Greenhorn-Did I find the problem transistor?

Yankee Dog

Well-Known Member
Posted earlier about a freebie Nikko NR-1015 a coworker gave me. Problem is no am or fm. Unit powers up, everything else works (aux, and phono). Does not go into protection mode. Just no AM or FM. Did a little checking here and there, found a few broken/cold solder joints, but, never got fm/am to work. Reason it died: "Spilled the bong water in it". :D

Took out a "suspect transistor" on regulator/protector board (at Q801) and tested it per instructions here. All appears fine. The reason I say suspect is the transistor looks to be replaced before. The transistor is a 2sd613 (actual number on transistor is d613). Data is at this link

:http://www.datasheetcatalog.com/datasheets_pdf/2/S/D/6/2SD613.shtml

Anyways, service manual shows up today and it lists a 2sd381 to be used (again at Q801). Data can be read here:

http://www.datasheetcatalog.com/datasheets_pdf/2/S/D/3/2SD381.shtml

So, my question is, did I find the problem? Or at least one step closer? All the other transistors on the board appear to be original and match up to the manual.

Sorry, I am new at this, and looking at the values, it appears it is not a very good match, but I confess, I don't know what the values mean all that well. Just comparing these values, I am hoping it is the wrong component and might be the reason the tuner section is not working? The receiver behaved exactly the same with or without the transistor (q801) in place when powered up.

This is tuner that I decided to throw a few things at it to see if I can get it to live, but, not spend a ton of $$ on. To many things going on, but on the same note, if I can get it up and running with minimal pain, then all the better.

BTW, I believe a suitable replacement for the original 2sd381 would be a MJE15030 (also found by searching on this site). Thanks for your time/effort, and again, sorry, I am new at this, but learning. YD
 
It's a reasonable enough substitution....

What would help more is to measure the voltages on the leads when the unit is turned on (and the transistor installed).

Of course a schematic diagram of it would be a great help....
 
Markthefixer, thanks for you interest. Here is what I have come up with.

With unit turned on, the voltage I have at the suspected replacement d613 is: base 1.5, coll 51, emitt 0.5

On the other NPN that is probably original (2sd381) the values are: base 31, coll 52, emitt 30

And on the PNP 2sb536 it is base -32, coll -53, emitt -32.

So what it all means? As far as I can tell, no voltage (slight trace less than 1 volt) is getting to the tuner board. I just did not wnt to go poking around to much.

Thanks again, YD
 
Not sure what to do next at this point, I ordered replacement transistors MJE15030G, and MJE15031G from allied electronics. Going to replace all three of them on the regulator board.

I am suspicious of the one replacement transistor (D613), but am going to replace the set of 3 (the two NPN, one PNP) and go from there. YD
 
Markthefixer, thanks for you interest. Here is what I have come up with.

With unit turned on, the voltage I have at the suspected replacement d613 is: base 1.5, coll 51, emitt 0.5

On the other NPN that is probably original (2sd381) the values are: base 31, coll 52, emitt 30

And on the PNP 2sb536 it is base -32, coll -53, emitt -32.

So what it all means? As far as I can tell, no voltage (slight trace less than 1 volt) is getting to the tuner board. I just did not wnt to go poking around to much.

Thanks again, YD

Sorry I didn't post earlier.

All three transistors appear to be operating correctly, but the garbage-in - garbage-out principle is in operation... The base voltage on d613 is very low. Without a schematic I can't tell why, as I have nothing to go on. Somehow the base voltage is supposed to be a lot higher, but without a schematic, (or the actual unit to trace the circuit) I have no idea what they intended the voltage to be or how they got the voltage there.

Normally the base will be about about 0.6 v higher in voltage value than the emitter, as you can see on the 2sd381 and the 2sb536. So the emitter voltage of about 0.5v is reasonable with a base voltage of 1.5 and a collector voltage greater than... say... 5v .... so 51v is sufficient...
 
OK, thanks again. Let me figure out how to post a pic or possibly a .pdf file and we can go from there. I assume you want the regulator/protector board and the tuner board schematic?

I will also try and post the entire schematic, but it is pretty small even in the factory Nikko manual. I need a magnifying glass to read it with my 45 year old eyes. Thanks, YD
 
Yankee, I suggested 2 weeks ago that you probably have a regulated power supply problem that operates the tuner board. Did you verify if the 12 volts is present? I think you are barking up the wrong tree just changing transistors that "look bad" The regulator will have an unregulated voltage that is higher on the collector the regulated 12-15 volts will be on the emitter. A wire will cary that voltage to the tuner board.
 
Grateful, yes, I'm beginning to realize that I am "barking up the wrong tree". I just can't seem to find any "magic" wire that carries any voltage to the tuner board. Or any "readable voltage" on the tuner board. I have found wires that go from the selector switch (aux, phono, fm, am) to the tuner board, and have found a few that go directly to the tuner board, but can not really make any sense out of them.

In my extremely limited experience, the only thing I can come up with is the tuner board is powered from the selector switch. I just don't want to go poking around without a purpose and screw something else up or making things worse.

