Princeton 112 plus potentiometers

[SmogFighter]

Hi guys,

I found this Princeton 112+ on craigslist. It was listed as "Works, but
volume is dodgy. Also missing some knobs..."

As I was inspecting it, I noticed 6 knobs missing, and 5 plastic pots with
loose shafts. One shaft broken & loose.

I found the schematic at:
http://www.freeinfosociety.com/elect...nceton_112.pdf

I removed the chassis from the cab and inspected from the back and found
the loose pots to all have broken off the little tip that protrudes through the
PCB type backs.

Now to my actual question... Do I HAVE to use the plastic shaft pots or can
I use a more robust pot?

I found the replacement plastic pots at:
Fender Amp Parts

And it looks like someone has a package of 6 knobs for a reasonable price
through Amazon.com.

Also, what does the 30C mean at the end of "250K 30C"?

Thanks,
Raul

[Enzo]

You don't HAVE to do anything, but really, I'd just use the right control, the original type. Just be nice to your amp, and don't bash it around. The controls will have a nice long life then. You COULD engineer some other odd pots in there, but they need to mount somewhere, and all you have now are clearance holes for the shafts. You'd be drilling out holes on your panel. It is nice to have a row of the same knobs, but if your odd pot has a different shaft, then it takes a different knob too.

250k 30C, the 30C refers to its audio taper.


From the parts list, here are the controls:
(qty, part #, descrip., circuit location)
2 037324 CONTROL 100K 30C SNAP IN R23,32
2 037323 CONTROL 50K 15A SNAP IN R8,9
2 034719 CONTROL 50KB SNAP IN R30,44
2 038658 CONTROL RTRY 50K 30C R16,31
1 040552 CONTROL 250K 30C R37

SO your 250k is part# 040552 for example. If you order the parts from a Fender dealer or parts supplier, use the part numbers.

The web site you found your parts on seems to have the right control, but $6.95 is really steep, it seems to me. That is over twice list price, I believe. Price the stuff at someplace like www.fenderparts.com

Here is your knob:
026403 KNOB POINTER BLACK 180 °

There are two kinds of knobs that look the same. You need the right type or they will point the wrong direction.

And under each knob there should be a small plack plastic spacer - just a short piece of what looks like tubing. This keeps the shaft centered and supported, and helps prevent a hit on the knob from pushing out the back of the control. And here it is, order enough to replace missing ones:
033206 BUSHING KNOB SPACER

[SmogFighter]

Thank you

I was hesitant to leap into the purchase of the pots
from there. Adding up all the broken pieces brought my
"monies invested" close to the "percieved value" of this
unit.

And, thank you very much for the part numbers & link.
I will head over there place my order.

Thanks again,
Raul

[SmogFighter]

recieved e-mail from fenderparts.com....

this is what they sent:

2 037324 CONTROL 100K 30C SNAP IN R23,32 in stock $5.00 each
2 037323 CONTROL 50K 15A SNAP IN R8,9 in stock $5.00 each
2 034719 CONTROL 50KB SNAP IN R30,44 in stock $4.00 each
2 038658 CONTROL RTRY 50K 30C R16,31 in stock $5.00 each
1 040552 CONTROL 250K 30C R37 in stock $4.00 each

6 026403 KNOB POINTER BLACK 180 ° BACKORDERD $3.00 EACH4
7 033206 BUSHING KNOB SPACER IN STOCK $2.65 EACH



THANKS

A little better, but not much. Hmmm....

[SmogFighter]

Enzo...

Pm sent..

[fenderjazz]

I believe the 30C refers to the temperature the resistance is measured at. Resistance changes with temperature.

[SmogFighter]

Wow, has it really been that long?

Thank you Fenderjazz and Enzo for your help and support.

I recieved all the parts (the knobs I recieved were reversed
though ) and replaced the broken pots. It sounds great until
you turn up the reverb.
I think the reverb tank is trashed, but that is a job for
another day.

Thanks again.
Raul

[amapaulo]

You don't HAVE to do anything, but really, I'd just use the right control, the original type. Just be nice to your amp, and don't bash it around. The controls will have a nice long life then. You COULD engineer some other odd pots in there, but they need to mount somewhere, and all you have now are clearance holes for the shafts. You'd be drilling out holes on your panel. It is nice to have a row of the same knobs, but if your odd pot has a different shaft, then it takes a different knob too.

250k 30C, the 30C refers to its audio taper.


From the parts list, here are the controls:
(qty, part #, descrip., circuit location)
2 037324 CONTROL 100K 30C SNAP IN R23,32
2 037323 CONTROL 50K 15A SNAP IN R8,9
2 034719 CONTROL 50KB SNAP IN R30,44
2 038658 CONTROL RTRY 50K 30C R16,31
1 040552 CONTROL 250K 30C R37

SO your 250k is part# 040552 for example. If you order the parts from a Fender dealer or parts supplier, use the part numbers.

The web site you found your parts on seems to have the right control, but $6.95 is really steep, it seems to me. That is over twice list price, I believe. Price the stuff at someplace like Parts Is Parts - Guitar, Amplifier, and Korg Keyboard Parts | AUTHORIZED NATIONAL PARTS DISTRIBUTOR FOR KORG, VOX, BLACKSTAR. PARTS FOR FENDER, GIBSON, GRETSCH, HOFNER, SWR, GUILD...

