1966 Fender Princeton Reverb, Part 1: Disassembly and Evaluation

[@Scholbr]

Excellent video. My dad bought me a used amp back in the 70's. Turned out to be a 1966 Fender Princeton! Looks almost exactly like your video right down to the Fuse cover which I think is original based on my amp.

[@UncleDoug]

What a wonderful gift, S. You're a lucky guy :)

[@gavinrussell2755]

Your knowledge of vintage fender amps is remarkably educational. You should write a book about these amps detailing the specs with pictures.

[@UncleDoug]

Thanks, Gavin. Books are available, but the internet is a readily searchable free source of all knowledge.

[@kimmassey6596]

Thanks so much Uncle Doug. I really liked the details on the knobs. I don’t think I’ve seen this info documented anywhere. Your videos are so great and so helpful getting us through these tough times.

[@UncleDoug]

You're quite welcome, Kim. We're glad the video was helpful and entertaining.

[@miistika13]

Uncle Doug, I learn more from your videos than any other resource. Can't wait for Part II and more videos to come!

[@UncleDoug]

Thanks so much, Shlep. Part 2 will be posted soon.....I'm still waiting for parts to arrive.

[@mozilla2576]

Can't wait for part 2. Heading to watch it now. Thanks Doug!

[@UncleDoug]

Hope you like it, M.

[@johngeddes7894]

Uncle Doug this is what I think of as an In Depth look at a Princeton Reverb. Very educational. One of Fender’s best amps in my opinion. They sound even better hot rodded.

[@UncleDoug]

Thanks. I agree, John, definitely one of Fender's best-ever amps.

[@Dan79istheman]

Thanks again Doug! I just love watching your video's!

[@UncleDoug]

Thanks, Dan. I'm glad you enjoy them...:)))

[@srinip]

I just LOVE watching your videos, my friend!

[@UncleDoug]

Thank you so much, S......glad you enjoy them :)

[@jameswooldridge8757]

I have a 65!! Love your videos!

[@UncleDoug]

Thanks, James :)

[@Koosh1984]

As someone who is interested in working on amps I feel like I hit the KZbin jackpot. Wow!

[@UncleDoug]

Welcome aboard, KB. I hope you enjoy the videos :)

[@Noitpure]

Excellent video. I just used this as a reference to go thru the '66 PR I picked up this week. Good news for me is that mine is almost completely original.

[@UncleDoug]

Thanks, I'm glad the video was helpful. Congratulations on a great purchase :)

[@lego40404]

Thank you, I will write that down in my amp building and trouble shooting book I getting together for my next build

[@UncleDoug]

Happy Holidays, Lego, and best of luck with your next build.

[@markparee99]

My first amp.Coupled it with an LPB-1 power booster and homemade extension cab with 2 12's. It roared.

[@UncleDoug]

I'll bet, Mark. You started out with one of the best.

[@audiotechlabs4650]

I used to get an amp that looked like it was left in a barn and the tolex had dust and grime umbedded into ever little crivace. I would take everthing out of the cabinet including the baffle and handle and hardware and take it to the local carwash and clean the heck out of it and let it dry for a couple of days and reassemble.Now days you could use a powerwasher. The key was to wipe it dry right after you wash it! If you like it shiny you could apply a thin coat of Amorall. Thankz!

[@UncleDoug]

Audio Tech Labs I guess this would be a whole lot quicker than my toothbrush and Armorall method :) Thanks for the input, ATL.

[@cassvirgillo3395]

Hey Uncle Doug & Rusty, I hope your both doing well. I cant tell you how much I love your channel, I watch it every chance I get and really dig the amp reviews, tutorials, etc.. Perhaps you have, but, I was wondering if you would do a series of video tutorials that trace the "flow" shall I say from the power in through the rectifier tube to the other tubes and signal "flow" from input through the preamp tube, phase inversion, power tubes, to the speaker with detailed explanations about tube operation, plate and cathode voltage, biasing and effect of screen and grid, etc.. I know that sounds like a lot to ask, but, between you and Rick at All American Five Radio I can actually learn from people who know, the voice of experience which you cant put a price on, my moneys on you and Rick, oh and lets not forget Rusty. Thankyou, take care, be good, C.

