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-   -   Can I use MJL0281A & MJL0302A in place of Sanken FN1016 & FP1016 in my Rotel RB-991 (http://www.diyaudio.com/forums/solid-state/83573-can-i-use-mjl0281a-mjl0302a-place-sanken-fn1016-fp1016-my-rotel-rb-991-a.html)

dtm1962 22nd July 2006 12:01 PM

Can I use MJL0281A & MJL0302A in place of Sanken FN1016 & FP1016 in my Rotel RB-991
 
Any concerns with this substitution? I have 10 pairs of these devices to sub in. They will physically fit on to the heatsink with minimal adjustment.

The original bias is for 7mV (across its 0.22 emitter resistors = 32 mA). I probably have to adjust to ?
This amp is rated for 200W/Ch.

The driver devices are 2SB817/2SD1047 are rugged and they are sometimes that are found as output devices in some amps (i.e. older ROTEL Amps)

The schematic says it uses Sanken 2SA1492 & 2SC3856 output devices but I got the dreaded FP1016 & FN1016 in its place.

Are these devices equivalent?

Any help would be appreciated!

MikeB 22nd July 2006 12:24 PM

2 Attachment(s)
Hmm, the MJLs show ~2 times higher ft and higher beta, they might be too fast. They should work, but you need to verify with a scope if the amp oscillates.
Are the old ones blown ?

Mike

dtm1962 22nd July 2006 12:38 PM

I have one blown FN1016 and a blown input trans. 2SA1016 and a few blown diodes and a resistor that out of spec.

I am just disappointed that a 200W/300W into 8/4 ohms use these 5 pairs of 70W 8A devices (FP1016/FN1016)!
The driver stage uses higher current devices (2SB817/2SD1047)!!!!!
Is it really equivalent to a 2SB1587/2SD2438????

FN/FP1016: are they really equivalent to 2SA1492/2SC3856 as Rotel uses either unit as interchangeable in the RB991

How can a 70W 8A device be equivalent to a 130W 15A device as used in the 991???

jaycee 22nd July 2006 01:30 PM

Have you owned this amp from new? It sounds like some idiot has repaired it at some point in the past, and used the wrong transistors.

If the schematic says that it should be using 2SA1492 & 2SC3856 i'd assume thats what should be in there. As you say in the other thread, the Aiwa house devices sound like darlingtons, and this would fit my expectations having serviced a few Aiwa stereo systems.

I think the MJL0281/0302 will work but you will undoubtedly have to alter the bias. You will also need a 'scope as suggested to make sure there is no oscillation, but from what I remember about the 2 Rotel schematic's i've seen, they tend to be pretty well compensated.

dtm1962 22nd July 2006 01:37 PM

Jaycee: See other post. It looks like Rotel supports the 2 different sets of devices and believes they are equivalent!

jaycee 22nd July 2006 01:43 PM

I would more likely say the Rotel guy you spoke to hasn't a clue what he's talking about!

edit: I've seen this service manual myself. There is no way they would substitute darlingtons in there. Someone has done this by mistake.

My hunch is on my original theory, someone else has repaired the amp and used the wrong devices, possibly misled by Rotel's service department.

dtm1962 22nd July 2006 07:31 PM

Here is a link to the RB991 schematic:

http://www.zero-distortion.com/downlaod/x1.htm

Can someone comment on the use of the FP/FN1016 in this circuit instead of the 2SA1492 & 2SC3856.

Assuming if it is a Darlington.

SO is it possible to drop in a MJL0302A & MJL3281A.

Any help would be appreciated.

Thanks

MikeB 22nd July 2006 08:01 PM

Another guess would be that fp1016 for Rotel are different...
The only way to find out would be measuring the Vbe on these devices when amp is turned on, immediately showing if these are darlingtons or not.
How do the cases look like ? MT100 or FM100 ? The FM100 looks more like a TO220, the MT100 is well known as the TO3P.
The 2SB1587 has a completely different case than 2SC3856...

The link does not work for me... (server offline ?)

Mike

dtm1962 22nd July 2006 09:44 PM

The FP/FN1016 case unfortunelately looks like the 2SB1587.

So this is more ammo that to the fact it is like the Darlington-based 2SB1587.

With this Darlington on the output with a 2SB817 & 2SD1047 as the "Darlington drivers". Is this kosher and do they call this a triple Darlington configuration?

Will this work properly versus just having the 2SB817 & 2SD1047 drive the 2SA1492/2SC3856 as shown on schematic.

dtm1962 22nd July 2006 09:53 PM

The link works now for the RB-991 service manual.


http://www.zero-distortion.com/downl..._schematic.pdf

Have a look and let me know if this Darlington-based (?) Output Devices (5 pairs) FP/FN1016 will work in the place of the stated devices (5 pairs) of the 2SA1492/2SC3856's.

Any comments will be helpful.

Thanks in advance.


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