# Magnetron Delay Problem



## Jovi Bon Kenobi

Here's the problem. When I test the board out of the enclosure I get two possible outcomes:
a.) I only get one repeat turning the full range of feedback knob with self oscillation at the very end, the dry signal is quieter than the repeats, there is faint RF, and my overall guitar signal is quieter when the pedal is engaged than when it is bypassed.
Or b.) It works perfectly with none of the above issues so I put it back into the enclosure and the problems come back.

Upon wiggling connections and stuff I can't seem to force replicate a vs b. I thought I may have solved it when I noticed that the OPA2134 was slightly lifted from it's socket and it cleared when I pushed it back in. However, once back in the enclosure the problems came back.

Link to schematic here: Magnetron Delay

I built the PCB with a couple mods added:
1. Momentary feedback footswitch
2. Internal gain trimpot moved to external control

I drew this up to make it easier to understand:




Photos incoming as soon as my housemate is out of the shared music room/my work area. ?


----------



## Jovi Bon Kenobi

Ok, here's some photos. Let me know if a clear shot is needed somewhere specific. Also, I omitted the LFO indicator LED because I didn't like it in the first one I built.


----------



## Jovi Bon Kenobi

I just noticed that the first relay bypass modules from last year aren't on the site anymore and that's what this is. Not sure that's an issue but I imagine it would be easier to troubleshoot without it. I should have tested before adding it.


----------



## Jovi Bon Kenobi

*edit* The following did not work.
I think I solved it! Something was telling me that it was a grounding issue on the gain pot as it seemed the most noisy variable upon turning. Pinching it between my fingers would produce all kinds of grounding noises. Also, I was getting continuity between lugs 1 and 3. Pretty sure that's wrong. Put a new pot in and everything works! Just gotta box it up one last time (I hope) ?


----------



## moonlightpedalbuilds

Are you using stranded or solid wire? Gauge?


----------



## Jovi Bon Kenobi

Dang, nope its back again. it's gotta be a grounding issue somewhere. it's so close to working.



moonlightpedalbuilds said:


> Are you using stranded or solid wire? Gauge?


24 awg stranded. not pre bonded


----------



## piapium

Maybe when you cut the legs of the pots, you broke them. It happened to me once. They stopped working when I cut the lugs.


----------



## moonlightpedalbuilds

From previous experience when dealing with stranded wire, I single strand of wire may touch other parts. Especially when try to insert stranded wires into the holes in the pcb, potentiometers and switches. What I do is to make sure they at tinned before inserting them into holes.

Another thing to look at are the through-holes. Make sure your solder bleeds to the other side of the board.

Do you lose the sound when you tighten the potentiometers?


----------



## Robert

With the board out of the enclosure connect a wire (or clip lead) to a known ground point on the board.

Now touch the metal body and shaft of each pot and see if the problem reappears.


----------



## Jovi Bon Kenobi

piapium said:


> Maybe when you cut the lugs of the pots, you broke them. It happened to me once. They stopped working when I cut the lugs.


Seems to read ok still, but note taken thanks!


moonlightpedalbuilds said:


> From previous experience when dealing with stranded wire, I single strand of wire may touch other parts. Especially when try to insert stranded wires into the holes in the pcb, potentiometers and switches. What I do is to make sure they at tinned before inserting them into holes.
> 
> Another thing to look at are the through-holes. Make sure your solder bleeds to the other side of the board.
> 
> Do you lose the sound when you tighten the potentiometers?


Visual inspection with lighted magnifying  shows most pads with wire attached are clean joints and through holes filled but some are obscured by the insulation on one side. No stray wires. Will inspect those and redo if needed, thanks!


Robert said:


> With the board out of the enclosure connect a wire (or clip lead) to a known ground point on the board.
> 
> Now touch the metal body and shaft of each pot and see if the problem reappears.


On it! Much appreciated. Will report.


----------



## Robert

I missed the part about it sometimes misbehaving out of the enclosure, my idea might not help.


----------



## Jovi Bon Kenobi

Robert said:


> With the board out of the enclosure connect a wire (or clip lead) to a known ground point on the board.
> 
> Now touch the metal body and shaft of each pot and see if the problem reappears.


touching a jumper between the ground point on the board and to all pots shafts and housing produces only one noticeable difference and it's to the gain pot. it produces what seems like RF.


----------



## Jovi Bon Kenobi

Robert said:


> I missed the part about it sometimes misbehaving out of the enclosure, my idea might not help.