[@UncleDoug]

Cass Virgillo You're welcome, Cass. Rusty and I thank you for your kind words and wish you well. I believe if you review my video list, you will find virtually all of the topics that you requested.....pre-amp, power tubes, rectifiers, power supplies, tube construction and function, tube biasing, speakers, cathode biasing, etc. etc.

[@frankymcdonald3081]

your a national treasure.

[@UncleDoug]

Thanks, Franky. I wish you would tell that to my wife.....she thinks I'm just an eccentric, obsessive-compulsive, semi-crazy old coot.

[@donaldheitger6731]

@@UncleDoug You old coot,your still a national treasure.

[@captainamerica9353]

franky mcdonald, that would be "you're" a national treasure. But, yes, these are cool video's.

[@3MonkeysGarage]

You mention the numbers on the cabinet wood. I spent some time as a sawyer in a cabinet shop. When the sawyer was cutting his list of cabinets for the day, he would number each set, then send them over to assembly as a set. Even if it were the same cabinet, they would be as a set because the box joints could shift slightly or some other imperfection that would magnify itself if mixed with another set.

[@UncleDoug]

That makes excellent sense, AZ. Thanks !!

[@billmiller7138]

Another variation to the knobs: I have a 68 Super Reverb, Blackline, Dripedge Silverface. Snowman 8 all plastic knobs with silver slot head setscrews at #1 position.

[@UncleDoug]

There are all sorts of variations, if you look carefully. Thanks, Bill :)

[@lego40404]

I have already done that investigation already in fact, I love Hoffmans Board for that circuit, the entire circuit is on one board, but would need to measure and see if it would fit if reissue chassis.

[@momsazombie1]

For me, the driver's license number etched into the chassis is not sad but a characterful scar that tells a story about the amp's life and something about 60s crime prevention technology. I've heard stolen amps sound best.

[@UncleDoug]

You're right about numerous pieces of electronic gear from the 60's.....all with somebody's very personal information scrawled all over them in a shaky, almost illegible script. Sadly, I'll never get a chance to test your theory, but it does make sense :)

[@Kalkaekie]

Interesting ! Thanks !

[@UncleDoug]

You're welcome, Kal. I'm glad you liked it.

[@lego40404]

Happy Holidays as well to you an your family. I am torn between Allen amps version of a BFPR(SweetSpot) or Marsh's 5G9 for my next build. I built one if Allen's amp already and it's top notch

[@UncleDoug]

Greetings, Lego. I have no personal experience with either kit, but looked them both up and was impressed by what I saw. Either would probably result in a great amp, but I would like to offer two more options: 1.) Since both kits cost $1200, what if you found a real vintage BFPR in that price range that needed work? It might take some time and luck to find one, but you could then exercise your technical skills and end up with a valuable, original amp. 2.) Scratch build your own version of the BFPR. Your kit-building experience would serve you well and you could personally select each component for a custom-built, optimum result. Regardless, thanks for your comments and best of luck with your project.

[@scottm121]

I have so enjoyed watching these princeton videos. A joy to see and learn. Thankyou yet again Uncle Doug. You are well loved by a few great musicians here in Victoria BC (that would be freinds of mine. My skill is merely adequate ) The handwired princeton i steward gives me great joy. Yes its new.. however it is hand wired by a gentleman in corona California.. , indeed replicated as close as was in 1964 with what im lead to believe is a slightly modified circuit? Its designated AA1164. Tube rectified. Tube trem and reverb and is my number one amp for the band now. It does seem quite hot on the faceplate by jewel when i play steadily for a few hours. Not too hot to touch but kinda close Was that the way they ran back in the day originally??

[@UncleDoug]

That's great to hear, Scott. Thanks so much. You may have the wrong bulb in your pilot light. If you have a #44 bulb, switch to a #47......it puts out much less heat.

[@AnonymouseZillenial]

I highly enjoyed this vid :)

[@UncleDoug]

Greetings, AW. Rusty and I really like your icon.....we have a similar photo on the wall in our shop.....and we're glad to hear that you liked the video. Thanks for watching :) ^. .^

[@tremorrs]

Uncle Doug, I have a 66 pr. Reverb similar to this one. I am looking to replace the 2 prong power cord with a grounded one (after a shocking experience with a PA). What gauge cord would you recommend? I've heard 16g is best but a 18g would fit in the original strain relief. Thanks for all you do.

