SKA6516

The SKA6516  (P/N 151-0367-00) is an NPN Transistor. Note: possibly incomplete info, service manuals to be checked.

Key Specifications

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Suspected mass failures

Zenwizard Studios found thirteen of these in a 475 and showed that thirteen of those tested as "having a parasitic reverse diode junction" on a cheap component tester.

There is no such diode, parasitic or not – the cheap tester displays this symbol when the DUT has a low reverse breakdown voltage as seen in the traces below.

See the thread at https://groups.io/g/TekScopes/topic/101335545#201002 – Prof. Tom Lee says:

It's relevant to mention that many high-ft transistors have vey low breakdown voltages in inverted mode (i.e., collector and emitter exchanged). Depending on how those Chinese component testers do their analysis, it's possible that the transistor is actually driven into reverse avalanche breakdown, which could very well be (mis)interpreted by the tester's algorithm as a diode being present and forward-biased when the emitter voltage is above that of the collector. For grins, I tried some 5 GHz microwave transistors (Toshiba 2SC3302) that are known good (my students use these by the bushel in the microwave circuits class I teach). They (the transistors, not the students) all behave the same on the Chinese component tester as the "bad" 151-0367-00 transistors. The tester insisted that these transistors had the infamous C-E diode. A standard DMM diode test does not show this diode, because the DMM's applied voltage is too low to provoke reverse breakdown.

So, the tester is the problem, and not the transistor. Based on this set of results, an automatic "replace on sight" policy for these transistors based solely on a component tester's say-so seems unjustified, especially since the tester is most likely to make an error when evaluating possibly expensive high-ft devices.

Since reverse breakdown can damage the DUT, small-signal RF transistors should not be tested on component testers that may trigger that breakdown. They should be checked only on a curve tracer.

Suitable Modern Replacement

The 475 Service manual lists some of the transistors with alternatives, and some without, i.e. some may need to be closer in spec than others. A list of eighteen has been extracted from the Service Manual and is shared on the 475 Repairs page.

In his video, Mr ZenWizard Studios used Fairchild/On Semi KSP10BU from Mouser. Farnell has them, too.

In the 1982 Common Design Parts catalog, -0367 is Cross referenced as AST3571 which appears to be a custom 2N3571.

Pinout

The pinout of this transistor does not correlate with most modern BJTs. With the flat part facing you, from left to right, the pin is collector, base, and emitter. Incorrectly inserting a modern replacement thinking that it follows a standard emitter base collector can potentially bring down the equipment.

Pictures

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  Typical curve trace of 151-0367-00 in positive direction (x-axis: 0.5v, y-axis: 1mA)

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  Typical curve trace of 151-0367-00 in negative direction; the transistor has a low reverse bias breakdown voltage (x-axis: 0.5v, y-axis: 1mA)

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  Typical reverse bias curve trace of a good 2N3053 transistor (note this is a low-frequency power device with large junctions so it is not comparable to the 151-0367-00)

Used in

Some instruments using part SKA6516

Instrument	Manufacturer	Class	Model	Description	Introduced
465	Tektronix	Oscilloscope	465	Portable 100 MHz dual-trace scope	1972
465B	Tektronix	Oscilloscope	465B	Portable 100 MHz dual-trace scope	1980
466	Tektronix	Oscilloscope	466	Portable 100 MHz dual-trace storage scope	1974
475	Tektronix	Oscilloscope	475	Portable 200 MHz dual-trace scope	1972