How on earth did you get the separated/connected switch out? I am very impressed!!
Thanks for the explanation, I will be doing this when my pre-amp comes out of service for a bit of maintenance...Very carefully, it's a pain in the butt to get to, that's for sure. You first have to take off the big gray trim/frame piece and the black metal faceplate panel, then with the edge of a jewelers flat-blade work the 4 black push pins out that hold that board on. This is delicate work and it's not hard to damage or destroy them, thankfully I've had to remove several before on Sherwood and Pioneer receivers, so I've had practice. Even after those are all loose it doesn't have much slack to move, you have to create it. After that there just enough wiggle to turn the board to pull the switch out after you de-solder it. Funny enough taking apart the switch itself is the easiest part. One note though, be very sure you note exactly how it comes apart, you can put it together backwards.
Oh my word yes it does!! I had the same experience, I thought something was wrong with my Distortion analyser, I actually checked it as I could not believe what I was seeing.....Its an extraordinary tuner....easy to align.....I like the way the Zero adjust works on the tune meter, "move the stub".this thing has got a stupendous tuner and it's very easy to align, this one was a joy as it appears it's never been touched and it was very clean as well, so no sticky or intermittent coils. I was able to improve the sensitivity a bit and get the dial aligned back to normal. But the distortion. Let us talk about the distortion. HOLY FUDGEPICKLES. After fine tuning it as far as it would go, at 65dBf with a 1KHz tone, the distortion was .0162% THD+N. I didn't even know a tuner could get that low! Stereo separation was 50.57dB. Trying it out on actual stations, the selectivity and sensitivity is amazing, this is easily the best tuner I own. Can't wait to get the power amp done!
I have never found the Molex connectors to be much of an issue on the Sansui's but if I'm in there I often do it anyway.This is some really nice work. @mattsd, I was wondering if you are planning on flowing or re-flowing the molex connectors on the boards. I know the flat amp boards hang upside down on these things and can jiggle around when the unit is moved or jostled.
Very nice job Matt, she was a bit dirty inside right!! Hilarious THD!! Just a testament to the Sansui designers.....Power Supply Board (L-CH and R-CH) (F-2902 and F-2903)
The left and right power supply boards on this unit were a bit of a mess, a lot of dust and dirt along with glue issues. These boards aren't too difficult to access but it requires you to unplug all the connectors that can be unplugged and two more de-soldered to be able to flip the board over. These boards have a couple of unusual caps, C14 and C19 which are the local de-coupling/smoothing caps and are rated at 470uF 120v. Somewhat hard to find as the overall height of the cap cannot be more than 40mm. 45mm would put it uncomfortably close to the bottom panel. I was able to find some Nichicon 470uF 160v caps that worked perfectly.
For the other caps, I went with stock values, upping voltages here and there. For the left and right channel PS boards, C15, C20, C29 and C30 are 100uF 100v and were replaced with the same value. C17 and C22 which shunt ZD01 and ZD02 were 100uF 35v and were replaced with 100uF 50v. C18 and C23 are 3.3uF 100v and were replaced with the same value. C24 on the left channel is a 220uF 50v and was replaced with the same value. C24 on the right channel is a 1uF 50v and was replaced with a 1uF Wima film. C27 on both boards was a 100uF 6.3v bi-polar and was replaced with a 100uF 16v Nichicon EP bi-polar. I used a EP as it has a 105C temperature rating vs the 85C rating of the ES series. C31 is only on the left channel, it shunts ZD03 and is rated at 47uF 50v and was replaced with the same value. In addition, the right channel adds C11, C12 and C13. C11 and C12 are 100uF 25v and were replaced with the same value. C13 was a 470uF 10v and was replaced with a 470uF 16v.
There are 3 zener diodes per board, the left channel has three 24v diodes and the right channel has two 24v and one 6.2v. All were replaced with Vishay 2% tolerance zeners. The right channel also has a MV-12 diode that was replaced with two 1N4148 diodes in series. Both boards have 3 fuse resistors, R08, R16 and R44. R08 and 16 are 47 ohm 1/2w and were replaced with the same value metal film. R44 is a 4.7 ohm 1/4w and was replaced with the same value metal film. Several glue damaged resistors and a polystyrene cap were also replaced. All the fuses were also replaced with ceramic equivalents.
The filter caps are straight forward, pretty easy to do, though the space is a little cramped.
Two of the filter caps showed significant leakage, both look like the one below:
And after! I also cleaned the chassis, it looks much, much better than before.
Details on initial power up and impressions coming shortly! I will also be doing a full performance test, I recently got a new toy to help with that. (yes, that is .0003% distortion)
I have never found the Molex connectors to be much of an issue on the Sansui's but if I'm in there I often do it anyway.
This is some really nice work. @mattsd, I was wondering if you are planning on flowing or re-flowing the molex connectors on the boards. I know the flat amp boards hang upside down on these things and can jiggle around when the unit is moved or jostled.
Very nice job Matt, she was a bit dirty inside right!! Hilarious THD!! Just a testament to the Sansui designers.....
Off topic, have you found a place to get Pansonic service manuals for the line of gear like your THD analyser there? I have a Panasonic Multiplex generator of the same vintage, and although its functioning fine, I'd like to find a service manual.....