I have in which some resistors and transistors were burned.I replaced them and it seemed to work for a while but after incresing the sound resistors and one transistor were burned.While iwas testing it i noticed that when turning it on my fluorescent lamp made a sudden little blink.I read that there is probably a short.HOW CAN I FIND THE SHORT.
The amp has relay.Two pairs of 2sc3281/2sa1302 transtors.HOW CAN I FIND THE SHORT
The amp has relay.Two pairs of 2sc3281/2sa1302 transtors.HOW CAN I FIND THE SHORT
Hi pavlos,
Do you have the schematic? A DVM? Anything else?
The reason it burned again was that it wasn't repaired properly the first time. Sorry. Now it's time to get into some detail on it. You may have an intermittent open, so try to consider other possibilities. Keep an open mind and the facts will lead you to the truth.
Also, please take a picture of it and post.
-Chris
Edit: Is there a small bias PCB on teh heat sink? Check all the connections, an open here will do what you describe.
Do you have the schematic? A DVM? Anything else?
The reason it burned again was that it wasn't repaired properly the first time. Sorry. Now it's time to get into some detail on it. You may have an intermittent open, so try to consider other possibilities. Keep an open mind and the facts will lead you to the truth.
Also, please take a picture of it and post.
-Chris
Edit: Is there a small bias PCB on teh heat sink? Check all the connections, an open here will do what you describe.
I have a DVM and some basic kwonledge in electronics but i don't have the schematic.I had made some measurements while trying to repair.At the moment i cant send any foto but i can describe a little the board. The amp has two pairs of high power amplifiers and between them there are are six smaller transistors which are in pairs too.I had change them all.There must be a defective part which i couldn't found.
The capacitors seemed to work.
The capacitors seemed to work.
Hi pavlos,
Your subs are mostly correct
I'll list a bit.
2SA970BL with 2SA970GR - Okay, just gain differences.
2SA1248 S with 2SB649A -Okay 160V 0.7 A compared to 160V 1.5A, the gain is the problem here(?). 2,000+ compared to 320 max for the B649A.
2SC3116 S with 2SD669A -same as above, at least they are compliments
2SA1303 with 2SA1302 -different case styles. At least the new ones are compatible and higher rated.
2SC3284 with 2SC3281
-same as above.
It appears that your driver transistors are completely wrong. I have attached the data sheet from Sanyo, it's not the "S" version and looks like a little higher gain, not a ton like my data book shows. It is entirely possible that your 2SC3281/2SA1302 are fake as ilimzn stated.
Try the On Semi parts from a proper distributor (MJL3281/MJL1302). They should be okay.
-Chris
Your subs are mostly correct
I'll list a bit.
2SA970BL with 2SA970GR - Okay, just gain differences.
2SA1248 S with 2SB649A -Okay 160V 0.7 A compared to 160V 1.5A, the gain is the problem here(?). 2,000+ compared to 320 max for the B649A.
2SC3116 S with 2SD669A -same as above, at least they are compliments
2SA1303 with 2SA1302 -different case styles. At least the new ones are compatible and higher rated.
2SC3284 with 2SC3281
-same as above.
It appears that your driver transistors are completely wrong. I have attached the data sheet from Sanyo, it's not the "S" version and looks like a little higher gain, not a ton like my data book shows. It is entirely possible that your 2SC3281/2SA1302 are fake as ilimzn stated.
Try the On Semi parts from a proper distributor (MJL3281/MJL1302). They should be okay.
-Chris
Hi pavlos,
Instantly I can see one source of potential troubles. A more clear picture would be needed to say much else.
You have not used the original "plate" style non-inductive resistors. Instead I see inductive, wire wound "bathtub" style resistors. These can easily cause the output stage to oscillate. You must use low inductance resistors or the original "plate" style.
-Chris
Instantly I can see one source of potential troubles. A more clear picture would be needed to say much else.
You have not used the original "plate" style non-inductive resistors. Instead I see inductive, wire wound "bathtub" style resistors. These can easily cause the output stage to oscillate. You must use low inductance resistors or the original "plate" style.
-Chris
Hi pavlos,
We can not guarantee anything. It's you with the soldering iron and the eyes. It's your senses and reactions after your decisions that will determine what will happen.
The suggestions that we make are based on what you are telling us. If you miss something, we will too. If the unit were on my bench, then the outcome would be known to me. There are all kinds of clues that experienced servicers look for that we simply do not have access to.
So, the only thing you can really do is look at facts only. Write down things you know and no assumptions are allowed. Wishful thinking will hurt you. Just deal with facts and report them as you see them.
The current gain of your new drivers is much lower than the original numbers. This may present a problem, or not. Too hard to say.
-Chris
We can not guarantee anything. It's you with the soldering iron and the eyes. It's your senses and reactions after your decisions that will determine what will happen.
The suggestions that we make are based on what you are telling us. If you miss something, we will too. If the unit were on my bench, then the outcome would be known to me. There are all kinds of clues that experienced servicers look for that we simply do not have access to.
So, the only thing you can really do is look at facts only. Write down things you know and no assumptions are allowed. Wishful thinking will hurt you. Just deal with facts and report them as you see them.
The current gain of your new drivers is much lower than the original numbers. This may present a problem, or not. Too hard to say.
-Chris
I opened one 2sc3281 and from what i saw i realized tha it was fake.It didn't had die on the chip.I can't find on semi parts.I must order them from another counrty distributor.Is there any complementary transistor
except 3281/1302 that i can find easily.
The fake tr now has C and E short circuited like the original had about
three resistor must have been burned.When i will have time i would make one last effort to fix it.
except 3281/1302 that i can find easily.
The fake tr now has C and E short circuited like the original had about
three resistor must have been burned.When i will have time i would make one last effort to fix it.
Hi pavlos,
Please give the unit some more chances. You have unfortunately found some fake parts. Not the unit's fault at all. I do understand why you are frustrated though. I would be too.
The On Semi parts are the most reliable ones I know of. I don't know what your supply chain is like, and so I would suspect that all Japanese parts you can easily get may be fakes also. You must order from a "clean" distributor.
With this track record, even EeekBay gives you better odds. It is entirely up to you to get good parts. It is not the fault of the unit at all. I wonder if there are any members selling these parts in "trading Place"? You could put a request also.
-Chris
Please give the unit some more chances. You have unfortunately found some fake parts. Not the unit's fault at all. I do understand why you are frustrated though. I would be too.
The On Semi parts are the most reliable ones I know of. I don't know what your supply chain is like, and so I would suspect that all Japanese parts you can easily get may be fakes also. You must order from a "clean" distributor.
With this track record, even EeekBay gives you better odds. It is entirely up to you to get good parts. It is not the fault of the unit at all. I wonder if there are any members selling these parts in "trading Place"? You could put a request also.
-Chris
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.