Panasonic VCR model AG1980P no HiFi sound on record or Playb

I own six of these machines which I picked up several years ago for a dollar apiece at an auction. I've been using four of them around the house and until recently they have been great machines. These had belonged to a town cable TV access station and it was my understanding that despite the fact that they were in pristine condition when I received them the town was simply upgrading to DVR's and had considered these obsolete. I now have three of them with the same problem. They will not record or play back in Hi Fi mode. Is anyone aware of this being a common known problem with these machines? I only have an operating manual for these but truthfully I've never chased a Hi Fi problem in a VCR so I don't really know where to look. Thanks for any help or advice. Lenny

 

The first thing to do is confirm the problem. this might sound stupid but it's easiy to overlook. Make sure you have the problem on both record ansd playback. Taker a tape from a bad one and put it in a good one, in fact note whether or not the machine indicates it is a hifi recodring or not. Determine if it recording an unmoduilatd carrier or no carrier at all. Also take a known good tape in hifi and see if the defective machines play it in hifi and/or if they even recognize the hifi carrier.

If you truly have no carrier on either machine as well as no rsponse to a tapae with a hifi carrier, that points on a certain direction. On VHS ifi is handled by its own heads and therefore its own associated preamps and recording amps. The problem could well be riht there and you don't have to mess with the actual hifi circuitry, just treat it as another set of rotary video haeds, just at a lower frequency.

At this URL :

http://forum.videohelp.com/threads/329513-Fixing-my-Panasonic-AG-1980-NV-FS200

Right clock on the omage in post #5 to download the service manual. It's abour 10MB in PDF format. I just opened it so it is good.

For the most part, the chips that do the DBX encode and decode as well as the FM modulation/freq switching are dual purpose. (I didn't look, they simply almost ALL are). They encode and a line goes high or low and they decode.. You could be losing moidulation or demodulation in any of them, but only certain parts of it will lose you the carrier.

That is what we need to know. Is the entire hifi subsystem dead as far as the carrie goes ? If so, one direction, if not you go in another direction. And do check all the machines and make sure they have the exact same problem.

There are alot of parts in those things made of unobtainium, mainly the hybrid ICs. Some of those have enntsy teensy caps on them that can leak and corrode the traces. If that happens welcome to the world of linear audio. If that's the case in all if the affected units your days are numbered on the rest of them. As such, pick up a DVD recorder and dub baby dub, all your stuff that means anything. If you CAN fix one you can probably fix them all. I still recommend dubbing anythig important to DVD. In fact now they have long life DVDs because even the regular kind have a finite life. Either still outlasts any video tape though.

 

On Monday, February 10, 2014 11:37:22 AM UTC-5, captainvi...@gmail.com wrote:
> I own six of these machines which I picked up several years ago for a dollar apiece at an auction. I've been using four of them around the house and until recently they have been great machines. These had belonged to a town cable TV access station and it was my understanding that despite the fact that they were in pristine condition when I received them the town was simply upgrading to DVR's and had considered these obsolete. I now have three of them with the same problem. They will not record or play back in Hi Fi mode. Is anyone aware of this being a common known problem with these machines? I only have an operating manual for these but truthfully I've never chased a Hi Fi problem in a VCR so I don't really know where to look. Thanks for any help or advice. Lenny

Thank you very much for the help Jurb. I'm going to look over the manual and see what I can do. You've assisted me on more than one occasion over the years with TV's and other things and your help is very much appreciated. Lenny

 

Well, like I said, the first thing is to determine if you have carrier being recorded and/or carrier being detected on playback. Without that there is no way to really know what to look for on the print. You can figure this out using the machines that do still work correctly.

 

Are you getting no HIFI only or no sound at all? If no sound, verify that the audio head is clean and aligned properly. I would not expect major electronic failures here. Usually the problem is either debris or alignment. THese are solid units with few problems.

Check the simple stuff first. Scope the head signals, the audio output etc.. Use a known good tape preferably a pre-recorded one.

Post any status here.

Dan