Which replacement transistor for Sanken C3856/A1492?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I'm looking for some replacement transistors for Sanken (2S)C3586 and (2S)A1492, can't seem to find them anywhere.

Mouser lists NTE2328/NTE2329 as equivalent replacements and I saw on another post on here about someone using Toshiba 2SC5200/2SA1943 as replacements.

Which would be a better match and/or sound better, etc... these would be used in a Samson S1000 power amplifier.

The Toshibas are much cheaper at $2.25 each while the NTEs are $6.12 and $7.25. If the Toshibas would work, they seem to be the better deal.

Also, anyone know where I can find schematics/service manual for the Samson S1000?
 
I tried searching individually before with no results. So after your suggestion, I searched for both at the same time and I found some!

http://www.ampslab.com/trans_2sa1492.htm

Not too bad of a price either, it's cheaper than the NTE pair, though not quite as good as the Toshiba pair.

Although, I'm not even sure these are the correct transistors for the amp now because as I posted in the Solid State forum, I found that each transistor looks like it was aftermarket modified. Unless someone had to replace all the transistors, I'm guessing they put these in because they thought they'd be better.
 
Hi,
try comparing specs for these;-
2sa1294, 2sa1302, 2sa1386 (only160V), 2sa1943, 2sa1962 and their complements.

Why do you need to replace the originals? Do you want to consider selecting something that can take a bit more abuse or add extra devices in parallel?

All of these 130W/150W plastic semis are not very robust and suffer terrible SOAR at elevated voltages. I would keep the supply rails below +-55Volts or be prepared to use multiple outputs.
 
Yeah, I was wondering why a pro amp would be using Sankens, plus there were only 5 pairs per channel, which is supposed to put out 500w into 4 ohms.... that's another reason why I believe these are not the original transistors.

Would the MJL21193/MJL21194 be a good bet for original parts?
 
Hi,
I guessing that your transformer is about 50Vac giving PSU voltages of +-74Vdc.
MJL21193/4 would be an excellent choice and 5pairs at those voltages can drive 4ohms reactive load at 60degree phase angle.

These transistors are about 5 times slower than the Sankens you have taken out but can cope with about twice the power I would expect the gain to be a bit lower which will load the drivers.
In both these respects the 21193/4 may well be better than the unknown originals.
 
Yeah, the output sounds about right, it has 100v filter caps. I'll go ahead with the MJLs, but now I have some other parts needing replacement....

there are the drivers (?) 2SA1659A and 2SC4370A. It looks like these may have been put in along with the Sankens, are they appropriate for this amount of power? There are one each that were heatsinked and 2 3470s and 1 1659 not heatsinked. One of the 1659s (heatsinked) was bad in channel damaged worst.

http://www.datasheetarchive.com/semiconductors/specsheet.php?specsheet=127411

http://www.datasheetarchive.com/semiconductors/specsheet.php?specsheet=138011

Also, there is a unknown zener diode that I can only make out Z10M (I think) on it that need replaced. Can't find anything about it anywhere.


If anyone would like to buy the Sankens I have, I don't need them. I have 6 pairs (2SA1492/2SC3856), 3 individual 2SA1492 and 1 2SC3856. The pairs were the ones there were matched in the circuit, whether they actually do "match" I have no idea. All same transistors have the same code ("8N P" for the 1492, "80 P" for the 3856)
 
I was able to contact Samson and get a schematic for the amp. It turns out that the Sankens ARE original parts.

What would need to be done to use the MJL parts instead of the Sankens? The Sankens I believe are rated for 100w and the MJLs are 200w. I'm assuming I wouldn't need 5 of each transistor per channel like with the Sankens. Or if I did decide to fill all the spots, would I need to change any other parts to accomodate?
 
Hi,
now that you have confirmed that the Sankens are the original fitment then it appears you are proposing to fit a non equivalent substitute.

As I see it you are losing both speed and gain in return for power. I would expect this to have some effect on performance.

I do not know if this would be audible but the concensus on this forum is generally that fitting faster outputs can improve the sound provided the amp is refettled to remain stable. You are going in the opposite direction.

I would expect the stabilty components will need to be reselected to optimise the circuit.

Any protection circuit will be completely wrong for the new outputs. Even farther astray if you change the number of output pairs.
 
Thanks for the help Andrew.

As you probably know, I'm not very knowledgeable about amplifier design, but I am good with a multimeter and soldering iron. So, I like to fix amplifiers for fun.

For now I'm just waiting for the original replacements (or equivalent because some of these parts are hard to find) and I'm going to hold off any experimenting.

The schematic is too large to attach to the board, so I uploaded it to a schematic website. You can get it here:

http://www.eserviceinfo.com/downloadsm/20235/Samson_S1000.html
 
AndrewT said:
Note there have been zero downloads in the recent past.

read the line below the download table: the counter is set to zero daily !

Safe operation relies for a great deal on the parts around Q127 and Q137, in combination with a temperature sensor and a relay.
Q127 and Q137 take voltage of the gate of the MOSFET drivers Q109 and Q110 in case of too high output currents and fast transients.
If that part of the circuit does not work properly the output devices are bound to be blown.
 
Well, I got replacement parts for the one channel, and tested it out and it worked fine... for about 10 min. Lights dimmed and the amp smoked... oops.

The channel I fixed was fine, but the other channel blew some outputs. So, I again bought entirely new outputs transistors for the channel and replaced the drivers as well. Checked it over thoroughly and figured it was just because I had mixed some of the "good" transistors left over from each channel previously to fix the 2nd channel, but they may have been unknowningly damaged.

Then I had another problem which I finally just solved!

After I repaired ch 2, when I tested the amp, the protection light would not come on when I turned it on and the relay would never click on the channel.... so after countless hours of searching components and tracking down the source of the problem, I noticed a small crack on the edge of the volume control board which happened to run through the leads of a couple components, and with the ohmmeter saw that the trace that powered the LEDs for the channel was open. So, I repaired the trace and secured the crack with some epoxy and it worked!

It's been a long an arduous journey to repair this amplifier, so I hope it will finally work correctly! I think I just want to get rid of it now, so I no longer have to be concerned with it.

I've definitely not been impressed with Samson's amplifiers. I also have a servo 120 which had it's fair share of problems. These included a few component's that must have had cold solder joints as the solder cracked right off the board... most annoying being the relay to turn on the speakers which manifested itself as the speakers randomly turning off and having to give the thing a whack to turn them back on :D

Oh, and if anyone is looking for the 2SC3856 or 2SA1492, I bought some from this company and even smashed one open and they are genuine for a great price!

http://www.bdent.com/search/part.jsp?partnum=2SC3856
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.