My first receiver restoration attempt: G-6700.

Enjoyed Steve's visit :)
Things of note---
His board work and soldering skills are outstanding
The 6700 needs about 20-30 minutes for the output transistor temps to stabilize. If they are adjusted cold they will rise to over limit levels once warm.
Although the relay contacts looked ok the change certainly helped the circuit energize without complaints.
Checked the amp for oscillation and saw no trace of such off the Inductor-resistor section of the amp.
Ran the amp pretty hard for a while (we had to stand outdoors) :D due to our delicate ears and it passed with flying colors.
In reference to the outputs, having Sankens on one channel and MJE's on the other did create an imbalance in the driver circuits +/- 20mv or so. Not enough to be audible and need balance adjustment to compensate.
All in all a productive morning.
-Lee
 
Awesome result guys.....great to see AK bringing people together......

Sounds a bit like my G7700 project.....I ended up going to a friends place who is also a tech and we worked it out between us.....its good having another person there, I find it quite helpful.....

Most importantly, good to see it running.....:thmbsp:
 
Steve stopped over last night. We listened to near 11:00, past my regular bedtime.

It was a very good visit. He is a great guy and a careful builder. I wish my kits were as nice looking as his work.
 
Grainger49 said:
I wish my kits were as nice looking as his work.
Click to expand...

Hah!!! The only reason he is saying that is because most of you have not seen his rig, or his listening room. Never thought I'd hear such a clean and sweet 3¼WPC, and he even let me sit in the center chair! I think that was the first time my hearing aids have been able to really perceive a sound stage, and locate instruments. A truly enlightening experience.

The G-6700 made it home today, after a 2,150 mile round trip. I'll give it a good listen and checkout on the bench before I replace the Sankens.
 
First, thanks for the kind words. Visitors always sit in the center seat, ask Fasterdamnit and BigBill.

ghazzer said:
. . . I'll give it a good listen and checkout on the bench before I replace the Sankens.
Click to expand...

Yes, by all means! Before touching it get some listening time in. Let it warm and you cool.
 
I removed the Sanken outputs and will replace them with NJEs after I test for gain and search for the best match in my meager supply.

The molex pins I modified for jumper pins need an additional mod. the ones in the pic are too long, and the height above the 2980 board would have made contact with the bottom cover (metal). I removed the upper clamp, bent the wire to 90° and spread out the fingers at the bottom. Does anyone have a source for replacement jumper pins?

New Jumpers & Pins B.JPG

I have plotted out the traces on the F-2583 board and now have a clue as to how these push button switches work. Just cannot figure out the rationale that Sansui used in assigning designators to the pins. I'll post some pics later.

Hope everyone has a gorgeous day for Easter - - -
 
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My first receiver, which I still have, is a G-4700. As far as I can tell, all is still well with it. I suspect it's time to get it into a local pro to get it cleaned up inside.

As Clint Eastwood said, "A man's gotta know his limitations," and I know mine. The best tool in my toolbox? My checkbook.

I hope your restoration turns out beautifully. They really are awesome receivers, even mine, the baby of the bunch, with the beveled glass, looks massive. I think this line of receivers serves as an interesting first step into the digital realm. I've still yet to see a receiver from that era that has the good looks these puppies have.

And while looks count for something, I've always felt that even at 50 wpc, my G-4700 plays nicely.
 
How ambitious are you? Couple of things I thought of after your visit. I have a spare switch in my parts bin you are welcome to if you want to pull the board and replace the offending critter. Come to think of it I may have a few original pins I would pull for you as well. Let me know (freebie).
For anyone perusing the thread later on yes Molex pins make a dandy fix for the original Sansui pins that attach the wires to the outputs to the main board as long as you do not replace the bottom cover :D
-Lee
 
I appreciate the offer - Thanks!

On the run to the National Zoo this morning. My wife wants to see the panda cub while it is still a cub.

Will post a pic of the 2583 tracks and pin layout later.
 
F-2853 bottom-04.jpg Here are the tracks, jumper numbers, switches and contact pin numbers. It is interesting to note that Sansui was not consistent in their conventions of numbering the contact pins of the switches. In any 3 pin set (a-0,a-1,a-2) the two closest to the front are connected when the button is out and the rear two are connected with the button in.

I also noted that the tuner section of the G-5700/6700 schematic in the SM shows the MODE and MUTING switches as P/O F-3055 board. I have not needed to use the front end schematic, but I am wondering if the 6700 & 7700 should be combined and the 5700 a separate page??????

Anyway, the switches on the 7700 page are not labeled correctly. Assuming that contacts for a,b,c&d are all on the same switch, the MODE switch is S02d and the MUTING switch is S02e.

I would appreciate any feedback if anyone else has taken a close look at this.
 
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Since you have the board out at this point I would disassemble the switch for inspection and cleaning. Beware all the tiny parts that will run and hide on you. Then verify continuity across the pins and then across the traces.
 
Ahaa!!! I was cheating. I scrounged the pic from an auction on fleabay.

I pulled the right ch F-3058 bd and removed the Sanken output TRs. Was gonna just replace them with another pair of NJW0302/0281s like I have in the left channel, but decided to look for another pair with a better gain match.

Now I have to replace the output TRs before I can check out the switch.

I gave it another shot of deoxit when I got home and then exercised the switch a couple hundred times.
 
As farbas the pins go you could also tin the wires and direct solder them to avoid interference with the bottom cover. Suspect there may be a mechanical issue with that switch. Only disassembly will find out if there are still continuity issues.
 
These pins will work OK, especially since I don't use many of them on a daily basis (haha). I cut off the upper clamps and bent the lower flaps out to 90°. You also have to consider the other side of the PCB to make sure that the pin does not extend far enough to interfere with anything else.

I will continue searching for a better option.
 
I re-checked my box of transistors and found that I have two pair of NJW1302/3281 with a better match of Hfe for the output transistors than the remaining NJW0302/0281s. Virtually identical specs but the 1302/3281 are rated at 200W vs 150W for the 0302/0281s. The original Sankens were rated at 100W.

Here are the Beta/Hfe of my stock:

NJW1302.. A) +98/558 . . . B) +92/550
NJW3281.. C) 108/499 . . . D) 119/489

NJW0302.. E) 103/566 . . . F) 132/507
NJW0281.. G) .88/553 . . . H) *99/548

(Punctuation marks used to line up the values)

My question now is will it make any difference which combo (A&C or A&D) to place together in a channel? It is probably no big deal, but since I have a choice I thought I'd try to do it the best way practical.
 
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