Sansui 210 Output Transistor Replacement - Step by Step

[americannigh]

Forgot to ask if the scratchy sound was in both channels or just one?

Right channel only. Thanks for the ideas here. Really appreciate it. If the problem surfaces again then I will do some prodding for cracked or bad joints. I'm leaning towards that now as well knowing that I've replaced all the transistors in the preamp/amp and resistor values check out OK. If it gets to the point where I suspect D002/3 then I would probably swap the diodes and see if the problem migrates to the other channel. Really hope it's not those diodes. There is an area on the board where, when the problem is happening, if I breath on it, then the scratching noise gets worse. I was thinking this meant it was a heat issue but the components in that area all check OK. Maybe the hot breath causes the joint to expand and thus exacerbate a bad joint. Anyway, when I do the caps and new outputs later this week, I'll reflow solder in that area just to be safe.

FYI - have replaced TR701/2 but not TR001.

 

[two.dogs]

Yes, right side. You mentioned that in several posts. So TR001, ZD001, or D002/3 are probably OK because those would affect both channels. You've got all new transistors on the right side, so that doesn't seem to be the problem either. So...

• Dirty pots or switches - Deoxit F5 on pots, D5 on switches
• bad solder joint - poke
• cracked/corroded resistor - poke
• Bad SV3 on the right side - hit it with freeze spray when you hear the crackle

I've got my Sanui 210 open on the bench now and will order parts tomorrow. Left channel barely works, right channel is a scratchy mess, and all light bulbs are shot. Voltages are good, so the power supply isn't shot. I'm thinking recap, and look for bad transistors. Sound familiar? Also an LED relamp.

 

[americannigh]

@two.dogs look forward to seeing your 210 come together. I tried doing LEDs but for the two main side lamps I wasn't satisfied with how they projected through the glass. Seemed really dim so used incandescent. You might order some incandescent lamps just in case, or maybe you have those on hand already. Just a suggestion.

 

[a95sonoma]

Hi first post here. I guess I'll introduce myself first. I,m currently restoring a Sansui 210, its the third classic receiver I've restored in the last year. Other receivers I have restored have included a Onkyo 2500 MK1 and a Sherwood S-7450cp. I have also built my own tube amps including a 12w6g, 6l6g, 6y6 and a GU50 SE amp. I joined this site years ago but have never posted, just used it occasionally for information.

Anyway back to the 210, I thought I should mention that I used NTE175s TO66ers still available at quite few places http://dilp.netcomponents.com/cgi-bin/nteinc.asp?partnumber1=NTE175. I got mine at Parts Express, (currently listed as out of stock until 3/23/2018) I think I got their last 4. They have worked fine.

I currently have one channel working perfectly, and the other works but has distortion in one channel that was there before I started working on the thing so its not the NTEs. Signal goes into R802 fine, but comes out distorted to its input of TR802. Going to shot gun all the components around that transistor next.

In the middle of working on this thing the tuner section went dead so besides replacing all the transistors in the amp I replaced the tuners also. I recapped the tuner and it worked OK, but then went dead soon after, hence leading me to replace the transistors thinking the news caps killed off a weak transistor. I now have the AM working fine, FM works also, but I need to tweak the alignment. I going to do this when I get a old FM sweep generator I bought restored.

If interested I can give a list of all the transistors I used, all are available and few quite common like 2N2222A's in the tuner.

 

[dlucy]

@a95sonoma sounds like a good start.

Many people have been burned or disappointed by parts from NTE since they relabel other manufacturers' parts and you can't tell which two are matching without careful testing. If yours works well, then you got a matching set (same internal part) and that's great.

 

[a95sonoma]

OK looks to me like TR301/302 are part of the AM section. That said looking at the schematic I don't see anything that would prevent noise from one of those transistors from being injected into the amp section even when AM is not the selected input. Transistor equivalents for 2SC930 look pretty slim picking but was able to find a source (not ebay) online just now. In a bit I'm going to do an experiment and try listening to some AM to see if that makes the problem come back. For now I'm enjoying music so I don't want to ruin a good time. Thanks everyone.

 

[a95sonoma]

I used 2sc1815's in mine for the these 2sc930's since its for the AM. I used 2n2222A in the FM section for those 2sc930's, since the bandwidth is higher. Just don't shotgun replace like I did, replace one and test. I did put one 2sc930 that measured ok back in position TR201 because FM was barely functioning at first, but while doing so I found a soldering error so I think the 2n2222A would have been OK in that position also, if I had soldered it correctly. Best not to solder after working the night shift you might miss a pin. I will probably try it again after I fix the amp section as the FM is working OK for right now.

Incidentally as the service manual for the 210 has no alignment procedure you can use the alignment procedure listed in the Sansui 200. The tuner section is the same design just slightly different component values in spots and different transistors. The RF coils and transformers are labeled different, so I just printed out both schematics and labeled the 210 schematic with the 200 designations, so I could follow along. Like I mention in my last post the AM is working fine FM is a little off, but I need to get my FM sweep generator recapped so it can get a proper alignment.

 

[two.dogs]

Thanks a95sonoma, those are the most helpful first 3 posts I've ever seen. And Americannigh, thanks for the tip on the dial lamps.

 

[americannigh]

Very helpful indeed. I have a bunch of 2N2222 transistors I got at a garage sale from an old man who used to have a TV repair business. It's a fun little box of goodies that comes in handy from time to time!

