Princeton 112 Plus Repair: Volume Control Mod and More (Long Version)
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- เผยแพร่เมื่อ 16 ก.พ. 2018
- Annoying turn-on "POP" gone! Nearly full volume at "1" gone! I walk you through the implementation of Steve Ahola's Master Volume mod (music-electronics-forum.com/t3...) applied to my personal amp. Also: three other mods to make this a great amp.
Don't do this unless you've been trained to work around lethal voltages! - เพลง
I'm a fan of these 90's era amps. Regarding the common "power popping" issue, a series resistor / capacitor (RC Snubber) across the primary side of the power transformer is a simple fix and works great.
Hi gusto the Power popping is the issue I have with this amp, can you help on how to do this and where can i get the resistor/capacitor (RC Snubber)? help with direction or any video that is out there? thank you
I played one tonight on the clean channel with a green OD pedal, fantastic vintage tone! I made a simple volume box with a 500k logarithmic pot (audio) and 2 mono jacks and plugged it into the preamp out /power amp in (effects loop) to act as a master volume controller. I was able to get a smooth volume sweep on the preamp volume with the master volume box in the effects loop (preamp out / power amp in). It will work in any loud amp without a master volume.
AWESOME MODS! I just picked up one of these & can't wait to try them. Really really great work, love the recycled shielded cable trick..Brilliant! Thanks so much
Thanks for your kind words. I hope the video helps you with the project. Be careful: unplug the amp before you poke around and watch for stored voltage on the electrolytic caps! Okay, enough lectures! Enjoy!
I have one exactly as yours. 112 Plus. It died a few years ago, and at that time I sent to a renowned amp-tech in my region and he ressurected it. However he couldn't handle the known issues of this amp. The "pop" when you turn it off and specially the volume control are the only things that drives me crazy and makes me think about purchasing another amp. On the other hand I still can't find anything on its price range near to the quality of its tone. The amp-tech didn't know how to fix the "pop" nor how to make the volume more linear. I live in a loft and need to play at bedroom volume. Therefore I rarely use the 112+ at home as I can't set a volume good to my ears that wouldn't bother my neighbours. Your video worths gold and I can't thank you more. I'll take it to the amp-tech or maybe another one in order to try to implement at least the volume mod and the "pop" fix. On the other hand, why don't you think of travelling to Brazil for tourism... and then you could take a look at my amp :) Jokes apart, congratulations!! Thumbs up for you man! GREAT initiative sharing these info!
+JoaoGomesYYZ I hear Brazil is very nice this time of year! Thank you for the kind words and I wish you success getting the mods done. Good for your renowned amp-tech, even though he didn't implement the "fixes." Troubleshooting is a dying art as we tend to throw away items that could be restored-- come to think of it, good for you! Without folks paying to refurb their equipment, there would be no market for repairs! Rock On!
If you are unable or don't want to mod your Amp just plug a cable into the headphone out, it disconnects the speaker and stops the pop
I have this exact amp and it's my favourite, I use it over my blues junior. I have the popping noise too! I just have both clean and gain volumes at 0 when I turn it on and off. Then no pop!
I have a 1/4" to 1/8" headphone adapter that I leave in the headphone jack. Pushing it in silences the speaker, so there's no pop when turning it on and off, and I just pull it out when ready to play.
The volume going from 0% to 90% by the time you hit 1 on the dial is really annoying, though.
I have this amp and it’s great but it has the popping issue at well only when shutting it off. Thanks for the video
You can replace the stock 50K Fender snap-in anti-log taper volume potentiometers with audio taper pots - they are available here:
darrenriley.com/store/fender-control-50k-15a-snapin-0037323000/
or here:
www.amprepairparts.com/fenderpots.htm#snapin (scroll down to part # FPBJ-50KA)
The above 50K audio taper snap-ins are used in this amp for the treble & bass on the clean channel. Perfect fit, and no more going to 11 on 1 and a half.
This is the Full Length Version for those who wish to learn: all the mod details, desoldering, soldering, making twisted pairs, modifying panels to add controls, and a little bit of theory. I'm doing a condensed version that should drop soon.
Note that the reverb tank I ordered was the Accutronix 8EB2C1B from Antique Electronic Supply (tubesandmore.com).
And watch for the inter-comparison video, also coming soon, that compares this Fender Princeton 112+, a Marshall MG100 HDFX Half-Stack, and a "wimpy" Kalamazoo 5 Watt (?) tube amp!