Ok. Yeah, it's weird. It either works just like my first mag delay out of the enclosure or it has those problems. when I handle the PCB while testing it makes it more noticable


----------



## Jovi Bon Kenobi

I have another Magnetron board. If at first you don't succeed...
Round 2...FIGHT!


----------



## zgrav

1. sometimes it works when it is not in the board
2. sometimes it does notw work when it is not in the board (only one repeat)
3. it never works in the enclosure

Is that right?

I wonder if you have a cracked trace on the board creating an intermittent connection that is part of the input to the feedback.

you can try flexing the pcb when it is out of the enclosure to see if it affects whether it works. if you can find a wonky spot you can bypass it.
 also suggests the board is under some pressure in the enclosure.  slightly enlarging the holes for the pots might fix that issue.


----------



## Jovi Bon Kenobi

zgrav said:


> 1. sometimes it works when it is not in the board
> 2. sometimes it does notw work when it is not in the board (only one repeat)
> 3. it never works in the enclosure


Yes to all 3 if you meant enclosure instead of board for 1 and 2


zgrav said:


> I wonder if you have a cracked trace on the board creating an intermittent connection that is part of the input to the feedback.


Interesting. I mean, I use a lighted optivisor and visually inspect and throughly clean PCB's before use. This one looked and still looks fine but it's worth a shot.


----------



## Jovi Bon Kenobi

Also, with all my builds I allow a hefty gap between the pots and the board. In this case, the nubs of the pot lugs are sticking out only about 1mm above the pads before soldering. I like doing that for extra wiggle room if needed.


----------



## zgrav

I would try reflowing the connections going from the first amp stage to the PT2399 input.  Something is intermittent.  A bad trace is a possibility, but it could  be something odd like a bad lead on a resistor.


----------



## Jovi Bon Kenobi

zgrav said:


> I would try reflowing the connections going from the first amp stage to the PT2399 input.  Something is intermittent.  A bad trace is a possibility, but it could  be something odd like a bad lead on a resistor.


Sadly, that is beyond my scope of fully understanding but I have the schematic printed out. I'm also populating another magnetron board. 
I think I went about 30+ PCB's without any problems and I hit this and my confidence gets shook. I really want to learn to read a schematic but don't know where to start.


----------



## twebb6778

I only know the basics but being able to read schematics, even just a bit, is a huge help when troubleshooting.

Take a look here if you get a chance https://learn.sparkfun.com/tutorials/how-to-read-a-schematic/all


----------



## Jovi Bon Kenobi

Here's the problem. When I test the board out of the enclosure I get two possible outcomes:
a.) I only get one repeat turning the full range of feedback knob with self oscillation at the very end, the dry signal is quieter than the repeats, there is faint RF, and my overall guitar signal is quieter when the pedal is engaged than when it is bypassed.
Or b.) It works perfectly with none of the above issues so I put it back into the enclosure and the problems come back.

Upon wiggling connections and stuff I can't seem to force replicate a vs b. I thought I may have solved it when I noticed that the OPA2134 was slightly lifted from it's socket and it cleared when I pushed it back in. However, once back in the enclosure the problems came back.

Link to schematic here: Magnetron Delay

I built the PCB with a couple mods added:
1. Momentary feedback footswitch
2. Internal gain trimpot moved to external control

I drew this up to make it easier to understand:




Photos incoming as soon as my housemate is out of the shared music room/my work area. ?


----------



## moonlightpedalbuilds

Try checking the continuity of the IC legs to the underside of the pcb where the sockets are soldered. Those kind of sockets are less reliable than the rounded hole type. Any bend on the pcb(when being mounted) may affect the connection of the IC to socket.


----------



## Jovi Bon Kenobi

moonlightpedalbuilds said:


> Try checking the continuity of the IC legs to the underside of the pcb where the sockets are soldered. Those kind of sockets are less reliable than the rounded hole type. Any bend on the pcb(when being mounted) may affect the connection of the IC to socket.


will do, first thing tomorrow. appreciate it!


----------



## Jovi Bon Kenobi

twebb6778 said:


> I only know the basics but being able to read schematics, even just a bit, is a huge help when troubleshooting.
> 
> Take a look here if you get a chance https://learn.sparkfun.com/tutorials/how-to-read-a-schematic/all


Thanks, I am liking it so far! No time like the present. May as well try to get something productive out of 2020.


----------



## zgrav

and you can build the other board and set this aside to come back to later if you prefer.  odds are pretty good it is one thing to find and fix and then it will be OK.


