Dark Rift Delay

[digitalsea]

Hi all,

Tearing my hair out with this one.

I’m only getting clean signal when engaged. I’ve switched out all the ICs and checked over too many times.

Is there anything that you guys can see that I’m missing?

Thanks for looking.

 

[Chas Grant]

The 78L05 isn't a transistor, but a voltage regulator, and you have already checked it. The PT2399 needs +5V power to operate. This is pin 1 which is 4.99V. It gets the 5V from the 78L05, so since pin 1 of the PT2399 is 4.99V the 78L05 is good.

The LM833 actually has an input coming from the PT2399 into pin . The output from the 2399 is 2.5 volts and that's what you have on the I\O pins of the 833, so its good. (I missed the 2.5 input from the 2399, that's why I thought it may have a low voltage)

The Tl072 has low Vref on pins 3 and 5.Need to see if this is normal or an issue. Try resoldering the the pins on this op amp, if you dtill have low Vref after, the try removing TL072and re-measure voltages'

Also the LM324 has a low voltage on pins 12, 13, and 14. Pin 12 is referenced straight to pin 12, it should read 4.5V. If you can resolder pins 12, 13 sns 14, then recheck their voltages

 

[r.nandez54]

The 78L05 isn't a transistor, but a voltage regulator, and you have already checked it. The PT2399 needs +5V power to operate. This is pin 1 which is 4.99V. It gets the 5V from the 78L05, so since pin 1 of the PT2399 is 4.99V the 78L05 is good.

The LM833 actually has an input coming from the PT2399 into pin . The output from the 2399 is 2.5 volts and that's what you have on the I\O pins of the 833, so its good. (I missed the 2.5 input from the 2399, that's why I thought it may have a low voltage)

The Tl072 has low Vref on pins 3 and 5.Need to see if this is normal or an issue. Try resoldering the the pins on this op amp, if you dtill have low Vref after, the try removing TL072and re-measure voltages'

Also the LM324 has a low voltage on pins 12, 13, and 14. Pin 12 is referenced straight to pin 12, it should read 4.5V. If you can resolder pins 12, 13 sns 14, then recheck their voltages

Thanks for correcting me re/78L05

I got the same values after trying to resolder. I should mention that mine are socketed as well. I'm not sure if this is supposed to happen but if I take out Tl072 and test the socket itself I get a different reading 2.950 vs 2.778 with IC pin 3 and 4.342 vs 3.290 with the IC pin5.
On LM324 there is no change at all.

 

[Chas Grant]

The 2.9 to 2.7 on pin 5 is not a biggie, but pin 3 going to 3.2 is weird. Try swapping the TL072. If you don't have another TL072, any dual op amp with the same pin out should work.

 

[r.nandez54]

The 2.9 to 2.7 on pin 5 is not a biggie, but pin 3 going to 3.2 is weird. Try swapping the TL072. If you don't have another TL072, any dual op amp with the same pin out should work.

I have a few so I tried 3 different TL072's last night as well as 3 different LM324. Should've mentioned that too, sorry.

 

[Chas Grant]

Actually lets back up a second. With the TL072 removed you have 2.95 volts on pin 3. It should be 4.3 like pin 5. With the IC removed, measure voltage from both sides of R3, its the 1Meg resistor below the TL072. It should be ~4.5V on both sides if TL02 is removed

 

[r.nandez54]

For R3 this is what I'm getting with TL072 removed
Negative probe to the left reads: -1.064
Positive probe to the left reads: 1.067

Actually lets back up a second. With the TL072 removed you have 2.95 volts on pin 3. It should be 4.3 like pin 5. With the IC removed, measure voltage from both sides of R3, its the 1Meg resistor below the TL072. It should be ~4.5V on both sides if TL02 is removed

 

[Chas Grant]

Somethings not right, R4 and R3 are the 2 resistors below the TL072, with the chip removed you should have about 4.5 V on both sides of both resistors. Check the build doc to make sure your on the right resistors and double check voltage on them if you can. Make sure the black lead is to a good ground and check the voltage with red lead.

 

[r.nandez54]

Somethings not right, R4 and R3 are the 2 resistors below the TL072, with the chip removed you should have about 4.5 V on both sides of both resistors. Check the build doc to make sure your on the right resistors and double check voltage on them if you can. Make sure the black lead is to a good ground and check the voltage with red lead.

Ok, so this morning I was just going positive and negative leads on the resistor. Now I'm putting the negative lead on the main negative point from the power jack. I confirmed that R4 is correctly a 47k resistor and is directly below TL072 and R3 is correctly a 1M resistor and is directly below R4. Here are my readings:
Left side of R3 is 4.357
Right side of R3 is 2.986
Left side of R4 is 4.358
Right side of R4 4.330

 

[Chas Grant]

It looks like the right side of R3 has a partial path to ground. It could be C2 is leaking or you have a small bridge somewhere. Check DC voltage on both sides of R2. It should be zero.