I have one just like this one and I like it a lot. I avoid the "POP" problem when the amp is turned off by lowering the volume and unplugging the cable before turning off
@SetupMyGuiter (OP) thanks so much for this video. I have the same amp that has an issue with a different jack (the input jack, of all jacks….. of course…)
I was hoping you could clarify/answer one question that you briefly touched on in your video. The heat sink bars inside the chassis. As you saw, they have holes drilled through them that line up. Mine doesn’t seem to have any “sticky” stuff, but what I’m wondering is what, if anything, you Andes up doing in regard to the heat sinks that lay on top of each other inside the chassis? Is there some kind of thermal paste I should apply? Bolts to have go through both blocks that line up? Just leave it as is and reassemble with the two parts of the same sized sink lined up? I’m just about finished fixing this, I just wasn’t sure what to do (if anything) when it came to that heat sink that just sort of slides around when you take out the PCB. Thank you so much for your time, help & dedication. I wish you and yours the happiest of holidays!
Do you have any insight on where to get parts for this amp specifically the master volume , Bass ( on the overdrive channel), reverb pots knobs and collars ? Also need an input jack
hey man, insted of placing a pot in the back of the amp you can put a external volume pot in the input jack wick a cable and placed in a stomp box, so you can regulate the input volume
I have the same problem 3 broken jacks .... Where did you buy the connector parts ... My English is not very good. Sorry greetings mty mexico
I too have this same amp. I've noticed that if I unplug the guitar then turn it off it doesn't pop. But still, it needs to be fixed. I was hopeful that changing out the electrolytic capacitors would quiet down the amp and get rid of the annoying buzz but I see that it didn't. You still have the buzz. I have it too and wish I could make it quiet. The buzz is my biggest complaint, the pop is second. I've not noticed an issue with the volume control. Some of these amps were made in USA and some made in Mexico. Mine is from south of the boarder.
Greetings from Mexico! I recently bought a Princeton 112 plus, found it in a pawn shop, and I just loved it sound!
It also has some issues that needs to be fixed (that's why I'm here). Thanks to this video now I know that I may not be able to fix the amp by myself
But thanks a lot, glevideo, I've just done what you said about unplug the guitar first and it worked! Now I have a little solution to the pop, while I save some money for the repair
Greetings again! Apologies if my English isn't perfect haha
I have a 112 Plus that's not passing signal due to a broken headphone jack it seems. It looks like the main signal passes through the headphone jack even if the headphones are not in use so Im hoping a new jack fixes the problem. Can anyone confirm if I'm correct that the signal does indeed pass through the headphone jack?
i'd reccomend 3 conductor mic cable to the mv pot... ground the shield at a groundpoint on the pcb only, not the pot. and the 470k resistor should be removed and replaced with something far smaller, maybe 10-47k instead. changing the 470k resistor is a great idea, but by putting it in series with the pot, you're actually increasing the gain of the feedback loop in the amp... you can turn it down more, but its gonna make the chip's gain quite a bit higher in that stage. and if someone uses the wrong side of the resistor, it could make it a bit weird for them to figure out. a small resistance will make it so that your mv will work great, but can ensure there's no short to the feedback loop.
Which capacitors, or other components can l tamper with to "sweeten" the tone? The brights aren't as blooming, or musical as I would like. I know from experience, that larger, and more primative components have always' made sweeter tones in fender amps. What are my target caps, or resistors on this particular circuit? I know the "tracking", or multiple notes, and brights can be far more mature sounding.
Depends on what you mean by "sweeten." In your elaboration, it sounds like you want brighter high ends. But many people want that "buttery" tone associated with the Les Paul neck pickup and some recording by Les himself. If you want brighter tone, meaning more treble, you could shift an RC circuit or two to roll over at a higher frequency, meaning a lower value capacitor.
Although replacing the electrolytics in the power supply wouldn't be a bad idea, for your purposes I'd start with the main and drive tone circuits: R8/C3 & R32/C21 & C22. You can check sensitivity to each cap by solder tacking a similar value in parallel, which will increase capacitance, and if that produces a big effect, remove the original and replace it with a lower value. You should use similar voltage ratings and type, although some folks decades ago insisted on "orange drops." Polystyrene replacements might deliver the brighter tone you're looking for.
Ideally, you could play around with a bunch of dielectric material (the stuff between plates of a cap) to see which has the characteristics you're looking for. By that I mean buy a few different types, swap them in one-at-a-time and decide which you like best (if there's any noticeable difference at all). Also: you may actually get the tone you're looking for by changing the caps associated with the bass tone controls (C4 & C23).
Let us know what works! (And be careful in there! Use safe practices when you're working on anything that plugs into line current!)
Thankyou Greg.
If polystyrene are those old medium dark blue ones with the white lettering I used to see in old amps; those, and the paper caps used to sound good. I reckon the size of those components also create a moody playspace for electricity as well.
