Magnetron Delay troubleshoot

[u439857293874]

This was one of my first builds I'm trying to get working. Just redid the wiring but I'm not getting the effect. I'm going though the schematics but I'm a little unsure how to read it.

Should I have sound on both sides of R2 and R3?
R10 I'm not getting anything at all.

On the PT2399 chip I can hear the delay happening on one of the pins and on R25/R26 but R11 and R14 sound like the bypassed signal. Any help would be greatly appreciated, thanks!

 

[jimilee]

This was one of my first builds I'm trying to get working. Just redid the wiring but I'm not getting the effect. I'm going though the schematics but I'm a little unsure how to read it.

Should I have sound on both sides of R2 and R3?
R10 I'm not getting anything at all.

On the PT2399 chip I can hear the delay happening on one of the pins and on R25/R26 but R11 and R14 sound like the bypassed signal. Any help would be greatly appreciated, thanks!

Looking at the schematic, the basic audio path goes straight across the top. So yes. R2, 3 opamp pins and gain pot.

 

[u439857293874]

Thanks, thats what I was thinking. My next step will be to replace R2 and R3 and see what happens.

 

[u439857293874]

Replaced R2 and R3 still the same. R3 sounding quiet. Nothing on the gain and I'm only getting audio from one of the pins in IC1 (the one in red).

 

[jimilee]

Replaced R2 and R3 still the same. R3 sounding quiet. Nothing on the gain and I'm only getting audio from one of the pins in IC1 (the one in red).

Check for any solder bridges in that area.

 

[u439857293874]

I don't see any solder bridges. It looks Ike one in the photo between r2 and r3 but that's just the light.

 

[jimilee]

I don't see any solder bridges. It looks Ike one in the photo between r2 and r3 but that's just the light.

Does pin 1 have clear audio? What about the gain pot?

 

[u439857293874]

Yes I'm getting clear audio from pin 1 also from pin 7 but it's a little quiet. Nothing from the gain pot at all. One side of r6 has audio and one side has no audio.

I'm thinking about replacing the gain pot.

 

[jimilee]

Looking at the schematic, to get to pin one, you’ve got to go through r2, 3 and the gain pot. That’s a head scratcher. @Robert we may need backup.

 

[u439857293874]

Took out the level pot which was probably unnecessary and broke a pad off in the process. The pot looked fine and tested to the right resistance so I put it back.

No sound in the level pot at all. R6, R3, R2 only have sound on one side. C2 has sound on both R4 on one side.

 

[Locrian99]

Isn’t the gain pot on this the trimmer…

if I’m understanding correctly you are getting sound but not hearing the effect. Do you have the level pot turned all the way up? The level as I recall is basically your repeats volume.

 

[Coda]

Can you swap in a different 2399?…

 

[jimilee]

Isn’t the gain pot on this the trimmer…

if I’m understanding correctly you are getting sound but not hearing the effect. Do you have the level pot turned all the way up? The level as I recall is basically your repeats volume.

Nope, no sound at all. With an audio probe, no sound from C2 up to the opamp, but has audio on pin 1. Real head scratcher.

 

[u439857293874]

I just swapped out the 2399 and made sure the trim pot was turned up but still the same result.

 

[u439857293874]

I was confusing the level pot with the gain pot. I am getting sound in the gain pot on all 3 pins. Still nothing on one side of both R2 and R3. I could add some jumpers but not sure where to put them.

 

[Locrian99]

Yes I'm getting clear audio from pin 1 also from pin 7 but it's a little quiet. Nothing from the gain pot at all. One side of r6 has audio and one side has no audio.

I'm thinking about replacing the gain pot.

View attachment 44493

if you’ve got audio coming out of pin 7 your dry signal is making it through. Not sure why you’re not hearing it…. There’s a couple components after it. Can we see some of voltages?

Also for the sake of checking audio probe the output pad and work back from there til pin 7

Also you should have audio at both pin 15 and 16 of the 2399, do you? One should be the delay signal I think 16. You’ll have to wait to hear it for however long the delay is set to.

 

[u439857293874]

if you’ve got audio coming out of pin 7 your dry signal is making it through. Not sure why you’re not hearing it…. There’s a couple components after it. Can we see some of voltages?

Also for the sake of checking audio probe the output pad and work back from there til

I can hear dry signal on pin7 and on the output but I think what Im hearing in the output is the bypassed signal or the ground since there is no effect. I can hear the effect coming out the of the 2399 chip and on r25 and r26. What voltages do you want to see?

 

[Locrian99]

I can hear dry signal on pin7 and on the output but I think what Im hearing in the output is the bypassed signal or the ground since there is no effect. I can hear the effect coming out the of the 2399 chip and on r25 and r26. What voltages do you want to see?

You wouldn’t hear bypassed signal at pin 7, it wouldn’t be bypass if you did. What you are hearing is the dry signal.


I think your issue then lies between the output of tbr 2399 and the level pot. Follow the audio path there.

 

[Locrian99]

Looks like really it’s pin 2 of the feedback pot and then on to the level pot pin 3. I’d check there first I guess.

 

[u439857293874]

I was getting the effected audio on only one side of r13 so i ran a jumper from r12 to r13 and now i can hear the effect on the output. It doesn't sound great and I'm only getting audio on pin 3 of the feedback pot. At least we're getting closer! Will try some more after work. I'm on the old version btw. Build doc says 2020.