Pics of the area in question. The issue is with the first output device top left.
I have other pics of vanilla boards , dont want to inundate u guys.
Repaired is a few times so traces are gone from top a few places but actual traces are below the board. The connections are fine.
I have other pics of vanilla boards , dont want to inundate u guys.
Repaired is a few times so traces are gone from top a few places but actual traces are below the board. The connections are fine.
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Pic 2
The key here is that all 4 base stoppers originate from a 180 ohm resistor tied to the drivers emitter, so its not like they are getting different voltage drives , they all get the exact same drive.
The key here is that all 4 base stoppers originate from a 180 ohm resistor tied to the drivers emitter, so its not like they are getting different voltage drives , they all get the exact same drive.
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Fine.
Then do what I did to avoid junking 100 TDA2050 ... specially since there are NO "reliable supplier" sourced ones, Mouser and others show "0" stock available, "out of production" ,etc. so next best was to DERATE them.
Who wants 91V rails on a Home Theater system? 😕
Since you have them, use your available boards and 96 transistors but at, say, 60V rails or so, where in general your transistors worked fine, except *one*.
To avoid blow up you must use them within their **actual** ratings, period.
You still have crazy high power available for your intended use.
Are these Ebay boards? Where did the output devices come from? As Nigel suggests, it's not really much use changing a single transistor, normal practice with On Semi parts is use devices from the same production batch. If a device fails the devices in the preceding stage should be replaced as well, as they would have taken a hit when the output device failed.
You dont have to buy 96 to prove the problem just one set for one amp.
If that fixes the amp you know where you are.
If it doesn't fix it then the problem is elsewhere.
Where did the original 96 comes from ?
If that fixes the amp you know where you are.
If it doesn't fix it then the problem is elsewhere.
Where did the original 96 comes from ?
Yes eBay boards.
Should I just start putting in MJL21193/94’s in, I have a few of those... from a known source.
Should I just start putting in MJL21193/94’s in, I have a few of those... from a known source.
Those devices are pretty slow by todays standards and are prone to cross-conduction failures in faster amplifier designs.
We are assuming they are fake... I just put the photos of the uncovered njw0302 on the fake bjt thread. Looking at the pics, they are saying it looks like an oem part. That’s what I feel too.
JMF, should I derate base or ER?
JMF, should I derate base or ER?
I have a couple of pull out original 2sa1302/s3281’s that are fast... but not enough to fill the entire rail. Some a1987/c53xx’s too...
As far as I know you don't get original 2240/970 transistors any more, maybe they are fake as well. Increase the Re to 0.47 or 0.68R, the voltage drop over the emitter resistor will be lower.I will not trust any components in that kit.
Same story over again. Semiconductors from Ebay.
Countless pages of:
"Are you sure they are fake?"
"Maybe they are real?"
"Why would they be fake?"
(...)
Just because these transistors are from Ebay - 50% chance they are fake.
Now, because they come from China - 95% chance they are fake.
And finally, since one of them already died for no reason - 99.99% chance they are fake.
Do not fool yourself.
This was said many times already - do NOT buy semiconductors via Ebay.
As we all can see, it does not save any money.
If you need Soviet germanium transistors GT308B, and Ebay seller is from Tomsk, Siberia - yes - they gonna be real.
But otherwise - I guess not 🙂
Countless pages of:
"Are you sure they are fake?"
"Maybe they are real?"
"Why would they be fake?"
(...)
Just because these transistors are from Ebay - 50% chance they are fake.
Now, because they come from China - 95% chance they are fake.
And finally, since one of them already died for no reason - 99.99% chance they are fake.
Do not fool yourself.
This was said many times already - do NOT buy semiconductors via Ebay.
As we all can see, it does not save any money.
If you need Soviet germanium transistors GT308B, and Ebay seller is from Tomsk, Siberia - yes - they gonna be real.
But otherwise - I guess not 🙂
Tks Jan.
I used a 0.47e. The vdrop on the ER went from 10.4mV to 16.3mV. I wood have expected an increase in vdrop but decrease in Current. But the bias on that device is still 35mA vs 25mA for the others. I can try 0.68, but this will be amost 3x derating vs the rest.
That's what I would do. I guess you can't return it...
Also, it's safe to assume that this kit will have "mediocre" audio qualities at best (especially after "derating"),
not what was expected.
There is no point in trying to rescue this, and take more risks..
One transistor died - apparently couldn't handle the voltage, we are not even talking high amps at this point.
What's gonna happen when you really try to "pump up the volume" ?
If you decide to do so - keep fire extinguisher handy 🙂
Also, it's safe to assume that this kit will have "mediocre" audio qualities at best (especially after "derating"),
not what was expected.
There is no point in trying to rescue this, and take more risks..
One transistor died - apparently couldn't handle the voltage, we are not even talking high amps at this point.
What's gonna happen when you really try to "pump up the volume" ?
If you decide to do so - keep fire extinguisher handy 🙂
It’s not as bad. Before I fried it with hi volt rails on this kit. I had it running in bridged mode with 60v rails, with full power ( I was rigging up a crossover for a driver with alligator clips) via safety resistor. I did something stupid... with all the cables running, I accidentally shorted the output at full power... I heard a 4 kHz tone either from the PSU or the other channel that was not being driven for a moment and baam, DC fuses obliterated. I thought I blew the amp, but after checking everything and replacing the fuses, it was back working again. I have never shorted a power amp at full power and it only blew the fuses... it’s always the other way around....
I intend to keep on ploughing with this 🙂.
I intend to keep on ploughing with this 🙂.