Ludwig Phase II Clone Tech Notes

[R.G.]

OK, just to keep from digging through 20 pages of notes.

You can (probably) power an LPII clone from Mouser Part number 553-WAU24-200, which is 24Vac, 200ma, $10 in a voltage doubler arrangement.

With two 220uF/100V caps and two 1N4007 diodes, this turns out about 58-74Vdc on the filter cap. Putting this into the regulator on the LPII console board (in a simulator) gives the desired 35Vdc out at up to about 75ma. If the current gets higher, you have to increase the size of the 220uF caps up to 470uF. And the pass transistor may burn up. It may anyway. The simulator doesn't tell me how hot my finger gets if I touch the transistor.

It's enough raw voltage anyway, and cheap.

I think the 553-WAU20-500,Xicon 412-224034 work too, but they're $10.25 each. Same circuit, a voltage doubler. 220uF/100V caps cost about $0.60 to $0.80 each depending on brand.

[R.G.]

@keppy:

Hmmm...I have an unregulated 15v supply that puts out 21-22v. Doubling that might be JUST high enough to drive the Zener without burning anything out. Maybe I'll try that first.

Simulation says that a 20V open circuit AC adapter with an internal resistance equivalent of less than 12 ohms will ...just... do it at a 50mA load current. We don't know the load current, but I'm guessing.

Could you list all the points where you want me to take readings from?

Console board pads 2 & 3 for the AC input, pad 17 for DC output from the regulator. While you're at it, it might be worthwhile to take readings at all the test points noted on the layout. I say MIGHT because I haven't looked thoroughly enough to know if those points are carrying any DC bias or would have any bearing on the settings of the trimpots. Probably just reading the power supply is fine for now.

Across C11, as well.

[Keppy]

You can (probably) power an LPII clone from Mouser Part number 553-WAU24-200, which is 24Vac, 200ma, $10 in a voltage doubler arrangement.

Would this be any improvement on the 24Vdc supply I just bought at a thrift store for $1.49? (which I believe is also 200ma)
I was thinking using the DC supply might cut down on ripple with the existing filtering. I was planning on connecting the output of the doubler either just after D4/D5, or just before to drop the voltage a smidge.

[digi2t]

Hi Kep,

Decided to post here as well, just in case....

OK, first off the pots. Bypass balance is a 10K, and the Z pot is 5K.

For the voltages, the unit settings were as follows;
Footswitches;
BYPASS OFF (meaning effect on)
All other switches OFF

Treadle-Toe down

Console;
All sliders set to 0 (minimum)
FUZZ switch-FUZZ/VOICE
SELECT switch-BOTH
SLOW START
All Formant switches - OFF

Voltages;
Console pad 2 to GND = 37.0 vac
Console pad 3 to GND = 37.0 vac
Console pad 2 to 3 = 74.3 vac
Console pad 17 to GND = 33.45 vdc (took about 1 minute to stabilize)
Console capacitor C11 to GND = 46.0 vdc
Motherboard pad 5 to GND = 33.45 vdc (took about 1 minute to stabilize)

Motherboard Test Points (all to GND pad 14);
TP1 - 0.624 vdc
TP2 - Toe down = 1.01 vdc  Heel down = 13.85 vdc
TP3 - 3.807 vdc
TP4 - 2.292 vdc
TP5 - 3.74 vdc
TP6 - 3.81 vdc
TP7 - 3.80 vdc
TP8 - 9.26 vdc
TP9 - 18.54 vdc

Anything else you need?

[R.G.]

Would this be any improvement on the 24Vdc supply I just bought at a thrift store for $1.49? (which I believe is also 200ma)
I was thinking using the DC supply might cut down on ripple with the existing filtering. I was planning on connecting the output of the doubler either just after D4/D5, or just before to drop the voltage a smidge.

AC output lets itself be doubled with only diodes and capcitors. DC has to be chopped/modulated to make AC, that doubled/rectified, and then filtered to DC. By starting with 24VAC, you eliminate having to chop or modulate the DC. You can't simply connect a passive diode/capacitor doubler onto a DC output and have it work. It requires an active oscillator/charge pump/switching whatever to make it AC first. That's why AC output wall warts are so handy - they produce pre-made AC for you to work with.

Fundamentally, that's one reason why George Westinghouse's AC distribution systems won out over Thomas Edison's DC distribution systems back in the late 1800s.

Actually, the 24Vdc supply from the thrift store *might* work, if you were to open it up and remove the diodes and filters that make 24Vdc. If it's not a switching power supply internally, but a standard (heavy!) transformer wall wart, then the transformer will be about 17-20Vac. This is marginal, but you may be able to do something with it if the unit doesn't absolutely have to have 35Vdc.

