Princeton Reverb Build

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Bruce Weldy
Posts: 8539
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Princeton Reverb Build

#16 Post by Bruce Weldy »

First move was to take care of one of my two mods that I'm doing to the amp. The kit is true to the original '65 Princeton with the attached AC cable, however, I'd prefer the IEC connector. So, it took a little planning and measuring to put it where it's accessible and not in the way of anything else. I used a Dremel tool with a cutoff wheel to make the cuts and then a hacksaw blade in a handle to finish it off.
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Drilled the holes and installed it.

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Time to crack the book of instructions and the wiring layout and get to work. By the way, the little jig to hold the chassis at different angles is amazing! Can't imagine how hard this would be without it.

Installed all of the Jacks, Pots, Indicator light on the front panel along with the transformers and the reverb driver.
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Flipped it around the installed the jacks, switches, fuse holder on the back. My second mod is on this panel - I installed a TRS jack to handle the footswitch for Reverb and Vibrato. The original used two RCA jacks......I didn't like that, thus the mod. And I'll replace the RCAs on the footswitch cable with a single TRS.

The Reverb pedal jack is a dummy RCA that won't be used or hooked up to anything. Same with the Ground switch. They send you the switch to make it look correct, but there are no wires going to it.
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That was all for today.....brain fried. I'll hit it again tomorrow.....time to get out the soldering iron and start stripping wires. Here we go!

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Bruce Weldy
Posts: 8539
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Princeton Reverb Build

#17 Post by Bruce Weldy »

Started the actual wiring.....

Got the transformer and driver section done. Next up is the eyelet board......noticed that my eyelet board, diode board, and the fiberboard backers were missing the mounting holes. Guess I'll have to drill those out before going any further. Don't really want to wait for the proper boards to be sent. I hope this is the only mistake in the kit. So far all of the parts have been there.
IMG_2907.JPG

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

NukePooch
Posts: 371
Joined: Mon Jun 30, 2014 8:07 pm
Location: Berea, Kentucky

Re: Princeton Reverb Build

#18 Post by NukePooch »

Bruce Weldy wrote: Sun Feb 16, 2020 9:00 pm By the way, the little jig to hold the chassis at different angles is amazing! Can't imagine how hard this would be without it.
I don't have to imagine. Picture balancing the chassis on random stacks of blocks which slide and squirm whenever you move anything.... :roll: Man, I wish I'd have known about the jig before I did mine...

That's a sweet kit for sure. I think it's worth the money just to get the plastic trays, LOL.
Built:
4 Jack 112L- 3012HO, melded array
17.5 wide AutoTuba with Infinity 860w
6 Wedgehorn W6 w/ Panel Mount Piezos
2 T48 Slims (15" wide) with 3012LF
4 T48 Fattys (32" wide) with 3015LF

Bruce Weldy
Posts: 8539
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Princeton Reverb Build

#19 Post by Bruce Weldy »

NukePooch wrote: Thu Feb 20, 2020 6:41 pm
Bruce Weldy wrote: Sun Feb 16, 2020 9:00 pm By the way, the little jig to hold the chassis at different angles is amazing! Can't imagine how hard this would be without it.
I don't have to imagine. Picture balancing the chassis on random stacks of blocks which slide and squirm whenever you move anything.... :roll: Man, I wish I'd have known about the jig before I did mine...

That's a sweet kit for sure. I think it's worth the money just to get the plastic trays, LOL.
And even with the trays, I missed the slot and ended up putting two of the resistors in the wrong place. Fortunately, I caught it this morning and fixed it. Only mistake so far....that I've caught.....hope there aren't any more.

I'll post some pics later tonight or tomorrow. The eyelet board is in and I'm in the process of tying all of those wires back to the chassis - tube sockets, jacks, etc. Easy way to get brain-fried quickly.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Bruce Weldy
Posts: 8539
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Princeton Reverb Build

#20 Post by Bruce Weldy »

Ok, time to catch up on the build......

Laid out and populated the diode board and the main board....

From the top...
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From the bottom....
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Once all the parts are in place, it's time to start soldering the components and jumper wires to the board.....yes, this takes a while...
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Now it's time to install the board and wire it up to all of the sockets, jacks, pots, and every other damned thing that seems to be lurking under the hood.....

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6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Bruce Weldy
Posts: 8539
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Princeton Reverb Build

#21 Post by Bruce Weldy »

So, those few pictures took quite a while to complete.....my brain was getting fried every couple of hours. After every thing was complete, i checked and double checked every connection on the board before continuing. I did catch a couple of mistakes while I was building out the board and got them fixed right away.....

