Hello,
First off im new on diyaudio and if im posting in the wrong section please move me if needed.
Im also new to amplifier repairs but until now it has been an fun project.
I have an aiwa sa-p22 amplifier with an shorted output transistor. This is an 2sa1093 transistor, but these are not manufactured anymore and i think the ones that are still up for sale are fakes. So im looking for an good replacement transistor. I could not find much information regarding replacing a transistor so im not quite sure which specs need to be matched. I found in some old pdf with transistor replacements that an 2sa1186 would be an good replacement. But this one has an Ft of 60 mhz and the 2sa1093 is 90 mhz.
So is this a good replacement transistor or would i be better of looking for another one?
Also the service manual states that the output transistor is an 2sa1077 and this one has a ft of 60mhz. But the aiwa and my wega 205(aiwa-sa-p22 clone) have both the 2sa1093.
Thanks in advance,
ti 30xb
First off im new on diyaudio and if im posting in the wrong section please move me if needed.
Im also new to amplifier repairs but until now it has been an fun project.
I have an aiwa sa-p22 amplifier with an shorted output transistor. This is an 2sa1093 transistor, but these are not manufactured anymore and i think the ones that are still up for sale are fakes. So im looking for an good replacement transistor. I could not find much information regarding replacing a transistor so im not quite sure which specs need to be matched. I found in some old pdf with transistor replacements that an 2sa1186 would be an good replacement. But this one has an Ft of 60 mhz and the 2sa1093 is 90 mhz.
So is this a good replacement transistor or would i be better of looking for another one?
Also the service manual states that the output transistor is an 2sa1077 and this one has a ft of 60mhz. But the aiwa and my wega 205(aiwa-sa-p22 clone) have both the 2sa1093.
Thanks in advance,
ti 30xb
AS long as you replace both sides with a suitable replacement. The frequency doesn't matter because we do not use anywhere near the limit.
Make sure the power and voltage is the same or higher and the case is similar. TO3p
Make sure the power and voltage is the same or higher and the case is similar. TO3p
thanks for the quick answers.
i will order the FJA4210/4310 pair and replace all outputs.
could one of you explain or point me to an article or book where is explained when a transistor is a suitable replacement? If i ever run in this problem again i would like to be able to solve this myself. And googling didnt give me anything useful, only that the voltages should be higher or the same. but nothing about hfe or other parameters.
i will order the FJA4210/4310 pair and replace all outputs.
could one of you explain or point me to an article or book where is explained when a transistor is a suitable replacement? If i ever run in this problem again i would like to be able to solve this myself. And googling didnt give me anything useful, only that the voltages should be higher or the same. but nothing about hfe or other parameters.
BOB.... again by the usual suspects
there is two kinds of approach
A make the thing play some music
B make it properly or if possible better than before
you have to imagine that output transistors are like car tires you CANNOT change only left or only right you need to change both ...these need to be equal and properly allied ...
Voltage should be close bit bigger will add more safety
amperes should be the same bit bigger will add more safety
Watts should be the shame bit bigger will add more safety
now its said bit bigger because if much bigger previous stages might not be able to drive them properly
Speed should be alike close if possible lower speed is a degrade for the amplifier higher or much higher speed might also cause complications since there is "speed guards" specifically made for the specific choice of manufacturer transistor . So either you degrade the amp and you are safe or upgrade the amp and work with what i called "speed guards" which in electronics is called in general compensation and are the actual speed limits for the transistors .
speed limits in amplifiers are used to prevent that very fast transistors might start running on their own a phenomenon called in electronics oscillation which is enough to destroy an amplifier
Capacitance ( extremely critical ) Every transistor will behave also like a capacitor or a complex load for the previous stages ...So one transistor might be an other wise correct replacement but having too much capacitance might cause previous stages that drive outputs unable to work properly , to provide enough drive , or drive without problems like ones mentioned above like oscilation .
Gain or hfe is the gain of a transistor that also should be close but less critical ...An amplifier is based on 3-4 stages and gain should be distributed under some logic you cannot expect one of the stages to do all the work ...these are rules to be kept .
In general though differences like the above is screaming that a bad choice will have drive / bias/idle or compensation issues
Your case is far more sensitive since behind your output transistors there is a drive IC ( in a schematic that probably nobody bother to look ) In other amplifiers there is discrete parts so tweaks are allowed and probably adjustments like idle also a very critical function of one amplifier .
So one IC might have far more troubles driving one "unknown " output transistor and IN NO CASE none of these transistors is a drop in replacement .
So in your case one should see from the service manual settings like bias record this on a paper choose outputs under the above rules , and see if these can be driven and biased same way like the working ones ....dropping anything available might work but will not work for life ...
One other option might be is to read the datasheet of the drive IC and see what is able to drive then you will know what is capable off
Specifically
2SA 1077 120V 10A 60W 300-470pf 30-60Mhz
2SA 1093 120V 8A 80W 150pf 90-Mhz ( yes that is close )
2SA 1186 150V 10A 100W 110pf 60-Mhz (also close but not the best)
FJA 4210 200V 10A 100W 400pf 30Mhz ( no way Jose )
In all of these cases there is mechanic work to be done since package is different all of these transistors if found are expected to be fake and its just a question of luck to find an original ( except the FJA though )
In fashion now days there plenty of available 2SA 1694 and can be found cheap and original its a close replacement but slower 20mhz only and still will need mechanical work since those are bigger than the ones you have ...
finally i will take a look tomorrow in my stock to see if any 1077 original are available to save you trouble...In between though you should also start:
-- reading articles about how capacitors age through time in audio amplifiers
--making sure that no other parts are doomed inside your amp
--looking if drive IC is still functional
--Looking if drive IC is still somewhere available
my 2cents ...in plain Greek i expect the "experts" to excuse my sayings since i tried to keep it simple for a non experienced user to read
Kind regards
Sakis
there is two kinds of approach
A make the thing play some music
B make it properly or if possible better than before
you have to imagine that output transistors are like car tires you CANNOT change only left or only right you need to change both ...these need to be equal and properly allied ...