----------



## Mcknib

Late to the party as usual!

With the clues you've got e.g. 1 repeat, lower volume I'd look at what controls those two things, it may well be the same thing

If you look at the schematic the feedback path runs out from the PT2399 pin 14 and back in via pin 16 and obviously goes through the components in that path so it is very much like join the dots

The 1 repeat suggests too high a resistance on the repeats wiper could be a cold joint, the trimmer, the pot or a resistance off it.

The feedback volume is attenuated by the two diodes D1 and 2, I think it's a clamping arrangement whereby once the clipping threshold is reached it'll dump some signal to ground stopping it from getting too loud and clipping/distorting your guitar signal it should still get louder / distort a bit as you turn the pot and decrease the resistance between 2 and 3, like feedback generally does

For fun seeing as they're socketed remove those and see how loud it is or use schottky diodes with a lower vf, I've never built a PT2399 delay with those diodes it'd be interesting to know If it gets a bit  loud, mental and chaotic

They may well be causing the problem idk

Zooming into your pic I don't really notice anything other than left side of R8 doesn't look as shiny as the other joints.

Did you test it before the mods it wouldn't be that difficult to remove the feedback mod and see if it's ok that would at least narrow it down a bit ie the problems in circuit or with the mod


----------



## Jovi Bon Kenobi

Mcknib said:


> Late to the party as usual!
> 
> With the clues you've got e.g. 1 repeat, lower volume I'd look at what controls those two things, it may well be the same thing
> 
> If you look at the schematic the feedback path runs out from the PT2399 pin 14 and back in via pin 16 and obviously goes through the components in that path so it is very much like join the dots
> 
> The 1 repeat suggests too high a resistance on the repeats wiper could be a cold joint, the trimmer, the pot or a resistance off it.
> 
> The feedback volume is attenuated by the two diodes D1 and 2, I think it's a clamping arrangement whereby once the clipping threshold is reached it'll dump some signal to ground stopping it from getting too loud and clipping/distorting your guitar signal it should still get louder / distort a bit as you turn the pot and decrease the resistance between 2 and 3, like feedback generally does
> 
> For fun seeing as they're socketed remove those and see how loud it is or use schottky diodes with a lower vf, I've never built a PT2399 delay with those diodes it'd be interesting to know If it gets a bit  loud, mental and chaotic
> 
> They may well be causing the problem idk
> 
> Zooming into your pic I don't really notice anything other than left side of R8 doesn't look as shiny as the other joints.
> 
> Did you test it before the mods it wouldn't be that difficult to remove the feedback mod and see if it's ok that would at least narrow it down a bit ie the problems in circuit or with the mod


This is great. I will go through each and report back. I really appreciate you taking the time to help.


----------



## Mcknib

Jovi Bon Kenobi said:


> This is great. I will go through each and report back. I really appreciate you taking the time to help.


I'd probably start with removing the mod, intermittent faults are a mo'fo could be just about anything 

But if you remove the mod and it's all singing all dancing you'll know the mods the bad boy that's misbehaving


----------



## Jovi Bon Kenobi

moonlightpedalbuilds said:


> Try checking the continuity of the IC legs to the underside of the pcb where the sockets are soldered. Those kind of sockets are less reliable than the rounded hole type. Any bend on the pcb(when being mounted) may affect the connection of the IC to socket.


All points tested have continuity.



Mcknib said:


> I'd probably start with removing the mod, intermittent faults are a mo'fo could be just about anything
> 
> But if you remove the mod and it's all singing all dancing you'll know the mods the bad boy that's misbehaving


Removed. Problem still persists



Mcknib said:


> The feedback volume is attenuated by the two diodes D1 and 2, I think it's a clamping arrangement whereby once the clipping threshold is reached it'll dump some signal to ground stopping it from getting too loud and clipping/distorting your guitar signal it should still get louder / distort a bit as you turn the pot and decrease the resistance between 2 and 3, like feedback generally does
> 
> For fun seeing as they're socketed remove those and see how loud it is or use schottky diodes with a lower vf, I've never built a PT2399 delay with those diodes it'd be interesting to know If it gets a bit loud, mental and chaotic
> 
> They may well be causing the problem idk


Removed em and the only noticeable difference was that oscillation started sooner. The only Schottkey's I have on hand are 5817's. would those be suitable? I have lots of gen purpose, zeners, germies, etc.



