You know what, I haven't seen a dead TV on the side of the road here in a long time, so that might not be an option for me. Here it's kind of hard to find "free" TVs, I could scrap some stuff from goodwill but that's another story.
If you really don't think it's worth it, I might hold out, but this TV was going to the dump anyway. Wasn't really planning on selling it, was looking around on craigslist and it seems a little saturated with the same kind of deal, maybe could get $50 for it. At this point, I'm saving on not buying the heatsink from digikey, I have one in my garage, in a TV. Also 2 20 W speakers in there. Let me know what you think.
$50 is worth an hour of my time, to demo the unit to a craigslist fan. But I'm retired. The stuff you need is in 24" TV's too, and you can get those at goodwill etc for $20. Put an ad on craigslist you need a dead flat screen for $10, that will save someone the disposal fee. Don't leave your phone or text #, use the blind box that disappears when you kill the ad.
The flat screen ones are rare on the curb around here, but the projection TV's I've seen 3 of in the last 6 months, and dozens of the CRT kind. CRT TV don't have much useful in them. And those power resistors will be all the wrong value IMHO. That's why they don't put them on the curb here. They just changed over to mandatory electronic salvage stickers here, lots of people don't have the news yet and TVs sit for weeks. I've got the LED TV boards sitting in my LR under the organ and I've only salvaged the heat sinks off it. None of the values I needed in 5 W resistors was there, had to order them.
The flat screen ones are rare on the curb around here, but the projection TV's I've seen 3 of in the last 6 months, and dozens of the CRT kind. CRT TV don't have much useful in them. And those power resistors will be all the wrong value IMHO. That's why they don't put them on the curb here. They just changed over to mandatory electronic salvage stickers here, lots of people don't have the news yet and TVs sit for weeks. I've got the LED TV boards sitting in my LR under the organ and I've only salvaged the heat sinks off it. None of the values I needed in 5 W resistors was there, had to order them.
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Hmm, well I appreciate your input, but I think I'm going to go through with destroying this bad boy. The heatsinks/experience alone are worth it for me, now I don't have to buy any.
I'm going to take a look at simming the two amps stacked on top of each other, but at, if I remember correctly, the 3 ish watts each. I don't need up to 7 really, and running a stereo mix is better IMO.
Thanks for all your help again today
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Hey,
I simulated two on top of each other with the RF choke at the speaker, seems to work out, you can see how much it attenuates towards 50-100 Mhz. My thought process for the two 1000 uF caps instead of one 2200 uF cap is that I'll get 2000 uF worth of capacitance, but mechanically the response of the 1000 uF caps will be faster, even just by a tiny bit, than the 2200 uF. Maybe there's a tradeoff in terms of noise/ESR/dialectric noise (if that's a thing).
What do you think about the Vcc/2 node into the 2 100k's in parallel? That's how I serve that voltage to the op amp, right?
Thanks.
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The one op amp giving reference voltage to the negative input of the other two op amps is fine. The spare you don't need, you'll have to tie one input to negative rail and one through a 1k resistor to output to keep it from oscillating.
Yeah, paralleling smaller caps gets lower ESR than bigger caps, and they are cheaper, too. But it takes time, to build the bus rail. I saved $20 by paralleling 3 each 3300 uf caps to make one 9900 uf cap X 2 for 2 channels, because 10000 uf caps were about $26. I had the 3300 in stock and they were getting old, 3 years old on a projected life of 20 without heat stess.
Speaking of life, you're probably not worried about it on a 10 W amp that you will upgrade or replace when you graduate. But I've replaced main caps in my college amp 4 times since 1970 when I bought it. Too much work. Those days I had to buy whatever was on the shelf of the TV parts shop, but now one can buy premium grade electrolytic caps. In future look for service life of 10000 hours on electrolytic caps up to 100 uf and 3000 hours on caps above that. They use cheaper rubber sealant on the high volume cheap e-caps, which deteriorates working or even sitting on the shelf due to oxygen in the air.
