure what board does that in this VCR, I know this VCR has 2 "Control Boards" but I'm not sure which of those boards if any of them would control the video head.

Thanks for your help in this matter.