Yes, you did offer that suggestion, and I tried without any luck. I am sure it was/is beginner error. I was hoping the manual would provide me with a clue, but I don't think I am any closer.

This is not my cup of tea. I can rebuild just about any type of gas or diesel engine, I know the anatomy and physiology of the human body (it's my job to know), and I can build a house start to finish from ground up, but this stuff is all new to me. Sort of frustrating, it seems worse than learning a new language.

I have uploaded some scans of the schematics here:

http://www.flickr.com/photos/19588762@N07/

Hopefully the above link will allow access for viewing. As soon as I am done posting this reply, I will check to make sure they can be viewed by "anyone".

They are rather large files and seem to load clearly enough to be readable. I am listing the receiver name and model again so that someone who may be searching will find this and hopefully will be able to copy the files if they need them. I will probably end up scanning and posting the entire Nikko NR-1015 manual this evening and placing in the same location.

EDIT: It appears the schematics can be viewed by anyone using the above link. The schematics show up the best when you view in "original size".

Thank you again, YD
 
Try q801 emitter that is the 13.2volt supply if you look at the schematic you will see that lead is connected to a post. I suspect the tuner b+ wire connects to that post. That post should measure 13.2 volts with the neg lead of your meter attached to ground. Take that measurement and report back you finding. Q801 is on the regulator board it is a 2sd381.
 
Q801 is the transistor in question (see earlier mention of the d613, I think post #1 mentions Q801).

It calls for a 2sd381 and somewhere along the line it was replaced with a d613. I removed it, tested it with my meter per instructions found here and it checked out ok.

I also listed the voltage of q801 found in post #3 but I just checked Q801 again. Same thing. 0.5 volts at the emitter and if I hold the meter on there long enough, it slowly drops it's voltage down to 0.1 ****************

BUT WAIT!!!! I HAVE MUSIC FROM FM AND AM!!!!!!

I have the receiver upside down looking at the bottom view of the regulator circuit board, and I measured the voltages like before, and got the same values as before on Q801. Then I started looking for a wire wound post that might have the elusive 13.8 voltage, started checking the posts with the meter, and started to follow the trace from emitter, checking at various points and all of a sudden I start seeing 13.2 volts on a post that previously had the the low voltage like on the emitter (white wire with red line). Hhmm, thats new! Have not read 13.2 volts before!

So I connected some speakers and I had static (never had that before). So I connected a dipole and I have music. I have stereo on FM and also receiving a good signal on AM. It is playing right now in the basement. Still upside down, as I don't want to move it!

So I am thinking a bad solder joint? Somewhere in the area that I was monkeying around probably. I checked all the posts on the regulator board, and followed the trace from emitter back a little and that is when I started to get the 13.2 volts.

So happy that it is working, but not sure what the heck I did to get it to work! What to do next is probably to go over all solder joints, and probably not a bad idea to solder the wires onto the posts as well as the posts. I am open to any and all suggestions.

I can't thank you guys enough, while I don't feel like I am out of the woods yet, I am further than I as before! YD
 
Grateful, thanks, I am grateful as well. (sorry couldn't resist). The poking around with the meter was at q801 base, emitt, and col. Then I moved over to c801 and c802, then I checked the pins 24,25,26,27,28. I also checked pins 21,22,23. I even checked r801, and a few of the solder joints from the jumpers in the area between c801 and pin 24.

Anyways, I am gonna touch them all in that area with a little solder and the iron. It is currently sitting in it's normal upright positon, and still playing nicely (knock on wood). YD
 
Well, after touching up the solder joints, I put the receiver on the bookcase, turned it back on and after about 10 minutes Capacitor C-803 gave up the magic smoke (it ran flawlessly for about 2 hours prior to touching up the solder joints). It split at the bottom press flange.

It started to "tick" kind of like the way an oven or stove sounds when first warming up and starting to heat up. I heard the ticking or clicking, started to investigate and as soon as I got my face near the board, poof! it let out the smoke and the brownish liquid. Again this was after running for about 10 minutes after solder joint touch up.

I had another cap (100uf 35volt), and replaced it. I ran the receiver after that for about an hour. I continued to check that replacement cap for heat (with my finger) while running for that hour. It did not get warm and seems to be running OK. I will run it again this eve for a few hours to see how it goes.

Question is, was this the bad component originally and my touching of the board made it work temporarily only later to give up the smoke? Or just happened to be the result of sitting idle for years and now suddenly put back into service? Or something else is still going on?

That was my last spare 100uf 35 volt cap, so we will know soon enough.

Otherwise, the unit sounds nice. Still fiddling with the functions, and the tuner indicator is off a little (the difference gets worse the further up the dial I go), but I can live with that for now. YD
 
Just got home and checked voltage at c803. Looks like -48 volts at the neg terminal of the cap. If I am reading the schematic correctly, it should be about -30.8 volts? Thanks YD
 
Yes there is something else wrong check the other 2 regulated supplies. Possibly a shorted transistor
 
OK, just checked voltages:

Q805: e-48, b-34.4, c-48

Q802: e 30.6, b 31.2, c 52

Q801: e 13.6, b 13.1, c 33

Thanks, YD
 
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