Ludwig Phase II tuning.

[Ry]

I used a 6027 and made the modifications mentioned in the build file.

I did the test you described and the collectors of q3 and q4 do indeed flip, as do the collectors of q7 and q8. It takes a little more than a quick touch of the wire (maybe 2 seconds), but they do swap voltages.  13.5 v on q3/q4, about 15.5 v on q7/q8.

It appears that my issues are now around qf4, q2, and q5.

I spent a great deal of time around qf4 this morning.  The voltage at either end of rf15 is only .1v different 21.5 vs 21.6.

EDIT:  I'm slapping my forehead I didn't populate r18...which explains the lack of voltage on q5. Looking through the bom, I don't see it listed, which is why I think I failed to populate it. I did check over the boards, but there are a lot of unused pads for things like trimmers. I just plain missed it.   The schematic shows it as a 120k resistor. Let's see what that does for me...

[Ry]

Alright, some success!  With R18 installed, Q5 is now working and I can tune the opposing voltages in COUNTER mode.  I get a perfect balance between 1.9 and 5.7v toe/heel!

I worked through the tuning procedures with ease, finding that 3.8 v at TP3 gave me a motorboating octave up sound.  4.5V sounds better in mine.  I haven't hooked up a scope to attack the parallel tuning yet.

Outstanding issues:

I still haven't solved the QF4 voltage concern.

Animation does not work.  I put Q2 back in (after socketing the position just in case I need to try something else).

There are a couple oddities with the rocker pedal.  There seems to be a dead spot in the middle of the travel, this may be normal as both filters reach 0v, I'm not sure.  Also, it sounds like there is a delay in one of the filters catching up when I stop a sweep.  I haven't noticed this is the demos, it's a little odd.  It's obviously not quite right yet, it's not nearly as vocal sounding as it should be.

Thanks to everyone so far, this has been a long process!

[Keppy]

Your animation troubles, especially with the flip-flop working manually, remind me of the problems I had in my own build. I had the UJT's bases reversed due to an error in the factory schem. Sounds like you might have a UJT/PUT problem. Triple-check your pinouts, then if it's still not working I bet R.G. can recommend a test circuit to verify whether the component is good. I remember rigging up a 700Hz test oscillator on my breadboard to confirm mine 2646 was working.

[Ry]

Hey Keppy,

I pulled up a data sheet and double checked the pins against the build article/my build.  I also double checked my components connected to Q2.  I may have bought another one of these, I will likely sub it and see if I get any different results.

[R.G.]

EDIT:  I'm slapping my forehead I didn't populate r18...which explains the lack of voltage on q5. Looking through the bom, I don't see it listed, which is why I think I failed to populate it. I did check over the boards, but there are a lot of unused pads for things like trimmers. I just plain missed it.   The schematic shows it as a 120k resistor. Let's see what that does for me...

DOH! R18 was not in the BOM.

It is now. It's uploading to Geofex as we speak. See, I told you that victi..., er, first prototypes lead a hard life.  

Animation does not work.  I put Q2 back in (after socketing the position just in case I need to try something else).

OK, let's work that one first. As a side note, I never liked UJT circuits.  

Note that the 2N6027 has a different pinout than the 2N2646. Referring to page 15 of the instructions, are the pins plugged in as shown?
I also notice that I annotated Ralt1 on the schematic at a different time than I wrote up the instructions; it's shown as 3.3K on the schemo and I found that I had to use 4.7K or 5.1K in the tinkering. It could well be that that value needs tinkering. Can you swap values or do the pot test on it?

Both PUTs and UJTs rely on exactitude of the pin voltages to work right, even more than bipolars.

For the rocker, measure the voltage between outside lugs, then put your meter on the wiper and see if sweeping the wiper also sweeps the voltage on the wiper, and if you find any dead spots.

With the animation footswitch set to ON, and the animation switch to fast, what are the pin voltages on Q2?

[digi2t]

Alright, some success!  With R18 installed, Q5 is now working and I can tune the opposing voltages in COUNTER mode.  I get a perfect balance between 1.9 and 5.7v toe/heel!

I worked through the tuning procedures with ease, finding that 3.8 v at TP3 gave me a motorboating octave up sound.  4.5V sounds better in mine.  I haven't hooked up a scope to attack the parallel tuning yet.

Outstanding issues:

I still haven't solved the QF4 voltage concern.