Mcknib said:


> Zooming into your pic I don't really notice anything other than left side of R8 doesn't look as shiny as the other joints


R8 is shiny and clean top to bottom. In fact, I usually have at least one or two resistor pads that don't go all the way through and make a perfect shiny wee peak on the business side, but in this case every resistor _looks_ picture perfect. 

After doing the above all problems still persist in and out of the enclosure. Aside from the previously stated problems the main thing that I'm noticing is the indicator if it is intermittently working or not is that there is RF whenever I touch the modded external gain pot. If I touch it and get no RF, it temporarily works. If I touch it and cumbia comes through the amp, it's a no-go.


----------



## Mcknib

So its not the mod it's in the circuit

With dry signal low

I'd check resistance between pins 1 and 2 with no power to the circuit and the op amp removed from the socket you should expect R3 value + whatever the pots at and check pin 4 ground

What's your op amp voltages

Have you tried another dual op amp


----------



## Jovi Bon Kenobi

Mcknib said:


> I'd check resistance between pins 1 and 2 with no power to the circuit and the op amp removed from the socket you should expect R3 value + whatever the pots at and check pin 4 ground


Resistance between 1 & 2 looks ok: around 47k to 142k.
Pin 4 is grounded


Mcknib said:


> What's your op amp voltages


Forgive my ignorance but I need a refresher on this. Been a while. Black lead anchored to ground point, then red lead to pins 1 through 8... but what do I set my meter to again?






Mcknib said:


> Have you tried another dual op amp


Just did. Same prob.


----------



## zgrav

I think you would set your dial on Auto V, which should measure DC voltage.


----------



## Jovi Bon Kenobi

OK thanks.
1: 4.2v
2: 4.2v
3: 4.2v
4: ----
5: 4.2v
6: 4.2v
7: 4.2v
8: 8.4v


----------



## Danbieranowski

Do you have a little DIY audio probe handy?


----------



## Jovi Bon Kenobi

Danbieranowski said:


> Do you have a little DIY audio probe handy?


Yes, but no looper pedal for signal generation. Also, I'd need to know exactly where to follow on the schematic and that would be difficult as I don't know what I'm doing. Why did I build an audio probe then? lol


----------



## Danbieranowski

I could probably help by highlighting the audio path for you although I’m not great at reading a schem either. I’ll try to sort that out later today.


----------



## Mcknib

Your op amp voltages look good

You could probe it see if it gives any clues ie where it's quite, I'm not sure with the nature of the problem if it'll be any good

I'd probe your IN pad see how loud it is then IC1.1 in's and out and so on

Here's a quick audio path not sure what kind of audio goes through R4 and C2 perhaps you can verify how accurate it is? I've not done a lot of tracing audio paths recently! But I think it's fairly accurate, good enough to blast through it anyway and that's all you need innit?

Red part obviously LFO so no audio


----------



## Jovi Bon Kenobi

Mcknib said:


> Your op amp voltages look good
> 
> You could probe it see if it gives any clues ie where it's quite, I'm not sure with the nature of the problem if it'll be any good
> 
> I'd probe your IN pad see how loud it is then IC1.1 in's and out and so on
> 
> Here's a quick audio path not sure what kind of audio goes through R4 and C2 perhaps you can verify how accurate it is? I've not done a lot of tracing audio paths recently! But I think it's fairly accurate, good enough to blast through it anyway and that's all you need innit?
> 
> Red part obviously LFO so no audio
> 
> View attachment 7047


You're a gd champ!


----------



## Chas Grant

Mcknib's drawing will get you through the audio path. The audio signal going through C2 and R4 should be the same as the clean signal. C2 will block the DC from the output IC1.1 to the inputs the PT2399, and R4 is a load resistor doing the same thing as R6, both 10K. Following the green path should be a lot of fun, that's where all the delay is created!


----------



## Mcknib

Chas Grant said:


> Mcknib's drawing will get you through the audio path. The audio signal going through C2 and R4 should be the same as the clean signal. C2 will block the DC from the output IC1.1 to the inputs the PT2399, and R4 is a load resistor doing the same thing as R6, both 10K. Following the green path should be a lot of fun, that's where all the delay is created!


Thanks Chas it's always threw me that bit on a PT2399 delay I was thinking clean with it being way before the level / mix pot, but thanks to your explanation I now know that wee bit more 

The thing that always throws me is what direction it's flows in! Can never suss it!

