Since you are getting some sound, I would assume nothing too critical is going on.
What opamp are you using? Ensure it’s a dual opamp, this has been a cause of one-channel sound before.
If it is dual, sometimes the opamp doesn’t seat properly on those extenders. Try removing it and reinserting it to see if it solves the issue? Or perhaps try a different one?
What opamp are you using? Ensure it’s a dual opamp, this has been a cause of one-channel sound before.
If it is dual, sometimes the opamp doesn’t seat properly on those extenders. Try removing it and reinserting it to see if it solves the issue? Or perhaps try a different one?
Thanks - just fixed it. One of the input leads wasn't grounded. I am getting a light buzz and I saw @6L6 has a cap between the RCA grounds and case/earth so I'll try that to see if it quiets it.
Love it!
Listening to Mark Knopfler's 5:15 AM and I'm floored by the sound in my Grados. No shortage of power and wonderful solid bass slam. Thanks Wayne and Jim! Also that Pass sticker works great covering up the hole I drilled in the wrong place.
It is not D7 at faultLook at the circuit and try and follow this:
You need to check now (and be super careful not to short anything) that the positive 33 volts you have on R37 and on D7 is making it to pin 1 of the 7815 regulator.
You could also (with it OFF) check for continuity (using a low ohms range on the meter) from the resistor to pin 1.
I would guess that an open circuit is more likely than a fault at this point tbh. If you have soldered the regulator to a PCB then look carefully around the solder pads and make sure the pad has not lifted and cracked away from the print. A voltage check or continuity check will reveal that.
Hello Mooly,
I'm sorry for delay, finally I'm back and I've just measured the voltage between Pin 1 of the 7815 regulator and the triangle point between C18 and C19... so multimeter says positive 30.2 Volts, it's not 33 but I don't know if this is correct.
I also checked for continuity with whammy powered off and there is continuity between R37 resistor and Pin1 on 7815.
Yes, I have soldered the regulator on PCB but there are no cracks or lifts around pads.
Any other idea to solve this "crazy" thing?
Please let me know.
Thanks a lot again! I really appreciate that.
Best,
DannyBarry
Just looking back to see where we were up to... and you are missing the PLUS 18v rail on pin 8 of the opamp.
30 volts on pin 1 of the 7815 is fine. Anything over the output voltage needed (18v in your case) plus a few volts for the regulator to work with is good.
Next step is to measure the voltage (very carefully) on pin 3 of the 7815. It should be 18v. It is 18 and not 15 because of the extra bits that lift pin 2 above ground.
So check that voltage on pin 3.
If that is OK then you have a continuity issue between pin 3 of the regulator and pin 8 of the opamp.
If the voltage is low on pin 3 (similar low value to the opamp pin 8 voltage) then we have to look at the possibility of something overloading the supply and causing the regulator to 'foldback' which is a form of current limiting.
At that point we would have to look at disconnecting the power supply (both -18 and +18 rails) from the main amplifier as a test and seeing if the voltage comes up on the power supply.
Lets see where this gets us first though.
30 volts on pin 1 of the 7815 is fine. Anything over the output voltage needed (18v in your case) plus a few volts for the regulator to work with is good.
Next step is to measure the voltage (very carefully) on pin 3 of the 7815. It should be 18v. It is 18 and not 15 because of the extra bits that lift pin 2 above ground.
So check that voltage on pin 3.
If that is OK then you have a continuity issue between pin 3 of the regulator and pin 8 of the opamp.
If the voltage is low on pin 3 (similar low value to the opamp pin 8 voltage) then we have to look at the possibility of something overloading the supply and causing the regulator to 'foldback' which is a form of current limiting.
At that point we would have to look at disconnecting the power supply (both -18 and +18 rails) from the main amplifier as a test and seeing if the voltage comes up on the power supply.
Lets see where this gets us first though.
Mooly,
thank you so much again for your support.
I just measured pin 3 on 7815 and it says positive 1,87 volts...
I suppose we need to disconnect power supply as you wrote before but I don't have any idea about the procedure...
-18 and +18 rails stands for neutral and live pad on pcb?
Thanks again... I'm very curious to hear te whammy... honestly can't wait!
thank you so much again for your support.
I just measured pin 3 on 7815 and it says positive 1,87 volts...
I suppose we need to disconnect power supply as you wrote before but I don't have any idea about the procedure...
-18 and +18 rails stands for neutral and live pad on pcb?
Thanks again... I'm very curious to hear te whammy... honestly can't wait!
