Going of the subject of the resistors a little, you guys sound very knowledgable so got a question for.
I had a blown left channel on this amlifier and ive repaired it, all blown sap15s, ive replaced all of the fourpairs in the whole amp as i had to buy quite a few so why not i though!
The channel that was blown took out a z diode and few resistors job done all working. The SLIGHT issue is that the damaged channels offset is 12mv and the good one is 0mv. I would love zero on both channels! Its a tall order but ive come to a dead end, checked everything! Im thinking of changing the op amps NE5532AP see if that has taken a hit when it blew up.
Your probably going to say 12mv is nothing, i know but i would love to match the other side 0mv. Could a poorley op amp do this or am i barking up the wrong tree and i should go back under my rock!
I had a blown left channel on this amlifier and ive repaired it, all blown sap15s, ive replaced all of the fourpairs in the whole amp as i had to buy quite a few so why not i though!
The channel that was blown took out a z diode and few resistors job done all working. The SLIGHT issue is that the damaged channels offset is 12mv and the good one is 0mv. I would love zero on both channels! Its a tall order but ive come to a dead end, checked everything! Im thinking of changing the op amps NE5532AP see if that has taken a hit when it blew up.
Your probably going to say 12mv is nothing, i know but i would love to match the other side 0mv. Could a poorley op amp do this or am i barking up the wrong tree and i should go back under my rock!
Hi, I'm having problems with my MF A5 integrated, after power on is switching on and off constantly to mute.
I bought it second hand 10 years ago. Apart from that had to take it once to a local tech cause it was not working. He said he changed some transistors...
Well, the thing is that I've opened the amp to take a look and whislt cleaning it I found a resistor down on the chassis. It's a 10ohm one and I think it's from the Control PcBoard, but have to disassemble it first to ensure of it.
But what really surprised me it's some differences between the channels, so probably this is what the technician changed. The transistors on the left channel are 2 SAP15N and 2 P with a blue potentiometer in between I guess is the original. However on the right side the transistors are SAP15P and 2 N (so switched with regard to the other side) and the pot is white/orange. And apart from it these last transistors don't look to be in very good condition.
I really don't know a lot about transistors, but I guess SAP15N and P are not exactly the same. Or is this normal?
And the other question is, in case I have to change one of the channels, if I could replace with something better both channels (the 8 transistors) without too much complication.
I attach some pics...
I bought it second hand 10 years ago. Apart from that had to take it once to a local tech cause it was not working. He said he changed some transistors...
Well, the thing is that I've opened the amp to take a look and whislt cleaning it I found a resistor down on the chassis. It's a 10ohm one and I think it's from the Control PcBoard, but have to disassemble it first to ensure of it.
But what really surprised me it's some differences between the channels, so probably this is what the technician changed. The transistors on the left channel are 2 SAP15N and 2 P with a blue potentiometer in between I guess is the original. However on the right side the transistors are SAP15P and 2 N (so switched with regard to the other side) and the pot is white/orange. And apart from it these last transistors don't look to be in very good condition.
I really don't know a lot about transistors, but I guess SAP15N and P are not exactly the same. Or is this normal?
And the other question is, in case I have to change one of the channels, if I could replace with something better both channels (the 8 transistors) without too much complication.
I attach some pics...
Attachments
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Hi, the transistors work in pairs, SAP15N is NPN and SAP15P is PNP. This is typical for transistor amp output stages. When you say 'reversed' that might just be the way the board has been laid out, each channel should be symmetrical. Definitely looks like at least one set of transistors has been replaced there, and the mounting screws look a bit rusted too.
These transistors are special types, there is an upgraded part SAP16N/P and some people seem to have also used STD01 or STD03. These may give you more reliability if something has failed but otherwise not really an upgrade.
These transistors are special types, there is an upgraded part SAP16N/P and some people seem to have also used STD01 or STD03. These may give you more reliability if something has failed but otherwise not really an upgrade.
Yes, thank you,
I've been reading quite a bit about Sanken Darlingtons these days. Problems with these SAP15 transistors seem to be more common in Arcam or Cambridge audio amps. Regarding Musical Fidelity a5, there are cases but there's not that much info outside, maybe because less people have this amp or maybe because the heatsink is better and they don't overheat that much.
All the 8 transistors will be replaced. I know this is diyaudio so I'd be supposed to do it by myself but I'm not confident enough to do this task. I talked to my tech, the one who replace already 4 of them 9 years ago, considering the two options; going again with the SAP15 and it's "unreliable" internal resistor, or going with the STD03 adding an external 0,22ohm. I was more keen on the STD03 option but after discussing the subject it will be SAP15.
Apart from that I'm replacing all the electrolytics with Nichicons KG, KZ, FG and muses. Some Cornell Dubilier 940C 0,1uF for bypass. Will see...
I've been reading quite a bit about Sanken Darlingtons these days. Problems with these SAP15 transistors seem to be more common in Arcam or Cambridge audio amps. Regarding Musical Fidelity a5, there are cases but there's not that much info outside, maybe because less people have this amp or maybe because the heatsink is better and they don't overheat that much.
All the 8 transistors will be replaced. I know this is diyaudio so I'd be supposed to do it by myself but I'm not confident enough to do this task. I talked to my tech, the one who replace already 4 of them 9 years ago, considering the two options; going again with the SAP15 and it's "unreliable" internal resistor, or going with the STD03 adding an external 0,22ohm. I was more keen on the STD03 option but after discussing the subject it will be SAP15.
