Is anyone familiar with the JBL Synthesis pre-amp?

I have a surround sound JBL Synthesis pre-smp. It is behaving VERY erratically. Some MODE functions work and some don't at all. It doesnt seem to make much difference which inputs are used, some of the modes either give one channel or no channels however high the volume is put. Hall 1 used to work fairly consistently but now it doesn't seem to work at all. Similarly the tuner input (I use S VID1 for this) used to work on JAZZ but now it usually doesnt work much at all.

The right hand lights light up when you accress an input which is connected but with most modes, no sound comes out and with some modes, only one channel works (not always the same channel!)

The only mode which consistendly works is MONO ENHANCE (with a kind of falsified sound which you cant use with television on any talk mode which is how I have it connected) and suspiciously when you try to access one of the channels which isnt working on both channels, the non-working channel occasionally flashes on at full volume, indicationg a dry joint somewhere. But even this isnt consistent between symptoms, indicating that the unit isnt absolutely sure where any dry joint is.

Has anyone worked on one of these please?

Reply to
dmanzaluni
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Try shutting off the unit, disconnecting it from the wall outlet, and letting it sit, "unmolested", for at least 24 hours. There is a slight chance this will fix the problem.

Reply to
William Sommerwerck

I have to say, though recently it had become worse, it has done this ever since I got it a few months ago when it had been siting on a friend's shelf for some years (though he reported that the last time he used it, it did work properly so I will try your suggestion)

Reply to
dmanzaluni

I have to say, though recently it had become worse, it has done this ever since I got it a few months ago when it had been siting on a friend's shelf for some years (though he reported that the last time he used it, it did work properly so I will try your suggestion).

Hmmm...

Does the unit uses a lithium coin cell for backup? Just wondering.

The fact that it worked before it was put into storage, doesn't prove anything about whether it would work several years later.

Reply to
William Sommerwerck

No, there is no lithium cell but there ARE some curious white (what look like) pot controllers by the L and the R of the phono connectors which dont figure on the manual for this unit. I wonder what they are? And I wonder if they contain the solution to the problem of the apparent dry joints? I am sure there is no way of spraying Tuner Wash into the pots under them if pots they are but I wonder if they have just become dirty?

Reply to
dmanzaluni

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