You're very welcome
I'm looking at the build guides (beyond looking at the circuit diagrams I'm not familiar with the practical build at all) and can see it all looks to be one PCB and so that makes things more difficult regarding isolating supplies.
A few more things to check first.
1/ Is the 7815 regulator definitely marked up as being 7815 and not the negative 7915?
2/ Switch the amp OFF and do a resistance between pin 3 and the middle pin. We are just looking to make sure there is no short there that could pull the output down via the LED (if that is what you have fitted). A bit tenuous but we need to check.
Looking in detail at the circuit and actually there isn't a very direct path an overload current could take however one remote possibility is if there was a short circuit from either or both amplifier outputs to ground.
3/ So with the amp OFF check for a short between PAD 1 and ground and then check between PAD 3 and ground. These are the amp outputs and are the junction of the 10 ohm resistors in each channel.
That is something worth checking.
4/ Check that any electrolytics on the positive rail (such as C9) are fitted the right way around. A reverse fitted cap like that would pull a high current and cause the regulator to foldback.
I'm looking at the build guides (beyond looking at the circuit diagrams I'm not familiar with the practical build at all) and can see it all looks to be one PCB and so that makes things more difficult regarding isolating supplies.
A few more things to check first.
1/ Is the 7815 regulator definitely marked up as being 7815 and not the negative 7915?
2/ Switch the amp OFF and do a resistance between pin 3 and the middle pin. We are just looking to make sure there is no short there that could pull the output down via the LED (if that is what you have fitted). A bit tenuous but we need to check.
Looking in detail at the circuit and actually there isn't a very direct path an overload current could take however one remote possibility is if there was a short circuit from either or both amplifier outputs to ground.
3/ So with the amp OFF check for a short between PAD 1 and ground and then check between PAD 3 and ground. These are the amp outputs and are the junction of the 10 ohm resistors in each channel.
That is something worth checking.
4/ Check that any electrolytics on the positive rail (such as C9) are fitted the right way around. A reverse fitted cap like that would pull a high current and cause the regulator to foldback.
Eureka!!!!
7815 is in the wrong place, it is inverted with 7915.
I don’t how this could happens as I marked every single piece before start solder, a big mistake no excuses, my fault.
I will remove remove regulators and switch them, it will not be easy but I have a desoldering station so it would be not so much difficul to do it.
I’ll keep you posted.
Thanks again!!!!!!!!
7815 is in the wrong place, it is inverted with 7915.
I don’t how this could happens as I marked every single piece before start solder, a big mistake no excuses, my fault.
I will remove remove regulators and switch them, it will not be easy but I have a desoldering station so it would be not so much difficul to do it.
I’ll keep you posted.
Thanks again!!!!!!!!
Now up and running finally!
Thank you so much to all of you nice people here in the forum and a very special thanks to Mooly that tooks my hand helping me to discover my error.
I really appreciate your efforts and this amp... it sounds good right now... can’t really wait to start rolling op-amp...
Thank you so much guys, you are great!!!!
Best,
DannyBarry
Thank you so much to all of you nice people here in the forum and a very special thanks to Mooly that tooks my hand helping me to discover my error.
I really appreciate your efforts and this amp... it sounds good right now... can’t really wait to start rolling op-amp...
Thank you so much guys, you are great!!!!
Best,
DannyBarry
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when not having desoldering station , easiest way of desoldering 3 legged parts ( TO220) is - apply some more solder on all 3 pins underside, place solder tip side-wise (crank temp to max) to heat all 3 pins in same time and just pull it gently ...... it's out when is time
later is easy to use solder sucker or wick to clean holes/pads
later is easy to use solder sucker or wick to clean holes/pads
Pin 8 is way to high.
There are only a few possibilities here.
1/ The regulator was damaged.
2/ Whatever is connected to pin 2 (middle pin) of the reg is damaged.
3/ Pin 2 is floating.
So as always we check basics first.
Measure the voltage on pin 2 of the reg. Whatever is here is 'added' to the 15v of the basic regulator. So you should see only around 2 to 3 volts on this pin.
If that voltage is high then either the 330 ohm or the LED is open circuit.
If it is low then the regulator has to be suspect.
There are only a few possibilities here.
1/ The regulator was damaged.
2/ Whatever is connected to pin 2 (middle pin) of the reg is damaged.
3/ Pin 2 is floating.
So as always we check basics first.
Measure the voltage on pin 2 of the reg. Whatever is here is 'added' to the 15v of the basic regulator. So you should see only around 2 to 3 volts on this pin.
If that voltage is high then either the 330 ohm or the LED is open circuit.
If it is low then the regulator has to be suspect.