[@UncleDoug]

According to most charts I've seen, 18 gauge is good for up to 10A. Since the PR is fused at 2A, and thus must not draw more than this amount of current, 18 gauge wire should be quite safe to use.

[@tremorrs]

Uncle Doug, thanks for your quick reply!

[@leonelrosano2596]

Great video, I have a princeton reverb the same as yours that when I turn it on, after 1 minute it starts making a rain noise that stays for 8 minutes while it heats up. After heating it is perfect. Do you have any idea what could be happening?

[@UncleDoug]

Does the noise respond to the volume control ?

[@leonelrosano2596]

@@UncleDoug Yes, when the noise is there and I turn up the volume more, the noise increases

[@UncleDoug]

@@leonelrosano2596 Then the source of the noise is in the input circuit, somewhere between the input jacks and the volume control pot.

[@leonelrosano2596]

@@UncleDoug Thanks, it turned out to be the valve from V1.

[@UncleDoug]

@@leonelrosano2596 I'm glad you found the culprit and resolved the problem.

[@cornhuskbag]

Hi Uncle Doug, Another nice video. Thanks for Fender knobs 101! Appreciate the explanations and info through out your videos. Rusty must have been on vacation though? Kind Regards, Steve

[@UncleDoug]

You're welcome, Steve. Occasionally Rusty has other commitments that prevent him from appearing, but I will try to keep this to a minimum in the next 100 videos:) Thanks for watching !!

[@jhowellkc]

Apologies if this has been asked before: is a GZ34/5AR4 a drop in replacement for a 5U4, or is modification needed? The PR I'm gonna embark on finishing the restoration of is a 1974 chassis that calls for a 5U4. That said, probably 80% of the resto is already done to Blackface specs, but even then I believe the AA764 calls for GZ34 and AA1164 calls for 5U4, so I need to sort it out either way. Thanks!

[@UncleDoug]

+J Howell The GZ34 is far more efficient than the 5U4, drawing much less filament current and yet producing higher voltage.....so a GZ34 is actually less stressful on the power transformer 5V winding, but you have to check tube biases due to the elevated voltages (and current) that are produced. I would recommend the GZ34 in both circuits. Let's face it, you are going to be checking the biases regardless of which circuit you have.

[@jhowellkc]

+Uncle Doug So aside from standard biasing concerns, there's nothing else to do? Awesome! I like the idea of the gentler warm up with the GZ34 on an amp with no standby. Thanks! Give Rusty my regards!

[@UncleDoug]

Yes, the GZ34 is vastly superior to directly-heated cathode rectifiers like the 5U4 in many ways, and higher voltages (i.e. biasing concerns) is the only issue. You're welcome :)

[@nikelquint]

I have the allenhead at one, snowman 8 on my ‘68 princeton reverb

[@UncleDoug]

No doubt there are some deviations from the norm to be found, N.....also, knobs get replaced over time.

[@mendamp1715]

If I remove old carbon composition resistors, which have drifted in value by 20% or more, how stable are these resistors? Can the resistors be reused safely or will they drift at a faster rate, now that the resistors are over 45 years old?

[@UncleDoug]

IMHO, any resistor that must be removed from a circuit should be discarded. You can buy new CC resistors for pennies that are identical to the originals.....except for having the proper amount of resistance.

[@johnhoskin7443]

Hey Uncle Doug, Just watched the video an the 1966 fender Princeton reverb. I have one just like the one you have in the video and it needs work. I think it's the transformer. How do we correspond so I might be able to ask questions directly?Thanks for the video and your time.john

[@UncleDoug]

Give me your e-mail address and I'll contact you directly, John.

[@johnhoskin7443]

Hi uncle Doug, thank you for responding so quickly, my email is [e-mail].I am very excited that I may get this little guy up and running again!!!

