Sansui 400 receiver,,,

[knockbill]

Picked this up at the antique radio show this weekend,,, It supposed to have good FM MPX,,, but weak output equally from both channels... Haven't tried it yet,, but seems to have 20W /8R output which is similar to my Sansui 800... will have to look for the service manual and schematic for this guy...
Pic is as found,,,

 

[knockbill]

I had to try the 400 before I quit for the day,,, its exactly as the note said, strong FM reception and weak output.. Its audible on the Right side,, just barely some sound on the left...
An AKer just sent me the service manual... Seems my hifiengine account timed out and they aren't taking new members...
Here's some inside as found pics...

 

[knockbill]

Not much interest in this one,, so I'll use this thread as repair log... So far I cleaned the selector switch, and replaced a couple PS caps to move some wires for access to TRM-7A (pre driver board)... Brought it up again, and find the R channel seems to work fine,, no output on the L tho... FM comes in very strong, and plays clear on the good channel... Next step is tracing the L channel to find the fault... I'm thinking the outputs were changed for a reason, but its possible if they failed on the L side, the drivers and others parts may be damaged... I'd like to remove the board to work on it, but the wires are brittle so may end up rebuilding it in place..
Found the original 2SC244 outputs have been replaced with 2N5038 OnSemi which seem to be overkill for this guy,,, I have a few sets of vintage RCA 2N3055s that may match up better...
An AKer sent me a copy of the service manual, but its too big to load here...
Any more info on this receiver is welcome!!

 

[knockbill]

Tracing the signal back on the L side and got to a 2SC536 transistor,, when I touched teh lead of it crumbled,,, all three leads were corroded, I was able to remove teh stubs from the holes.. but I need to find replacements,,,

 

[knockbill]

I swapped the damaged 2SC536 transistor with a 2N2222 that I had on hand,,, not sure if it helped, as its on the L channel which isn't working yet,,, I also pulled the new OnSemi 2N5038 outputs and measured them.. Read the 3rd one twice got same reading... They didn't have any grease on the new outputs,,, I cleaned and greased each one,,, but #3 dont read like the others!!! TR803,4 are the Right channel but that's the one that works! Signal seems to go thru the tone stack, but not the next transistor
Readings of outputs...

 

[Hyperion]

I'll be reading along on this one, good work so far, I wonder if there are other 2SC536 which are faulty? 2N2222 is ok as a temporary replacement, but power-wise I think it is overkill, I am thinking 2N3904 might be a better replacement?

 

[knockbill]

Thanks for replying,,, I been dancing with myself here!!! I also appreciate the input as I'm much more comfortable with tubes!!!
So far 2 of the 2SC536 leads broke by just putting a probe on them,,, IIRC the next one towards the output is a 2SC536. so if I cant get a signal thru it, I'll replace it... I only have 3 2n2222 of the same make, but I guess other can sub in also for testing...
2N3904 did pop up as a better sub, but I only had 2N3906s,,, Guess its OK to use American transistors as long as I watch the pin outs??? I mentioned the OnSemi outputs in here are really overkill, and one reads a bit off from the others,,, I have two sets of 2N3055s that I'll swap in after I make sure the amp runs OK,,,

 

[knockbill]

Swapped in the next 2N2222 on the bad channel, and get signal thru that point,,, but not thru the next trans (2SC538), which I don't have, and can't find a sub for... Then 2SC281 is the last one before the outputs,,, 2SB89A looks like the complementary one for the working channel...

 

[knockbill]

Got it!! Replaced the 2SC538 with a 2N2222,, and its playing well, no noise, hum hissing just clean music..
Now to bias, recap, and get proper subs for it,,,

 

[knockbill]

Well,, since I got it running, i've been searching for some caps to freshen up the PS and transistors to match channels, and get rid of the "works OK " ones I put in the bad channel,,, I replaced 7 of 9 of the big PS caps, some I had and got 4 more today from a buddy that had em... Need two more, to finsh the PS... I used two 2N2222s to replace the bad 2SC536s and one 2SC538 on the Left channel.. Trying to get it running good with common general purpose parts,,, and thinking of using 2N3904s for the 536s and 2N2222 for the 538s,, to keep overkill at a minimum,,, These little Sansui amps really sound way better than they have a right too,,, This one sounds very similar to the Sansui 800 I got in 1969,,, and recapped 10 or so years ago...
Problem is I can get a couple caps and 3904s from Digi, but they dont have any 2222s!!! I Also want to replace the bad fuse lamps for the dial,, and Digi doesnt have them either!!! I found these few parts on 4-5 different sites,, but shipping is way more than the couple parts they each have!!! I'm relativley new at vintage SS repair,,, but I just can't believe the that vintage tube stuff is so much easier to find/buy from parts houses!!! Ebay/amazon junk just scares me!!!!!
Rant over!!!!!

 

[knockbill]

Waiting for the rest of the PS caps and amp board transistors to arrive from Digi,,, I got FM to tune a lot of stations, and play pretty clear... MPX is the next step,,, I noticed the FM stereo lamp glows as the receiver is first turned on,, and goes on and off as stations are selected... I can also hear stereo seperation thru headphones... However, it only stays in stereo mode and lamp lighted for a few seconds,,, I think there is a part going out of value/overheating as it comes up to operating temp...
Heres a pic of the FM board,,, MPX board, and stereo indicator board,,, if anyone want to take a shot at the problem,,,
TIA

 

[knockbill]

Been working on the 400 all morning,, and found a discrepancy in a couple transistors on the MPX and stereo indicator boards...
FM board,,, TR405 should read E 1.3v, C 8v,,, reads .14 and 4.90v respectively
Stereo Indicator board,,, TR503 Should read E 2.25, C 21v reads 19.86 and, .26v... Values are off the manual schematic... This can't be good,,, TR405 is a common 2SC536, subs are coming coming in the Digi order...
I'll check resistors and caps in the circuits,,,

 

[knockbill]

Are film caps a good replacement for Suzuki oil caps?? .02/250V,,, .01/400V

 

[Lavane]

 

[knockbill]

Thanks again!!!

 

[Lavane]

Are film caps a good replacement for Suzuki oil caps?? .02/250V,,, .01/400V

Any luck with the .02uf caps John? With film caps, it's fine to go up in voltage ratings.
I've used 300v to 400v film caps where 100v would do.

 

[knockbill]

I only have tube stuff in stock,,, so I have .022/630V a bit overkill !!!!

 

[knockbill]

Got the PS/coupling caps and some 2N3904s from Digi, and replaced some 536s, 458s, 693s... These are useful little buggers!!
Waiting for teh 2N1815 and 2N1845s to arrive... In the meantime, I researched and fixed the meter circuit for AM,, seems a 1N60 diode was bad, and I found a couple in a scrapped 60s Philco tube radio! Also worked on the FM/stereo indicator circuit and found a bad 2SB54 transistor... A replacement is on its way... Been scrubbing the PCBs with 99% alcohol as I go,, they were pretty crumby when I got it!!!
Measuring and replacing small caps as necessary til the parts arrive...
Thanks to Lavane for all his help/info so far!!! This old Sui may sing again!!!

 

[knockbill]

Still waiting on parts from Digi,,, Found another diode (1S180) with a broken lead yesterday,, must have just happened as it's in the bias ckt,,, I had some 1N4148 so I replaced all four,, bias seems hold well, so another problem fixed...

 

[GrisPato]

Wrong place, sorry