Pioneer SA 520 transistors replacements

[Tektronik]

Hi

What replacement will be the best for :

2SD883A and 2SB773A ? , i think about 2SA1943 and 2SC5200

I am very particular about good sound

I'm also looking for replacement for:

2SC1384

2SC1735

2SA850


Photos of damaged transistors :

Im not sure about this one, they are lukewarm, but not hot

Sorry for my bad english

 

[orange]

Same as SA-6500 II and SX-3600 IIRC

 

[orange]

jbeckva rebuilt mine with different semis...let me find that thread real quick.

 

[orange]

http://forums.phxaudiotape.com/show...hums-The-Electric-Company-vs-Sound-Of-Silence

 

[Tektronik]

What are you think about BC 639 and BC 640 instead 2SC 1735 and 2SA 850 ?

 

[orange]

Lukewarm is not bad. You have to check them individually, but heat is normal. In the case of chip amps (STK ---- and the like) high heat is normal in many cases. If you can find the spec sheets online you will have a better idea of what the range of operating temperatures should be.

 

[Tektronik]

They are hot:

TA7318P , 2SC1384 (Q23) (very hot, burns finger) , resistor R98B 820Ohm (very hot, burns finger), 2SC1384 (Q22)

VFD display seems has poor brightness , shines more like a dark green, not blue, but on pictures looks like blue

Ok, i managed to capture this:

 

[orange]

Just replacing transistors and diodes isn't going to solve that, and the cover is vented on the top and sides for a reason. You've likely got another problem to solve as well.

Do you have the service manuals? Elektrotanya.com has all the ones you should need, you can get two a day without membership but there is a short electronics quiz you can take to get a membership that even I aced.

You want the ~4196 kb ZIP file and the SA-420 520 620 720 circuit description file.

Once you get past the part that is in a foreign language (use the SM kereső / finder section) enter the brand and model. http://elektrotanya.com/?q=keres

Or as I have pasted for you: http://elektrotanya.com/?q=showresult&what=Pioneer SA-520&kategoria=&kat2=all

Also the color of the display is correct. Pioneer started moving toward greens about 1981 when your integrated was built. The actual display is white and a filter is placed over it, something that is common, especially with 'multicolored' displays.

 

[Tektronik]

Thanks for manuals

I think is TA7318P is damaged, what causes uptake high current and and heat:

Overheated PCB

I thnk its strange it glows green, yet this blue series not green

 

[orange]

It's a really light film, perhaps it has oxidized some over time.

Just feel glad that your favorite Pioneer digital tuner wasn't TX-950...it looks to have been built for them by Yamaha and the preset buttons are a really bad design, they break too easily and are L shaped fingers that press down on a round microswitch at a 90 degree angle. The board is white with green printing. Pioneer PCBs tended to be brown with lighter green printing, and Pioneer favored wire wrapping over terminals for board connections.

And the Communication series of 1981 seems to be partly Hitachi's fault...Hitachi made OEM for RCA and others as well. The CT-x(R) cassette decks are built with daughterboards, practically all the ICs were theirs and the drives can be nightmares. I had a 1980ish Sanyo with most of the features except for analog meters and it needed ONE PCB, used it for just over 20 years with one head replacement.

 

[Tektronik]

I fell that something is wrong with the display circuit

I understand, that listet elements can may heat up, but so hard that it burn fingers, when i touch them ?

 

[orange]

The display is a vacuum fluorescent tube display, so there are probably much higher voltages involved than for LEDs. If it is still bright then that shouldn't be the true problem, it could be the display drivers. For SOME insight you could study the 'NIXIE' display tube, or eye tubes, which are somewhat simpler than VF displays.

 

[Tektronik]

Could you please check in your pioneer, whether R98B resistor, Q23 transistor and TA7318P is hot ?

 

[orange]

I don't have heat problems with mine, and you'd want to consult the thread I linked for you as I've also forgotten what Jerry repaired and substituted without looking it over thoroughly.

Of course, I don't have a matching tuner for it and tend to use it for a second (rear) amp with a surround processor or to check out other components.

So what I'm gathering is that you've overheated a part and the either something else if bad behind it in the circuit and caused a voltage spike or continuous overvoltage or the part itself is bad and letting current flow without resistance? R98B perhaps?

And hey, I'm learning with you here...somebody chime in and add some dialogue please.

And look at this please...

​

 

[Tektronik]

Yes, its scorched

Bottom side:

I check with multimeter R98B and its ok. Q23 its also ok

When i desolder Q23 , R98B is still burn fingers 0_0

I wonder what pulls so much current , when i desolder TA7318P , R98B is still burn fingers

Elements on the display board are okay

 

[orange]

That transistor's joints look like they were deep fried, or is that what you unsoldered? Well, I think you've probably found the end of the bullwhip...let's see, is that the Base, Collector or Emitter that the 820 ohm resistor is connected to (to the left, underneath to the RIGHT of the transistor)?

 

[Tektronik]

That transistor's joints look like they were deep fried, or is that what you unsoldered?

Yes

is that the Base, Collector or Emitter that the 820 ohm resistor is connected to ?

Collector is connected to resistor, but it has no impact to heat up the R98B