Hi,
My Luxman M4000 power amp suddenly started acting up last week.
It was working fine but suddenly the left channel cutoff. On switching off and
powering it on again both channels worked but the left channel cut off after a
few seconds.
I took the amp to a service tech. who traced the fault to the front end
transistors.(first differential amplifiers)
The transistors are 2SA810. Part number Q301 and Q302 as per the M4000
service manual.
I require four of these transistors.(I will change the ones in the right channel
also.)
Please tell me a source for these transistors.
Regards
Rajiv
My Luxman M4000 power amp suddenly started acting up last week.
It was working fine but suddenly the left channel cutoff. On switching off and
powering it on again both channels worked but the left channel cut off after a
few seconds.
I took the amp to a service tech. who traced the fault to the front end
transistors.(first differential amplifiers)
The transistors are 2SA810. Part number Q301 and Q302 as per the M4000
service manual.
I require four of these transistors.(I will change the ones in the right channel
also.)
Please tell me a source for these transistors.
Regards
Rajiv
Hi,
2SA970 should work. Very similar specs. I've always used these when replacing differential pairs in vintage gear.
They are rated at 120V vs 150 of the originals, though.
2SA970 should work. Very similar specs. I've always used these when replacing differential pairs in vintage gear.
They are rated at 120V vs 150 of the originals, though.
The M4000 differential input runs at +/-68V, the 2SA970 will be running above its rated voltage. Try a 2N5401 instead.
I suspected something such.
Also remember to get a handful of them, not just the bare minimum. Get at least 10, preferably more. You need to match them closely (use a multimeter with hFE testing capability), for the best possible performance.
Also remember to get a handful of them, not just the bare minimum. Get at least 10, preferably more. You need to match them closely (use a multimeter with hFE testing capability), for the best possible performance.
The diff pair only need withstand the one rail voltage, not the P-P.
The Vas must withstand the P-P.
The Luxman M4000 suffers from poor solder joints and speaker relay issues as well. I would check for these issues before replacing the diff pairs (unless they actually measure defective).
The Vas must withstand the P-P.
The Luxman M4000 suffers from poor solder joints and speaker relay issues as well. I would check for these issues before replacing the diff pairs (unless they actually measure defective).
Replacing the differential pair is always a good idea in vintage equipment. Regardless if they work or not. They are rarely well matched, and having the lowest possible dc offset is, at least to me, an important thing.
That is probably not the problem in this amplifier, unless one of them has actually failed.
Cross-coupled full-complementary diff inputs are subject to temperature drift, no matter how well they are matched.
Cross-coupled full-complementary diff inputs are subject to temperature drift, no matter how well they are matched.
Hi,
Thanks for all the inputs.
The transistors from the working channel were swaped into the defective channel and the channel started working.
When the transistors from the defective channel were put into the working channel it stopped working.
Regards
Rajiv
Thanks for all the inputs.
The transistors from the working channel were swaped into the defective channel and the channel started working.
When the transistors from the defective channel were put into the working channel it stopped working.
Regards
Rajiv
In this case it sounds like one was bad.
HiFi Engine has the M-2000 schematics, basically the same. Also download the M-4000 manual for the parts list.
HiFi Engine has the M-2000 schematics, basically the same. Also download the M-4000 manual for the parts list.
Last edited:
Hi,
I have ordered some 2N5401 transistors for the M4000.
The specs for the 2SA810 show the Maximum collector power dissipation (Pc): 700mW
The specs for the 2N5401 show the maximum collector power dissipation as 310mW.
Will there be a problem using the 2N5401 in the Luxman M4000?
Regards
Rajiv
I have ordered some 2N5401 transistors for the M4000.
The specs for the 2SA810 show the Maximum collector power dissipation (Pc): 700mW
The specs for the 2N5401 show the maximum collector power dissipation as 310mW.
Will there be a problem using the 2N5401 in the Luxman M4000?
Regards
Rajiv
As the diff input?
No problem for power.
Just remember the pin-out for the 2N5401 is EBC though.
No problem for power.
Just remember the pin-out for the 2N5401 is EBC though.
On the choice of input transistors(and there are more good ones), a low noise figure like the
2SA970/2SC2240 complements is a better choice than 2N5401/2NSSS1.Just beware they are
obsolete and fakes will be around. For the cost difference, you may as well do the best you
can if you want the effort to be worthwhile. Check this spreadsheet
http://www.diyaudio.com/forums/soli...ata-sorting.html?highlight=transistor+sorting
2SA970/2SC2240 complements is a better choice than 2N5401/2NSSS1.Just beware they are
obsolete and fakes will be around. For the cost difference, you may as well do the best you
can if you want the effort to be worthwhile. Check this spreadsheet
http://www.diyaudio.com/forums/soli...ata-sorting.html?highlight=transistor+sorting
Last edited:
Are you sure 2SA970 is obsolete? It is still very easy to come by, being sold in lots of "serious" stores. Can you recommend a comparable transistor that is still in production?
See above spreadsheet for Fairchild KS types and salient details. KSA 992/C1845 have proven good from resellers or direct - which is how I buy.
I should have been specific, as last I looked, Toshiba had not deleted but they were on final production status or such and had been for ages, so assumed by now obsolete. The stock position is interesting; there is a lot about everywhere on Ebay and cheap. A friend bought 100BL "pairs" and got 200 rubbish and another bought through RS from UK stock, and got something bad for noise figure too. Otherwise, they seem OK here at E14, Mouser &, Digi-key but I would no longer use them if the part wasn't mandatory.
We might wonder how fakers would profit from low cost TO92 parts.
I should have been specific, as last I looked, Toshiba had not deleted but they were on final production status or such and had been for ages, so assumed by now obsolete. The stock position is interesting; there is a lot about everywhere on Ebay and cheap. A friend bought 100BL "pairs" and got 200 rubbish and another bought through RS from UK stock, and got something bad for noise figure too. Otherwise, they seem OK here at E14, Mouser &, Digi-key but I would no longer use them if the part wasn't mandatory.
We might wonder how fakers would profit from low cost TO92 parts.
Hi,
Can some one tell me a source for the 2SA762 and 2SC1431 transistors?
What would be the correct replacement transistors ?
Regards
Rajiv
Can some one tell me a source for the 2SA762 and 2SC1431 transistors?
What would be the correct replacement transistors ?
Regards
Rajiv
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