Different pinouts for the same transistor

[62vauxhall]

In looking to replace 2SA850 / 2SC1735 pairs, I discovered something that was a bit confusing. I found only a single online 2SA850 data sheet and that indicated a B-C-E pinout. But, the component testing device I used displayed a B-E-C pinout.

I posed the question to Google and Google AI provided this bit of info:

The 2SA850 is a classic Silicon PNP epitaxial transistor housed in a TO-92 (or elongated TO-92L) package
, commonly manufactured by brands like Mitsubishi and Toshiba

When looking directly at the flat side of the transistor with the leads pointing downwards, the pinout order from left to right is B - C - E (Base, Collector, Emitter), though some historic circuit schematics note a B - E - C physical circuit configuration depending on the exact variant or regional manufacturing standard.

 

[Bradbrews]

Measure the old ones and the new ones and just put the proper legs in the right place. Why sweat what AI or an old data sheet says?

 

[gadget73]

Is there a suffix by chance? I've run into that a couple times before where different suffix letters indicated a different pinout rather than just an HFE range difference or whatever.

 

[62vauxhall]

Is there a suffix by chance? I've run into that a couple times before where different suffix letters indicated a different pinout rather than just an HFE range difference or whatever.

The graphics on the transistors themselves are too faint to be legible. The entry on the KA3500 parts list is:



This is what came up when I searched using the term "2SA850 data sheet".

 

[painttoad]

The graphics on the transistors themselves are too faint to be legible. The entry on the KA3500 parts list is:

View attachment 3841044

This is what came up when I searched using the term "2SA850 data sheet".


View attachment 3841046

the pcb is silkscreened properly on the ka3500.

 

[62vauxhall]

Thanks. If that line diagram is in the service manual available on HFE, I overlooked it.

I did see however, the silkscreened diagram on the PC board but was uncertain of how to interpret it.



I am about to create another thread with a question about R49 just below Q20.

 

[painttoad]

If that line diagram is in the service manual available on HFE, I overlooked it.

that is not in the sm. i had to scour the web for it a few years back.

i came up with a saying to help me remember:

'thru the base, to the emitter.'

q20 needs replaced as well.

r49 is a 2watt 4.7 ohm metal film. it's part of the snubber network that keeps the amp from oscillating.

what's your question?

 

[kwayde]

I did see however, the silkscreened diagram on the PC board but was uncertain of how to interpret it.

View attachment 3841241

I am about to create another thread with a question about R49 just below Q20.

Here you go.

 

[62vauxhall]

that is not in the sm. i had to scour the web for it a few years back.

i came up with a saying to help me remember:

'thru the base, to the emitter.'

q20 needs replaced as well.

r49 is a 2watt 4.7 ohm metal film. it's part of the snubber network that keeps the amp from oscillating.

what's your question?

Yes, I have replacements coming for Q20/Q19 & Q18/Q17.

Question is contained in this other thread:

Thread '2W 4.7 ohm metal film resistors within Zobel network of KA3500'

Sep 21, 2026

Another thread, I'm afraid, about this KA3500.

Earlier today, I was examining some photos I took, primarily to determine orientation of Q20. The photo revealed that the resistor just below it was in visually poorer condition than when seen with the naked eye. My naked eye anyway. The discoloration and corrosion at the end caused me to check it's value and it measured 5.2 ohms instead of 4.7 ohms. The difference is beyond it's supposed tolerance of + or - 5%.

The parts list describes them as metal film resistors. I posted the photo in a different thread but here it is again...

• 62vauxhall
• Replies: 8
• Forum: Kenwood-Trio/Kensonic-Accuphase

 

[62vauxhall]

Here you go.

View attachment 3841293

Thanks, I will keep that handy.

A few years ago I persued reviving a Sony TA1150 integrated. It had symbols silkscreened at transistor positions but different than those in this Kenwood.

This is that symbol at Q402 on that Sony board. Despite it having an E-hole indicated, I found the symbol frustratingly confusing because at some positions, the E was obliterated.

 

[kwayde]

Thanks, I will keep that handy.

A few years ago I persued reviving a Sony TA1150 integrated. It had symbols silkscreened at transistor positions but different than those in this Kenwood.

This is that symbol at Q402 on that Sony board. Despite it having an E-hole indicated, I found the symbol frustratingly confusing because at some positions, the E was obliterated.

View attachment 3841404

Don't trust circuit board screen printing. Always verify.