Of course not. I have a power supply board with 4700uf cap and a bridge rectifier
Can you measure the resistance (with power disconnected, of course, and after the caps have had a bit to discharge) between the positive side of the 2200 uF cap and ground?
Okay, got a minute, Talledega NASCAR race was red flagged for a while. This hobby is cheaper than that one, except when race is on free TV channel like today.
You need to run the transformer from a light bulb box, 100 W light bulb in series with the primary. I use a grounded box so loose wires don't shock me or start fires. That will give you enough time to make measurements.
These transistors possibly didn't come from farnell via UPS. In some countries, if the store didn't substitute counterfeits, the postal or freight forwarders will substitute genuine parts from farnell/mouser/digikey with counterfeits. Repack, you'd never know. Some repairmen check a few from every batch shipped.
I'd check all drivers and output transistors for Iceo leakage. 22k resistor in series with ma scale of a dvm, then plus to npn C, minus to npn E, base open, how many milliamps. Opposite polarity on the pnp. Current should be less than Iceo on the datasheet. Most counterfeits will fail with 12 vdc out of a car/motorcycle battery charger, but you have 50 to play with.Use clip leads so you don't touch the voltage.
You need to run the transformer from a light bulb box, 100 W light bulb in series with the primary. I use a grounded box so loose wires don't shock me or start fires. That will give you enough time to make measurements.
These transistors possibly didn't come from farnell via UPS. In some countries, if the store didn't substitute counterfeits, the postal or freight forwarders will substitute genuine parts from farnell/mouser/digikey with counterfeits. Repack, you'd never know. Some repairmen check a few from every batch shipped.
I'd check all drivers and output transistors for Iceo leakage. 22k resistor in series with ma scale of a dvm, then plus to npn C, minus to npn E, base open, how many milliamps. Opposite polarity on the pnp. Current should be less than Iceo on the datasheet. Most counterfeits will fail with 12 vdc out of a car/motorcycle battery charger, but you have 50 to play with.Use clip leads so you don't touch the voltage.
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I thought that might be the case.
Perhaps the collector of the bottom power transistor is shorted to ground? It might be a defect in the insulating washer/system.
Perhaps the collector of the bottom power transistor is shorted to ground? It might be a defect in the insulating washer/system.
With the power transistors removed there is no short connection to ground. And it takes just seconds for the transistor to fail. I dont know why it happens. Maybe faulty transistor. Or maybe because i use Tip41C/Tip42C as drivers ?
I didn't think you were connecting the transistor pads of TO220 to the printed board. Those should just go to miniature aluminum heat sinks.
I use TIP41c/42c as drivers, my AX6 board is going over a year old. Mine are genuine Fairchild shipped direct from the US farnell warehouse (newark). I use 70 v rail voltage, regulated.
Some of the heat sinks I use on drivers and VAS are just pieces of aluminum window frame, with holes drilled in, bolted to the TO220 package with heat sink compound between. Gave me time to sort things out when I had a major wiring error. My boards are point to point, not PCB, and I had the function of various 220 ohm resistors confused for a long time.
The light bulb box will slow down the failures so you can make some voltage drop measurements across the 10 ohm base resistors and 220 ohm driver resistors to see where the fault lies. But as I said your supply chain may not be as rock solid reliable as farnell(US) to UPS to my door has been. Iceo test at 50v should give you some confidence in your TO220 transistors or condemn them as fake. If you don't have transistor datasheets, download them from datasheetcatalog.com in pdf format. pdf reader is a giveaway, I got mine from the US govt IRS website.
I use TIP41c/42c as drivers, my AX6 board is going over a year old. Mine are genuine Fairchild shipped direct from the US farnell warehouse (newark). I use 70 v rail voltage, regulated.
Some of the heat sinks I use on drivers and VAS are just pieces of aluminum window frame, with holes drilled in, bolted to the TO220 package with heat sink compound between. Gave me time to sort things out when I had a major wiring error. My boards are point to point, not PCB, and I had the function of various 220 ohm resistors confused for a long time.
The light bulb box will slow down the failures so you can make some voltage drop measurements across the 10 ohm base resistors and 220 ohm driver resistors to see where the fault lies. But as I said your supply chain may not be as rock solid reliable as farnell(US) to UPS to my door has been. Iceo test at 50v should give you some confidence in your TO220 transistors or condemn them as fake. If you don't have transistor datasheets, download them from datasheetcatalog.com in pdf format. pdf reader is a giveaway, I got mine from the US govt IRS website.
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Hi guys
I've just built the amp and works just fine with low volume but when I turn up the volume low frequencies start to crash but high frequencies are just fine
Thanks
I've just built the amp and works just fine with low volume but when I turn up the volume low frequencies start to crash but high frequencies are just fine
Thanks
Has anyone tried running this amp in bridge sort of like a crown floating grounded bridge?
If it distorts on low frequency it could be due to insufficient current or type of oscillation called motorboating put a 100Hz signal in and check with a scope
If it distorts on low frequency it could be due to insufficient current or type of oscillation called motorboating put a 100Hz signal in and check with a scope
I know It's a dumb question but can I modify this amp in order to run it from dual +-40v power supply ?
It could be done. The main problem would be DC stability of the amplifier output and so a servo (OpAmp) would normally be used. There are a few other small things to change as well.
Why do you want to try doing this ?
Why do you want to try doing this ?
Just use the 80 volts as a single rail and ignore the center tap? Of course keep the output coupling cap....
The beauty of this amp is its single rail. There are countless other dual rail amps to choose from in this Forum or even in Apex Audio's collection of amps. Why try to make an orange out of an apple? If you like oranges, eat an orange. 🙂
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I'll leave it with the single supply and try with +80v
Another question : Maybe instead of 1N4148 I'd use 2x double Schottky To220 and mount it on top of the TO3 transistor ? I'd improve much the temperature compensation I guess.
Another question : Maybe instead of 1N4148 I'd use 2x double Schottky To220 and mount it on top of the TO3 transistor ? I'd improve much the temperature compensation I guess.
Mr. Mile,
Just came across this thread, apologies, if the question is already answered. Can the o/p be modern devices like MJL4281 and drivers MJE150XX
regards
Prasi
Just came across this thread, apologies, if the question is already answered. Can the o/p be modern devices like MJL4281 and drivers MJE150XX
regards
Prasi
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Sure, why not? I had TO3 heat sinks in my single supply chassis, blown up, so I used NTE60 (white box MJ15003). If I were building from scratch I'd use MJL4281 or MJL21194, since the single hole is easier to drill and tap with a hand drill motor. Hard to get four holes to line up right with a hand drill motor.
MJE15028/29 or MJE15032/33 should work better for drivers than the TIP41C/42C I used. Just they were $4.50 each a couple of years ago, now down to $1.25 from Newark.
You can't use the PCB layout on page 1 if you are going to use TO3-P transistors. It is for TO3.
MJE15028/29 or MJE15032/33 should work better for drivers than the TIP41C/42C I used. Just they were $4.50 each a couple of years ago, now down to $1.25 from Newark.
You can't use the PCB layout on page 1 if you are going to use TO3-P transistors. It is for TO3.
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