Animation does not work.  I put Q2 back in (after socketing the position just in case I need to try something else).

There are a couple oddities with the rocker pedal.  There seems to be a dead spot in the middle of the travel, this may be normal as both filters reach 0v, I'm not sure.  Also, it sounds like there is a delay in one of the filters catching up when I stop a sweep.  I haven't noticed this is the demos, it's a little odd.  It's obviously not quite right yet, it's not nearly as vocal sounding as it should be.

Thanks to everyone so far, this has been a long process!

Excellent news Ry. And the fact that your COUNTER voltage are working, is great news as well.

I've mentioned it before, but I say it again; If you need any voltages, or readings of any sort from the originals, just say the word. Your success is our success.

[Ry]

R.G.,

I'll tack a 10k pot in there tomorrow morning and report back my findings.  I have triple checked the pinouts and I had a 4.7K resistor in there.

Dino,

I think I'm good for voltages so far.  I'm a little baffled by QF4, but I'll keep looking at it before asking you to crack yours open.

Thanks guys!  I think we're almost there!

[R.G.]

ON Qf4, can you measure both sides of the resistors RF14, 15, 17, and 18 with the Fuzz footswitch in both positions?

I think I can see how a footswitch miswire could do this. Just a guess.

[Ry]

ON Qf4, can you measure both sides of the resistors RF14, 15, 17, and 18 with the Fuzz footswitch in both positions?

There are four different answers for each setting based on the state of the Voice Fuzz switch and the Fuzz DPDT footswitch:

                                                             Fuzz footswitch off/             Fuzz footswitch on/      Fuzz footswitch off/       Fuzz footswitch on/          
                                                             Voice Fuzz selected             Voice Fuzz selected      Fuzz selected                Fuzz selected
RF14 junction with CF5:                                      9.4v                                   8.7v                         8.5v                             8.1v        
RF14 junction with RF17:                                   20.9v                                  16.7v                       15.7v                           13.5v
RF15 junction with CF5:                                     21.5v                                  17.3v                        14v                             16.3v
RF15 junction with QF4 base/RF17/RF18:            21.6v                                  17.4v                        16.4v                          14.1v  
RF18 connection with ground:                              0v                                       0v                            0v                              0v

With the animation footswitch set to ON, and the animation switch to fast, what are the pin voltages on Q2?

With a 4.7k resistor in the RALT1 postion:

A: varies between 3.2 and 10.02v
G: 11.35v
C: .52v

I removed RALT1 and replaced it with a 10k pot.  There is no audible difference when I sweep the pot and see if the animation is working.  What else in the circuit can I be looking for here?

For the rocker, measure the voltage between outside lugs, then put your meter on the wiper and see if sweeping the wiper also sweeps the voltage on the wiper, and if you find any dead spots.

I did this and found no dead spots in the voltage readings during travel.  The oddities I'm hearing may be tuning issues.  I don't have the parallel filters tuned, there may be other issues.  This will be the last thing I worry about.

Thanks again!

[pinkjimiphoton]

ry, there is ONE pot that controls the total sweep of the pedal...you may be past it on the setting. i'm not sure on the clone layout, but on the original, its trimmer R31.

if it's turned up too much, it could sweep the pedal to the point where nothing's working...maybe it's above the range where the oscillation happens, or it's too high or something..


try this...center all the trimmers.... with heel down on the treadle, counter and vowel switch on, fuzz on and animation on, dial that trimmer up until it starts to oscillate. the heel down position should pretty much sound like a %^&*ed wah in the bass region. back off the trimmer just to the point where oscillation stops.

also make sure r65 is full blast...i think it's there just to trim down gain somewhere if needed, at least that's how it works on mine.


r 41 and r 62 will fine tune the pedal...if the formants aren't working, you can probably adjust one HELL of a fuzz here, as well as the gain.

again, on mine, when r 29 failed, i lost animation...sounded like a %^&*ed wah...that's what kinda tunes the frequencys of the sweeps.

man....this sounds like gobbledegook...but i hope it helps.

you'll get this bro, don't give up!!!!

[R.G.]

There are four different answers for each setting based on the state of the Voice Fuzz switch and the Fuzz DPDT footswitch:

I'll have to sit and think for a while with the voltages and schematic in front of me on that one.

With a 4.7k resistor in the RALT1 postion:
A: varies between 3.2 and 10.02v
G: 11.35v
C: .52v
I removed RALT1 and replaced it with a 10k pot.  There is no audible difference when I sweep the pot and see if the animation is working.  What else in the circuit can I be looking for here?

