If anyone can provide this I would appreciate it.
Not needed now, with help from Bredgeo and a lot of patience, its restored and is now 100%!
Thanks Bredgeo.
Cheers.
Heres the info.
I noticed on the 9797 I got from lav that the sound on the left channel was pooped. So I set about oening it up and checking the usuals, connectors and continuity across the speakers etc. The only thing I had noticed is that the volume knob was very loose and didn't really have any friction to it. I was suspicious of this but didn't think it was the root cause, silly me.
Checked the amp chip by jumping the left and right pins and wallah sound came out of the left channel so amp chip was good. Could it be in a more awkward place ? I had to remove the entire board section to get at it from underneath, painful.
So, thinking the problem lay further towards the input I bought a signal injector and started to put that together so I could inject a signal along the various points to see where it was failing. At the same time for whatever reason I hadn't before, I turned the volume to full while listening to white noise from the radio and noticed that there was a tiny 1mm section that actually made the left speaker come into action! DOH!
So I set about getting the board out with the pots on it, which is a complete ballache. Opened the pot which is held closed with 4 little angled clips underneath to reveal the brushes.
In the pic you can see there are 2 brushes. The inner and smaller one was loose when I opened it and you might just be able to tell that all the brush ends were bent and a bit shot. So I simply cleaned this section up and checked the contact side and proved that there was continuity throughout and give them both a good clean, they were covered in too much grease.
After useing a bit of super glue to reseat the smaller brush and straightening out the brush ends as best I could before going completely bogeyed, it looked in good shape again.
Left it to set for an hour or two and set about putting it back in the board and the board back in to be able to do a test.
Plugged it in and set to radio and the volume was really low, full whack on the volume and could barely hear it. BALLS! what have I broken now?
The board with the pots on it has a ribon cable that solders directly into the board and connects to the main pcb underneath the tape deck. These are usually secured in place with a touch of glue to the pcb where it is soldered to take the strain off the soldered joints. Needless to say the glue had long since gone and as a result 3 or 4 of the 8 pins had disconnected. Restripped the ribbon, desoldered the underneath of the board and resoldered each wire on the ribbon back into place. Continuity test showed it all to be good.
Reseeated the board again and did the test.
PERFECT !!!!!!
Audio is even out of both speakers!!!!
I love it when a plan comes together with a little patience.
great stuff DOCS, can i have it back now
quote:
Originally posted by LAV LOO:
great stuff DOCS, can i have it back now
hehe yeh sure just add a few more 1s
Those pots don't like grease at all anywhere near the points of electrical contact. They should only be on the shaft and other slide surfaces. I wonder if it's been opened before?
Great to hear it's fixed though. Knowing that the amps were working really helps to narrow down where to search for the problem though, doesn't it?
Yes and thanks for the tips. I've now got a signal injector that will help in the future.
I tried to ensure all that grease was removed from those contacts and used a bit of contact cleaner on the surface. It does look to me like it has been atttempted to be fixed before, seeing as the antenna connector was unfastened inside. Nevermind though, I repaired their effort and its going either on ebay or for swaps
