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-   -   JVC HR-S9600U random audio mute? (http://www.digitalfaq.com/forum/vcr-repair/8026-jvc-s9600u-random.html)

dpalomaki 05-28-2017 08:41 AM

JVC HR-S9600U random audio mute?
 
The JVC HR-S9600U will randomly mute the audio output on playback. It will play OK for periods of time ranging from 10 to 120 minutes, but unpredictably mute the audio.
The audio will come back during a later use session.
However, cycling power on/off for, say, 30 seconds or so does not clear it.
The audio meters still indicate expected audio levels when it is muted.
The same tape will play audio properly during a different session.
It does not appear to depend on audio track (stereo or normal) selected, or tape used.
Tried different audio cables and no change.

Anyone encountered this? Found the cause/solution?

lordsmurf 05-28-2017 10:07 AM

Check the output board. I've had video and audio issues on the 9800, and got them repaired. The 9600, 9800 and 9900 are essentially the same, and the soldering can be weak in this location. This is the main reason I use extension cables for the inputs, and give them slacked. Tugging on the outputs is not good.

dpalomaki 05-28-2017 11:01 AM

Thanks. Too bad the transport needs to be removed to get to the main board. A project for whats left of a long weekend!

dpalomaki 05-29-2017 09:08 AM

Go figure! This AM it ran for 3 hours without a problem. So I was able to reach the jack connections to the main board from under the chassis (after trimming some plastic) and re-solder them. After another 15 minutes muted again.

I note the main board has a provision for a second set of rear input and output jacks that are not used.

dpalomaki 06-24-2017 04:39 PM

Well, turns out some selective pressure on the output jacks, or output/terminal board could cause the audio to cut in/out. But the jacks and connections to them weer OK. No opens or shorts. I suspect that the problem was with the several thru-board connections that connect traces on both sides of the main board and carry the audio output from the mute circuit to the output jacks. Rather than try resolder these connection, I am trying a bypass of the connected traces with wire. We shall see if it holds up.

deter 06-25-2017 02:54 AM

Just reading this post it seems weird cause it works than cuts out. Had this problem with a 1970's Pioneer Quadraphonic 125 watts per channel Amp, and it was a fuse problem.

We need more information, for example the audio outputs are sent to an Amp? If so how do you know that the amp is not shorting out or you have crossed wires?

It seems like a short from your post, but I don't know all the variables.

Try running the audio out from a coaxial cable to see if it shorts.

dpalomaki 06-25-2017 06:07 AM

The system was VCR to Toshiba DVD recorder used as a pass-thru and also VCR to monitor. (Analog Video was always OK.) Also had VCR audio to desktop audio monitors.
1. Tried different audio cables - problem persisted. The audio always appeared OK on the metering and CH3/4 output, just the RCA audio outputs would go silent apparently at random, but generally within 10-to-40 minutes of starting play.
2. Tried resoldering the output jack connections to the main board - problem persisted.
3. Opened the system up. removed the main board, measured control voltages in the muting circuit - it behaved as expected - but the audio still would cut out even if muting was not on.
4. Found that if I pressed "in" on the RCA output jacks, on the terminal panel, or on the main board near the terminal section it would sometimes drop the audio, and usually return when released. Similarly if the audio was already dropped, pressing on the listed locations would sometimes restore it briefly.

The HR-S9600 main board is two layer with components mounted on both sides, and very few daughter boards. It is far more cluttered with narrower traces than the boards in the AG-1980 (but no SMD electrolytic capacitors thankfully, plenty of SMD resistors, transistors and ICs.).

I checked the circuit and board traces from the audio IC to the terminals. I found several points where the audio output circuit trace jumped from the bottom to the top layer and then back. This jumping back and forth was required due to crossing signal paths, and was accomplished by using "VIAs," a hole lined/plated with metal that connected the upper and lower layer at that point, rather than jumper wires. I suspect that some of thru-board connections were intermittent (the randomness and self healing were probably thermally driven), so I bypassed them with jumper wires. So far (4+ hours running and no problem.


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