Panasonic VCR model AG1980P no HiFi sound on record or Playbac

The first thing to do is confirm the problem. this might sound stupid but i t's easiy to overlook. Make sure you have the problem on both record ansd p layback. 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. Determ ine 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 t apae 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 reco rding 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 vid eo haeds, just at a lower frequency.

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Right clock on the omage in post #5 to download the service manual. It's ab our 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 t he FM modulation/freq switching are dual purpose. (I didn't look, they simp ly 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 t he 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 probl em.

There are alot of parts in those things made of unobtainium, mainly the hyb rid ICs. Some of those have enntsy teensy caps on them that can leak and co rrode 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 st uff 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 l ong life DVDs because even the regular kind have a finite life. Either stil l outlasts any video tape though.

On Monday, February 10, 2014 11:37:22 AM UTC-5, snipped-for-privacy@gmail.com wrot e:

lar apiece at an auction. I've been using four of them around the house an d until recently they have been great machines. These had belonged to a tow n 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 sim ply 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 m ode. Is anyone aware of this being a common known problem with these machi nes? I only have an operating manual for these but truthfully I've never c hased 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 an d 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. Le nny

Well, like I said, the first thing is to determine if you have carrier bein g 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 o ut 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 ele ctronic 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