 

[americannigh]

OK AK friends, I feel really dumb right now. I just figured out that when my cell phone is close to the receiver then the static noise emits from the right channel. Actually it comes out of both channels but it's stronger on the right so more noticeable. It is definitely a shielding and RF interference issue going on here. I feel so dumb right now because I have also been using my cell phone flashlight when looking closely at the board and poking around trying to figure out what component might be responsible for the noise. I've been using it to look at schematics and all kinds of things while working on the receiver. This totally explains why the receiver works great for days and then all of a sudden the issue happens. Likely I had my cell phone in my shirt pocket or hand at those times. Also when I'm working on the receiver then the cover is off and my cell has been on the table right next to it. I also have one of those mini cell phone hot spots here in my office near the receiver to boost the cell signal because our coverage used to be so bad (my cell provider calls it a network extender) which could be to blame also during some times of the day if it's in use boosting signal. At this point I'm not too worried about needing to "fix" the problem so long as I know what's causing it and to keep these kinds of devices away from it. @two.dogs when you get yours hooked up, hold your cell really close to the volume and input selector knob and tell me if you get the same noise.

 

[americannigh]

Moreover, I have just figured out the cell close to the receiver does not cause the noise all the time, only if the phone has an active call on it or is doing certain things. If the flashlight is on, that seems to cause the noise especially bad. I incidentally discovered this because I was listening in dim light and went to hold the cell with the flashlight on near the input selector knob to see what I was doing. As soon as I turn off the flashlight the noise stops.

 

[a95sonoma]

Very helpful indeed. I have a bunch of 2N2222 transistors I got at a garage sale from an old man who used to have a TV repair business. It's a fun little box of goodies that comes in handy from time to time!

Watch the pinout, not all 2n2222s have the same pinout I used the 2n2222A.
https://en.wikipedia.org/wiki/2N2222

I also used MPS2222s in the driver stage after the tone controls, with 2n2907s for the PNPs. I used ksc1845s for the tone control transistors and preamp. Still need to figure why I still get the distortion that's been there since the beginning in the left channel. At least I got one properly functioning channel so I know its not my replacement transistors in theory. The left channel is now much stronger anyway so I made a gain there.

I bought this hoping it would be a easy recap, only to find out some body had been in there before, with some of worst soldering I've have seen. Good thing though was they replaced all fuse lights with leds and added a few Nichicon audio grade caps, before they gave up on it. Bad thing they killed a few circuit traces so this thing will win no prize when I'm done.

 

[two.dogs]

That's funny. I'm glad you got me to look at my 221 - its been on the to-do list for too long. I should be finishing my Onkyo 4500 in the next day or two and should have the 221 parts in by then. I'll take pics and if its an interesting repair I'll open a thread.

 

[americannigh]

Now I'll need to decide whether to put the 2SD315 outputs back in or install the KSD1408YTU I ordered. I am leaning towards using the KSD1408YTU for two reasons. I think a modern transistor "should" be better, especially given I don't know what kind of mileage and abuse the original 2SD315s have been subject to. Would like this receiver to be rock solid once I'm done with it. I also have already moved the two diodes and bent the clips for them to fit so it would be quicker for me to just trade out the TO-220 with another TO-220 transistor at this point. If there's something magical about those 2SD315s though please anyone feel free to chime in.

 

[dlucy]

I think the trailing TU on your KSD1408YTU part number is just Mouser's packaging format of a KSD1408 or KSD1408Y. Your posts are very valuable and if the TU is just a packaging suffix then leaving it off in your posts will help future AK searchers (like me) find your post when looking just for the model number.

 

[dlucy]

Now I'll need to decide whether to put the 2SD315 outputs back in or install the KSD1408YTU I ordered. I am leaning towards using the KSD1408YTU for two reasons. I think a modern transistor "should" be better, especially given I don't know what kind of mileage and abuse the original 2SD315s have been subject to.

. . .

If there's something magical about those 2SD315s though please anyone feel free to chime in.

This is interesting to me and if you've got time for me to look it up, I'll share what I find after work.

There is definitely a higher fT question to answer, but I'll look for that in particular.

 

[kevzep]

Now I'll need to decide whether to put the 2SD315 outputs back in or install the KSD1408YTU I ordered. I am leaning towards using the KSD1408YTU for two reasons. I think a modern transistor "should" be better, especially given I don't know what kind of mileage and abuse the original 2SD315s have been subject to. Would like this receiver to be rock solid once I'm done with it. I also have already moved the two diodes and bent the clips for them to fit so it would be quicker for me to just trade out the TO-220 with another TO-220 transistor at this point. If there's something magical about those 2SD315s though please anyone feel free to chime in.

Nah, 86 those old transistors....Output transistors have little influence on the character of an amplifier.
Put the new ones in, set the bias and call it done.
Those KSD are pretty much exactly the same specs as the originals.
Modern transistor manufacturing is far superior than what was achievable back in the day....

 

[americannigh]

Nah, 86 those old transistors....Output transistors have little influence on the character of an amplifier.
Put the new ones in, set the bias and call it done.

Speaking of bias, I don't see anything in the service manual about setting the bias specifically. I have been adjusting two variable resistors making sure there is 21V across C817/818 and calling it good. Is there anything else you'd recommend?

 

[dlucy]

Those KSD are pretty much exactly the same specs as the originals.

Yep. The specs are nearly identical. The only way to judge better would be to run both through a curve tracer or compare graphs from the datasheets.

 

[americannigh]

Yep, Doug. I was leaning heavily towards using the KSD transistors and what you and @kevzep said pretty much confirms that. Genuinely excited to get the Mouser order on Friday and then dedicate some quiet time Sat afternoon to doing the recap and KSD transistors in the outputs. Hopefully all goes well and then I'll be enjoying a cold one and some music on the Sansui 210 Saturday night. I'll hold on to the 2SD315 originals for just in case.