chongmagic
Well-known member
Finished up the bathtub reverb, but the LED is not coming on and am getting no sound. I have gone through it several times but I thought a pair of fresh eyes might find something I did not.
Bathtub Reverb - Issues
- Thread starter chongmagic
- Start date
chongmagic
Well-known member
Anyone?
Tassieviking
Active member
I can not see anything wrong but the photos are not that clear, have you got voltage on the reverb module ?
Pin 1 should be +5V and pin 2 should be ground.
Pin 1 should be +5V and pin 2 should be ground.
Not sure if you ever got this fixed. Mine looks like yours and I've got the same issue. The LED doesn’t turn on but the reverb works. I get 8.65v on the positive side and 6.85V on the negative side. Measuring as Diode turns the LED on. If I measure the LED in Diode I get -2.31v and the LED turns on. Any ideas?
Chongmagic, From the photo it is hard to check the soldering. I would recommend cleaning up any suspicious ones using some copper braid and re-applying fresh fluxed solder.
I can’t see your DC reverse protecting diode in the photos. Could this be in back to front?
I’ve accidentally reversed wired up my DC jack before with similar results.
Otherwise, careful voltage mapping against the schematic might be what’s needed.
I can’t see your DC reverse protecting diode in the photos. Could this be in back to front?
I’ve accidentally reversed wired up my DC jack before with similar results.
Otherwise, careful voltage mapping against the schematic might be what’s needed.
Any chance the LED is in back to front? A simple test is using one of those flat 3V button batteries (with DC power disconnected obviously!
) Or you could compare with a spare unused led? (long lead is +’ve).
drew.spriggs
Active member
Or you get some red LED's from that Tayda batch that are all backwards....Any chance the LED is in back to front? A simple test is using one of those flat 3V button batteries (with DC power disconnected obviously!
Hi guys, I finally had time to go back and check SamueG's suggestion. Swaped the LED and no response. The LED does work, emitting light using the Diode setting on the multimeter. Any other suggestion? Also, I notice that the effect takes away the low frequencies when engaged. Will it be a matter of changing the values of the caps? I would like to make it sound as close as posible to the dry signal. Thanks!
Tassieviking
Active member
Check the voltages on pin 3 and 4 of the foot switch PCB, (1 on left and 6 on right), pin 3 should go to ground and pin 4 goes to R12.
R12 is the voltage drop resistor for the led, the left side goes to the LED and the right side goes to the foot switch (pin 4).
R12 is the voltage drop resistor for the led, the left side goes to the LED and the right side goes to the foot switch (pin 4).
Thanks, I measure 0 volts at the pins, 0 volts at the Resistor and 8.78v at the +side of the LED
Tassieviking
Active member
You should have voltage on the left side of R12, the right side of R12 goes to pin 4 of the switch PCB which is grounded through the switch and then to ground at pin 3 of the PCB.
The left side of R12 goes to the 2 right pins that go to the tube PCB, the 2 pins then go to the right side of the LED (round terminal)
There should be a dead short between the left side of R12 to the right side of the LED, they go through both of the right pins of the dual row right angle pin header.
With power of see if you have continuity from the RHS of the LED to the RHS pins on the header and then to the left side of R12.
The left square terminal of the LED goes to pin 5 of the tube socket which is at + input voltage (- the voltage drop over D1, 1n5817 diode)
This voltage sounds correct at about 8.78 volts like you got.
I think you might have a broken trace somewhere between the left side of R12 and the right side of the LED, the only thing in-between is the 10 pin header which uses the 2 pins on the right to link the PCB's.
EDIT: I made a quick drawing in KiCad that shows approximately the traces to the foot switch.
If you cant find any cut traces then check R12 resistance is 1k or less, you should be able to go down to 500 ohms easily at a 9V supply and stay below the 20mA the LED is rated at.
The left side of R12 goes to the 2 right pins that go to the tube PCB, the 2 pins then go to the right side of the LED (round terminal)
There should be a dead short between the left side of R12 to the right side of the LED, they go through both of the right pins of the dual row right angle pin header.
With power of see if you have continuity from the RHS of the LED to the RHS pins on the header and then to the left side of R12.
The left square terminal of the LED goes to pin 5 of the tube socket which is at + input voltage (- the voltage drop over D1, 1n5817 diode)
This voltage sounds correct at about 8.78 volts like you got.
I think you might have a broken trace somewhere between the left side of R12 and the right side of the LED, the only thing in-between is the 10 pin header which uses the 2 pins on the right to link the PCB's.
EDIT: I made a quick drawing in KiCad that shows approximately the traces to the foot switch.
If you cant find any cut traces then check R12 resistance is 1k or less, you should be able to go down to 500 ohms easily at a 9V supply and stay below the 20mA the LED is rated at.
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Thank you very much for taking the time Tassieviking. You were right, it must've been a broken trace, after going through your trouble shooting guide, there was no continuity between the left side of R12 and the 2 pins on the right of the 10 pin link to the tube PCB. The jumper solved the issue. Now, in the sound, do you have any suggestions to incorporate more low frequencies?
Tassieviking
Active member
The frequency range is usually determined by basic high pass and low pass filters in amplifiers, there are other filters as well like the bright caps which are like a treble pass pass filter, I am still trying to get up to speed on all this since I have only worked on industrial electronics and some domestic stuff as an electrician.
Lets start with the capacitors since most filters use capacitors and resistors to for a filter, first C1.
