In opposite direction, I have ordered from Mouser and I am quite happy. Costs weren't too high and they have a network of representatives in several European countries. Delivery from Texas to Europe was indeed supersonic: "Mr. Spock, Warp speed, please!?
I wouldn't have ordered "suspicious" products but my main source is company Reichelt and I can rely on their expert judgement. I don't think they would risk their reputation by selling bad semiconductors.
Tolerance has exceeded 1% for the most of resistors, but the worst were C5551: two ft values differed more than 50% and couldn't be matched to any of 5401. I used ON semi 2N5551 and crossed their legs to match the pinout of C5551. The same story with all other semiconductors. On top of all of that they have packed 1659A and 4379A instead of 1930 and 5171. Blasphemy.
The whole matter with components of L20.5 was like Russian Roulette on steroids where you have all six bullets in the barrel and you have to fire them all into your own brains. It is impossible to build a Blameless amplifier from a pile of junk. All respect to LJM but... Fortunately I have ordered a DIY kit so I have got away without having to de-solder everything.
But, don't forget to replace these pathetic D669 and B649 in L12-2 and MX50SE with something decent, perhaps NTE 373 and NTE 374 which are original US products. For me Chinese ISC SA1220/SC2690 did the magic.
I'm perplexed: did you mean "Kamala..."
Help needed
Hello,
I have build a MX50SE with the Sanken and I was very happy with it. I connected it to a valve préamp for a try and it was perfect, except gain too high.
So, I changed the resistors to reduce the gain but I didn't pay attention that I reverted + and - on the boards. One was supplied with +35/0/+35 and the other with -35/0/-35 😡😡😡
Obvioulsy it does not work anymore... Before desoldering everything, could you please tell me what may have burn? The chemical capacitors seems ok (externally) and I did not have any offset on the output (still 0v).
Thank you,
Didier
Hello,
I have build a MX50SE with the Sanken and I was very happy with it. I connected it to a valve préamp for a try and it was perfect, except gain too high.
So, I changed the resistors to reduce the gain but I didn't pay attention that I reverted + and - on the boards. One was supplied with +35/0/+35 and the other with -35/0/-35 😡😡😡
Obvioulsy it does not work anymore... Before desoldering everything, could you please tell me what may have burn? The chemical capacitors seems ok (externally) and I did not have any offset on the output (still 0v).
Thank you,
Didier
Maybe You've to replace only the power output bjts.
I would try first to power the circuit without the power transistors measuring the current through both power rails at the same time.
I would try first to power the circuit without the power transistors measuring the current through both power rails at the same time.
Folks, how about MX50SE on a +/-50V supply with 16 ohm speaker load (HF compression driver in the case)? - Forum members have earlier commented on SOA of some components ...
Off course 🙂 - actually that cap (20uf) both protects and defines one of the poles in the crossover function. Incidentally another pole is defined by the input cap. But what about the +/-50V supply?
In opposite direction, I have ordered from Mouser and I am quite happy. Costs weren't too high and they have a network of representatives in several European countries. Delivery from Texas to Europe was indeed supersonic: "Mr. Spock, Warp speed, please!?
I wouldn't have ordered "suspicious" products but my main source is company Reichelt and I can rely on their expert judgement. I don't think they would risk their reputation by selling bad semiconductors.
Tolerance has exceeded 1% for the most of resistors, but the worst were C5551: two ft values differed more than 50% and couldn't be matched to any of 5401. I used ON semi 2N5551 and crossed their legs to match the pinout of C5551. The same story with all other semiconductors. On top of all of that they have packed 1659A and 4379A instead of 1930 and 5171. Blasphemy.
The whole matter with components of L20.5 was like Russian Roulette on steroids where you have all six bullets in the barrel and you have to fire them all into your own brains. It is impossible to build a Blameless amplifier from a pile of junk. All respect to LJM but... Fortunately I have ordered a DIY kit so I have got away without having to de-solder everything.
But, don't forget to replace these pathetic D669 and B649 in L12-2 and MX50SE with something decent, perhaps NTE 373 and NTE 374 which are original US products. For me Chinese ISC SA1220/SC2690 did the magic.
I'm perplexed: did you mean "Kamala..."
believe me. You don't have to change any components.
5551 is a separate amplifier. It is a single ended amplifier. 5401 is a constant current element.
