Mooly thank you again!
I placed black probe on Pin4 V- on Op Amp and red probe on resistor R37 and I confirm I read 16,34V on outer side of R35 and 16,20V on the inner one.
I also unmount the resistor to check that is value confirm to be 47,3 ohm.
Any other idea?
Thanks again!
I placed black probe on Pin4 V- on Op Amp and red probe on resistor R37 and I confirm I read 16,34V on outer side of R35 and 16,20V on the inner one.
I also unmount the resistor to check that is value confirm to be 47,3 ohm.
Any other idea?
Thanks again!
For voltage measurements you really need to be measuring from ground (use that as a reference and connect the black meter lead there). Ground is the zero volt line in the power supply.
Done that way and you should see negative 18v on pin 4 (which is what you mentioned) and positive 18v on pin 8.
So it looks like your positive 18 volt rail is missing from the power supply. Check those upper 5.1 ohm resistors are OK and not open circuit. Just measure the voltage on them, don't take them out. You should have 22v or higher on those.
Done that way and you should see negative 18v on pin 4 (which is what you mentioned) and positive 18v on pin 8.
So it looks like your positive 18 volt rail is missing from the power supply. Check those upper 5.1 ohm resistors are OK and not open circuit. Just measure the voltage on them, don't take them out. You should have 22v or higher on those.
Attachments
Mooly thanks.
I've 33 Volts on R37 and R20 and -33 Volts on R38 and R21 using black probe on ground chassis as you described before.
What's next?
Thanks a lot again!
Best,
D
I've 33 Volts on R37 and R20 and -33 Volts on R38 and R21 using black probe on ground chassis as you described before.
What's next?
Thanks a lot again!
Best,
D
Last edited:
Those DC voltages look high given the capacitors are rated at 35V. The original transformer was rated at 15-0-15AC but yours is 22-0-22AC. I remember that there was discussion on this point much earlier on but I don't recall the detail.
Hi Logic,
I'm copying from Mr Colburn original first post about Whammy:
"Transformer 15VA or 25VA 15+15 to 22+22
25VA 22V+22V is best and used in this guide"
So I have a 25VA 22V+22V transformer made by Talema Mod. 70065K
I'm copying from Mr Colburn original first post about Whammy:
"Transformer 15VA or 25VA 15+15 to 22+22
25VA 22V+22V is best and used in this guide"
So I have a 25VA 22V+22V transformer made by Talema Mod. 70065K
Lets start at the beginning 🙂
Your mains voltage will not make any difference as far as we are concerned.
Look at the diagram here and if any component reference numbers are different then just make sure you are measuring on the correct points according to the circuit diagram.
Put your meter on DC volts and connect the black lead to the junction of C18/C19 and C14/C15. That line with that triangle symbol is our zero volt point. We measure from there...
R20 should have between positive 22 and positive 35 volts on both ends.
R37 should be similar.
R21 and R38 should be a mirror image, that is to say negative 22v to negative 35 volts on all the resistor legs.
If that is OK then check for positive 18v on the diode D7. One end will have the voltage you measured above whatever that might be, the other should be a steady positive 18 volts.
Now measure on D8. This again is a mirror image with negative voltages this time. So a steady negative 18v on one end of the diode.
Your mains voltage will not make any difference as far as we are concerned.
Look at the diagram here and if any component reference numbers are different then just make sure you are measuring on the correct points according to the circuit diagram.
Put your meter on DC volts and connect the black lead to the junction of C18/C19 and C14/C15. That line with that triangle symbol is our zero volt point. We measure from there...
R20 should have between positive 22 and positive 35 volts on both ends.
R37 should be similar.
R21 and R38 should be a mirror image, that is to say negative 22v to negative 35 volts on all the resistor legs.
If that is OK then check for positive 18v on the diode D7. One end will have the voltage you measured above whatever that might be, the other should be a steady positive 18 volts.
Now measure on D8. This again is a mirror image with negative voltages this time. So a steady negative 18v on one end of the diode.
Attachments
Mooly, thanks again!
I checked R20 and R37 and I read 33,6 Volts, -33,6 Volts on R21 and R38.
Then D7 says 33,6V one side and -2,09V on other side and D8 -33,6V and -18,4V
I’m thinking that D7 diode is fault and needs to be changed or am I wrong?
Thanks again!
I checked R20 and R37 and I read 33,6 Volts, -33,6 Volts on R21 and R38.
Then D7 says 33,6V one side and -2,09V on other side and D8 -33,6V and -18,4V
I’m thinking that D7 diode is fault and needs to be changed or am I wrong?
Thanks again!
It is not D7 at fault 🙂 Look 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.
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.
Mooly thanks again!
Unfortunately I’m out of office for a location job until next week so I don’t have the Whammy with me to test this last thing. I will do as soon as I’ll be back and I’ll reply to this post.
Thanks a lot again!
Unfortunately I’m out of office for a location job until next week so I don’t have the Whammy with me to test this last thing. I will do as soon as I’ll be back and I’ll reply to this post.
Thanks a lot again!
to baeijsman #3812
Hello Baeijsman,
very nice Whammy! Let your ears be flooded by its nice sound....
Cheers
Dirk
Hello Baeijsman,
very nice Whammy! Let your ears be flooded by its nice sound....
Cheers
Dirk
Need help with 4N35 orientation
I bought these optocouplers:
https://www.mouser.com/datasheet/2/427/4n35x-1767321.pdf
And they have no pinout marking or dot on them. There is a groove on one side. Any advice on how to install them?
I bought these optocouplers:
https://www.mouser.com/datasheet/2/427/4n35x-1767321.pdf
And they have no pinout marking or dot on them. There is a groove on one side. Any advice on how to install them?
That's strange isn't it! On the 'alldatasheet' page 7 (Vishay document 83717) the indent is clearly shown but on the one linked via the 'mouser' it shows a plain surface
You might be able to determine pins 1 & 2 using a multimeter/led tester - the resistance should show something like 100 -150ohms and the other pin on same side will show nothing = disconnected.
Perhaps someone else with first hand experience can be more helpful ...
You might be able to determine pins 1 & 2 using a multimeter/led tester - the resistance should show something like 100 -150ohms and the other pin on same side will show nothing = disconnected.
Perhaps someone else with first hand experience can be more helpful ...
Need troubleshooting help
I finished the build last evening and fired it up. The PS tested good previously. I'm getting no sound in the left channel and tinny sound in the right. Here are some voltages:
AD823 Opamp:
1 -.416v
2 0v
3 0v
4 -16.65v
5 0v
6 0v
7 -.43v
8 16.52v
Vishay 4N35-X006 Optocouplers
1 .495v
2 -.559v
3 0v
4 -.583v
5 5.32v
6 -.508v
Anything obvious here? This is my first amp fail after a number of builds.
I finished the build last evening and fired it up. The PS tested good previously. I'm getting no sound in the left channel and tinny sound in the right. Here are some voltages:
AD823 Opamp:
1 -.416v
2 0v
3 0v
4 -16.65v
5 0v
6 0v
7 -.43v
8 16.52v
Vishay 4N35-X006 Optocouplers
1 .495v
2 -.559v
3 0v
4 -.583v
5 5.32v
6 -.508v
Anything obvious here? This is my first amp fail after a number of builds.