[@i.shadrin]

Hello Uncle!!! I bought the new Princeton Reverb 65 reissue amp and have problem with my reverb. When i turn on the amp at low volume reverb doesn't work and there is a very loud noise instead. If i crank the volume and play a chord - it makes the reverb work, but if i lower the volume back it can disappear again within 5-7 minutes. After playing at least for a half an hour the problem goes away. I tried changing the 12at7 tube and this doesn't help. What can be the reason? I considering changing the reverb cable and tube socket. I can make a video for you to show the noise. There is no amp techs in my town, please help! I can make soldering etc

[@UncleDoug]

+Ilya Shadrin Ilya, since the amp is new, have you considered returning it to the store for repair, refund, or exchange? I have never experienced such a problem and find that long-distance amp repair is a real challenge, especially with hybrid, printed circuit board circuits. Bear in mind that there are two tubes involved in the reverb circuit, the 12AT7 and one triode of a 12AX7. Perhaps you could try changing it too. Good luck.

[@i.shadrin]

Uncle Doug there was a big story behind that. I ordered it online from Germany. So it's diffucult to return it. It is now the half of year i have been own it and have this issue. Thank you very much!! I'll try to change all 12ax7s today (already have a set of tung sols)

[@UncleDoug]

Good luck, Ilya.

[@i.shadrin]

+Uncle Doug it helped!! i ended just swapping v3 and v2, coz that groove tubes seems to be the important part of the tone. Thank you very much, it was very helpful!! Prevent me from making a mistakes. You probably saved my amp :)

[@UncleDoug]

You're welcome, Ilya. Rusty and I are glad the suggestion worked and your amp is now functioning properly :)

[@lego40404]

Love the Videos Doug, could you do a video showing you how to check a coupling capacitor? When you take one leg of board and use a meter to check DC current, I thought it was in one of your videos but I cant seem to find

[@UncleDoug]

I have converted to using the ESR meter to test capacitors, but am aware of the process you are describing. A quick way to test coupling capacitors is to remove the output tubes, connect the (-) lead of your DC multimeter to chassis ground, and use the (+) lead of your multimeter to measure the voltage on the grid pin. If the amp is cathode biased, the grid pin(s) should be at 0 VDC, not positive at all. Positive = leaky. If your amp is fixed (grid) bias, the grid pin(s) must be at a negative voltage, i.e. -15 to -60 VDC. If they are more positive (less negative) than -15, you probably have a leaky coupling cap. I hope this makes sense and helps you. Good luck.

[@patrickpost3269]

Hello Uncle Doug; I have a question for you. I recently restored a 1968 Fender vibro champ and it sound very good!However the tolex has come loose from the cabinet in places. I was thinking about injecting glue with a hypodermic needle where needed. What do you think? What kind of glue would you use. Thanks

[@UncleDoug]

+patrick post For large areas of loose material, I would use Titebond II glue, and for very small areas, particularly near edges and corners, Superglue.

[@aagazkhan1545]

Sir, I would like to ask you a question. Why do they use a 7025 tube in the pre-amplification stage? I mean what is the need to use it, the 12AX7 tubes are already good enough.

[@UncleDoug]

It's my understanding that 7025 tubes were a particularly high-quality, low-noise version of the 12AX7, to optimize pre-amp fidelity

[@SuperCarver2011]

Nice shape for '66 at least on the outside. Good to know the knob trivia. ya I remember those vibrating engraving tools. Is this the CBS era amp? You are definitely the "Sherlock Holmes" of Fender amps. Nice clean looking chassis...Rusty would approve, I'm sure.

[@UncleDoug]

SuperCarver2011 Thanks, SC. Yes, Rusty helps me sniff out all the little details on these old amps :)

[@JamesOrcutt]

Love your videos,,,love vintage amps Love your knowledge you should be a teacher ...great stuff. Do you collect them?

[@UncleDoug]

Thanks, James. I actually was a middle school math and science teacher for 17 years, but have since "retired".....to work twice as much on my own projects...:)) Yes, I do collect amps and occasionally sell them (to make room for more). Unfortunately, it's not like collecting stamps, in a nice compact album.....they tend to take over the house.

[@musiclife9690]

I have this amp serial number a18111 does any one knows what year it is... thanks...

[@UncleDoug]

Based on info from this site: www.ggjaguar.com/fendamp6.htm it was constructed in 1967.

