P-38, Lace Sensors, Piezo, Schaller Switch.

[monchavo]

Good Afternoon from London. Exquisite set of diagrams and information - highly useful!

Enclosed are some images of the underside of a partially finished, aborted, forgotten and restarted project that a friend has contacted me about.
The essential concept is this: the chap wanted to adapt/ modify his Parker - he thinks it might be a P38? - by inserting an HSS set of Lace Sensors in it, a good quality switch (he chose an Oak Grigsby). Once he had started to put the bits together he discovered that the switch was too deep and there was insufficient clearance.

He then sought a switch which would be acceptable- he located something called a Schaller Mega Switch S.

His challenge (and I've agreed to help him with this) is concocting a wiring diagram which will enable the use of the Piezo system alongside these pickups and the Schaller Mega Switch S, then actually wire the thing up!

Information on the Schaller switch is here: https://schaller.info/en/megaswitch-s
Sample wiring diagrams of HSS units for Lace sensors: https://cdn.shopify.com/s/files/1/0026/ ... il.pdf?235

I am competent at following wiring diagrams and can solder adequately, but have no experience of designing them, or how to incorporate the piezo system.

Are there folks here who could help adapt the diagram to show me what to solder where?

Thanks!

[mmmguitar]

Are you wanting someone to take the color codes from the Lace page and draw them over one of the HSS diagrams from the Schaller page, then draw another diagram including the Fishman preamp? Because you really do have all the info you need between the two links you posted and the Parker diagrams from this site.

The signal path is

The pickups’ leads get soldered to the 8 or so numbered contacts on the pickup selector switch, according to whichever HSS diagram you choose > selector switch out to volume pot in parallel with tone pot > volume pot out into 3 way switch for preamp input, then jumpered from switch contact to input of preamp board (depending on year of production, the piezo volume pot is likely already soldered to preamp board; so you won’t need to deal with it) > pair of output wires from preamp to TRS jack that has battery and main ground soldered to the appropriate lugs.

Attached is the factory P38 diagram that’s been posted here and in the Facebook groups.

[monchavo]

Are you wanting someone to take the color codes from the Lace page and draw them over one of the HSS diagrams from the Schaller page, then draw another diagram including the Fishman preamp? Because you really do have all the info you need between the two links you posted and the Parker diagrams from this site.

The signal path is

The pickups’ leads get soldered to the 8 or so numbered contacts on the pickup selector switch, according to whichever HSS diagram you choose > selector switch out to volume pot in parallel with tone pot > volume pot out into 3 way switch for preamp input, then jumpered from switch contact to input of preamp board (depending on year of production, the piezo volume pot is likely already soldered to preamp board; so you won’t need to deal with it) > pair of output wires from preamp to TRS jack that has battery and main ground soldered to the appropriate lugs.

Attached is the factory P38 diagram that’s been posted here and in the Facebook groups.

E49297E1-CBE2-477F-96E6-CED493AAFCEC.png

Firstly - thank you so much for your reply and the contribution - I am very grateful.

On the subject of the diagram - In my dreams - that would be the ideal thing - but I appreciate time is money and some may not find that a useful way to spend their time. I am worried that I will draw up a diagram, attempt to follow it and screw up through an error in the wiring design, rather than the execution. I have thirty years of soldering experience and have put together several dozen pickguards of various types, unfortunately my wiring design skills are amateur. Covid means I can't spend very much time with the person who owns the unit so getting it right, first time, is really important to me rather than going through a process of trial and error.

The additional complexity is that I don't really understand the operation of the Schaller S Switch and how those variables add additional complexity to the situation.

Lastly I have a setup of an unknown quality - the previous guy working on this had no idea what he was doing so I may have a volume of reverse engineering (get it back to parts!)

here's some photos which illuminate my point somewhat

[monchavo]

Photographs:

Closeup is probably the most useful image.

[monchavo]

This is the current status. (The Oak Grigsby will of course be removed)

[monchavo]

Lastly, I would point out that it's not beyond the pale to suggest to the owner that ignoring the Schaller switch and getting an alpha to reduce the complexity may be worthwhile.

I have a handy diagram which compares the wiring across switch types:

[mmmguitar]

It *seems* that unsoldering and resoldering the pickups’ leads from the old switch to the new one will be the bulk of the work, with tracing the wires along the (relatively linear) signal path for troubleshooting being the rest of the job. I recognize the frustrating circumstances, but the elements of the unknown to do with Lace’s hit-or-miss QC (I’ve experienced dead or shorted pickups from them), the previous soldering job potentially creating shorts or cold joints, and the potential for component failure on the Fishman Powerchip board sadly mean that getting everything sorted in one pass isn’t as likely as setting aside an afternoon to search for gremlins.

I’m experienced with the Schaller switches and, though it’s you stuck doing the work, I can vouch that they really are as simple as soldering the pickup leads to the numbered contacts according to one of the three HSS diagrams linked in the OP. As I recall, it’s only their rotary switches that are a pain to decipher.

[monchavo]

I have relatively few qualms about qc on Lace sensors. Far more worrying is the actual wiring - which wires go where - I am somewhat baffled as to how to merge the three wiring diagrams to make one which will result in acceptable functioning system.

[monchavo]

Are you wanting someone to take the color codes from the Lace page and draw them over one of the HSS diagrams from the Schaller page, then draw another diagram including the Fishman preamp? Because you really do have all the info you need between the two links you posted and the Parker diagrams from this site.

The signal path is

The pickups’ leads get soldered to the 8 or so numbered contacts on the pickup selector switch, according to whichever HSS diagram you choose > selector switch out to volume pot in parallel with tone pot > volume pot out into 3 way switch for preamp input, then jumpered from switch contact to input of preamp board (depending on year of production, the piezo volume pot is likely already soldered to preamp board; so you won’t need to deal with it) > pair of output wires from preamp to TRS jack that has battery and main ground soldered to the appropriate lugs.

