Are you sure you did not short some output cable/connector during the dragging?
This is the most possible thing that I can think of.
About original Motorola (now ONSEMI) 15003 / 15004 I can vouch for them ruggedness. I have used them by the hundreds. Some of them are in my toolbags as spares and have done hundred of thousands Km by car and airplane, with so much vibrations that often the labels get erased . Never had one of them damged (i.e. internal wiring disconnected). They fail, conistently by thermal breakdown (and output shorts of course) and you always find them shorted.
Other brands I found less relaible, not sure why. Of course I am speaking of original parts, bought directly from the manufacturer or reputable suppliers.
This is the most possible thing that I can think of.
About original Motorola (now ONSEMI) 15003 / 15004 I can vouch for them ruggedness. I have used them by the hundreds. Some of them are in my toolbags as spares and have done hundred of thousands Km by car and airplane, with so much vibrations that often the labels get erased . Never had one of them damged (i.e. internal wiring disconnected). They fail, conistently by thermal breakdown (and output shorts of course) and you always find them shorted.
Other brands I found less relaible, not sure why. Of course I am speaking of original parts, bought directly from the manufacturer or reputable suppliers.
On opening one of the transistors, I found the internal lead of one transistor is melted and the collector/body shows fireworks. So, I suspect this lead sparking on the collector(due to vibration) has blown the transistors. To make matters worse, I had left the 100 ohm resistors across the fuses which gave current path to the complementary transistors.
Gajanan Phadte
Gajanan Phadte
A few possibilities. What you are seeing is the typical destruction due to external overstress. Something shorted causing the magic smoke to be released. Could it have been vibration caused a open that sent one side to the rails? Speaker lead? Who knows. Would it just be vibration causing the transistor fail? I seriously doubt it. One very doubtful, is back in the 80's we had some Moto's where one pin was too close to the case. We saw some parts where the glass passivization layer had thin spots and weld splatter inside the case would get knocked loose and cause a short. Again, I really doubt it.
Depending on your hardware stack, sockets can easily cause issues with connection to the case. People do stupid things like use star washers instead of a stack of bevel washers, and they rely on the screw threads into the socket for the electrical connection rather than putting lugs right on the case under the hardware stack. 10 years in Failure analysis, I will not use TO-3 packages.
Depending on your hardware stack, sockets can easily cause issues with connection to the case. People do stupid things like use star washers instead of a stack of bevel washers, and they rely on the screw threads into the socket for the electrical connection rather than putting lugs right on the case under the hardware stack. 10 years in Failure analysis, I will not use TO-3 packages.
There is a possibility of connecting wires if needed but there are no generally used connectors. I decided not to struggle to buy/get the unobtainium in this part of the world. I pull out terminal strips, were different in length.
The transistor, as I mentioned in my post has blown due to the internal lead touching the collector(body). The small lead also shows the ball end due to melting.
Gajanan Phadte
The transistor, as I mentioned in my post has blown due to the internal lead touching the collector(body). The small lead also shows the ball end due to melting.
Gajanan Phadte
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No doubt many of you have read this ESP article and stared in disbelief at the images.
Counterfeit Transistors
I'm fairly certain by visual comparison, that the die in your pic is way undersize and that alone says you have a fake,
despite the base and heat spreader appearing to be correct size.
Counterfeit Transistors
I'm fairly certain by visual comparison, that the die in your pic is way undersize and that alone says you have a fake,
despite the base and heat spreader appearing to be correct size.
Those distributors often price their products according to the local maket. Here, we pay 2-3 times the US price for Sanken Allegro power transistors - from the same supplier organisation and UK stock! For DIY, I'm happy to wait a few days and get better prices from other sellers.
Surely in a vast population like India, there are other local, authorized distributors of On-Semi parts. These are a world industry standard and widely specified in commercial equipment where nobody, in any country, can afford failures due to fakes or incompetence in maintaining their mission-critical equipment.
I SERIOUSLY doubt it. This is NORMAL when it ARCS to the case due to overstress. We saw this all the time in the FA lab.
This is for info and not defense...
When this happened, the amp was doing hardly 10 watts per channel communication(not music).
My wife never increases the volume beyond 15 Watts and this amp is hardly used for music.
This was constructed to prove(to myself) the readings at DIYAUDIO. Never increased it to reach even 100Watts for one minute. You can't sit in the small living room, if done.
It is connected to the STB and what comes out is the irritating communication of the family dramas running whole day, six days a week.
Gajanan Phadte
Speaker SENSITIVITY: 97dB @ 2.83V / 1m
When this happened, the amp was doing hardly 10 watts per channel communication(not music).
My wife never increases the volume beyond 15 Watts and this amp is hardly used for music.
This was constructed to prove(to myself) the readings at DIYAUDIO. Never increased it to reach even 100Watts for one minute. You can't sit in the small living room, if done.
It is connected to the STB and what comes out is the irritating communication of the family dramas running whole day, six days a week.
Gajanan Phadte
Speaker SENSITIVITY: 97dB @ 2.83V / 1m
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With speakers that sensitive, I can't imagine TV listening would require more than a few watts in an average dwelling. If you have a large room...well how large? The power demand could be orders greater but I don't think we are really talking that big.
As before, I'm convinced from your pic. that the transistor is fake but it could still work fine at low power as it did, since the chip could be from many TO220 types that could perform well enough but who can say after failure, how long or precisely where the bonding wire was located in that example.
The amp is still working on the fakes. I have bought more of them and when blown up for some time, nothing will go wrong. The only thing I found is that there could be some originals also. Presently, I don't know how many are fakes or originals are in the other channel as they cannot be seen without dismantling. The replaced ones are all fakes, 100% sure. Now I know how to identify them by looks.
Gajanan Phadte
Gajanan Phadte
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Its just too small!
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