Amazingly Original Pre-War OAHU Amp Gets a Tune-Up

As a change of pace from giant Fender Twins, I thought you might enjoy joining me for the evaluation and repair of an absolutely stunning pre-war Oahu (Valco) amplifier. We inspect the amp thoroughly, inside and out, discuss the very early and unusual tube set and the evolution of rectifier tubes, then begin a step-by-step repair of the somewhat troublesome circuit utilizing a typically inaccurate Valco schematic. Once the repairs are completed, the amp is subjected to an audio test to demonstrate its surprisingly good tone. In addition, we have an exciting announcement around the middle of the video that will be particularly interesting to loyal viewers and subscribers.....so don't miss it !!
If you enjoy videos like this one and would like to support our channel, please SUBSCRIBE and consider becoming a Patreon patron at this link: / uncledougsvintageamps or making a contribution to our PayPal account: [e-mail].
Here is the site for the cloth-covered 3-wire power cord: grandbrass.com/12ft-brown-clo...
Finally: Don't fret about the exposure of the gift card number......the card was used up (by Jack, ordering gourmet catnip) long before the posting of the video ;)

[@orionwarren4244]

Congrats on 100K, Doug. Your dry sense of humor was the draw for me. Your electronics acumen keeps me coming back!

[@UncleDoug]

Thanks so much, Orion.

[@stevem.1853]

@@UncleDoug somehow didn't see this when you first uploaded... Glad to see you finally got your Play button 😀👍👍👍.

[@UncleDoug]

@@stevem.1853 I hope you enjoy it, Steve :)

[@stevem.1853]

@@UncleDoug the sound quality in the demo segment is the best I've heard from any of your video. if you have changed anything, it's made it even better 👍👍👍

[@John375PD]

Congratulations on the 100,000 subscribers. I as well as your followers greatly enjoy your educational videos. To have Uncle Doug as a teacher in a classroom would be an excellent experience, although You Tube is just fine. 100,000 followers is nothing to sneeze at. It is a valuable statistic that proves what you are teaching is very important and needed by 100,000 followers. I personally feel your contribution, dedication to teaching and your expressive personality is the best that KZbin has to offer. Thank you for what you do.

[@UncleDoug]

Wow, thanks so much for your very nice comments, John. We really appreciate them :)

[@tomstiel7576]

@@UncleDoug I second the sentiment Uncle Doug,,,,just a few observations,,,,I have missed your videos to the point I was concerned about the fact maybe no more videos,,,,and two,,,,I sorely miss the cat scans,,,hope all is well with the furry creatures as well !!!

[@UncleDoug]

@@tomstiel7576 It's nice to be missed, Tom. We're already working on our next video, so stay tuned :)

[@LTJR.]

@@tomstiel7576 And I will "thirdle" it! Ha!

[@234dilligaf]

@@UncleDoug . . I'll 4th that. If I were raised with teachers like you I would be a lot smarter today :)

[@danielsaturnino5715]

I wish you could see the smile on my face when your video showed up on my notifications. I'm sure I'm not the only one. Thanks Uncle Doug.

[@UncleDoug]

That's great to hear, Daniel. I hope you enjoy it :)

[@forthwithtx5852]

43:07 Oh my goodness, UD! The imagery. 😂😂😂 Congratulations on your plaque! Well deserved.

[@UncleDoug]

I'm shocked that anyone could misconstrue my accurate description of events as being salacious ;) Thanks !!

[@Starcrunch72]

Congrats on the milestone and "major award" Uncle Doug! 25 years ago, a fella brought a similar Oahu amp to me to try to get up and running. This was in the very beginning of my amplifier repair journey and all I had for reference information, was the Tube Amp Book and could not find anything similar and sadly had to return it to the customer--it was also badly hacked up by TV repairmen over the years, and I just couldn't make heads or tails of that little amp. This example is museum quality. Thanks again for all you do for all of us!

[@UncleDoug]

Thanks for sharing, SC, and for your nice comments.

[@y00h0011]

Congratulations, Uncle Doug. An award well deserved. And again, another great old school lesson on the early years of tube design. This video defined a great deal. So glad to see you back... I was having Uncle Doug withdrawals. And as always.. Thank you, Professor.