NOTE ==>> I DO NOT RECOMMEND YOU OPEN UP AND MODIFY A WALL-WART ADAPTER OF ANY KIND, BECAUSE OF THE ELECTRICAL SAFETY ISSUES. IT'S NOT WORTH DYING FOR.<<==

Voltages;
Console pad 2 to GND = 37.0 vac
Console pad 3 to GND = 37.0 vac
Console pad 2 to 3 = 74.3 vac
Console pad 17 to GND = 33.45 vdc (took about 1 minute to stabilize)
Console capacitor C11 to GND = 46.0 vdc
Motherboard pad 5 to GND = 33.45 vdc (took about 1 minute to stabilize)
...
Anything else you need?

Wow. That'll about ice it for the power supply. Thanks.

With 37Vac under load, the DC at C11 unloaded would be about 52.3V. As it is, it's 46, which means there's several volts of ripple, which makes sense for a small, low-current power supply.

Actually, I guess if you measured the DC across R22, it would tell us the actual DC current used by the whole thing. That's really maximal icing on the cake if you can do that.

Anyway, given that the voltage out is 33.5V, using a wall wart with 20 to 24Vac and a diode/capcitor doubler would work fine.

Thank you!

The other voltages will be used in debug, I'm sure.

[R.G.]

R.G., got a link to the Fuzz switch candidate you found?

It's Mouser part 612-100-L1111, here:
http://www.mouser.com/ProductDetail/E-Switch/100DP6T1B1M1QEH/?qs=g8hxKYs5b3wZWJef%252bd%252bvLw%3d%3d

The almost matching DPDT, no center position for the others is the Mouser 612-100-F1112. You can get other brands of toggle switches, but the F1112 will match cosmetically, I think. Probably so well I would mix the up when wiring. 

[pinkjimiphoton]

fall board transistor voltages,...

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

[R.G.]

Yeee- haaaa!

(as we say here in Texas...)

Thanks!

On the power supply front, here's the recipe for powering this thing from a 21Vac to 26Vac **AC output** wall wart:
Ingredients:
1 - 21.0 to 26V AC output wall wart. At least 200ma rated
1 - 1N4004 through 1N4007 diode
1 - 220uF 50V minimum, 63V preferred, 100V is fine, to taste; electro cap
1 - AC input jack to match the wart

Prep and install the input jack in the selected box. Connect the 1N400x diode with anode/arrow end to pin 1 of the console board, this being the contact that used to go the the transformer center tap in the original. Connect the cathode/bar of this diode to either contact 2 or 3, or both if you like. Connect the (+) lead of the 220uF cap to this same position, leaving the (-) end free for the moment. Finally, connect one incoming AC lead from the wall wart jack to the contact 1 (where the diode anode is) and the other transformer lead to the free (-) end of the 220uF capacitor.

The added capacitor/diode and transformer connection form a voltage doubler with the pre-existing diodes and C11, and pump C11 up to about 45-70Vdc, depending on the transformer, load, and phase of the moon. This should be sufficient to get 33-35Vdc out on contact 17 of the console board.

Test carefully for done-ness and serve with a hot single coil strat on a plate of 4x12 Marshalls.

[pinkjimiphoton]

yeeee haaaw works!!


we're getting closer...check the other thread too bro...do u need voltages from the caps etc too?

[digi2t]

Test carefully for done-ness and serve with a hot single coil strat on a plate of 4x12 Marshalls.

And don't be shy with the fuzzy entree!!

Actually, I guess if you measured the DC across R22, it would tell us the actual DC current used by the whole thing. That's really maximal icing on the cake if you can do that.

If you need it, it can be done. Let me know.

[R.G.]

If you need it, it can be done. Let me know.

Yes, please.

[digi2t]

After 1 minute to stabilise, 46.0 vdc before R22, and exactly 34.0 vdc on the other side of R22.

Umm, you did want volts, and not amps? Just thought I'd check, since the measuring setup is different.

[R.G.]

After 1 minute to stabilise, 46.0 vdc before R22, and exactly 34.0 vdc on the other side of R22.

Umm, you did want volts, and not amps? Just thought I'd check, since the measuring setup is different.

Yep, I wanted volts. Well, I wanted amps, but I framed it as the voltage across the 100 ohm resistor, which tells me a few other things at the same time.

Your circuit is pulling (46V - 34V)/100 ohms = 120ma, within the tolerance of the readings and resistor. That's more than I had thought it would, and it means I need to look at the power supply again.

[R.G.]

Given the new bit about the current being 120ma more or less, there are some caveats on the power supply.

I'm thinking that the voltage regulator, Q6, may be a darlington, or else it may be quite hot in normal operation. There's not much base drive through that 3.3K resistor for it, and that would make it get relatively hot. The simulated power is about 1/2W steady state, which is conceivable for a TO-92, but HOT. A TI darlington in a TO-92 in that position would be much more reliable.

I guess it could be running saturated, in which case it's not doing any good for regulating and filtering. I guess that would account for the hum issues reported. Just guessing.

[digi2t]

Well, Q6 is listed as a 43121, which led me to this in my research;

http://www.datasheetcatalog.org/datasheets2/40/407167_1.pdf

Looking at the numbers, wadda ya tink? Maybe bolt a heatsink to it as insurance?