I suspect your output inductor may stop even 610 khz, which is AM radio band. Peavey says their 15 turn standard part is 0.8 milliHenry. If not, that is why they put the .01 uf series 1000 ohms "zobel" parallel to the output, too. My silent amp (a little hum due to bad solder joint sometimes) has both. Peavey have 47kohm series 2.2 uf parallel on the output, but that besides a zobel filter is the trigger to the DC voltage crowbar triac. That triac blows the breaker (you hope) if the amp produces DC on the speaker.
Yeah, paralleling smaller caps gets lower ESR than bigger caps, and they are cheaper, too. But it takes time, to build the bus rail. I saved $20 by paralleling 3 each 3300 uf caps to make one 9900 uf cap X 2 for 2 channels, because 10000 uf caps were about $26. I had the 3300 in stock and they were getting old, 3 years old on a projected life of 20 without heat stess.
Speaking of life, you're probably not worried about it on a 10 W amp that you will upgrade or replace when you graduate. But I've replaced main caps in my college amp 4 times since 1970 when I bought it. Too much work. Those days I had to buy whatever was on the shelf of the TV parts shop, but now one can buy premium grade electrolytic caps. In future look for service life of 10000 hours on electrolytic caps up to 100 uf and 3000 hours on caps above that. They use cheaper rubber sealant on the high volume cheap e-caps, which deteriorates working or even sitting on the shelf due to oxygen in the air.
I suspect your output inductor may stop even 610 khz, which is AM radio band. Peavey says their 15 turn standard part is 0.8 milliHenry. If not, that is why they put the .01 uf series 1000 ohms "zobel" parallel to the output, too. My silent amp (a little hum due to bad solder joint sometimes) has both. Peavey have 47kohm series 2.2 uf parallel on the output, but that besides a zobel filter is the trigger to the DC voltage crowbar triac. That triac blows the breaker (you hope) if the amp produces DC on the speaker.
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THD at 0.4%, which for me I guess is good, I saw some other amps they get all the way down to 0.0001 huh, that's insane.
I think I want to order some parts today, while I have the motivation. Build this damn shitty thing. I'm going to do a one quick last sweep, get the 200p's in there, look at the higher rated cap you suggested, remove the bad resistors in the 1000s minimum quantity, remove the heatsink, I'll probably post it here in 30 minutes.
Edit: another thiing I realized, is that my input signal is going to be on the value of 50-150 mV, as I plan to play music from my phone, gotta redo some gain stuff.
EDIT2: Final bom, what do you think? i took out the 100 uF ceramic, I have some electrolytes, couldn't find one above 6.3 V that wouldn't break the bank
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Cap C9 if electrolytic has to be non polar. Or digikey is now calling them bipolar. As this one UVP1J101MHD Nichicon | Capacitors | DigiKey
Regular electrolytics if subjected to > 20% rated voltage backwards, pop the top & leak the fluid out.
Regular electrolytics if subjected to > 20% rated voltage backwards, pop the top & leak the fluid out.
Okay. I'm gonna see what they have at school. I just ordered everything without that cap. In the digikey order I also got some male banana plug headers. So I can make some connectors to the speakers with the wire I bought.
Twisted pair. If I do the power supply circuit on another small perforated board, and connect that to the main board for the rails etc, should I make that connection with twisted pair? Or is that unnecessary?
Twisted pair is not usually necessary for short power supply runs. Don't include any magnetic field generators like power transformers in the area of the separation of the two wires.
Twisted pair is useful for long runs of medium impedance (50 to 10000 ohms) signals, as for example the microphone signals from the stage to the mixer 15 m out in the audience.
I also run base drive and voltage rail signals individually from my AX6 driver board, to the output transistors 2" away on the heat sink. Not twisted. It hasn't been a hum issue, since the power transformer is in the other end of the chassis.
Twisted pair is useful for long runs of medium impedance (50 to 10000 ohms) signals, as for example the microphone signals from the stage to the mixer 15 m out in the audience.
I also run base drive and voltage rail signals individually from my AX6 driver board, to the output transistors 2" away on the heat sink. Not twisted. It hasn't been a hum issue, since the power transformer is in the other end of the chassis.
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Okay sounds good. I'm excited to get this thing built.
Again, thanks for all your thoughts and input on this project.
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