Apart from that I'm replacing all the electrolytics with Nichicons KG, KZ, FG and muses. Some Cornell Dubilier 940C 0,1uF for bypass. Will see...
It went really well. As I said all the transistors were replaced, but that shouldn't make any difference in sound cause they are the same than the original ones. Apart from that all the jamicon caps were replaced. This is what I did:
(8) - 4700uF 80v D30mm - (4) Nichicon LKG (type II) 4700 80v D35mm 9.51€/u
- (4) " LKS 4700 80v D25mm 7.29€/u
I made a mistake here. Couldn't find the type-I (the only KG available in 30mmD), so went for the type-II in 35mm diameter, thought that very tigh but they would fit.,They don't. So as not to get 8 new ones, I got 4 LKS, which according to Nichicon are same than type-I but smaller and high-tone quality.
(3) - 2200uF 25v D10mm - Nichicon UFG 2200uF 25v D16mm 1,47€/u
(6) - 1000uF 16V D10mm - Nichicon UKZ 1000uF 25v D16mm 1,35€/u
(6) - 10uF 63v BIPOLAR - Nichicon UES 10uF 50V 0,32/u
(2) - 10uF 16v BIPOLAR - " " " "
You can go with 50V ones here replacing the 63V ones, my technician has the A5 schematics and he checked this.
(2) - 100uF 16v BIPOLAR - Nichicon UES 100uF 25v 0.67€/u
(2) - 1uF 100v - Nichicon UFG 1uF 100V 0.25€/u
(9) - 10uF 50V - Nichicon UKZ 10uF 100v 0.39€/u
(2) - 47uF 16v - Nichicon UKZ 47uF 50v 0.54€/u
Those prices are without VAT, so in total around 110€ if one does it by himself. I paid a bit more due to my mistake with the KG's and because I ordered some caps for bypassing that finally I decided not to install.
The sound. First let me say that among all the different opinions out there (from the ones who say that there are not differences between a plain red/black cable speaker and a thousand € one, to the golden ears who can tell the difference between 100 different brands of capacitors) I'm on the sceptical size. This A5 amp is connected to a pair of ATC SCM40 mk1 speakers more than 10 years ago, so I know very well how they sound. I've tried several things (interconnect, power, speaker cables, stands etc) and the only clear big improvement to my ears is when I biwired the amp to the speakers. That said, I think the impact of this recapping work in the sound it's been even bigger. The overall sound is clearly more refined and the improvement in the bass area is huge. My speakers have never sounded better. That's all I can say.
(8) - 4700uF 80v D30mm - (4) Nichicon LKG (type II) 4700 80v D35mm 9.51€/u
- (4) " LKS 4700 80v D25mm 7.29€/u
I made a mistake here. Couldn't find the type-I (the only KG available in 30mmD), so went for the type-II in 35mm diameter, thought that very tigh but they would fit.,They don't. So as not to get 8 new ones, I got 4 LKS, which according to Nichicon are same than type-I but smaller and high-tone quality.
(3) - 2200uF 25v D10mm - Nichicon UFG 2200uF 25v D16mm 1,47€/u
(6) - 1000uF 16V D10mm - Nichicon UKZ 1000uF 25v D16mm 1,35€/u
(6) - 10uF 63v BIPOLAR - Nichicon UES 10uF 50V 0,32/u
(2) - 10uF 16v BIPOLAR - " " " "
You can go with 50V ones here replacing the 63V ones, my technician has the A5 schematics and he checked this.
(2) - 100uF 16v BIPOLAR - Nichicon UES 100uF 25v 0.67€/u
(2) - 1uF 100v - Nichicon UFG 1uF 100V 0.25€/u
(9) - 10uF 50V - Nichicon UKZ 10uF 100v 0.39€/u
(2) - 47uF 16v - Nichicon UKZ 47uF 50v 0.54€/u
Those prices are without VAT, so in total around 110€ if one does it by himself. I paid a bit more due to my mistake with the KG's and because I ordered some caps for bypassing that finally I decided not to install.
The sound. First let me say that among all the different opinions out there (from the ones who say that there are not differences between a plain red/black cable speaker and a thousand € one, to the golden ears who can tell the difference between 100 different brands of capacitors) I'm on the sceptical size. This A5 amp is connected to a pair of ATC SCM40 mk1 speakers more than 10 years ago, so I know very well how they sound. I've tried several things (interconnect, power, speaker cables, stands etc) and the only clear big improvement to my ears is when I biwired the amp to the speakers. That said, I think the impact of this recapping work in the sound it's been even bigger. The overall sound is clearly more refined and the improvement in the bass area is huge. My speakers have never sounded better. That's all I can say.
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Help with schematic diagram for MF-A5 please
Hi All,
I am in the process of repairing an A5 which has been blessed with fire and holy smoke when SAP15 P & N blew up.
Also on the death list are resistors and bias trim pots charred beyond recognition.
Wondering if anyone has a copy of the schematic that I could access please. Otherwise have to file it into the never-ever land.
Thanking you in anticipation.
Hi All,
I am in the process of repairing an A5 which has been blessed with fire and holy smoke when SAP15 P & N blew up.
Also on the death list are resistors and bias trim pots charred beyond recognition.
Wondering if anyone has a copy of the schematic that I could access please. Otherwise have to file it into the never-ever land.
Thanking you in anticipation.
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