Adjustable potentiometer
So basically this is what I need but adjustable to 1k. Although as mentioned it has three legs? Would I have to be I solder one of that legs to another? Or just use two of them.
The kit came with the board and components, would've it been better to supply R2&R3 with adjustable trim pots? Unless it's pre set to use on 12v rail voltage. Mine measures 17.2v without load, I'll have to check it with some load.
So basically this is what I need but adjustable to 1k. Although as mentioned it has three legs? Would I have to be I solder one of that legs to another? Or just use two of them.
The kit came with the board and components, would've it been better to supply R2&R3 with adjustable trim pots? Unless it's pre set to use on 12v rail voltage. Mine measures 17.2v without load, I'll have to check it with some load.
Bend the one in the middle to one at the side and solder it together. Like that the trimmer size roughly will be the same as a resistor and will feet nicely.
Set up a 550R bot and replace the two 1K resistors. and from there you can adjust to the req. value.
Make sure after 30 min. warm up readjust and again later when 100% warmed up. Good luck with your project. I hope you like the sound.
ok so used 100R to replace R2 and R3. I tried 500R but the voltage was 2.3V. With 100R the voltage started at 0.418V, after about 1 hour it stayed at a steady 0.635V and the heatsinks and resistors werent at boiling temperature, warm to the touch!
I have one worry though, i thought i would connect my DMM to the speaker output and measure the any voltage, bloody thing is measuring over 14V
that doesn't seem like a good thing??? Another thing i noticed was one of the transistors is hot where as the other one isn't. I mean one transistor is much warmer then the other, it almost feels like one is not working?
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Very likely that transistor is fried, dead from the previous tests.
When you measure such a high bias that will blow up your transistor even at low rail voltage.
Next time when you start up an amplifier using a protection like this.
If the light bulb glows that mean something wrong, I would use a 50W light bulb at the start. Please use normal light bulb (the good old regular bulb)
I also like to connect the DMM between the positive rail voltage and the amp circuit board measuring A.
That case when you power up your amp you can see it right away your PC board draws a tremendous amount of power and you can shut it off much faster. Second reason at this low rail voltage you will get much precise bias measurement.
I would test those driver transistors also for short.
When you measure such a high bias that will blow up your transistor even at low rail voltage.
Next time when you start up an amplifier using a protection like this.
If the light bulb glows that mean something wrong, I would use a 50W light bulb at the start. Please use normal light bulb (the good old regular bulb)
I also like to connect the DMM between the positive rail voltage and the amp circuit board measuring A.
That case when you power up your amp you can see it right away your PC board draws a tremendous amount of power and you can shut it off much faster. Second reason at this low rail voltage you will get much precise bias measurement.
I would test those driver transistors also for short.
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really blew up a transistor! I feel honoured it's my first and probably not my last haha.Ok i have spares so no drama.
Thanks gaborbela, rookie mistake i actually have a variac but a friend is borrowing it, and i did think lets do a light bulb test.
But i checked the PSU, all was fine and working as it should (well from my own knowledge and experiences, which lets be honest is limited and growing as i do this project)
I Assumed the board and its components are designed to take it as a diy kit, plug and play like hell it is.
Anyway getting my variac back and ill build a light bulb tester.
This is getting more fun by the day.
If you want to fry your speaker caused by massive DC at the output before adjustment you're welcome to connect your speaker before doing that
. No, really. The offset have to be adjusted before (!) you connect any speaker to it.
Hi vishalk, me again...
Nothing to do with your current fault, but noticed you have wrapped your transformers in copper foil? Is there a reason for this?
Not sure if it is a good idea, as it is really easy to create a 'shorted turn' on a toroid if the mounting bolt touches both sides of the foil at the same time... It will try to melt the foil and then melt the transformer windings - be careful.
Alan
Nothing to do with your current fault, but noticed you have wrapped your transformers in copper foil? Is there a reason for this?
Not sure if it is a good idea, as it is really easy to create a 'shorted turn' on a toroid if the mounting bolt touches both sides of the foil at the same time... It will try to melt the foil and then melt the transformer windings - be careful.
Alan
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Hi Alan, well I thought I would try some emf screening, so I used copper foil tape just to cover the transformers. I actually just covered the sides and top making sure nothing was touching or shortening out. Also used rubber between the mountings. Just thought I'd try it but since you're concerned I will double check that, aside from blowing transistors I dont really want to melt any transformers.
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If you want to fry your speaker caused by massive DC at the output before adjustment you're welcome to connect your speaker before doing that
No, really. The offset have to be adjusted before (!) you connect any speaker to it.
Lucky I measured it before connecting a speaker then! I need to write a to do list of all the things I should be checking and doing.
10N20 10P20 Audio Mosfet TO3P TO247 Exicon Plastic Lateral ECX10P20R/10N20R | eBay
Guys I found some of these transistors in my stock of parts, would these be OK to use? I looked at the parameters from what I understand these are well within limits.
Also got a pair of
MJL21194G+MJL21193G .
Or what do others here like? Recommended trannies? And if so can I Just replace them or do I have to start changing components based on transistors I use?
Guys I found some of these transistors in my stock of parts, would these be OK to use? I looked at the parameters from what I understand these are well within limits.
Also got a pair of
MJL21194G+MJL21193G .
Or what do others here like? Recommended trannies? And if so can I Just replace them or do I have to start changing components based on transistors I use?
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Thanks guys, well I thought this would be a good time to try different transistors see how they have an effect on sound.
There are many types, makes, brand etc.
For example
2SA1943 / 2SC5200 TOSHIBA High Power Matched Audio Transistor,x2 - BRAND NEW | eBay
These are cheap, I just want to mess around with biasing, practice and see how hot things get, what transistors can cope with etc and if they blow it doesn't matter as they are not expensive.
I thought audio transistors are all similar even those Mosfets. Not sure why you cant use Mosfets as I don't know enough about them
Anyway my point is I would like to buy some good transistors high quality and some cheap ones to practice on.
So will the above Toshibas fit my testing needs.
There are many types, makes, brand etc.
For example
2SA1943 / 2SC5200 TOSHIBA High Power Matched Audio Transistor,x2 - BRAND NEW | eBay
These are cheap, I just want to mess around with biasing, practice and see how hot things get, what transistors can cope with etc and if they blow it doesn't matter as they are not expensive.
I thought audio transistors are all similar even those Mosfets. Not sure why you cant use Mosfets as I don't know enough about them
Anyway my point is I would like to buy some good transistors high quality and some cheap ones to practice on.
So will the above Toshibas fit my testing needs.