Thankyou for pointing out which specific circuit card correspondence to locate the "possible" targets to beautify the tone.
The treble seems a bit crisp; although I do like that there is plenty to spare. I suppose I was thinking more harmonic reactiveness: perhaps a little electrical "sag", and "bloom".
Now for a financial question. This amp on Reverb and eBay goes for 200.00......I found one with similar issues on the popping and reverb plus a very loud buzzing but I noly paid 100.00 for it. If you did these fixes and took care of the buzzing what would you have charged for the job? Would my 100-200.00 amp now cost me 350 or 400.00? Jusr wondering if it's worth the repair.
May I ask why you don't use a solder sucker? It's agonizing watching you use that solder wick!
My theory is one can remove more with wick. (It was good enough for NASA spec!)
Cant find a schematic for this amp haha
Were you able to repair the reverb?
+Bouldering Yes! I know this is a LONG video, but at around the 58 minute mark I demo the unit with reverb. The tank description is in one of my comments: it's an Accutronix 8EB2C1B from Antique Electronic Supply (tubesandmore.com). All that was wrong with mine was that I had put in a tank better suited for an old tube Princeton Silverface because that customer preferred the sound with my stock unit-- so I gave it to him!
@@setupmyguitar7973 Great Thank You. I am pretty sure I need a new tank. I cleaned the RCA connections but still some noise and it will cut out time to time when on. I will look for that tank. Also got a dodgy fall input jack. So, Thank you for the video! It gave inspiration and instruction how to keep enjoying the amp; Despite it's common issues.
@@PhoShoTheatre Hope that takes care of it! There is a chance that something else is wrong, but unless you have mad troubleshooting skills, this is a good way to proceed and there's a high probability of success! :-)
Ive this amp, the clean is awesome and takes pedals extremely well but the drive channel is awful lets be honest! I've bought a second one that i found cheap on ebay and plan to convert to a head!
My question for you is could the amp switch be replaced with a silver toggle switch?? If so how?
Also i want to change the ugly control knobs for vintage looking chicken head controls
Great Video btw
+Phil_Insane Welcome! It should be straightforward to use a toggle switch in place of a switch integrated into the back of the "Master Volume" control. You could just mount it next to it. Not sure if you can find chicken head control knobs to fit the PCB-mounted "snap-in" controls Let us know if you succeed! There are several forum threads on the subject to help you on your way.
after long time not playing mu drive channel dont work, no sound
A follow-up. 100 Ohm 2 Watt Resistor, 1 Micofarad 630 Volt Polyester film Capacitor.
+John Albanese I always wondered if there was a simple, safe approach to doing something like this. The "obvious" (to me) approach was to put a capacitor to ground on the switched hot side or simply across the switch. But there were horror stories from the late 1900s of caps failing and bad things happening! I chose the switch on the back of the pot approach because the "too much gain" issue is well dealt with by employing a Master Volume control, so the switch is a simple add.
Seems you know what you're doing with this stuff. I've read a little bit about snubbers, but it might help people to see a sketch of your suggestion. Too bad TH-cam doesn't seem to support uploaded pictures in the Comments-- maybe you could post something on my FaceBook Page? I'd be game for giving it a try. SetUpMyGuitar at FaceBook: facebook.com/CraigsCustoms/
Thanks for taking the time to share this!
RE: Master volume..... See Easiest "modification" for Fender Hot Rod amps....." from Wampler Pedals. Or a volume pedal between the Preamp Out and Power Amp In works great. don't even have to open the amp. I'll see what I can do about posting the snubber mod.
Cool. The Princeton 112 Plus does come from the factory with "Preamp Out/Power Amp In" jacks, so you could certainly package a volume control and put it between the two jacks. I'm looking forward to checking out the snubber circuit.
man i got the same amp and its not easy to find the fucking 50k 15A volume pot here in this side of the world, only the ceap 47k are awaylable but the resistane it to low, nothing for 15A :)
I just replaced the normal channel volume pot in a 112 plus . old / new were 43.7k / 46.6k . Within the normal + -- 10%. . The 15A does not mean amps .
dale 🥰
Try searching "replacement jacks for fender 112+ amp" and see if a distributor near you pops up. I use Amazon a lot...don't know if that's available to you. These guys are great: www.tubesandmore.com/search/node/fender%20pcb%20jack
Best wishes on getting it straightened out!
Search Solid State Guitar Amp Power-off Snubber video
Friggn wild theyre considered antique now.. fuck getting old..
Did you the time between 1980 and 2021 is the same as 1980 to 1939. Yep, let you have a moment for that…