Kingslayer issues

[jingyjangy]

Hey all! I recently built the Kingslayer board, installed it into an enclosure, and spent the last couple of days plugging in different clipping diodes to get the right balance of crunch for each clipping option afforded by the 3-way switch. I opted to leave out the OD switch and jumpered it so D2 & D3 are always in the circuit. Everything was sounding great and after trying numerous combinations of clipping diodes I finally settled on - D2&D3:D9J&BAT46, D4&D5:1N34a&1N34a, D8&D9:OA126&D9J(asym.)&1N34a. The pedal was sounding wonderful and the world was a bright shiny place! I was about to seal up the back and put it on my pedalboard and put it through it's paces but I plugged in one more time to make sure I really dug my clipping choices when I suddenly had an issue with the Gain control - turned fully clockwise(100%) the clipping became farty, ratty?! Turned to the noon position it quiets down but has no noticeable clipping, then turned fully counterclockwise it gets louder again with no clipping?!!! I replaced the dual gang pot, reflowed all solder points on the entire board and changed out the TLC274 with a new IC and same problem! Aye Carumba!! Right now frustration level is high so I was hoping fresh minds and fresh eyes might help.

[midwayfair]

Sounds a bit like your gain pots might be wired backwards.

[jingyjangy]

The control was working properly, then after playing with the clipping diodes the problem arose. I double checked lug/pad orientation when I installed the new pot and just triple checked - lug1 to pad1, lug2 to pad2, etc. That's what is so perplexing and frustrating me right now - how could there be a problem now when it was working fine and correctly before and no changes made to the pot wiring? I changed out the pot because I thought my plugging in and out the different diodes might have put too much pressure on the wires (and pot lugs) either connected to the pot or the board. That's why I re-flowed all the solder joints on the board as well. I'm wondering if maybe something else came loose on the board?

[jingyjangy]

Hey Jon, it turns out the problem is the D2 diode (D9J). I don't know how to measure forward voltage but I suspect that the FV of the D9J is either too low or too high (as suggested in the build doc). With 1M in R11 and BAT46's in both D2&D3 the Gain knob responds exactly as it should. With the D9J in D2 and the Gain knob completely counterclockwise the volume is loud, at 12 noon the volume dips, at completely clockwise the volume is loud again with a ratty breakup.

1.How do u measure the FV?

2.In your great Klon style pedal demo you list 1N34a/OA126&D9J as your diode choice but don't mention in which position and what diodes are in the other positions? D2&D3? D4&D5? D8&D9?

[midwayfair]

Hey Jon, it turns out the problem is the D2 diode (D9J). I don't know how to measure forward voltage but I suspect that the FV of the D9J is either too low or too high (as suggested in the build doc). With 1M in R11 and BAT46's in both D2&D3 the Gain knob responds exactly as it should. With the D9J in D2 and the Gain knob completely counterclockwise the volume is loud, at 12 noon the volume dips, at completely clockwise the volume is loud again with a ratty breakup.

1.How do u measure the FV?

2.In your great Klon style pedal demo you list 1N34a/OA126&D9J as your diode choice but don't mention in which position and what diodes are in the other positions? D2&D3? D4&D5? D8&D9?

2. Use the diode setting on your multimeter. :-) You can also put the diode in series with a 100r and measure the current.

2. My soft clippers were MOSFETs + BAT41. The D9J was one of the hard clippers.

The Fv being too low would just be very distorted. Too high would just be that you don't really hear must distortion. I don't think they would cause what you're describing, especially not a volume dip, but if using different diodes makes it work right, then go ahead. It could be diode leakage or reverse conductance. Diodes can do interesting things at inopportune times, and I'm not entirely up on the workings of op amps.

[jingyjangy]

I have a Mastech 390-545 and it has 3 sections that measure voltage:
1.V--- (straight line on top of dotted line)
2.V~
3.hFE (can measure PNP or NPN)
Which one of these would be appropriate for measuring FV?

Your soft clippers are - 1 mosfet on one side or 2 mosfets (asymetrical) & 1 BAT41 on the other side?

By the way I absolutely love your Youtube video demo Holy Klones! Your tone is fabulous! I really dig that Tone King. It is also soooo refreshing to hear a demo with an amp set clean so you can actually get a better idea of an effects pedals true sonic qualities especially when you're listening for differences in OD's! Do you listen to Dire Straits at all? I thought I detected some Mark Knopfler influence? Very tasty!

Jon, thanks mucho for all the help!

[midwayfair]

I have a Mastech 390-545 and it has 3 sections that measure voltage:
1.V--- (straight line on top of dotted line)
2.V~
3.hFE (can measure PNP or NPN)
Which one of these would be appropriate for measuring FV?

Your soft clippers are - 1 mosfet on one side or 2 mosfets (asymetrical) & 1 BAT41 on the other side?

By the way I absolutely love your Youtube video demo Holy Klones! Your tone is fabulous! I really dig that Tone King. It is also soooo refreshing to hear a demo with an amp set clean so you can actually get a better idea of an effects pedals true sonic qualities especially when you're listening for differences in OD's! Do you listen to Dire Straits at all? I thought I detected some Mark Knopfler influence? Very tasty!

Jon, thanks mucho for all the help!

If your multimeter doesn't have a diode/continuity setting (they're the same), then you should really consider getting one that does. To test diodes without that setting, pull them from the sockets, pull out the breadboard, and put the diode in series with a 100R from +9v to ground. Measure with the black probe on the cathode and the red probe on the anode. The 100R is a current limited resistor.

I can't find a picture of that multimeter anywhere, but other Mastechs definitely have that setting. It looks like a diode schematic symbol.

My softclippers are a mosfet and BAT41 on one side, and a mosfet on the other. It's asymmetric, but I believe one side is a body diode and the other isn't. I honestly can't remember at this point.

>Do you listen to Dire Straits at all?
Tons.

[jingyjangy]

If your multimeter doesn't have a diode/continuity setting (they're the same), then you should really consider getting one that does. To test diodes without that setting, pull them from the sockets, pull out the breadboard, and put the diode in series with a 100R from +9v to ground. Measure with the black probe on the cathode and the red probe on the anode. The 100R is a current limited resistor.

I can't find a picture of that multimeter anywhere, but other Mastechs definitely have that setting. It looks like a diode schematic symbol.

Here's a photo of my DMM:

My softclippers are a mosfet and BAT41 on one side, and a mosfet on the other. It's asymmetric, but I believe one side is a body diode and the other isn't. I honestly can't remember at this point.

Body diode?

>Do you listen to Dire Straits at all?
Tons.

When they first came out in "78 or so I was a big fan but haven't listened in a long time. However the day I watched your video I was listening to Communique. Maybe It was the gorgeous clean tones and the hours of breathing too many solder fumes but some of your runs sounded pleasingly derivative. 

[midwayfair]

Again, the diode tester is the setting that looks like a diode schematic symbol. It's also the continuity setting.

A body diode is just using a transistor as a diode. You use the outside legs and then solder it in. In regular silicon (or germanium) transistors, this results in what's basically a ... silicon diode. Not terribly exciting, but it's about .65v, which is slightly higher than other common diodes in a pinch.

In a MOSFET, one direction works like that; the other direction works a bit differently, because MOSFETs have an internal compensation diode. You have to put a diode in series with it or it'll just conduct when the wave swings the other way. See the Spark Plug documentation for instructions how to wire it up this way. This is the more exciting version, but I'm not totally certain I did it that way in my Kingslayer.