Help:"Darlington" FP1016 measures like a Bipolar???

[dtm1962]

So this "Darlington" FP1016 measures like a Bipolar Device.

I noticed that my Rotel RB-991 amp has FP1016 & FN1016 output devices instead of the 2SA1492 & 2SC3856 as shown on the schematic. So this is how my curiosity begun as I bought a broken RB-991 off EBAy for $162 USD.

I am assuming that a Darlington measures 1.2-1.4V across the emitter and base. Is this correct?

Please enlighten me on this please. I have been pulling my hair on this one for 2 days.

What I found with a good FP1016 out of the circuit is as follows:

Using multimeter diode mode it measure 0.589V with + on E & - on B.

It measures 0.560 with + on C and - on B.

Its open for the other 4 measurements.

This measures like a standard Bipolar.

I have a feeling that Sanken named these FP1016 & FN1016 as the designation for generic OEM usage and it is overlapping with the Darlington version of a FP1016 & FN1016.

I am going to compare the physical structure of these transistors in order to determine which bipolar it actually is if my assumptions are correct.

Maybe it is a repackaged 2SA1492 & 2SC3856 and tagged them as FP1016 & FN1016 to disguise their actual device.

Any thoughts as I could not see with the help of fellow member jaycee that they could be putting a Darlington where it is formed already with the previous 2 transistors in the driver stage.

Here is the link for the RB-991 schematic showing the correct output transistors.

Please comment.

Thanks in advance,

http://www.zero-distortion.com/downlaod/extra/schemati/rb_991_schematic.pdf

 

[djk]

The schematic clearly shows the outputs are not Darlingtons.

"Maybe it is a repackaged 2SA1492 & 2SC3856 and tagged them as FP1016 & FN1016 to disguise their actual device."

Not probable. May be a Rotel ' house' pn, but I doubt it. Try for the original pn or you may have to fiddle with the frequency compensation.

 

[AKN]

Can your transistor look something like this inside and therefore explaining your low vbe readings?

 

[MikeB]

Can your transistor look something like this inside and therefore explaining your low vbe readings?

Good point, for very low currents Vbe (measured as diode) can read 0.6v...

Mike

 

[dtm1962]

So if it a darlington with the appropriate diode, the current gain would be 10000 (roughly 100X 100). Would this respond differently in terms of frequency response and stability versus the 2SA1492 and 2SC3856.

How can Rotel assume that they are interchangeable?
2SA1492 is 130W 15A & the 1016's are 70W 8A.

What the heck are they doing?

Rotel Parts Manager (in Canada) was going to sell me either one for the same price!!

I think I might just have to contact Rotel Service and ask them what the heck is going on!

Thanks for your help so far!

 

[MikeB]

Yes, contact them, it became too confusing...
You can get correct reading from this darlington if you feed it with a current > 30ma, then measure Vbe.

Mike