. Will see how this goes till the end.
A friend asked me to recap it and hopefully solve a distortion problem in one channel. Swapping the pre-outs and main-ins told me the distortion was in the power amp board.
I did a complete recap (electrolytics) and the distortion remained. @jdurbin1 and others pointed out the caps in my before photos were not originals, so I dug a bit deeper to find plenty of evidence of prior work.
My friend, the current owner, was not aware of any prior work or prior problems, but he was not surprised when i reported my findings.
I did a complete recap (electrolytics) and the distortion remained. @jdurbin1 and others pointed out the caps in my before photos were not originals, so I dug a bit deeper to find plenty of evidence of prior work.
My friend, the current owner, was not aware of any prior work or prior problems, but he was not surprised when i reported my findings.
It's not back together yet. I tested every single component except the two inductors and the one relay. Only one resistor was out of range and that BC5xx small signal transistor was the only dead component.
So, I don't know for a fact the distortion is gone, but I do know one of the transistors was not operating.
I'll post once the very low noise 1% metal film resistors arrive and get installed. It is still possible the problem lies between the pre-out main-in jacks and the power amp board or between the power amp board and the output jacks, but into doesn't seem likely.
Well, it could lie in a bad solder joint or one the dozen lifted traces. I'll let everyone know once I install and test.
Did they break on you while working on it?
Yep. I had to disassemble the tuner board to get to the tuning dial lamps and I broke the 30 year old string when re-routing it.
I'm glad I took lits of photos so I can properly route the replacement string but JUST attaching a new string and cutting it to proper length will be a challenge (for me).
I guess this is one of the exams AK'ers have to pass to go from grumpy young newbie to grumpy OLD newbie....
That along with your first lifted trace. 
That along with your first lifted trace.
Doh! (forehead palm slap)
I've done a few lifted traces. Easy enough to make a functional repair but they do violate my "do no harm" philosophy of repair. 
You can do the lamps from the front, just pull the dial screen. Beats messing with that rear mounted lamp board. Also if you ever need to just replace the FM stereo indicator lamp, that part of the PCB is on a breakaway (perf) section. Just pull the one screw, bend the board back to break the perf, replace the lamp and screw the board back in. I usually do the whole thing from the front because I'm doing all six dial/meter lamps and the indicator in one pass.
These are easy restring projects and the manual has a good drawing in it for reference. I built jigs for these and for the 3000-series tuners a long time ago (using intact original cords and steel brads as pins stuck into a thick piece of cardboard to create a dimensionally accurate template that locates the key parts) so I can do a new string on the jig and then install it and tie off the one end before cutting the excess.
John
These are easy restring projects and the manual has a good drawing in it for reference. I built jigs for these and for the 3000-series tuners a long time ago (using intact original cords and steel brads as pins stuck into a thick piece of cardboard to create a dimensionally accurate template that locates the key parts) so I can do a new string on the jig and then install it and tie off the one end before cutting the excess.
John
You don't, by chance, have a video you could upload to YouTube showing how you do this?
The stringing jigs? No, but the process isn't hard even with a broken string. If you temporarily superglue the broken ends together, you can use that to make a jig and then use fresh cord to replace the string element of that broken cord while recycling the other parts. Those little crimped parts can be carefully spread open with a pick to get the string released, can unthread the loop that secures to the spiral pulley etc.
I can post a picture of one, if it helps. You'll still have to use that manual drawing to get the turns around the pulley correct, and set the dial indicator in position accurately once the rest of the assembly is back in place.
John
I can post a picture of one, if it helps. You'll still have to use that manual drawing to get the turns around the pulley correct, and set the dial indicator in position accurately once the rest of the assembly is back in place.
John
For future reference, what's the best material for the cord?
Blue Shadow
Waiting for Vintage Gear from this century
I just did the string on a Yamaha CR-820, four times. Well one was a learning experience, the second I cut the string too short, the third would have been fine but I had to go back in to replace the volume control and wasn't happy with stringing. Fourth worked out well and dial indicator is aligned exactly per manual.
Trick I learned is tying the final knots at the spring, pull the string tight and use hemostats to hold the spring and string. Once the knots are tied, releasing the hemostats allows the spring to tension the string and that spring retracts to a 'proper' extension instead of being stretched before the knots were tied.
Not sure on the Tandbergs but most I have seen have a fixed end then the end with the tensioning spring. Probably better ways to handle it but I'm done with this one. More practice will be on a different unit. Seal the knots with paint.
Trick I learned is tying the final knots at the spring, pull the string tight and use hemostats to hold the spring and string. Once the knots are tied, releasing the hemostats allows the spring to tension the string and that spring retracts to a 'proper' extension instead of being stretched before the knots were tied.
Not sure on the Tandbergs but most I have seen have a fixed end then the end with the tensioning spring. Probably better ways to handle it but I'm done with this one. More practice will be on a different unit. Seal the knots with paint.
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