Attached is the factory P38 diagram that’s been posted here and in the Facebook groups.

E49297E1-CBE2-477F-96E6-CED493AAFCEC.png

She ain't pretty but I think this is correct. [edit --- updated to change tone circuit slightly]

[mmmguitar]

Two things, @monchavo:

1. The tone pot is wired for a left-handed sweep (which may be what you were referring to in the edit), and
2. The bridge Alumitone in the guitar is different from the Dually referenced in the diagram: The humbucker-sized Alumitone codes are orange =hot, green and white =ground, and black/white stripe = coil tap (An actual tap; and not a split). If the owner ends up wanting the B+M selector position to have the bridge pickup “split”, solder the black/white stripe wire to contact 7, and 5 (the common for 6 and 7 in positions 2 and 4) going to ground.

I have a wired Powerchip I pulled out of a Fly laying around, if you end up needing photos for reference. But it looks like you’re all set.

[monchavo]

Two things, @monchavo:

1. The tone pot is wired for a left-handed sweep (which may be what you were referring to in the edit), and
2. The bridge Alumitone in the guitar is different from the Dually referenced in the diagram: The humbucker-sized Alumitone codes are orange =hot, green and white =ground, and black/white stripe = coil tap (An actual tap; and not a split). If the owner ends up wanting the B+M selector position to have the bridge pickup “split”, solder the black/white stripe wire to contact 7, and 5 (the common for 6 and 7 in positions 2 and 4) going to ground.

I have a wired Powerchip I pulled out of a Fly laying around, if you end up needing photos for reference. But it looks like you’re all set.

Extremely grateful for your assistance. Not sure when I will get to him to actually do the soldering - August maybe - let's see. Cheers.

[monchavo]

Two things, @monchavo:

1. The tone pot is wired for a left-handed sweep (which may be what you were referring to in the edit), and
2. The bridge Alumitone in the guitar is different from the Dually referenced in the diagram: The humbucker-sized Alumitone codes are orange =hot, green and white =ground, and black/white stripe = coil tap (An actual tap; and not a split). If the owner ends up wanting the B+M selector position to have the bridge pickup “split”, solder the black/white stripe wire to contact 7, and 5 (the common for 6 and 7 in positions 2 and 4) going to ground.

I have a wired Powerchip I pulled out of a Fly laying around, if you end up needing photos for reference. But it looks like you’re all set.

Thanks.
RE: 1 - the tone pot - I made a small modification to the wiring diagram - is it now correct in your view? The guitar is right handed.
RE: 2 - the humbucker

The wires do indeed correspond with your very kind observation. However something new and unexpected has come to light.

The setup that resides in the scratchplate is a pre-wrired assembly the owner purchased on a strat scratch plate, disassembled and has dropped into his Fly scratchplate. It was put together by a company called 920D. If you look at the photo it's a volume and TWO tones, with the second tone having a coil tap circuit on it. This means essentially the task is swapping out the OAK Grigsby for the Schaller S switch and connecting the Piezo circuit.

Ill have to modify the diagram to reflect the fact that there's a coil tap, and a second tone.

[mmmguitar]

Ill have to modify the diagram to reflect the fact that there's a coil tap, and a second tone.

Looking forward to it. The tone pot needs to have the two left lugs utilized in order to sweep in a right-handed orientation - Your diagram has the far right lug utilized (rather than the left-most); which will reverse the sweep direction.

Considering you’re sharing one capacitor between two tone pots (unless I’m missing another component in the photo), having each pot’s left lug grounded in the same manner as the volume pot, with the capacitor bridging the center lugs of each tone pot, and the pickup-specific output contacts from the selector switch soldered to the center lug of the preferred pots, should work. It’s just a matter of whether the owner wants one tone pot affecting two pickups, or if one pickup will be without a tone pot.

[jb63]

I just need to say that I love threads like this. That is all.

[vjmanzo]

Same!!

[monchavo]

Ill have to modify the diagram to reflect the fact that there's a coil tap, and a second tone.

Looking forward to it. The tone pot needs to have the two left lugs utilized in order to sweep in a right-handed orientation - Your diagram has the far right lug utilized (rather than the left-most); which will reverse the sweep direction.

Considering you’re sharing one capacitor between two tone pots (unless I’m missing another component in the photo), having each pot’s left lug grounded in the same manner as the volume pot, with the capacitor bridging the center lugs of each tone pot, and the pickup-specific output contacts from the selector switch soldered to the center lug of the preferred pots, should work. It’s just a matter of whether the owner wants one tone pot affecting two pickups, or if one pickup will be without a tone pot.

Good morning and once again thanks for your help.

- Grounded switch body as a lug exists for this
- Changed the tone setup to reflect your suggestions
- Changed the wiring configuration of the humbucker to correctly reflect the wires on the pickup
- Added the coil tap

Your very kind suggestions of a photograph of the small PCB would be very welcome - yes please!

Thanks

[monchavo]

I just need to say that I love threads like this. That is all.

What is it about the thread that interests you?

Cheers

monchavo

[vjmanzo]

What is it about the thread that interests you?

For me, the dissemination of knowledge is where it’s at! This thread and these diagrams will continue to help others for years to come!

[monchavo]

What is it about the thread that interests you?

For me, the dissemination of knowledge is where it’s at! This thread and these diagrams will continue to help others for years to come!

Once I get a working system I will redraw the diagram in a much more professional way for the benefit of those in the future.

[vjmanzo]

Thanks, @monchavo! We’re glad to have you as part of this community!