Sourcing pots for Rothstein PTB Tone Stack and Dual Vol Mods

[Peckhammer]

I am building three Jazzmaster type guitars and became interested in the mods in the diagram of this article: https://reverb-res.cloudinary.com/image" onclick="window.open(this.href);return false; ... PDT_in13ck

Full article is here: https://reverb.com/news/upgrading-jazzm" onclick="window.open(this.href);return false; ... iring-mods

The mods, as described in the diagram, call for a 1 MEG mini audio taper pot, and a 1 MEG mini reverse taper audio pot. I cannot seem to locate those items and was hoping someone could point me to a source.

Also, it does not say in the drawing, but are the dual volume (full-size) pots audio or linear taper. Any help would be greatly appreciated.

[Peckhammer]

Is the silence confirmation that there are no 1-MEG mini audio taper and mini reverse audio taper pots that will work with roller knobs in a Jazzmaster, or that the Reverb/Rothstein Mod article is incorrect, or both?

Did some research and I still cannot answer the questions about whether there are 1-MEG mini audio taper and reverse audio taper pots that will work in the Jazzmaster rhythm circuit, and I may have confirmed that the wiring diagram in the article is incorrect. The mod does use two 1M audio taper (lower circuit volumes), but it's a 1M linear taper roller pot (treble cut) and 1M Reverse Audio Taper (bass cut) in the usual upper bout location. The diagram is mislabeled, but the parts list on Rothsteins web site confirms the pot values and type.

Armed with that info, one question remains: Where to get a 1 MEG mini reverse audio taper roller pot.

[qryss]

I found the pots at mammothelectronics.com, part numbers are RV16AF-10-15R1-C1M for the reverse log one and RV16AF-10-15R1-A1M for the normal log one.

The problem is that you will need to drill out the centres of the JM roller knobs to fit the shafts. In his parts list, Andy refers to 'Roller knobs, drilled to fit the Alpha Pots'.

I got all the parts for the same mod but I haven't yet had time to figure out how to drill the holes bigger. Got any suggestions?

I think it will entail filling the existing hole with something like Milliput so I can centre the drill for the bigger diameter. And working out how to hold the knob still while I drill it.

Hope this helps!

BTW I hadn't spotted the error in the diagram. I'll check that out...

[qryss]

Well, having searched round it seems that the way to make the holes bigger is with a reamer. Check this out, e.g.:

https://www.youtube.com/watch?v=0nZvhsggJBA" onclick="window.open(this.href);return false;

Sounds a lot safer than using a drill to do it anyway. There's still the problem of holding the knobs still without damaging them...

So I'm off to eBay to look for the right size reamer! I'll let you know when I find something.

[qryss]

I'll probably get one of these:

http://www.ebay.com.au/itm/like/4010331 ... 107&chn=ps" onclick="window.open(this.href);return false; (Hand Reamer HSS Spiral Fluted Imperial 1/4-in)

It's $23 with free postage in Australia (where I am) - I've seen others go up into the hundreds.

I'm new to the world of reamers so if anyone has any better advice on how to make the knob holes bigger I'm all ears!

[andy_tchp]

That seems like it'll be a shit of a job.

I wonder if the Fender Japan roller knobs will fit those pots. They have a larger hole than the Fender US rollers.

Hmm, I might have a pair of them floating around my parts bin/s I could send to you (I'm also in Aus). I'll check and let you know.

[qryss]

I did Google around in an attempt to find 1/4" roller knobs but I don't think they exist. There are 6mm ones and there are (apparently) 6.12mm ones (from Fender Japan, I think - check out the listing here: http://www.angela.com/fenderjapanjazzma ... oftwo.aspx" onclick="window.open(this.href);return false;).

I located some that claimed to be 1/4" but on enquiry they were 6mm after all.

The maddening thing is that Fender can obviously get the pots with 6mm shafts but they don't appear to be on general sale anywhere in the required values.

So if you do happen to have some with a 1/4" hole and are willing to part with them (I'd happily pay you for your trouble!) that would be awesome but I fear they are the proverbial hens' teeth.

I reckon if I can figure out how to hold the knob still then I can do it. I'm thinking along the lines of a wooden 'jacket' in two halves to clamp around the knob, using the grub screw hole as a way to hold it still by screwing in a long bolt. The wood will help protect the knurled edge of the knob and the bolt stops it spinning when I ream the hole.

I'm not sure whether this is better as a drill press thing on slow or as a hand operation. Not enough experience to tell!

:/

[andy_tchp]

Hi,

After going through everything, I remembered... I no longer have them, as I rewired the rhythm circuit back to stock configuration on my CIJ Jazzmaster when I put it up for sale a year or so back.

It sounds like they would not have been suitable anyway, although would require less reaming than US knobs which are smaller to fit the CTS 4mm shaft diameter.

The original pots in that (Japan) Jazzmaster were not from Alpha. They didn't have any brand on them at all in fact.

[qryss]

I'm modding a JMJM which has 6mm holes in its knobs so it's not too bad to get to 6.35mm I hope. Starting from 4mm would be much harder...