Cheers


----------



## Jovi Bon Kenobi

I'm taking a break from this for a bit. I will definitely come back to trace that schematic with my probe but I need to walk away for a spell. Haha. I just finished populating a second board. This time I ran a standard 3PDT and just ran the external gain pot mod. For the momentary oscillation pot mod I just wired one up and put it off to the side ready to test when needed. I could just solder it in after knowing the second one works. So, I fire it up out of the enclosure and it's perfect! Then I add the momentary oscillation mod by jumpering it in and it still works! Then I hardwire the mod in and box it up...and it has the same problems as the first one! ?
I'm starting to wonder if the initial drawing I made is the culprit.


----------



## Jovi Bon Kenobi

Here's the problem. When I test the board out of the enclosure I get two possible outcomes:
a.) I only get one repeat turning the full range of feedback knob with self oscillation at the very end, the dry signal is quieter than the repeats, there is faint RF, and my overall guitar signal is quieter when the pedal is engaged than when it is bypassed.
Or b.) It works perfectly with none of the above issues so I put it back into the enclosure and the problems come back.

Upon wiggling connections and stuff I can't seem to force replicate a vs b. I thought I may have solved it when I noticed that the OPA2134 was slightly lifted from it's socket and it cleared when I pushed it back in. However, once back in the enclosure the problems came back.

Link to schematic here: Magnetron Delay

I built the PCB with a couple mods added:
1. Momentary feedback footswitch
2. Internal gain trimpot moved to external control

I drew this up to make it easier to understand:




Photos incoming as soon as my housemate is out of the shared music room/my work area. ?


----------



## Chas Grant

Mcknib said:


> Thanks Chas it's always threw me that bit on a PT2399 delay I was thinking clean with it being way before the level / mix pot, but thanks to your explanation I now know that wee bit more
> 
> The thing that always throws me is what direction it's flows in! Can never suss it!
> 
> Cheers



Not a problem at all Mcknib! The PT2399 is a beast on its own, and the delay path can be bit confusing since the in and outs share the same path to give you the effect. Electrosmash has a good article on it here https://www.electrosmash.com/pt2399-analysis . All the articles there are good and explain a lot.


----------



## Mcknib

Right I think you may have sussed it

As I said in my pm initially I looked at the wiring but am hopeless pressing an imaginary switch in my head and tracing it through the mod

Now that you mention it the way it's wired you're not bypassing the pot so you're adding resistance with the trimmer giving you less repeats so like the wf mod you want to use a 5 or 2K trimmer or a 1K resistor and take it from the left side of R9 to feedback lug 3

Bypassing the pot and pressing the footswitch introducing 1K resistance or whatever you set the trimmer to infinite or almost infinite repeats regardless of the feedback pot setting

Whereas before you'd need to max the feedback pot to have no resistance between 2 and 3 and just 1K from R9

Should work!

Your grounding issue could have been because the pot wasn't bypassed, the more you turn it down the more signal it dumps to ground via lug 1, At the same time increasing resistance between 2 and 3 and decreasing repeats and volume

Can't draw with my fingernail on my phone but this


----------



## Jovi Bon Kenobi

On it! Yeah, the WF mod seems just the ticket. After my tea though ☕


----------



## Jovi Bon Kenobi

Mcknib said:


> you want to use a 5 or 2K trimmer or a 1K resistor and take it from the left side of R9 to feedback lug 3


So, like this? Specifically, how the pink and green wires are connected to the trimmer.


----------



## Mcknib

That's what I'd try as long as that's the side of R9 that has continuity with D2 cathode

When I say left side of R9 I meant in the schematic 

Let's see if the theory's bs or not


----------



## Jovi Bon Kenobi

Mcknib said:


> When I say left side of R9 I meant in the schematic


Phew glad I asked. It's the right pad. ? Ok, going in.


----------



## Jovi Bon Kenobi

Ok, so I didn't try it inside the enclosure but I'm pretty certain it is the same problem as before because I get the same squealing radio interference upon touching the gain pot.

Good news is that rearranged momentary mod works though.


----------



## Jovi Bon Kenobi

I managed to dial the feedback knob to get more than one repeat, but it's like a hairs width turn away from self oscillation.


----------



## Mcknib

Have you already tried another PT2399 just to rule that out

I'd check the feedback pot alters resistance as you turn it that's strange it going from a few repeats to infinate that quickly


----------



## Jovi Bon Kenobi

Mcknib said:


> Have you already tried another PT2399 just to rule that out


I've tried 2 chips. I have a few more. I'll give it a whirl.



Mcknib said:


> I'd check the feedback pot alters resistance as you turn it that's strange it going from a few repeats to infinate that quickly


Ok so, upon further testing I was wrong. The feedback knob seems to work normally as far as repeats are concerned. Now I'm not sure if the one repeat thing was happening before! I swear it was though.  Actually, the volume discrepancies are not appearing if I dial the gain in right. 

