Ludwig Phase II Clone Tech Notes

[pinkjimiphoton]

c1 ...

Looks consistent down to here:

c29 tantalum, orange, brown white

Schemo says 220pF. I didn't know they made tantalum that small. That doesn't mean they didn't. Maybe dip ceramic??

Thanks again, Jimi! I notice you measured R63 as 9.4k, but listed it as 82k in your final list (it's 12k in the schem). Which is it?

I think it's 12K.

the tantalum suffered the same prob as i had on others.. it's red red (super thick band i thought) brown white, not red brown white. it's definitely a tantalum, but a big one...the leads at the bottom are offset, kinda egg shaped with 1 leg going straight down from the bottom, and one kinda offset out the side of the bottom toward the center of the board, if that makes any sense at all.

i would call r63 12k, 10 k is probably close enough for rocknroll

[Keppy]

I believe there is a typo on the schem. C3 is listed as .01uF, but my little fishy in the tank is wearing 1uF colors (non-polarized)  . The capacitor colors are (tropical fish) Brown, Black, Orange, White, Red. My online calculator tells me 1uF/250V, and not .01uF as stated in the schem. Try that. 

Wait a sec. The colors you listed are in fact .01uF. Check the chart I posted earlier.

[Keppy]

R76   27K? 33K?......mine 27k [we'll go with 27k]

Jimi said this resistor is not original in his unit. I think I'll stick with the 33k I have in there already, unless you can give me a reason to swap.

[pinkjimiphoton]

yah, i was trying to nuke that hum problem. that resistor didn't seem to be critical, hell, a piece of wire would probably work. mine is actually going to ground on one end, seems to be the only way to keep c1 on the fall board from buzzing if ya touch the damn thing.

no, i still haven't gone thru the sucker to find the problem.

it'll happen...eventually.

[Keppy]

That resistor is just a pulldown resistor for the Lo Z input, which you're probably not even using. A wire would just sent that input to ground, but I bet you could take the resistor out completely and the thing would still work.

Dino, I'm looking at C7 and thinking you made the same mistake I think you made on C3. Check it out and see if you agree or if I've just been up too long. Also, I notice the discrepancy between schem values and the values you gave for C4/C5 is the same (100x) so if you could double-check those I'd appreciate it.

After sorting through all of these values, here are the changes I think I need to make from the original schem:
Fall Plate:
- R32=4.7k (awaiting verification)
- R36/R57=68k
- R38/R60=4.7k
Console:
- R3=1M (already done)
- R14=6.8k
- R15=10k
- C4/C5=470nF (probably)

I believe all other discrepancies have been explained away at this point. Let me know if you think I've missed anything!
[edited to include R32]

[Keppy]

Dino, I checked out your links, and the calculator's jacked. The other link actually uses a brown-black-orange code as an example and calls it .01uF, so I don't know what's up with the calculator. Please check C4/C5 for me, as the calculator might've misled you there, too. Also, it looks like R32 on the fall plate still needs verification, as noted earlier.

[digi2t]

Dino, could you verify R32 on the fall plate? Jimi's is different than the schematic, but that resistor connects to R33, the one that in his unit is paralleled with a 1M. Since you don't have the added 1M, I wonder whether yours will match the schem or not.

I confirm Jimi's finding on R32, another typo on the schem. It's 4.7K.

You're right about the calculator, it whack! C4, and C5 on the console are 0.0047uF. The color code gives 472. C3, and C7 are .01uF (code 103), and C13 is 0.22uF (code 224).

Don't worry, I ditched the calculator!! Froggin' internet!!

[Keppy]

Sweet! So here's the revised list of changes:

Fall Plate:
- R32=4.7k
- R36/R57=68k
- R38/R60=4.7k

Console:
- R3=1M (already done)
- R14=6.8k
- R15=10k

I believe all other discrepancies have been explained away at this point. Let me know if you think I've missed anything!

[R.G.]

I might have been unclear about this. The filters in my unit pass signal. They just don't filter, except for a small amount of treble filtering in parallel mode.

If they pass signal, it's worth measuring the DC conditions in the filters on all three units, and trying to get your clone to match the working units.

