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-   -   Panasonic AG-6400 Hi-Fi audio problem (https://www.vintage-radio.net/forum/showthread.php?t=156197)

TapeTwoK 1st May 2019 5:14 pm

Panasonic AG-6400 Hi-Fi audio problem
 
Hi all,

Iíve just recently got my hands on a Panasonic AG-6400 portable VCR but unfortunately noticed that the Hi-Fi (or what Panasonic calls HD) audio circuit isnít working correctly. I can hear the live feed from the headphone jack with perfect clarity, but playback or recording with Hi-Fi audio produces popping when recordings, or a very brief, low level crackly signal that fades into popping when playing a Hi-Fi stereo tape.

I have experienced a similar issue on NV-M10 camcorders and know it is capacitor related, but I have never personally carried out the repair before.

I have the service manual, but before I go digging through the block diagram and diagnosing each and every cap, I wondered if anyone has done this repair before, and knows of which caps tend to be the most troublesome?

All help is appreciated. If no one can help, I will attempt to figure it out myself and post the results for future reference.

Many thanks!

Maarten 1st May 2019 6:20 pm

Re: Panasonic AG-6400 Hi-Fi audio problem
 
I don't know the model, but I would suspect every SMD electrolytic between the audio heads and the AF-stage. If there are no SMDs the same goes for miniature wired electrolytics. You could try heating up the suspect area with a hairdryer while listening for improvements. If audio improves, the bad electrolytic is in the heated area.

Does it have a hifi-tracking meter? Is the hifi signal recognised even when it's popping? If so, the first few stages after the head amplifier are probably okay.

TapeTwoK 1st May 2019 6:58 pm

Re: Panasonic AG-6400 Hi-Fi audio problem
 
1 Attachment(s)
Thanks for the reply, Maarten.

I had forgotten about the hair dryer method for troubleshooting.

It did yield some results. By heating and touching the area in this photo, I got the left channel to come back quite significantly. I could also get some buzzing in the right channel by touching the top of a cap in the area. I think you’re right that I should just go ahead and replace the whole lot there, because if one or two have gone bad, I’m sure there’s a good chance the others have too. Thankfully, they are tiny wired electrolytic ones, so doable with a micro tip iron. i believe this is the FM circuit for encoding the audio to tape. I suppose I’ve got a big project ahead haha!


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