Hi, I have built a PSU useing LM7XXX Pos and neg regulators but they don"t seem to be working......
I am useing the 15v regulators and I am useing a 18v 0v 18v Torroid and the PSU is supposed to Provide 15v regulated for Preamps and Unregulated 25v for the Power amp stage.....
When I measure the Voltages I get -10v on the Neg regulator and 0 v on the Positive regulator but the unregulated power is Fine at 25v......
Here is a Pic of the Schematic and my PCB layout......
The only change from the Schematic is that I am useing 10,000uF caps as the filter caps as opposed to 1000uF used in the schematic.......
Can someone please point out were my Problem is???
Thanx a Lot.....
I am useing the 15v regulators and I am useing a 18v 0v 18v Torroid and the PSU is supposed to Provide 15v regulated for Preamps and Unregulated 25v for the Power amp stage.....
When I measure the Voltages I get -10v on the Neg regulator and 0 v on the Positive regulator but the unregulated power is Fine at 25v......
Here is a Pic of the Schematic and my PCB layout......
An externally hosted image should be here but it was not working when we last tested it.
The only change from the Schematic is that I am useing 10,000uF caps as the filter caps as opposed to 1000uF used in the schematic.......
Can someone please point out were my Problem is???
Thanx a Lot.....
That was the First thing I checked, and the regs are in correctly
Wait!!!! I think I have got it,....OK....I think I have found the Problem , I think I might have the Pos and neg regulators switched......
I"ll check later to make sure.....Thanx
Wait!!!! I think I have got it,....OK....I think I have found the Problem , I think I might have the Pos and neg regulators switched......
I"ll check later to make sure.....Thanx
I also thought he had got the pins wrong at first, but it turned out the pins are numbered in the order 1,3,2, not 1,2,3 for some obscure reason.
Edit: Or maybe not so obscure. It is probably so they can have the same pin number for the same function for all package types, but is confusing.
Edit: Or maybe not so obscure. It is probably so they can have the same pin number for the same function for all package types, but is confusing.
Thanx Guys....I figured it out....It was that I accidentaly put the Pos reg on the Neg rail and the Neg reg on the Pos rail....
After changeing the regs the Amp is working correctly, it still has a Pretty Bad Hum problem even though I star grounded everything to the same Chassis ground point.....
It was a simple 18w Guitar amp useing a couple BC550/560 and an OPA627 and a couple Tip41/42 Transistors for the Power amp stage and an all J-fet preamp stage.......
Cheers
After changeing the regs the Amp is working correctly, it still has a Pretty Bad Hum problem even though I star grounded everything to the same Chassis ground point.....
It was a simple 18w Guitar amp useing a couple BC550/560 and an OPA627 and a couple Tip41/42 Transistors for the Power amp stage and an all J-fet preamp stage.......
Cheers
minion , the fixed voltage regs tend to be more noisy than a properly used variable one.... you may want to increase the caps on output side to about 100uf... not more, as you will start the reg. ringing...
Just after the bridge, I would (if I desgned it) probably have used 2 sets of filtercaps (and probably only 2200uf each) seperated by a 1 or 2 Watt 10R resistor...
Just after the bridge, I would (if I desgned it) probably have used 2 sets of filtercaps (and probably only 2200uf each) seperated by a 1 or 2 Watt 10R resistor...
Hi, I actually Have some 100uF caps on the Preamp and Power amp PCB"s close to the Opamp pins and close to the Output transistors......
I was going to use the LM317/337 regs but It turned out that i ran out of the Positive 317 regulators so I use the 7XXX regs as that was all I had on hand.....
Cheers
I was going to use the LM317/337 regs but It turned out that i ran out of the Positive 317 regulators so I use the 7XXX regs as that was all I had on hand.....
Cheers
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