Even though it still makes RF turning to a specific range of the gain pot I'm going to box it up once more.


----------



## Jovi Bon Kenobi

It all comes back when in the enclosure. Both boards, both with the same problem. 
I will probably just revert them back to unmodded so it's not a complete loss except for the predrilled enclosure. Pretty sure they will both work fine once I take off the external gain pot mod as that's the area that seems to be causing all the issues. 

One last check then I think I might be done trying to sort this out. I really do appreciate all the help though.


----------



## Mcknib

It hopefully will dissapear when it's completely shielded

You're just having one of those faults with many possible causes, rf, could be a cap not filtering properly near the op amp or in the power supply, the power supply itself, something acting as an antenna etc, and just to add to your woes its intermittent

Try putting the gain pot back to a trimmer may even be the long pot wires causing the rf problem


----------



## Jovi Bon Kenobi

Mcknib said:


> It hopefully will dissapear when it's completely shielded
> 
> You're just having one of those faults with many possible causes, rf, could be a cap not filtering properly near the op amp or in the power supply, the power supply itself, something acting as an antenna etc, and just to add to your woes its intermittent
> 
> Try putting the gain pot back to a trimmer may even be the long pot wires causing the rf problem


Took the gain pot mod out of both and soldered the 100k trimpot back onto the PCB. both work fine now. Even with the momentary mod. Well, that was a fun adventure. Sorry for all the troubles.


----------



## Jovi Bon Kenobi

Hey, at least we learned something! And once I finish drilling and labeling a new enclosure I can add it to the mod thread with a note to *not* try both mods. Haha.


----------



## Mcknib

Well I never






Sometimes it's staring you right in the face and you did mention it more than once! Going with your gut is quite often a winner

The was the last shot haha
Glad it's sorted

Its all learning, nearly 10 years down the line I've still got my 'L' plates on

Good to meet a fellow Ashton Lane frequenter small world innit?


----------



## Danbieranowski

I was going to say you’re drawing for the momentary switch was at least accurate Bc that’s what I used when I did mine. Did not do the gain pot piece though. Glad you got it figured!


----------



## Jovi Bon Kenobi

Mcknib said:


> Good to meet a fellow Ashton Lane frequenter small world innit?


Yeah man. I miss living there, it was a great experience. 

So if I ever have troubleshooting again, like if my IC chips are good, I can say "gony geez a chip mate" and you'll know what's up.


----------



## Mcknib

Jovi Bon Kenobi said:


> Yeah man. I miss living there, it was a great experience.
> 
> So if I ever have troubleshooting again, like if my IC chips are good, I can say "gony geez a chip mate" and you'll know what's up.


Aye big man nae bother jizt geez a shout


----------



## zgrav

maybe use shielded wires to and from the gain pot ......


----------



## Jovi Bon Kenobi

zgrav said:


> maybe use shielded wires to and from the gain pot ......


That's so simple it might work. Pulling all but three wires out of some shielded cable (or whatever), connecting em up, then running the shield to ground points at each end. I just left home base and am on the road. Won't be back for a week, but that sounds promising


----------



## Jovi Bon Kenobi

Here's the problem. When I test the board out of the enclosure I get two possible outcomes:
a.) I only get one repeat turning the full range of feedback knob with self oscillation at the very end, the dry signal is quieter than the repeats, there is faint RF, and my overall guitar signal is quieter when the pedal is engaged than when it is bypassed.
Or b.) It works perfectly with none of the above issues so I put it back into the enclosure and the problems come back.

Upon wiggling connections and stuff I can't seem to force replicate a vs b. I thought I may have solved it when I noticed that the OPA2134 was slightly lifted from it's socket and it cleared when I pushed it back in. However, once back in the enclosure the problems came back.

Link to schematic here: Magnetron Delay

I built the PCB with a couple mods added:
1. Momentary feedback footswitch
2. Internal gain trimpot moved to external control

I drew this up to make it easier to understand:




Photos incoming as soon as my housemate is out of the shared music room/my work area. ?


----------



## Raspymcnasty

Hey Jovie Bon Kenobi,
I want to do the momentary mod too but im curious if you figured out a way to press the momentary mod and not let it spiral out to feedback oscillation, rather just repeat until I let go, and then let it come back normal gradually.

Also, was your first wiring diagram the correct way? or the second way?


----------