Thanks for looking! Much appreciated!

[Peckhammer]

Well, having searched round it seems that the way to make the holes bigger is with a reamer.

That is mostly likely correct. I use a reamer all the time for enlarging peg head tuner holes. Yeah, wood, but the idea is the same. A step drill might also work.

The challenge is to hold the roller knobs while using the tool. Since there are ribs on them, you might be able to drill a flat bottomed hole into a piece of wood using a forstner bit, and then pressing the roller knobs into the hole. Obviously the tolerance needs to be tight. This is similar to how tuner bushings are pressed in, and I doubt you could get them to spin.
A small hole drilled though a point or two in the diameter of the larger hole would help you tap the knob back out later. The reason to use a flat botton hole would be to ensure a good perpendicular angle if you are using a step bit or reamer in a drill press.

[brucer]

I bought 2 sets of roller knobs from Rothstein for my 2 modded JMs, but even those knobs weren't drilled out perfectly. There's a bit of wobble when you roll them. Not so you'd notice visually, but enough that they rubbed on the pickguard until I got them positioned just right. Next time I think I'll enlarge the holes myself, likely with a vise on my drill press and the knob wrapped in rubber (old dish glove?) to protect the knurls.

[guitar-mod]

Howdy. Someone brought this thread to my attention so I thought I would respond.

Although we sell the comlete DIY kits as a convenience, you can get all the parts needed anywhere. For the roller pots, the easiest thing to do is use Alpha brand 16mm solid shaft pots, which are commonly used on countless stomp boxes. Alpha pots are also widely available from various electronics suppliers including Mouser. I suggest using audio taper for the treble cut (although you may use linear taper), but you really must use reverse audio taper for the bass cut.

One thing about the Alpha pots though is that you will most definitely need to uyse a drill press to drill out the roller knobs to fit the Alpha pots though.....and yes you do have to be careful when drilling the knobs, otherwise they will wobble. We pre-drill the roller knobs using a drill press for all of our DIY and prewired kits. Brucer - sorry you got a wobbly knob from one of our kits. I would be happy to send you out a new set of roller knobs.....just shoot me an email to andy@guitar-mod.com

Peckhammer - the diagram is correct as we have wired up hundreds of these in prewired kits for many a happy customer. I have posted the diagram below for your reference.

Here is our info page on this wiring mod with a few variations: http://guitar-mod.com/rg_jazzmaster_stb.html" onclick="window.open(this.href);return false;

[Peckhammer]

The drawing is incorrect, or the parts list on your web site is incorrect. Your DIY kit on the website lists the following pots: "4 POTS - (2) 1M audio taper CTS pots (lower circuit volumes), (1) 1M linear taper Alpha roller pot (treble cut), (1) 1M Reverse Audio Taper Alpha roller pot (bass cut)."

Your drawing lists audio taper pots for the roller pots. You need to update the drawing or the parts list.

[guitar-mod]

The drawing is incorrect, or the parts list on your web site is incorrect. Your DIY kit on the website lists the following pots: "4 POTS - (2) 1M audio taper CTS pots (lower circuit volumes), (1) 1M linear taper Alpha roller pot (treble cut), (1) 1M Reverse Audio Taper Alpha roller pot (bass cut)."

Your drawing lists audio taper pots for the roller pots. You need to update the drawing or the parts list.

Hi, thank you for your response, and for catching the error in the DIY kit text. The diagram is correct, but the text in the DIY kit was indeed mistaken. I have corrected it.

Andy

[qryss]

Firstly: Andy, thanks for interjecting here with some additional help - and thanks in the first place for the circuit! Very much appreciated.

Secondly: I have now bought a 1/4" reamer and succesfully enlarged the holes. It was much easier than I thought. I had expected it to go like a drill where it's so easy for the drill to grab the piece and set it spinning like a mad thing. So I was expecting it to be really hard to hold the knobs tightly enough without damaging them.

As you can see in the photo, I used some foam padding to protect the knobs and just held them tight with the vice. I put a piece of scrap wood underneath to raise the knob up and to give it some support as the reamer pushed down on the knob. You have to drill a hole in the wood to allow the reamer to go right through - I nearly forgot that.



Then the trickiest part is lining up the knob but that's not so hard in fact. I just moved the vice carefully until the reamer could just enter the hole without touching the sides. I think the reamer must be slightly tapered at the end because it will fit into the hole a little bit.

I set the drill press to its slowest speed (220rpm on my drill) and slowly brought the reamer down.



Seconds later and it was all done. There was no grabbing of the knob like a drill would do - the cutting edges of the reamer are near vertical compared with a drill bit so the forces are all different.

And the hole is so precise - the shaft of the pot just fits perfectly. I am now a reamer convert.

BTW I bought a $23 (AUD) HSS reamer suitable for hand use (it has a square section on the shank but fits in a drill press, too) off eBay (as mentioned in my earlier post).

And just to clarify: the holes in my roller knobs (from a Squier JMJM) were 6mm but needed to be 1/4" to fit standard pot shafts.