Here is your knob:
026403 KNOB POINTER BLACK 180 °

There are two kinds of knobs that look the same. You need the right type or they will point the wrong direction.

And under each knob there should be a small plack plastic spacer - just a short piece of what looks like tubing. This keeps the shaft centered and supported, and helps prevent a hit on the knob from pushing out the back of the control. And here it is, order enough to replace missing ones:
033206 BUSHING KNOB SPACER

Hello!

I have a Fender Princeton 112 Plus and I want to change my reverb and my volume pot... how do I know what "K" are they? And if they are audio ou linear tape...

Is there a document where I can see what pots excaclty I need to buy to replace at my amplifier?

[DrGonz78]

Do you mean the volume pot on the clean channel or the dirty channel? Clean channel the volume pot is 30C50k, but a 15A50k pot is a better replacement. The 30C means it is a reverse log type pot and 15A is an audio log taper pot. Look up type A,B,C type pots for full description. The reverb pot is a 50K type B, linear type pots. It is all there in the schematic >>>

http://support.fender.com/schematics..._schematic.pdf

Trying to buy the exact pot is getting hard to find these days and the ones I use to see on Ebay are not even there anymore.

This one is hard to find, but will be better replacement on that amp for the clean volume pot. This is all I can find of these and it is not an active listing.
Brand NEW Genuine Fender 50K 15A PCB AMP Potentiometer POT Princeton 65 Volume | eBay

This is the exact replacement for that clean channel volume pot, but it is quite expensive.
Brand NEW Genuine Fender Potentiometer POT 50K 30C D Shaft 0038658000 | eBay

Here is a replacement for the reverb pot, and a way better price than those other ones. Looks like it should fit and be the same size as the 112+. Not positive that the shaft on this one is a D-Shaft.
Fender Blues JR 50K Linear Reverb Master Potentiometer | eBay

BTW I can not find these pots anywhere except on Ebay lately, but use to see them around online stores too. They are discontinued parts...

[Jazz P Bass]

I believe the 30C refers to the temperature the resistance is measured at. Resistance changes with temperature.

30C is the taper of the potentiometer.

[Jazz P Bass]

I recieved all the parts (the knobs I recieved were reversed
though )

You have to be carefull ordering those knobs.
Some have an offset to the flat (which matches to the correct pot)
There are sold as 90 & 180 degree.
Here are some examples:
Fender Amp Knob BROWN/WHT 180 DEG 0051018000
Fender Amp Knob 180 ROT w/CHR 0055776000

[SmogFighter]

What a blast from the past....

I still own and use my amp on a semi regular basis.
The reverb tank is still trashed.... Lol
I gave up on finding the correct knobs. The ones with the
chrome are too big around and obscure the numbers on
the face. So I decided to just leave them "naked"

Thank you DrGonz78 for trying to help the guy who
hijacked this almost 3 year old thread.... Lol
And thank you Jazz P Bass for (slightly delayed) help,
which reminded me to once again try to search for the
correct knobs. Maybe by now somebody might make a
reproduction of an original?
Thanks again,
Raul

[T9c]

Old thread, I know but I've been unable to find the 180 knobs for this amp. I ordered some 90's and found that if you cut out the flat side protrusions inside the knob, they will press on to the pot. Be careful not to push too hard or you could crack the wafer on the back of the pot, ruining it. If it is hard to push on, cut more of the protrusion off till it fits.

edit: oh yeah, I used an exacto knife to cut the protrusions out.

[paul88]

From the parts list, here are the controls:
(qty, part #, descrip., circuit location)
2 037324 CONTROL 100K 30C SNAP IN R23,32
2 037323 CONTROL 50K 15A SNAP IN R8,9
2 034719 CONTROL 50KB SNAP IN R30,44
2 038658 CONTROL RTRY 50K 30C R16,31
1 040552 CONTROL 250K 30C R37

Reviving an old thread here, hoping for some help. I acquired a Princeton 112 plus the other day and could not believe the volume "control" on this thing. "1" is more like "9" and it's really not something that works when you have neighbors below you

I have some electronics experience and would like to replace the 2 volume linear pots with audio pots. I found info about another amp (can't remember what it was!) where you could use the Tone pot to replace the Volume pot and it worked perfect since both pots were speced for the circuit. My question is: are any of the pots listed above "audio" pots that I could buy, and then drop right in the amp in place of the 2 volume linear pots that are there now? It would be great if that was a possibility!

[52 Bill]

Reviving an old thread here, hoping for some help. I acquired a Princeton 112 plus the other day and could not believe the volume "control" on this thing. "1" is more like "9" and it's really not something that works when you have neighbors below you

I have some electronics experience and would like to replace the 2 volume linear pots with audio pots. I found info about another amp (can't remember what it was!) where you could use the Tone pot to replace the Volume pot and it worked perfect since both pots were speced for the circuit. My question is: are any of the pots listed above "audio" pots that I could buy, and then drop right in the amp in place of the 2 volume linear pots that are there now? It would be great if that was a possibility!

Welcome to the place. The controls that are marked B are linear, A are audio and C are reverse audio. The pot that was recommenced was the 50K 15A (15% Audio taper).