Voltage should be close bit bigger will add more safety
amperes should be the same bit bigger will add more safety
Watts should be the shame bit bigger will add more safety
now its said bit bigger because if much bigger previous stages might not be able to drive them properly
Speed should be alike close if possible lower speed is a degrade for the amplifier higher or much higher speed might also cause complications since there is "speed guards" specifically made for the specific choice of manufacturer transistor . So either you degrade the amp and you are safe or upgrade the amp and work with what i called "speed guards" which in electronics is called in general compensation and are the actual speed limits for the transistors .
speed limits in amplifiers are used to prevent that very fast transistors might start running on their own a phenomenon called in electronics oscillation which is enough to destroy an amplifier
Capacitance ( extremely critical ) Every transistor will behave also like a capacitor or a complex load for the previous stages ...So one transistor might be an other wise correct replacement but having too much capacitance might cause previous stages that drive outputs unable to work properly , to provide enough drive , or drive without problems like ones mentioned above like oscilation .
Gain or hfe is the gain of a transistor that also should be close but less critical ...An amplifier is based on 3-4 stages and gain should be distributed under some logic you cannot expect one of the stages to do all the work ...these are rules to be kept .
In general though differences like the above is screaming that a bad choice will have drive / bias/idle or compensation issues
Your case is far more sensitive since behind your output transistors there is a drive IC ( in a schematic that probably nobody bother to look ) In other amplifiers there is discrete parts so tweaks are allowed and probably adjustments like idle also a very critical function of one amplifier .
So one IC might have far more troubles driving one "unknown " output transistor and IN NO CASE none of these transistors is a drop in replacement .
So in your case one should see from the service manual settings like bias record this on a paper choose outputs under the above rules , and see if these can be driven and biased same way like the working ones ....dropping anything available might work but will not work for life ...
One other option might be is to read the datasheet of the drive IC and see what is able to drive then you will know what is capable off
Specifically
2SA 1077 120V 10A 60W 300-470pf 30-60Mhz
2SA 1093 120V 8A 80W 150pf 90-Mhz ( yes that is close )
2SA 1186 150V 10A 100W 110pf 60-Mhz (also close but not the best)
FJA 4210 200V 10A 100W 400pf 30Mhz ( no way Jose )
In all of these cases there is mechanic work to be done since package is different all of these transistors if found are expected to be fake and its just a question of luck to find an original ( except the FJA though )
In fashion now days there plenty of available 2SA 1694 and can be found cheap and original its a close replacement but slower 20mhz only and still will need mechanical work since those are bigger than the ones you have ...
finally i will take a look tomorrow in my stock to see if any 1077 original are available to save you trouble...In between though you should also start:
-- reading articles about how capacitors age through time in audio amplifiers
--making sure that no other parts are doomed inside your amp
--looking if drive IC is still functional
--Looking if drive IC is still somewhere available
my 2cents ...in plain Greek i expect the "experts" to excuse my sayings since i tried to keep it simple for a non experienced user to read
Kind regards
Sakis
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2SA1077 seems to be not available in my stock but seems that a local shop has it in stock I will have to take a look verify the quality and get back to you .
Kind regards
Sakis
Kind regards
Sakis
hello sakis,
i really apreciate the detailed explanation, thank you. I know the schematics say that the output transistors are 2sa1077 but my amp has the 2sa1093 in it. Also i have an wega 205 this a clone of the aiwa 22 and this one uses also 2sa1093. So i think the 2sa1093 is what was originally put in the amp even tho the schematics say otherwise. Maybe there was a last minute change and they didnt put it in the schematics? Maybe the 2sa1077 will work but than i would need 2 sets of 2sa1077/2sc2527 tot test this. i will test the driver ic this weekend and look if they are still functional. Also as you said i tried to look up the data sheet for these but there doesnt seem te be one on the internet. Only thing i could find was that these where also used in a couple of sony amps. I looked for a replacement transistor for the 2sa1093 with the explanation you gave me but there seems nothing close in the 90 mhz range unfortunately. Most seem to be slower or are darlington transistors but they have a way to high hfe.
Dan
thank you for the ebay link. But i have read a lot of bad thing about buying transistors on ebay. And with shipping the transistor would be around 30 dollars for me and that is a little bit high, as it could be potentially a fake.
kind regards,
Bas
i really apreciate the detailed explanation, thank you. I know the schematics say that the output transistors are 2sa1077 but my amp has the 2sa1093 in it. Also i have an wega 205 this a clone of the aiwa 22 and this one uses also 2sa1093. So i think the 2sa1093 is what was originally put in the amp even tho the schematics say otherwise. Maybe there was a last minute change and they didnt put it in the schematics? Maybe the 2sa1077 will work but than i would need 2 sets of 2sa1077/2sc2527 tot test this. i will test the driver ic this weekend and look if they are still functional. Also as you said i tried to look up the data sheet for these but there doesnt seem te be one on the internet. Only thing i could find was that these where also used in a couple of sony amps. I looked for a replacement transistor for the 2sa1093 with the explanation you gave me but there seems nothing close in the 90 mhz range unfortunately. Most seem to be slower or are darlington transistors but they have a way to high hfe.
Dan
thank you for the ebay link. But i have read a lot of bad thing about buying transistors on ebay. And with shipping the transistor would be around 30 dollars for me and that is a little bit high, as it could be potentially a fake.
kind regards,
Bas
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