Hi Philip,
What store is that, do you remember the name? It sounds like somewhere to be checked out fer sure.
The bias supply absolutely should be protected. That diode should have been shorted and look normal, not completely cooked like it is.
-Chris
What store is that, do you remember the name? It sounds like somewhere to be checked out fer sure.
The bias supply absolutely should be protected. That diode should have been shorted and look normal, not completely cooked like it is.
-Chris
Hey Chris,
It was a Sayal in Cambridge--I've been to smaller Sayal stores before, but this one was huge!
Basically what I have is a direct connection from the transformer to the diode bridge, and from what I understand the output of those diodes is sent to each amp board for regulation. I can't see a fuse in this supply at all. I'm going to leave it with the 1A 1N4002 devices for now.
Looks like a diode did short, and then one of its legs disappeared...
It was a Sayal in Cambridge--I've been to smaller Sayal stores before, but this one was huge!
Basically what I have is a direct connection from the transformer to the diode bridge, and from what I understand the output of those diodes is sent to each amp board for regulation. I can't see a fuse in this supply at all. I'm going to leave it with the 1A 1N4002 devices for now.
Looks like a diode did short, and then one of its legs disappeared...
Hi Philip,
Another giant Sayal store. Cool, worth a look if I am ever out that way.
You are lucky the board wasn't damaged the way the diode shorted. But like I said, the diode should have blown a fuse. I hope it didn't cook a winding, do you still get AC from those leads? You can check that with the xformer disconnected (preferred).
-Chris
Another giant Sayal store. Cool, worth a look if I am ever out that way.
You are lucky the board wasn't damaged the way the diode shorted. But like I said, the diode should have blown a fuse. I hope it didn't cook a winding, do you still get AC from those leads? You can check that with the xformer disconnected (preferred).
-Chris
Another one, Chris??
No, the board isn't damaged electrically, just a small burnt spot.
I haven't powered the transformer up, but I get 2 ohms between each leg and the centre tap.
P.
No, the board isn't damaged electrically, just a small burnt spot.
I haven't powered the transformer up, but I get 2 ohms between each leg and the centre tap.
P.
Hi Philip,
Yup. The main store may not be as large, but they have the cool stuff. The one in Burlington is pretty large though.
-Chris
Yup. The main store may not be as large, but they have the cool stuff. The one in Burlington is pretty large though.
-Chris
Time for dinner. This is where I'm leaving it for now, waiting on parts at this point.
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Well they're not doing any good sitting there in the foam! Ultimately what parts did you find bad besides the rectifier diode?
On a mechanical note, use caution when tightening the 10-32 Allen/button head screws that go into the front and rear of the heat sinks. The aluminum is not very thick and therefore not many threads, real easy to strip out especially if been disassembled/assembled many times. If you pull the threads I have a very easy fix that is better than new.
Craig
On a mechanical note, use caution when tightening the 10-32 Allen/button head screws that go into the front and rear of the heat sinks. The aluminum is not very thick and therefore not many threads, real easy to strip out especially if been disassembled/assembled many times. If you pull the threads I have a very easy fix that is better than new.
Craig
I'm still at work!
I'm still going through and testing parts bit by bit. I've got all the new caps in and have almost got all the resistors tested out.
Fix for the threads? I've been careful, but my first thought is repairing the threads with helicoils. Or setting a nut in the T-slot... somehow.
I'm at a point where I've forgotten to buy thermal grease and will grab some after work so I can get the power supply testing going to start.
P.
I thought about Heli-coils but there just isn't enough material. I used McMaster-Carr P/N 95185A185, 10-32 press-in nut. Drill the hole out to 1/4" put the nut inside the long cavity and use a 10-32 Allen head screw and thick flat washer to pull the press-in nut into the aluminum. Works great, better than new. I did both of my NINEs. Don't use your SUMO screws though.
Craig
Craig
I know this is an old thread but my dad's old nine + just had its left channel fail. There is still a bit of sound coming through at max volume level. Any advice before I start taking it apart to have a look would be great (we've established that the amp itself is at fault, not another part of the audio chain).
I'm rebuilding a NINE+ now, gathering parts at least. Check all of the semiconductors and capacitors. There's not much you can do without removing all of the output transistors, that will release the circuit board from the heatsink. If you have ARC4700 output transistors they need to be replaced with MJ21194G from ON Semi. The ARC4700s were cheapo transistors that were used in later production. They are ring-emitter type with very little Safe Operating Area, SOA, made by Fujitsu. If the power xfmr is NOT a Bando, large black case, you need to check the solder joints on the power supply circuit board. The large stiff wires from the xfmr tend to break the solder joints when the board is moved around. The one I'm working on had been repaired before but not very well. The collector on one of the TIP31C drivers was not soldered and wiped out the MPSU56s, that's where I'm stuck right now. MPSUxx were used by SAE, GAS, and SUMO and very tough to find now. The MPSU56 screwed to the board HAS to be a Motorola because the other brands' collector tab is too long. Get into it, find what's bad and then ask more questions if need be.
Craig
Craig
Thanks for the quick reply and advice - tbh I'm not looking forward to dive into it given the way I hear it's put together (not service friendly). Luckily I can loan my old Audiolab to him while I look at it🙂
It's not service friendly but I'm used to it, just have to take it apart as there's no other way.
Hi again, I haven't yet gotten to the amp (wife wants me to finish off my current home project first) but I see a few listings for the MPSU56s on ebay which claim to be new (or rather I guess NOS). Should I be steering clear of these or is there an alternative?
Since there's not much demand for this style of transistor I don't think there's much in the way of counterfeits. They do however must be Motorola brand due to the mounting. The other currently available transistors from Central Semi have a much larger collector tab and won't fit on the board. They would probably be OK in the audio circuit but not the power supplies. If the Ebay transistors are by Motorola you might want to take the chance.
Craig
Craig
i have a nine plus,exuse me for my bad english..i would try if it is possibel to make the input symmetrical, the amp is full balanced i see, someone could give me an idea to change the assymetrical input to balanced . I have a soundcard from RME that provide a balanced output, a very good one!it cost me about 700 eur...about 800$...i buy a thule ia350b... but he have a big problem with the commutation from 5.1 to stereo, i spend almost 2 weeks trying repair this amp but..no way...don't function, this amp is full balanced and in stereo have a big power 2x350 w...So..if it is possibel to tranform my sumo to balanced input i will be very happy!!
Have a nice day...yvan
Have a nice day...yvan