Can anyone here confirm if I'm on the right track here? I replaced a broken Sansui AU-5500 dual pole power switch with a single-pole power switch but at turn on I found 58v on the positive and 12.40v negative on the collector of each output transistor? The collectors should read around 35v positive and 35 negatives, a total of 70v, the 58v and 12.40v I'm getting now both add up to 70v too? Would the single pole switch cause this or should I be looking elsewhere for the voltage problem? I can't find a proper dual pole switch at reasonable postage from the USA the new US Global postage company wants nearly $AU200, Fleabay wants even more for postage? I used the single pole switch because I thought it would work and the Sansui AU-5500 schematic shows a simple on-off switch so what could go wrong? Ha!
What would be useful is a drawing of how you wired in the new switch.
The schematic shows the two-pole switch, one pole directly, one via a fuse. How did you wire the new single pole switch?
Did you check the fuses?
Jan
The schematic shows the two-pole switch, one pole directly, one via a fuse. How did you wire the new single pole switch?
Did you check the fuses?
Jan
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Definitely not the switch. It sounds more like you are either not measuring from a true ground or a ground is floating. Measure from the junction of the two reservoir caps.
I installed the switch exactly in the same way as the service manual describes and yes, I have checked all the fuses.
Hi Mooly, do you mean to measure across the reservoir caps individually, or from positive to ground? Another thing, is it safe to do without the Dim Bulb Tester?
Mooly was suggesting you measure from the point highlighted with the arrow., that's the ground reference point for the amplifier. Measure the voltage on each cap relative to that point and at each board
I measured across the reservoir caps the DMM read +35.50v and -35.50v on each but to the chassis ground, it was 12.60v and 58.60v? I have tightened up the screws holding it all together but that didn't change anything.
Remove the chassis ground screws, check and if needed, remove any corrosion on the body.
Check the wire too, could be poor due to age, check the lug crimping.
And also check the resistance between circuit and chassis grounds after fitting the wire back, as Mooly said.
Did the amp actually work, or you are before that stage in your repair project?
And see if your meter batteries are in good condition.
Check the wire too, could be poor due to age, check the lug crimping.
And also check the resistance between circuit and chassis grounds after fitting the wire back, as Mooly said.
Did the amp actually work, or you are before that stage in your repair project?
And see if your meter batteries are in good condition.
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Circuit ground and chassis ground are entirely different things here. The common point between the supply caps is circuit ground...that's the one you care about.
Mike
The amplifier worked after I rebuilt it with a full recap, new sealed VRs, a new relay, replaced fail prone transistors, etc... It stopped working when I put in this switch and changed out a Germanium diode. I replaced the lN60 which was cracked, I ordered some in60P from fleabay but I was confused about them being silicon and not germanium? So I used a Germanium diode marked with 7B and two red stripes that read .310v from my junk box.
The others have it covered 🙂
Check to the 'ground' screw on the rear panel (used for a turntable ground).
Yes, I checked the back turntable ground and the front headphone ground, both are good. The voltage is +58.60 and -12.60v to the chassis ground. I will go all over this amplifier again and get back soon.
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Perhaps this one?
https://www.web-bcs.com/diode/dc/ga/G-7B.php?lan=cn&cl=1&stock=common
Maybe the diode isn't rated high enough for the application and failed?
There appears to be two earths grounds? One that goes from the reservoir capacitors to the F-2097 mainboard, speakers and headphones but not to the chassis at the headphones as the SM describes. Then another that earths the rest of the board's Tone, Volume, Inputs, etc... to the chassis. I have checked and reflowed all solder joints. I noticed that the headphone earth does not ground to the chassis? Once I have this grounding problem fixed and the voltages correct I will worry about the 1N60 Germanium diode. Yay! I found two plugs 23 and 24 that I had incorrectly plugged in around the wrong way! That was the first thing I thought of but when I checked them my scatterbrain was distracted by something else and I missed it. I will put the amplifier back together again and report back the result?
IT'S ALIVE! Its Aliiive! Ha! Ha! You were right again Mooly, it wasn't the switch at all or the Germanium diode just me overlooking the bleeding obvious. Thanks, everyone for your ideas and suggestions it is appreciated, I still learn a thing or two from them about circuit theory. The amplifier sounds great too, I think the original cracked Germanium diode may have had something to do with the loss of quality sound because the amplifier sounds better now just as a newly rebuilt, recapped, Sansui AU- series should.