From simulation, the filtering happens only at a particular few points on the trimmers. I'll go see what the sim says for DC voltages when it filters.

[pinkjimiphoton]

That resistor is just a pulldown resistor for the Lo Z input, which you're probably not even using. A wire would just sent that input to ground, but I bet you could take the resistor out completely and the thing would still work.

Dino, I'm looking at C7 and thinking you made the same mistake I think you made on C3. Check it out and see if you agree or if I've just been up too long. Also, I notice the discrepancy between schem values and the values you gave for C4/C5 is the same (100x) so if you could double-check those I'd appreciate it.

After sorting through all of these values, here are the changes I think I need to make from the original schem:
Fall Plate:
- R32=4.7k (awaiting verification)
- R36/R57=68k
- R38/R60=4.7k
Console:
- R3=1M (already done)
- R14=6.8k
- R15=10k
- C4/C5=470nF (probably)

I believe all other discrepancies have been explained away at this point. Let me know if you think I've missed anything!
[edited to include R32]

keppy, the values on the fall board have been verified bro. i not only double checked them, but metered them puppies, too. so i am triple sure they are right, other than the one resistor i had subbed. hope ya got some sleep and weren't up playing mad scientist all nite (like i would have been..)...

[pinkjimiphoton]

hopefully after making these changes it'll fire right up bro!!! 

[pinkjimiphoton]

I might have been unclear about this. The filters in my unit pass signal. They just don't filter, except for a small amount of treble filtering in parallel mode.

If they pass signal, it's worth measuring the DC conditions in the filters on all three units, and trying to get your clone to match the working units.

From simulation, the filtering happens only at a particular few points on the trimmers. I'll go see what the sim says for DC voltages when it filters.

r.g., tell me what to do, i've gotta couple hours free...no idea what to check or where...but if ya tell me say "check at both sides of r56 to ground with a voltmeter" i can probably handle that without screwing it up too badly.

[R.G.]

Keppy,
Got the filter fired back on the simulator, put the circuit mods in. None of the changes made much of a difference either way so far, at least as regards getting a filter sound.

What *was* critical was the setting of R29. Unless this is just right, you get no filtering. So pick a filter, set up points 8 and 9 on the filter board to be about 2.5V, then tweak R29 til you get a filter sound. If that doesn't work, I can read values off the sim for DC voltages that should get you closer. I suspect that as critical as the setting is in simulation, that may be one of the biggest remaining issues.

I can come up with rationales for the other trimmers.
R31 sets the amount of DC on the rocker pedal so it moves Q5 on the console the right amount to make the control voltages for the two filters.
R41 and R62 have to do with either the sensitivity/idle frequency/balance of the two filters as respects the voltage made on R29. They are much less touchy than R29.
R55 and R77 are a balance between the two halves of the filter sides; don't know exactly what they do yet, but again, much less touchy.
R65 seems to be an output level control for the high formant filter. It won't keep it from filtering.

r.g., tell me what to do, i've gotta couple hours free...no idea what to check or where...but if ya tell me say "check at both sides of r56 to ground with a voltmeter" i can probably handle that without screwing it up too badly.

Actually, you've been immensely helpful in running stuff down. What would be very useful is to clip your voltmeter black lead to ground (wires 13 and 14 on the bottom board are handy), then measure the voltage with the red probe on
- all the transistor collector pins; collectors only should be enough. The schemo shows you where the collectors are.
- voltage on the wipers of the trimpots.
- voltages at wire/connections 8, 9, and any one of the places labeled with the funny greek letter in the circle on the schematic. The schemo also shows you where the pick off points for it are.

Given how critical that voltage is, I maybe should put in a test point on the PCB for setting it.

[R.G.]

Simulator says the voltage for what I call "Lambda" ( I gotta look up what that symbol really is) has to be within the range of 1.75V to 2.3V to get filtering. Either side of that range seems to make the filter not filter.

One has to always be suspicious of simulators, but they form a useful guide to what happens. It's a good place to start.

[pinkjimiphoton]

Keppy,
Got the filter fired back on the simulator, put the circuit mods in. None of the changes made much of a difference either way so far, at least as regards getting a filter sound.