Once everything was in place, it was time to start the initial testing. Fired it up with no tubes - all ok. Installed the rectifier tube - all ok. Next up was the preamp tubes - not ok.

Seems as though some solder flowed through the socket while I was putting the wire on that connection.
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My amp-building friend told me I was screwed and would have to put in a new socket....and, oh by the way, "I always put the preamp tubes in while I solder the connections to keep from this happening." Would have been nice if Mojotone would have imparted those words of wisdom.....

Anyway, I wasn't about to wait a week for a replacement, so I set about trying to clear the solder. I had bought a solder sucker just for this build.....mainly because I needed to get a few more bucks in my Parts Express order to hit the free shipping.... Glad I did. It help in a couple of different places and a little bit with this problem. However, the final fix was heating it up and using a very tiny metal pick to push the solder back where it came from. Took a bit, but eventually it was clear enough to accept the tube.

Success!
IMG_2918.JPG
So, on with the testing!

Best I could tell, everything was fine with the preamp stage......

Now, for my second big screwup......When putting in the power tubes, one tube was rotated off by one pin. Inexcusable. But in my defense, the tube sockets came with the hold downs and they are really, really tight making it hard to put in the tube. I thought I had it lined up and pushed it in - I was wrong. I'm surprised that the key on the tube would even allow it to go in wrong, but it did.

So, with the tube situated incorrectly, I hooked up a speaker to give it a load and hit the on switch....about 3 seconds later the speaker made a GUHZZZ sound and that was all she wrote. It blew the fuse.

Obviously, something was wrong - when I looked down on the tube socket from the inside, it was clearly off by one pin. Re-positioned the tube and went in search of a 1A Slo Blo fuse. Guess what - they don't exist in my town on a Saturday afternoon. Tried the big box building stores and the Auto parts stores - no luck.

So, Amazon to the rescue.....when I found 'em - it said order in 35 minutes and have it tomorrow.....gotta love Sunday delivery.

Anyway, about this time I thought.....wonder if my Boogie uses a 1A fuse? Well, it does! I took it out and put it on my workbench intending to start testing Sunday morning.....fortunately, before I stuck it in there and took a chance on blowing it - I remembered that I had a gig Sunday afternoon.... So, I wasn't about to take a chance on losing my Boogie with a gig coming up. While I was playing that afternoon, Amazon dropped off my 5 new fuses.

If you think this story is long, well.....it's getting longer.

Monday morning I put in a fuse, held my breath and turned it on. Still alive....me and the amp. So, I started checking all of the voltage points to see if everything was getting what it was supposed to. The voltage on the rectifier tube was perfect. However, the voltage on the Power tube was showing 833 volts! Yikes - turned it off.

Started calling my friend and emailing Mojotone trying to figure out how that high of voltage could be there.

Well, while I may know a lot about PA systems, I don't know doodly-squat about building a guitar amp. After a bunch of back and forth, hand-wringing, and hair-pulling (had to reach for most anywhere on my body other than my head for that last one), it finally came to light that I was checking AC voltage instead of DC voltage. The rectifier is AC voltage coming in - but everything else is DC....oops...missed that. So, started to check DC voltage....oops, my volt meter only went to 200VDC....needed 600.

Off to Lowes for a better voltmeter. Should I tell you the part about putting the lead of the new meter on the wrong side of the meter and touching the amp with it? Thus, blowing another fuse? .....nah, let's skip that part.

Anyway, with everything sorted out, I started the testing phase from scratch. Pulled all the tubes and started over. Went through the whole process and everything was checking out within tolerances except one point on the board where the manual said it should be 1.3V and it was measuring 162V. Hmmmm......just a weeeee bit outside! (ok, who gets that joke?)

Too late to get a response as the east coast for some reason uses a different clock than the great state of Texas and they were already closed .....so, on the advice of my buddy - I plugged in a guitar and let it rip.

The amp worked fine. Volume, Treble, Bass were functioning. I don't have the Reverb tank hooked up yet and if I raised the knob a bit, it was motorboating. I'm hoping that attaching the tank will solve that problem.

The Vibrato/Tremolo isn't working at all. I modded the footswitch jack to use TRS instead of RCA, so I'll check today to see if something is wrong there.

Good news is that this morning, Mojotone got back to me and said the 1.3V in the plans was a typo and the 162V was fine at that point on the board.