 

[r.nandez54]

It looks like the right side of R3 has a partial path to ground. It could be C2 is leaking or you have a small bridge somewhere. Check DC voltage on both sides of R2. It should be zero.

Left side of R2 is 1.053
Right side of R2 is 1.054

 

[Chas Grant]

C2 is leaking, there shouldn't be DC there. Try replacing it. Not sure if this was the main issue, I think it would affect tone more, but with electronics you never know, especially when the component is deteriorated. (Got my but kicked by a deteriorated transistor for over a month one time )

 

[r.nandez54]

C2 is leaking, there shouldn't be DC there. Try replacing it. Not sure if this was the main issue, I think it would affect tone more, but with electronics you never know, especially when the component is deteriorated. (Got my but kicked by a deteriorated transistor for over a month one time )

I'll do this when I get home, I think this might be the problem. Question about those 1uf caps I'm using, the ones I got were polar I think. One leg is longer and the have a little plus sign on that side. https://www.taydaelectronics.com/1uf-16v-radial-tantalum-capacitor.html are those ok to use in this case?

 

[Chas Grant]

They will work, but not ideal. Thy have to go in a certain way. You have to look at schematic and figure out which side has the higher voltage, then the + side goes that way. You may be able to measure voltage to ground on each leg of the cap then see if the + side is on that side. It can be tricky sometimes. You could replace also them with 1uF MLCC caps, they can go either way and they are smaller than 1uF box film caps, so they will fit with no problems.

 

[Chas Grant]

Thinking about it, if you used all tantalum caps for the 1uF's, this very well could be the issue. They are in the signal path in quite a few places, if they are in the wrong way they will block the signal.

 

[r.nandez54]

Thinking about it, if you used all tantalum caps for the 1uF's, this very well could be the issue. They are in the signal path in quite a few places, if they are in the wrong way they will block the signal.

Once you mentioned that they do have to go a certain way I'm almost sure of it. And it looks like @digitalsea might be using the same caps I am. I tip my hat to you sir, thank you. I'll report back after getting this corrected.

Side question, how did you learn all these specifics? Is it your job or just long time hobby?

 

[Chas Grant]

I was an electronics technician in the US Navy. After getting out I stayed in the field and saw it change from through hole to SMD components( I hate SMD BTW). The equipment I worked on had nothing to do with audio, so the audio side is recent. But electronics are electronics. How I got into pedals, a while ago my daughter wanted to learn to play, so she hi-jacked my Fender Tele and started learning ( I had to buy her a Strat to get my Tele back ) . When she started to ask about pedals and I saw the price on some of them I decided to build them. There was a learning curve but not to bad, and still a lot I don't know. This here forum has helped me a lot, and helping out here makes me learn even more. I have learned that the pedal "Rabbit Hole" is very deep, I haven't got to the bottom yet! But it allows me to work with through hole components again and my soldering is back up to snuff, so all is good!

 

[r.nandez54]

I was an electronics technician in the US Navy. After getting out I stayed in the field and saw it change from through hole to SMD components( I hate SMD BTW). The equipment I worked on had nothing to do with audio, so the audio side is recent. But electronics are electronics. How I got into pedals, a while ago my daughter wanted to learn to play, so she hi-jacked my Fender Tele and started learning ( I had to buy her a Strat to get my Tele back ) . When she started to ask about pedals and I saw the price on some of them I decided to build them. There was a learning curve but not to bad, and still a lot I don't know. This here forum has helped me a lot, and helping out here makes me learn even more. I have learned that the pedal "Rabbit Hole" is very deep, I haven't got to the bottom yet! But it allows me to work with through hole components again and my soldering is back up to snuff, so all is good!

My man! That's some serious experience you got there. That's cool that your daughter got into something you both could share experiences in as well, I have a newborn and look forward to things like that.

I really appreciate the help. Like I mentioned before I'll report back after I figure out either the orientation on the tantalum caps or just buying some MLCC's. Thanks again!

 

[Chas Grant]

An easy way to figure the caps, but not always 100%, is to de-solder the cap, power up the circuit and measure voltage across the pads of the missing cap. One way the it will be positive and the other negative. When its positive, where the red lead is, that should be the + lead of the cap.

 

[r.nandez54]

An easy way to figure the caps, but not always 100%, is to de-solder the cap, power up the circuit and measure voltage across the pads of the missing cap. One way the it will be positive and the other negative. When its positive, where the red lead is, that should be the + lead of the cap.

So I gave it a go and I'm still not getting any effect sound. I'm using a sound probe to see if I can follow the sound but I'm still learning how to use it. I'm gunna wait till after the new year to order from tayda for those MLCCs.

 

[Chas Grant]

Understandable. Trying to sub polarity sensitive caps for non-polarity caps can be tricky. One or two, easy but there's a bunch of 1uF caps in this circuit. Another thing, if your mail is anything like mine, if you order today, and also order after Jan 1st, they would arrive at same time!, so waiting is the smart move! Keep the forum updated to how it goes once you get the caps.