[R.G.]

Well, Q6 is listed as a 43121, which led me to this in my research;

http://www.datasheetcatalog.org/datasheets2/40/407167_1.pdf

Looking at the numbers, wadda ya tink? Maybe bolt a heatsink to it as insurance?

That might work, although the gain is really low. And I didn't find any easily available.

I personally would use the TIP112G darlington. $0.77 at Mouser, in stock. This should not need a heat sink, as it can get rid of 2W without a sink.

I'm being belt-and-suspenders on this one. None of the pictures posted show Q6, but the board drawings show it as a TO-92. A TO-92 ...might... live there, but it's a crap shoot as to whether it will last. That one thing may account for Jimi's hum problems, because a shorted Q6 would still let the thing work, but let lots of hum through.

[pinkjimiphoton]

hmmmmmmmmmmmmmmmmm.....i really haven't messed with the top board....if that's the power supply filter for the whole unit, i guess that could explain stuff.
there IS  a hell of a ripple. would that explain why touching the case of the fall board c1 buzzes so crazy? is the darlington you talk about something i SHOULD replace? should i order one now, or wait till you guys figure that out? i am but an egg. 

[R.G.]

hmmmmmmmmmmmmmmmmm.....i really haven't messed with the top board....if that's the power supply filter for the whole unit, i guess that could explain stuff.
there IS  a hell of a ripple. would that explain why touching the case of the fall board c1 buzzes so crazy? is the darlington you talk about something i SHOULD replace? should i order one now, or wait till you guys figure that out? i am but an egg. 

C11 and C8 on the top board is indeed the power supply for the whole unit. The way this works is that the transformer AC is rectified to DC by the diodes on positions 2 and 3, and filtered by C11. That ripple-y DC is smoothed by Q6, the zener diode, and C8. Removing the ripple requires that Q6 be alive and active. If it gets shorted or overloaded, the ripple from C11 comes right through. Q6 will get hot in normal operation, by the info I have now. So it's conceivable that it would fail and let the ripple through.

It's a theory.

You replaced C11 and C8, as I remember. That would help, but Q6 needs to be there.

You probably ought to wait until we have more info if you can stand it. It is possible to measure the pertinent things by measuring Q6's pads from the copper side of the top PCB, but I don't know how hard it is to get at the back of the top PCB.

The "touch C1 and it buzzes" thing makes me think there's a ground wire off somewhere. Again, if I were you, I'd leave it until we have more info.

[pinkjimiphoton]

k. it would be nice to be able to drive this into some distorted tubes rather than have to run it into a clean amp and add distortion before it.

i did replace all the caps...it was difficult. the fall board was easy to just disconnect, but the control board is a b*tch to get at...i worked AROUND the wires and components rather than discombobulating everything when i did the cap job. the hum came back of course, but not as bad as before. i am suspecting that you're right, of course, and that from your explanations that it is indeed q6 that is shorted. later on, would it be helpful if i bit the bullet and took some voltage readings from it?

i'm thinking maybe it would be better on the work/soundalike (face it, a strict clone of this thing will be cosemetically impossible anyways) to add a couple more stages of filtering,
a true bypass rather than the buffered one it appears to have now, and maybe make a couple of the trimmers that control the formants and pedal range made external for tweaking goodness...also, going with standard rotary pots will make it easier to build, take up less turf, and in general be less crap to break or try to source.

just thinking on my feet, waiting for the drip drip drip of the coffee maker to finish so i can boot up some beans to pin the eyelids open...

[pinkjimiphoton]

this is the darlington rg is talking about here:
http://www.mouser.com/ProductDetail/ON-Semiconductor/TIP112G/?qs=xZq1yRCsb1ed56l%2fx2MUpw%3d%3d#AB

it's got me thinking....i was working on my bassist's music man rd100 amp head recently, should have been an easy fix...all i had to do was loosen up the main pcb to tighten down the jack for the reverb footswitch...pia on that amp, requires way more dissassembly than it should...

but when we put it together, it suddenly had a HUGE hum, tho it would work, and one tube's bias went nuts...within a couple seconds, one tube's plates would start to glow crazy red. 

i've been messing with tube amps for years, never met one i couldn't figure out....but this one had me stumped. all the voltages on the tube seemed insanely off, and the supplys seemed ok...it was just with one tube socket, switching tubes resulted in the same...but there WAS some kind of solid state regulator (i assumed) that looked similar to this darlington on the tube, and one was mounted directly to the chassism the bad socket was missing one of the insulators....i tried to use another, but no dice, the other somewhat isolated with nylon washers... 

not to hijack this thread anymore than i have, but now i suspect i know what the problem in the amp is...i bet it's a shorted regulator in the bias supply on that socket.

   

thanks r.g.....i learn more stuff from every single post you make than anyone else i've ever talked to. 

ya'll say yeeeeeeeeeee haw in texas....here in ct we say "righteous". 

thanks bud!