They don't work together. You can use the combination of MPSA92 + c5551 without any difference. The same HFE is not required.
In addition. A1930 c5171 Toshiba has stopped production. So the 1930 c5171 that can be bought on the market are basically fake. Do not use.
I measured a1930 and a1659 c4370 with APSYS 2722. The performance is exactly the same. The accuracy is 0.00001%.
So you don't have to buy another component to replace it.
In addition. 649 669 has excellent performance. At present, I have not found to-126 transistor with better performance.
I suggest you switch back to 649. 669 will improve the performance.
😀
You can rest assured. I'm very professional. I can tell the truth. Or fake Sanken.
Whether it's KEC 817 1047 or 2sa1295 2sc3264.
They have basically the same effect.
I can guarantee that they are all real transistors.
If you have extra transistors. You can break it with a hammer.
You can see the size of the chip with a magnifying glass. The original power tube may be produced in different places. Like the Philippines, Mexico, or China. It may not look the same.
But. It must have the same chip. The same size represents enough power.
In addition. You can also use the ONSEMI version of njw0302g.
They sell for the same price. I'm also worried about fake transistors.
So I need to take measurements. Use a transistor tester. In addition. I'll sample and break it.
Attachments
Hi Folks. I bought 2 MX50 SE on ebay and neither of them worked. Maybe some others will have the same problem; it's a tricky one to solve.
This version has a 5551 transistor as Q12 and no Q14.
Problem is Q12 silk screen is marked e b c but should be e c b.
You can twist the transistor legs to make it fit.
The symptom is that the output is stuck at the negative rail, Good luck!
This version has a 5551 transistor as Q12 and no Q14.
Problem is Q12 silk screen is marked e b c but should be e c b.
You can twist the transistor legs to make it fit.
The symptom is that the output is stuck at the negative rail, Good luck!
Perhaps first look at the D1047 & B817 BE & BC junctions with a meter. Then perhaps remove any failed outputs and then probe the B649 and D669 BE & BC junctions with a meter. Next probe the 5401 and NCC5551 (not standard pinout). (Q4 & Q12.)
Are the 47 Ohm resistors ok? What about the 0.22 Ohm resistors?
What was the supply voltage? What is the actual measured impedance of the speakers? (I ask since my "8 Ohm Compatible" speakers measure as 4 Ohms.)
I also suggest that you DO NOT get B649, D669, D1047 and B817 replacements from eBay or AliExpress.
Are the 47 Ohm resistors ok? What about the 0.22 Ohm resistors?
What was the supply voltage? What is the actual measured impedance of the speakers? (I ask since my "8 Ohm Compatible" speakers measure as 4 Ohms.)
I also suggest that you DO NOT get B649, D669, D1047 and B817 replacements from eBay or AliExpress.
Replacy with MJ15003/MJ15004?
Power supply is Us=+/-35V,
Speaker impedans is 4ohm!
P.S.
Can I replace output transistors D1047/B817...,with MJ15003/MJ5004, without modifications?😕
Thanks,
Power supply is Us=+/-35V,
Speaker impedans is 4ohm!
P.S.
Can I replace output transistors D1047/B817...,with MJ15003/MJ5004, without modifications?😕
Thanks,
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What is the measured current gain on the MJ15003 that you bought?
Which authorized distributor did you get the MJ15003 from?
I used genuine Toshiba 2SC5200N/2SA1943N from an authorized distributor (Mouser.) They have good current gain and it avoids the fake/failing/counterfeit eBay/AliExpress transistor problem.
But what about the 649/669 & 5401/5551? Are they ok? Did you probe the BC & BE junctions with a meter on the diode setting?
Which authorized distributor did you get the MJ15003 from?
I used genuine Toshiba 2SC5200N/2SA1943N from an authorized distributor (Mouser.) They have good current gain and it avoids the fake/failing/counterfeit eBay/AliExpress transistor problem.
But what about the 649/669 & 5401/5551? Are they ok? Did you probe the BC & BE junctions with a meter on the diode setting?
What is the preferred LJM board?
I read a review of these maybe 10 years ago and it wasn't favourable but there's quite a bit of activity on here now so maybe worth trying?
I read a review of these maybe 10 years ago and it wasn't favourable but there's quite a bit of activity on here now so maybe worth trying?
Hello Jonesy,
you will have more response in the seller's post, several members are viewing this post.
LJM Audio post vendors
Denis