So, I'm off to the garage to install the reverb tank, the speaker, and then see if the reverb works. Then I'll tackle the Trem.....I can live without that - but, I'd really like to have everything working.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Bruce Weldy
Posts: 8539
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Princeton Reverb Build

#22 Post by Bruce Weldy »

Got to work and finished it up. Everything works. The Vibrato is a little weak, but I'm not that interested in it anyway....reverb, like all Fenders, is way too much if you get past about 3. Otherwise, pretty happy with the build.

First a little tip when installing a speaker......use the circle cutout to place on the speaker while drilling and putting the screws....a little slip will hit the wood and save your speaker.
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On to the final product....
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6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Seth
Posts: 3007
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: Princeton Reverb Build

#23 Post by Seth »

That cab looks really nice. Do you have any pics of the one you built?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bryan Cox
Posts: 450
Joined: Sun Nov 22, 2015 3:01 pm
Location: Owensville, Mo

Re: Princeton Reverb Build

#24 Post by Bryan Cox »

Looking good, Bruce! I've read a ton of horror stories about amps blowing up during builds so I think your issues were minimal in comparison. Good job! And I love the cab. I think you pretty much nailed that blackface thing. Now it's just time to let her rip.

But out of curiosity, how far on the dial do you have to get to get breakup?
Otop 12 x 4 (Delta Pro 12-450a) 2x melded, 2x straight
Titan 39 x 4 (3012LF) 20" wide

Bruce Weldy
Posts: 8539
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Princeton Reverb Build

#25 Post by Bruce Weldy »

Bryan Cox wrote: Wed Feb 26, 2020 8:26 pm Looking good, Bruce! I've read a ton of horror stories about amps blowing up during builds so I think your issues were minimal in comparison. Good job! And I love the cab. I think you pretty much nailed that blackface thing. Now it's just time to let her rip.

But out of curiosity, how far on the dial do you have to get to get breakup?
7 is the magic number.......5-6 is pretty clean.

I took it to my Rock band practice tonight to give it a good burn-in. It sounded really good with my LP. It won't be taking the place of my Boogie in this band, but I'm really looking forward to some country gigs with the Tele now.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Grant Bunter
Posts: 6912
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
Contact:

Re: Princeton Reverb Build

#26 Post by Grant Bunter »

Damn Bruce, great lookin build from top to bottom.

I've dabbled in electronics for years, and, I'm about 50% on my amp repairs (eg returning amps to working condition) with no formal training.
Here you go and build one from scratch...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

ketoet
Posts: 383
Joined: Thu Jul 08, 2010 3:19 pm
Location: kortrijk , Belgium

Re: Princeton Reverb Build

#27 Post by ketoet »

Top tip with the circle cutout to protect the driver when installing.
Nice build on the amp too !

Greetz ketoet
building BFM speakers isn't a hobby , it's an addiction

1 x THT
1 x autotuba
2 x dr250 melded

2 x wedgehorn 10
2 x tlah

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Tom Smit
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Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: Princeton Reverb Build

#28 Post by Tom Smit »

Fine-looking cab Bruce!
TomS

NukePooch
Posts: 371
Joined: Mon Jun 30, 2014 8:07 pm
Location: Berea, Kentucky

Re: Princeton Reverb Build

#29 Post by NukePooch »

SethRocksYou wrote: Wed Feb 26, 2020 6:21 pm That cab looks really nice. Do you have any pics of the one you built?
Ooof. :owned:


:lol:
Built:
4 Jack 112L- 3012HO, melded array
17.5 wide AutoTuba with Infinity 860w
6 Wedgehorn W6 w/ Panel Mount Piezos
2 T48 Slims (15" wide) with 3012LF
4 T48 Fattys (32" wide) with 3015LF

NukePooch
Posts: 371
Joined: Mon Jun 30, 2014 8:07 pm
Location: Berea, Kentucky

Re: Princeton Reverb Build

#30 Post by NukePooch »

Great looking amp, for sure.

I almost got the Cannibis Rex speaker...I really liked the sound clips I heard of it. I ended up with a GB128...I think it was because I got it on sale. Now I wonder how much different the Rex would be...

It'd be cool if you could somehow get a badge for the upper left of the grille...in Fender script...that says 'Bruce"
Built:
4 Jack 112L- 3012HO, melded array
17.5 wide AutoTuba with Infinity 860w
6 Wedgehorn W6 w/ Panel Mount Piezos
2 T48 Slims (15" wide) with 3012LF
4 T48 Fattys (32" wide) with 3015LF

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