What *was* critical was the setting of R29. Unless this is just right, you get no filtering. So pick a filter, set up points 8 and 9 on the filter board to be about 2.5V, then tweak R29 til you get a filter sound. If that doesn't work, I can read values off the sim for DC voltages that should get you closer. I suspect that as critical as the setting is in simulation, that may be one of the biggest remaining issues.

r 29 will work over quite a range, rg, but some settings are unusable and just seem to cause oscillation.

[pinkjimiphoton]

r.g., tell me what to do, i've gotta couple hours free...no idea what to check or where...but if ya tell me say "check at both sides of r56 to ground with a voltmeter" i can probably handle that without screwing it up too badly.

Actually, you've been immensely helpful in running stuff down. What would be very useful is to clip your voltmeter black lead to ground (wires 13 and 14 on the bottom board are handy), then measure the voltage with the red probe on
- all the transistor collector pins; collectors only should be enough. The schemo shows you where the collectors are.
- voltage on the wipers of the trimpots.
- voltages at wire/connections 8, 9, and any one of the places labeled with the funny greek letter in the circle on the schematic. The schemo also shows you where the pick off points for it are.

Given how critical that voltage is, I maybe should put in a test point on the PCB for setting it.

ok r.g.  unfortunately, i'll be gone to appointments most of the afternoon, but will get on it as soon as i can this evening, see if we can narrow it down. on the other thread, i DID post the voltages on every single transistor...hang on, i may have them in my ludwig folder..sweet, i do...here ya go..

q1
e 0
b .63
c 2.99

q2
e 3.65
b 4.18
c 10.25

q3
e 0
b .60
c 7.69

q4
e 2.77
b 3.07
c 10.26

q5
e 3.31
b 2.63
c .20

q6
e 0
b .60
c .20

q7
e 3.57
b 4.23
c 8.77

q8
e 3.56
b 4.21
c 11.21

q9
e 19.77
b 19.12
c 11.21

q10
e 10.58
b 11.21
c 18.70

q11
e 19.35
b 18.70
c 15.80

q12
e 3.58
b 4.21
c 15.80

q13
e 3.58
b 4.22
c 14.88

q14
e 3.55
b 4.15
c 17.35

q15
e 3.55
b 4.21
c 11.40

q16
e 19.62
b 18.96
c 11.40

q17
e 10.77
b 11.41
c 18.88

q18
e 19.53
b 18.88
c 15.62

q19
e 3.59
b 4.21
c 15.62

q20
e 3.59
b 4.18
c 17.60

q21
e 3.31
b 3.83
c 10.26

[pinkjimiphoton]

sorry, those are only the voltages to ground on the fall board, i gotta defer to dino for the console board ones.

i will get the rest of the readings when i return early this evening.

we're getting closer...can feel it! 

[pinkjimiphoton]

also...resistance readings from the fall board, posted in the other thread...trying to keep everything in one folder here...

all readings from the BACK (non thumbwheel) side of the pot, 3, 2 (wiper), 1, left to right

r31 (25k)

3-2 = 4.7k
2-1 = no reading

r77 = 30k

3-2 = 13.8k
2-1 = 19.9k

r41 = 500r

3-2 = 420r
2-1 = no reading

r62 = 500r

3-2 = 175.9r
2-1 = no reading

r55 = 50k
3-2 = 15.9k
2-1 = 32.6k

r29 = 150r

3-2 = 106r
2-1 = no reading

r65 = 25k

set to 24.3k

treadle pot = 5k

toe down

3-2 = 4.1k
2-1 = 4.3k

heel down

3-2 = 4.5
2-1 = no reading

[R.G.]

ok r.g.  unfortunately, i'll be gone to appointments most of the afternoon, but will get on it as soon as i can this evening, see if we can narrow it down. on the other thread, i DID post the voltages on every single transistor...hang on, i may have them in my ludwig folder..sweet, i do...here ya go..

Hey! So you did. That's what I needed. More sim work. Go do the appointments. I have plenty to work on.

[pinkjimiphoton]

i have a 2 hour window before my next appointment, so i'll get the voltage readings at all the fall board test points now...more shortly, stay tuned!!