After solving the children's diseases on my tektronix, struggling with the proper electrolytes in the low voltage line,
and of course with a lot of help from the people on this forum - the thing worked.
Of course, like everyone who comes here, I've read a lot of texts about the problematic transistor that has a 100% failure rate.
According to the advice available I replaced these transistors, and I noticed that the trigger is no longer as good and stable as before.
Then I started reading texts about the SKA6516 transistor, wanting to find its characteristics.
In the book Semiconductors-catalog-1982 I found that it is a transistor A5T3571 which has the following characteristics:
Ft min - 1,2 GHz
Vce / Ice - 6/5
Hfe min - 100
Vceo - 30V
Vcbo - 40 V
Vebo - 3 V
Icbo - 10nA
Ccb - 1,5 pF
Vce(sat) - 300/20 mV/mA
Ic max - 50 mA
I've also read on the forums that people have swapped them with 2N2369 even 2N2222.
Most often, the advice was to replace it with KSP10BU, which is relatively easily available today.
I was also advised to try replacing them with BF199 which was used in CRT TVs and is also still relatively easy to obtain.
I grabbed my box from the CRT TV days, and found a bunch of BF199, BF198, BF311.
Then I got hold of that famous Chinese tester and I was amazed - absolutely everything and one on the tester was declared defective,
and it shows c-e leakage as an additional diode.
Also, the identical behavior as with Tektronix transistors can be observed, depending on the direction in which you put it in the tester,
one way it will show that it is a PNP, if you turn it the other way around it will show that it is an NPN transistor.
And this is where my doubt begins –
1. how is it possible that absolutely the entire stock high frequency transistors I have is defective, and that not a single one is good?
2. why did tektronix decide to hire semiconductor manufacturers to make such a transistor with custom characteristics,
when at that time all of transistors what is listed as replacement today, was available at the time of manufacture of the oscilloscope?
3. Is it possible that these Chinese testers cannot handle the characteristics of these transistors, so they declare them defective?
4. why didn't I know or feel the need to open my tektronix until one of the big electrolytes failed and the device stopped working because of it,
and most likely these transistors were in the same state the whole time?
5. if those transistors are so bad, why does my oscilloscope work at all when they are in there?
6. I put the original tektronix transistors back on the trigger board (luckily I didn't throw them away), and why does the trigger work better now?
7. Why does it say - selected from stock, in some places next to these transistors in the manual.
Does that mean that in addition to being custom-made, they also paired them?
What are your thoughts on these issues?