[@dragginleftnut]

Hello Doug,, NICE VIDEOS!!, I have an old blackface princeton reverb,, the chassis is excellent, the cabinet is pristine. However some one did a little gutting inside the electronics,, I have all most of all the parts,, can get the rest,, I was looking for a good source for a parts placement diagram, I have come across a few schematic diagrams already... I don;t want to screw this up,, want to get it back running,, I wish I could find another one to copy, but oh well.. Any help would greatly be appreciated. I haven;t found a great pictorial, maybe of how everything should be located, maybe thats what I need,, some pictures!! Thanks D

[@UncleDoug]

Greetings, DLN (great screen name, by the way :). About the best I can suggest is a Fender AA764 Layout diagram (readily available by Google search), which shows where every part is located and how they interconnect. Combine this with a close-up video of the chassis, and you will probably have all you need to put your amp back in order.....left nut and all :)))

[@phonotical]

I'd have thought the 68 patents would mean that maybe that's how many went into that amp design, like a mark of quality, or as a copyright beware to people copying the design

[@UncleDoug]

I have no idea what it specifically alludes to, but it's not a date.

[@TheOldOakSyndicate]

I think you're right up there with Gerald Weber Uncle Doug! I am currently going to a local community college, and I am enrolled in the Electrical/Electronic Engineering program. I have my current semester, and one more and I'll have 2 certificates in industrial electricity, and a diploma in Electrical/ Electronic Engineering. I have learned so much the past year and a half, and I was wondering how could I go about getting more experience in amp repair? I live in a small town, and music and guitars is the main reason I started the E/EE program. Should I run an ad in the paper or what? I'm already planning on selling some fuzz clones in the paper, but my main interest is gaining experience in amp repair. Any suggestions would be most appreciated. Many Well Wishes, Travis.

[@UncleDoug]

You're too kind, Travis. I really appreciate your kind words, but I have a long way to go to catch up with GW. Re developing your skills in amp repair, it would be very helpful if you could find someone in your general area who is an experienced, skilled tech and work with (or for) them. If that's not possible, then you can do what I did and simply study on your own, using the Internet as your primary resource. There are some helpful books (by Weber, of course :), but the Internet is an unlimited source of knowledge (and nonsense....you have to be able to distinguish one from the other). Next, start buying beat-up, non-working amps (travel to find them if you have to), repairing and refurbishing them, and selling them for a profit. There's less pressure when you're working on your own amps, and you can develop your skills. After you have sufficient knowledge and experience, start taking in amps from friends and customers. Further develop your skills and reputation. Don't hesitate to charge for your work, but don't overcharge and always be honest, accessible, straightforward, realistic about completion times, etc. In your spare time, scratch-build amps and effects for sale and display. There is no substitute for hard work and dedication. If you want it badly enough, it will happen. Good luck.

[@fugamantew]

Where do you order parts from?

[@UncleDoug]

+Fuga Mante I order all transformers from Triode Electronics and all other electronic components from Antique Electronic Supply in Tempe, AZ.

[@fugamantew]

Thanks for the reply! Have just recently acquired a PR '78 and the reverb is busted. Seems as though the tank works. The pre-amp tubes, although they are all ecc 83 (the 12ax7 analog, or so I've heard) they seem to be working well enough as to send and receive the signal from the tank, as it produces a strong and present sound when shaken. My guess as in who is the culprit is in the reverb driver. What do you think?

[@fugamantew]

I mean... the reverb is weak at best and it takes tone away from the amp when dialed to 10, which is the only setting at which the reverb is identifiable, at all.

[@UncleDoug]

The reverb driving tube in the PR is a 12AT7, FM, and the recovery tube is half of a 12AX7. Shake the tank with the amp on.....if you can hear reverb noises through the speaker, then the recovery is OK and the driver is probably faulty. If not, then the recovery is probably faulty.

[@fugamantew]

I am so grateful for this bit of info. I'm pretty sure is the reverb driver. I am going to order one today. Until then reverb pedals for me. The Princeton Reverb is such a gem of an amp. You got some of the finest videos on the matter, thanks! Keep 'em coming! :D

[@mikeymike4g63]

Would you be offended if I cut the part about the knobs out and sent it to you as a seperate video for you to be able to upload and reference to in the future? This is a great resource but I fear it being embedded in another video will make it hard for people to find. Thank you for all that you do!