Actually, if the anode is blipping from 3.2 to 10.02, the thing may be working. No change would indicate it was not triggering at all. That would seem to me to indicate that the sudden transient on the anode when it triggers is not getting to the flipflop. That is, not getting from R6 to R10 through C3. You could check this with an audio probe, but it's a huge signal. You could audio probe it with a 100K/1K resistor divider in front of the probe capacitor to get the signal smaller to not destroy an amp's input. If you do this, you should hear a periodic thump on R6 and a tick on R10 on the two sides of C3. It's possible for C3 to be bad, wrong value, bad solder joints, etc. to account for this hypothetical issue.

I did this and found no dead spots in the voltage readings during travel.  The oddities I'm hearing may be tuning issues.  I don't have the parallel filters tuned, there may be other issues.

I think you're right on this one. The continuous voltage indicates it's not in the pot. We can hit this one last.

[Ry]

you should hear a periodic thump on R6 and a tick on R10 on the two sides of C3

I probed R6 and R10.  I initially didn't get any ticking on R10.  I reflowed C3 (after checking that the value was correct) and now I get the ticking on R10 and thump on R6.  I still don't have any animation, but it's a step in the right direction!

[R.G.]

OK. That means that there was at least one bad solder joint. At this point, it would make sense to reflow them all. Otherwise, you'll have to find any more one at a time.

More to the constructive side, do the collectors of Q3, 4, 7 and 8 now switch up and down? (you have to have the Fuzz/FFM/both switch in the both position)

They should.

[Ry]

The collectors still don't switch.  I've also reflowed both boards with no effect on the switching. I think I'm down to checking through every resistor and capacitor value.

[R.G.]

Still no switching? Hmm.
I'm thinking back to when we tested them for any work at all:

I did the test you described and the collectors of q3 and q4 do indeed flip, as do the collectors of q7 and q8. It takes a little more than a quick touch of the wire (maybe 2 seconds), but they do swap voltages.  13.5 v on q3/q4, about 15.5 v on q7/q8.

I should have picked up on that earlier. The idea behind Q2's ticking and C3 coupling it into Q3 and Q4 is to make a short, sharp negative going pulse out of the sudden turn-on of the PUT/UJT as it discharges the timing cap. This sharp pulse makes the flipflop flip. In my simulations, and in long-ago labs, the necessary pulse to make a discrete transistor flipflop flip is about 1uS if you don't do special stuff to speed it up.

That's all to say, it should not take a couple of seconds to make the flipflop flip. For the test we were doing, removing Q2 and shorting the R6 side of C3 to ground, the flipflop should change instantly (to a human) after you touch the wire to ground. What you're telling me is that the flipflop is not triggering fast enough. If you're getting the thump and click on each side of C3, then it's likely that there's a problem with Q3/Q4.

[pinkjimiphoton]

but...
rg,
what if he maybe has the fast/slow switch on? if he does, then it will ramp up either immediately on fast, or take a couple SECONDS if set to slow...

that's the function of the fast/slow switch, how fast the "animation" (modulation) ramps up from no modulation to whatever speed is set in the animation speed setting pot....


could that explain why ry's PII is doing this?

just thinking on my feet here...cuz i remember watching this change when i was doing voltage readings months ago, and since you're not used to the quirks of the unit like the speed switch (or maybe you are, forgive my presumption...)

[Ry]

All of this givesme somewhere to start.  I'll check the components around q3/q4 for the correct values and double check the connections. I will also look at this with the fast/slow switch set differently. I had it set to Fast this afternoon.

[pinkjimiphoton]

maybe the fast/slow switch is wired backwards? if it's set to slow, the modulation should ramp up over a couple seconds...if set to fast, should be instantaneous.

but the speed control pot will control whatever speed the modulation will occur... if it's set in the middle of the travel available, it should become obvious whether the switch is right or not...

not saying you did it wrong, ry...but sometimes the damndest things happen.

[R.G.]

Good point, Jimi. I'm not familiar with how long it takes "slow" to start up. Probably ought to try it in both positions. I'm putting all of this into my pot of things for "how to bring it up".

[pinkjimiphoton]

just trying to use my limited knowledge to help, RG...i really wanna see this thing live!!


to think i thought about making a few of these commercially <shudder>