With tubes it becomes harder, we need to know the output impedance first and I use this calculator to work it out to be 16.91 k ohms on V1A.
www.ampbooks.com
Once I got the output impedance I use a coupling capacitance calculator to check the frequency response of C1, this calculator here:
www.ampbooks.com
Change the volume pot % and the capacitor value to see what happens.
It appears C1 is fine and not hindering any Bass response
Next we look at C3 the Cathode Bypass Capacitor, this is the calculator:
www.ampbooks.com
We fill in the 3 resistors and the capacitor values and we get a nice graph showing a fairly flat frequency response.
C3 is not a problem so we are left with C2.
C2 is more complicated since there is more happening but from what I can see increasing the value of C2 will improve the Bass response, I will not even try to work it out or get a graph up for C2 but it can benefit from being a lot higher.
If you can get a lot bigger capacitor value in then that is what I would do, you might be able to add a capacitor in parallel with the existing one through a switch, you can then call it a deep switch.
I would try 0.1uF to start with, then I would start changing it up / down till it sounds good
That was my long answer, the short answer would be increase C2, by a lot.
The calculators on the ampbook website is what I use to check my builds with, there is lots of really good information there and I think it is worthwhile to run calculations on all builds using Tubes just to get a better understanding of the circuits.
www.ampbooks.com
Let us know how you go
Cheers
Mick
EDIT: Here are more calculators for filters in normal circuits, this is a high pass filter using a capacitor and a resistor, look at the bottom of the page for more calculators.
Lets start with the capacitors since most filters use capacitors and resistors to for a filter, first C1.
With tubes it becomes harder, we need to know the output impedance first and I use this calculator to work it out to be 16.91 k ohms on V1A.
Preamp Gain and Output Impedance Calculator
Once I got the output impedance I use a coupling capacitance calculator to check the frequency response of C1, this calculator here:
Coupling Capacitor Calculator
It appears C1 is fine and not hindering any Bass response
Next we look at C3 the Cathode Bypass Capacitor, this is the calculator:
Cathode Bypass Capacitor Calculator
C3 is not a problem so we are left with C2.
C2 is more complicated since there is more happening but from what I can see increasing the value of C2 will improve the Bass response, I will not even try to work it out or get a graph up for C2 but it can benefit from being a lot higher.
If you can get a lot bigger capacitor value in then that is what I would do, you might be able to add a capacitor in parallel with the existing one through a switch, you can then call it a deep switch.
I would try 0.1uF to start with, then I would start changing it up / down till it sounds good
That was my long answer, the short answer would be increase C2, by a lot.
The calculators on the ampbook website is what I use to check my builds with, there is lots of really good information there and I think it is worthwhile to run calculations on all builds using Tubes just to get a better understanding of the circuits.
Guitar Amp Circuit Design Calculators
Let us know how you go
Cheers
Mick
EDIT: Here are more calculators for filters in normal circuits, this is a high pass filter using a capacitor and a resistor, look at the bottom of the page for more calculators.
High Pass Filter Calculator
This is a High Pass Filter. It calculates the range of high frequency signals that a filter passes through.
www.learningaboutelectronics.com
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Tassieviking
Active member
This is how I would add a deep switch, that way I could have it original or deep tone if I wanted to.
I would not mount C2 on the PCB, I would run 2 wires from the PCB holes for C2 to a DPDT switch and then mount the capacitors on the switch.
It would be a lot easier to change the caps on the switch if you want to keep trying different values.
There is a way to use a DPDT ON-ON-ON switch so you can have 3 different settings if you wanted Normal-Deep-Bass settings which I have used in the past, It gave me normal for guitar, deep for a deeper tone on guitar and Bass for Bass guitar.
If you would like to see it let me know, I would have to find it on my computer, I'm to tired now at 3.30am to look for it.
Cheers
Mick
EDIT: I couldn't help myself so I drew the 3 way switching circuit up in KiCad just to show everyone, I have been meaning to start a new thread just for mods and when I do I will place all this in there as well.
I would not mount C2 on the PCB, I would run 2 wires from the PCB holes for C2 to a DPDT switch and then mount the capacitors on the switch.
It would be a lot easier to change the caps on the switch if you want to keep trying different values.
There is a way to use a DPDT ON-ON-ON switch so you can have 3 different settings if you wanted Normal-Deep-Bass settings which I have used in the past, It gave me normal for guitar, deep for a deeper tone on guitar and Bass for Bass guitar.
If you would like to see it let me know, I would have to find it on my computer, I'm to tired now at 3.30am to look for it.
Cheers
Mick
EDIT: I couldn't help myself so I drew the 3 way switching circuit up in KiCad just to show everyone, I have been meaning to start a new thread just for mods and when I do I will place all this in there as well.
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Tassieviking
Active member
It makes it a lot easier to understand when you see the graphs for the frequencies, that's why I love the Ampbooks calculators.
I only found them last year myself, I have hardly ever worked on anything with tubes until very recently, the only times I did was on some very old machines in a factory but that was some high voltage insulation testers between 10,000volts and 60,000volts.
I really like the 3 way switching with the ON-ON-ON switches since it gives you normal/ low/lowest settings, I like things in order.
I only found them last year myself, I have hardly ever worked on anything with tubes until very recently, the only times I did was on some very old machines in a factory but that was some high voltage insulation testers between 10,000volts and 60,000volts.
I really like the 3 way switching with the ON-ON-ON switches since it gives you normal/ low/lowest settings, I like things in order.
