Restoring Sansui 1000a Tube Receiver

I acquired this unit from local Craig's list seller. This unit is  in clean shape for it's age. It still has most of original tubes except 2 driver tubes on both channels. Unit was DEAD silent but all of tube heaters are glowing red when it was turned on.
As you can see on the schematic, Sansui 1000a uses tube circuitry except Phono and Mic equalizer section which uses 2 BJT transistor circuit. It is push pull design with 50w /ch power. I was surprised with huge transformers and output  transformers. Unit weighs around 50 lb!! for 100 w total power.

After inspection and diagnosis of unit, I found it has blown 1 ohm 5W resister/current limiter on 470v rectifier circuit. Rectifier diode was shorted. ...When diodes go bad, they became shorted and burning things around it. It is good idea to put current limiter or fuse to prevent disaster..ie ..blowing expensive power transformer.
I temporally patched unit with 0.2ohm resistor with 600v diode and put it on Variac to see if it has life. Amazingly, unit is singing again without FM stereo. I found FM MPX decoder section of one tube is stone cold. I replaced with new 12AU7 tube. Now FM stereo is working, but stereo indicator is constantly lit brightly. I looked and poke around MPX circuit with no resolution.  Last night I played receiver for 30 min and start to " feel the tubes" by touching it. I found some one accidentally switched 2 tubes in MPX section. I switched them back as should. Now stereo indicator is working perfectly when I tune the station.

At this point functionality of Sansui 1000a is perfect condition. I still need to replace all electrolytic caps and all Suzuki  Paper in oil capacitor to polypropylene caps. And replace temporary patches ( 1 ohm and diodes) to permanent parts. Units volume and tone & balance control pots been cleaned with some kind oil by previous owner. You do not want to use oils on volume pots because it can be mixed with dust and become dust paste. This will kill the volume like putting polishing compounds.  Before order the parts, I need to clean volumes to see if I need to replace with new ones.  Finding replacement parts for volume and tone control potentiometers will be real challenge. We will find out tonight if I need new ones.
Here are the issues with my Sansui 1000a
 1) Blown 1 Ohm current sensing Resistor at 470v supply
 2) Shorted Diode @ 470v supply
 3) Dirty Volumes
 4) Burnt bulbs- LED mod comming
 5) Electorlytic capacitors need to be replaced
 6) Suzuki paper in oil capacitors may need to replaced with Orange Drop caps??
 7) Modifying tuner heater circuit to turn on & off tuner section as needed to save tubes
 8) Clean  & polish ??
 9) Distortion on left channel at high volume levels
Sound of unit is so mellow, I listen to it hours and hours past few days without much progress on To Do List.
1/20/11
Last night, I cleaned volumes with Radio Shack electronic cleaner to clean out oils. Every dials improved and almost all of scratch sounds gone. But I found Distortion one left channel at high volume levels. I did not noticed because I have not cranked volume up until last night. I fiddle with some new tubes and not much resolution to the problem. I replace them with Slovakian J J tubes.  Sound improved but I still need to listen more and hook-up the function generator and scope to see any distortion on  wave forms at near clipping. I also manage to realign tuner section with my new  Panasonic RF generator. Panasonic RF generator is much better than Wavetech 3001 RF generator which I will be selling on the Ebay very soon.  According to the service manual, Sansui 1000a has very odd input arrangements. It has " complete phono section with 2 level input types" , Mic input (Karaoke in 1960's?) , Tape head input ( Do not confuse with tape or cd input) with very low input level,  Aux1 with mid level input like ceramic cartridges and Aux2 with 160mv level which is still too sensitive for modern  day CD or Tape player (3V). Aux2 is 100k ohm paralleled to Aux1 input. I need to change that to variable resistor (VR) or some thing.
1/24/11
I worked over the weekend to replace most Electrolytic caps and all rectifier diodes to modern high speed silicone with higher voltage  tolerance. I replaced most "lytic caps" with on hand Nichicons and Panasonic modern equivalent with higher voltage ratings. Some versions of Sansui 1000a  has different cap values on the  schematic. I adjusted some values of Lytic caps based on different versions of Sansui 1000a. ...ie   30uf 12v was replaced with slightly higher modern  values..ie.. 33uf 50v ( because newer version of Sansui 1000a calls for 50uf 16v etc). I ordered all coupling caps and paper oil cap replacements from Digikey with some thermistor to limit inrush currents when unit is turned on.  I am contemplating to turn heater filaments of tuner and MPX section on and off by putting relay on selector switch to conserve tubes while it is not in use. I am working on LED light mod on all of display light.
1/25/11
Here are the pictures of after replacing all the oil caps and electrolytic caps from Sansui 1000a.

This is MPX section with new polypropylene and electrolytic cap installed.

I replaced all oil caps with Panasonic  polypropylene caps with 650v to 1.2kv  rating. It was lot of work. I brought unit back up to full voltage with Variac and every thing was working. Balance and Bass control knobs responding normally and FM reception is much better than before recaping. I noticed all high volume distortion with even old o/p tube is gone. I played amp for couple hours listening FM stations. To night I will hook it up to my function generator and Oscope to see any premature wave distortions in TTL, sign and saw tooth wave forms.  4 big can caps are still working strong but I will disconnect them to test out. I am thinking about replacing 2 singles with modern equivalents and stuffing 2 multi sectional caps because multisectional replacements are old stocks ready to fail or inferior in quality against single quality caps.
Things Finished so far
1) Replaced Power supply diodes and 1 ohm resistor with thermistor to limit inrush current.
2) Replaced All oil caps and electrolytic caps on Tuner, MPX, Amp section excluding large can caps and left channel phono equalizer ( ran out of parts)
3) Cleaned all control knobs
Things plan to do more
1) Finish phono EQ section re caping
2) test out all Germanium diods in tuner section and MPX if any of it is bad I will replace all of them with modern silicon RF diods.
3)Test Caned Caps and replace if any of them are bad
4)LED mod on lights
5) Put relay or on-off switch on tuner and MPX section heater circuit to save tubes when they are not in use.
6) Update bias circuit to newer version of 4 independent controls.
2/1/11
Things did not progressed as scheduled because I have been just listening this receiver for hours and hours without doing any thing. I am listening to internet radio through my SqueezeBox Touch.. Sansui 1000a has very mellow and deep sound that I did not get from my Adcom GFA5800 or  Rotel 1080 amps. This is keeper for sure.
I managed to finish LED mod which brighten the whole unit up. All germanium diodes are good at this point. Mouser has germanium replacement diodes in case I need them. I ordered parts for 4 pot bias mod and to finish eq section capping. I will listen some more before I decide to stuff the can multi sectionals. I decide not to put relay on MPX and tuner section.
I got lazy to update ...
I did 4 pot bias mod for output tubes. This will give me to use any none matching tubes because I can control bias current for each tube.  Meantime, I replaced all lytic caps in eq section to. I used  Nichicon Muse caps. For power supply, I went much bigger higher  and stuffed for the multisectionals. To open multisectionals, I used pipe cutter to cut at the end of can.
I just picked up Scott 340b tube receiver.
9/20/2011
I got busy playing golf. Sorry for not updating . I just pick up golf simulator for my basement. I will be busy tinkering and building for little while. I will get back to Sansui 1000a when I finish it. I moved everything from man cave to remodel it to golf sim/ electronic/ home theater/ wood working area. Wood working area is already set and self contained. But Golf simulator, electronic bench and home theater will get big make over. I will finally build well deserved amp rack to display my proud possessions. I think Pic is coming soon..