[@UncleDoug]

Not offended at all. You are welcome to excise the knob portion of the video and post it yourself, Mike.

[@alfredbbp]

"no dead spiders" hahahahahahahahahahahahaha epic!!!!!!!

[@UncleDoug]

Glad you liked it, Alfred :)

[@bullthrush]

"Heavy undies" dent .......that will take a few days to get out of my head. :))

[@UncleDoug]

They were either "heavy duty" or had a lot of starch !!! :)

[@catdumpling]

"coarser and broader numbers"...is that the civil way of saying "the ugliest"? ;) i actually have my grandfather's little engraver thing. i borrowed it a couple years ago to mark a second serial number on my mountain bike (which i never recovered after it was stolen. so much for that idea!) i don't know what else i'd use the engraver for, and it's incredibly uncomfortable to hold when it's on. plus everything looks like i tried to write it while i was in the middle of having a stroke. my grandfather used to mark _everything_ with it, at least when i was a little kid. he's still got all sorts of stuff that he engraved numbers into years ago.

[@UncleDoug]

Engraving personal information, like your SSN, all over your possessions was quite the fad back in the 60's and 70's, and probably a complete waste of time, as you found out. The only thing it accomplished was the defacement of all sorts of future collectibles, and gave the thieves quite a laugh as they not only stole your possessions but also your identity. Yes, the engraver is a nightmare to hold and "write" with.....much like trying to write on a paint can while it's being shaken in a mixer.

[@UncleDoug]

Re the "coarser" numbers, I must agree. To me, the Silverface knobs are the most attractive, even though they have no metal insert or, far more importantly, no cute little snowmen on them :)

[@catdumpling]

Uncle Doug i'll second that. i like that thin font. i think the plastic is thick enough that it wouldn't be much of an issue not having a metal insert, as long as someone didn't really crank down on the set screw. then again, i've stripped out those screws even on knobs that DID have a metal insert, so...

[@UncleDoug]

To be honest, I doubt that pot metal offers much greater strength to the threads than plastic, but ANY security in these trying times is appreciated.....even if it's false :))))

[@markbrooks7257]

Uncle Doug, here's a note for you. I just got in a 1966 bassman, that says Patented 66. Maybe those designations are just CBS patented designs in chronological order. Maybe the Bassman and this Princeton Reverb are just simply close to each other in a stack of patents that CBS was filing? I did my own video (as an homage in the style of this one, giving you full credit and reference) but it ended up 40 minutes long. So I took screenshots and added comments. Here's a link to the album of pictures. It's like a classic Uncle Doug video, but still pictures. facebook.com/media/set/?set=a.10208924734588998.1073741832.1634566121&type=1&l=6a774671f7

[@UncleDoug]

I really like the style of this photo-tour, Mark. The captions are both entertaining and informative. My guess is that a previous owner replaced the PT simply by cutting and splicing the wires, rather than un-soldering and re-soldering them intact. When confronted by an eyesore like this, if the PT is fully functional, I generally remove the tape and resolder all the cut wires, then cover the repair with a suitable color of shrink-wrap tubing. It's interesting that the amp came from my area. I may have seen it on Craigslist at some time. Best of luck with your continued restoration. It really looks like you're headed in the right direction.

[@markbrooks7257]

Thanks! Oddly enough, the transformer date code has the same date codes as choke and output transformer. Either way, it needs significant attention. What you suggested is the same thing another amp guru I trust suggested, so that's what my plan is for now. I didn't know you were that far west, but the '66 Bassman came to East Texas and my '77 Twin Reverb went to El Paso in a trade. So if you see a '77 Silverface Twin Reverb for sale around El Paso in the coming years, it may be my old one.

[@UncleDoug]

I'll keep an eye out for it, Mark. Meanwhile, best of luck with the re-wiring.

[@PeterWalkerHP16c]

LOL I'm a '60 model but I show considerably more wear n tear than that amp.

[@UncleDoug]

As a 1940's model, I understand completely :)