Can I use MJL0281A & MJL0302A in place of Sanken FN1016 & FP1016 in my Rotel RB-991 - Page 2 - diyAudio
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Old 23rd July 2006, 03:13 AM   #11
jaycee is offline jaycee  United Kingdom
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The triple darlington output stage in this amp is formed by:

Q619/Q621 - pre-drivers
Q635/Q633 - drivers
Then the 2SC3856/2SA1492 devices as the outputs.

There is no way the darlingtons should be there.
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Old 23rd July 2006, 04:19 AM   #12
dtm1962 is offline dtm1962  Canada
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I appreciate your help as you can see why I am confused.

So the situation is one of the following:

1) I believe that these devices are misapplied in this case if they are Darlingtons and put in by someone who is misinformed.

2) Is this designation of FP1016/FN1016 another (Aiwa type) OEM designation that Sanken does for all their OEM transistors that are unique to one product (far-fetched as it will cause confusion)

3) Rotel designed it to be compatible with Darlingtons & standard bipolars

Any other scenarios?

I will measure them to see the Vbe voltage across the base & emitter. I use a current limiter (a light bulb in series with the AC line to limit current to 0.5A (110VAC with 60 Watt light bulb).

So a darlington will measure 1.2 V @ min Ic in this case probably in the mA range with no load and the Bipolar will measure 0.6V at the same range.
These are from the graphs of Vbe vs IC and temperature. I assumed the current will be well under 1 Amp with no load.
I assume because there is 2 transistors in a Darlington.

I will measure and let you know.

Thanks for your help.

Dan
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Old 23rd July 2006, 04:36 AM   #13
jaycee is offline jaycee  United Kingdom
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Personally, I think scenario 1)

Did you buy this amp new, secondhand, from eBay, etc?
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Old 23rd July 2006, 04:37 AM   #14
dtm1962 is offline dtm1962  Canada
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I couldn't measure in circuit since I am missing the whole front end plus some rail diode. The voltage across the Base and emitter was varying all the time.

I measure a known good PNP out of the circuit and it measures a voltage drop of 0.55 V across the B & E using the diode mode.

Does this indicate a Bipolar as I thought the Darlington would be double that because of the 2 junctions of the dual transistor.

Let me know.

I will research the net in the meantime.

What are the characteristics of a Darlington outside of an active circuit?

Thanks again
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Old 23rd July 2006, 04:47 AM   #15
dtm1962 is offline dtm1962  Canada
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Yes I did buy it on EBay. It is in good shape and all the PS voltages are right except for the 8 failed1N4148, 2 out of spec resistors (R613/614) and 1 bad FN1016 and 4 bad 2SA1016 and 3 bad 2SC2362's.

It looks one channel had a bad output device (Q639) with a bad input transistor (Q607).

The other channel had a short from the R663 (10 ohm) to the standoff that holds the circuit board away from the heatsink. A portion of the tracing is missing and the brass standoff is scorched. A screw was missing on the standoff and the board shifted enough to short out. This side has almost has all the input transistors as well 4 transistors in the predriver stage shorted but no output devices damaged.

With the light bulb in the circuit as a current limiter the light is barely on. Turn power and it is bright for a second and slowly dims out to a slight illumination. I have to turn the lights off to see the glow. So the outputs are good. Under load it may be a problem.

Thanks again
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Old 23rd July 2006, 04:51 AM   #16
dtm1962 is offline dtm1962  Canada
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By the way I bought it off EBay - requiring repair for $162 USD.

I believe they go for $400-550 USD on EBay currently.
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Old 23rd July 2006, 05:23 AM   #17
dtm1962 is offline dtm1962  Canada
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So this "Darlington" FP1016 measures like a Bipolar Device.

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

What I found with a 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.
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Old 23rd July 2006, 10:21 AM   #18
MikeB is offline MikeB  Germany
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Quote:
Originally posted by dtm1962
Its open for the other 4 measurements.
What do you mean ? Full voltage drop or zero voltage drop ?
Yes, ~0.6v indicate non darlington.
Can you confirm that you have 5 x TO220 like cases and one TO3P case mounted to the heatsinks ?

There is no way how a darlington output device should fit here.

I guess you have to order spare parts drom Rotel...

Mike
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Old 23rd July 2006, 01:06 PM   #19
dtm1962 is offline dtm1962  Canada
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I have 5 FM100 (TO3PF) - FP/FN 1016 like the 2SB1587 (Darlington).

I have one MT-100 (TO3P) for the 2SB817/2SD1047 (driver).

And of course they are mounted on the heatsink.

Thanks,

Dan
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Old 23rd July 2006, 01:16 PM   #20
dtm1962 is offline dtm1962  Canada
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For the measurements in the diode mode using the meter they are infinity or technically open which is like measuring a diode with the leads reversed.
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