[@UncleDoug]

Thanks so much, y0 :)

[@peteleoni9665]

Every time I rewatch these I get more from them! I just restored a 1927 Atwater Kent 37 with an 80 rec and transformers and caps potted in tar.(fun) I don't think those old guitar amps can scare me much anymore (thanks to you of course)

[@UncleDoug]

That's great to hear, Pete. I'm glad the videos are bolstering your confidence.

[@Gunsmith-4570]

The award could not go to a nicer guy, and as always a very informative and top notch video thanks for everything!

[@UncleDoug]

Thanks so much, GS :)

[@iroffman]

That is a sweet sounding little amp... now. Nice work Uncle Doug. Thank you, especially for the in-depth descriptions! You're the best. Congratulations on the plaque!

[@UncleDoug]

Thanks so much, Kort :)

[@mp-ov9dh]

Great as always. my world stops when a new uncle Doug video gets posted!

[@UncleDoug]

Thanks so much, MP :)

[@Finom1]

Bless you for sharing your wisdom with your growing community 109K plus!!!

[@UncleDoug]

Thanks, F1.

[@jeffmarshall9420]

It is always a red letter day when a new Uncle Doug video is posted. Thanks.

[@UncleDoug]

I hope you enjoy it, Jeff :)

[@3MonkeysGarage]

Congrats on a very well deserved Award. Hope to see you with many more.

[@UncleDoug]

Thanks so much, AZ.

[@snowhyt77]

Terrific Video Uncle Doug!! Can't wait till it gets home to play its matching steel through it. Congrats on the 100,000 subs!! BigDave

[@UncleDoug]

Glad you liked it, Big Dave. It will be home soon :)

[@chadwickhurlburt6529]

I think that old amp has a beautiful tone. Very informative video. As always, thank you for sharing your wisdom. 👍

[@UncleDoug]

Thanks, Chad. We're glad you enjoyed it.

[@rdykes828]

Keep the vids. coming they are "the best", and greatly enjoyed !

[@UncleDoug]

Thanks, RD. Will do :)

[@aaronatwood9298]

Congratulations Uncle Doug. It’s a good milestone to achieve. I have commented several times and find your videos highly informative and entertaining. Watching your videos has inspired me to and shaped my direction in building my own guitar amplifier. Thank you so much. I would love to share my own progress with you. All the praise aside. Looking at that Oahu amplifier, it looks very similar to a Kay Amplifier that you did a year or 3 ago. Similar build, components, nice fret work, umbilical for the the field coil/speaker, and the additional choke. I like them both, but they are definitely odd.

[@UncleDoug]

Thanks so much, Aaron, for your nice comments and observations :)

[@TheGuitologist]

Glad you got your plaque, Doug. Back when you emailed me about it and said you didn't think you'd get one if you're not in the partner program, I told my wife I was thinking of sending you mine (which is still unopened on a shelf) as a thank you for being an inspiration to me and for being a friend. The only thing that stopped me was my wife said I should keep it and give it to one of my girls who might like to have it. But alas, all's well that ends well. Susan has given you your well-deserved mark of approbation.

[@johnlund2654]

Cool, Brad!

[@UncleDoug]

Greetings, Brad. It's always good to hear from you. Apparently, it was the backlog in plaque production that caused the delay, rather than punishment for allowing no revenue gathering by YT. But as my old, drunken granny used to say, "Better late than never"......a sentiment never shared by previous landlords and tax collectors :)

[@PandemoniumMeltDown]

@@UncleDoug XD

[@Bob-Whiting]

@@UncleDoug This just goes to show you that you can learn from anyone, even a drunken Granny! I always learn from you Uncle Doug AND from Brad, unless he's ranting again and then... Wait! Brad's here?!! I gotta run Doug, got things to do!

[@williambock1821]

Awe, man… why not display yours? It didn’t occur to me that you don’t have one on display until now. There’s nothing wrong with being recognized for a job well done from time to time. It’s no mean feat getting 100k subs! You’re good at what you do. No need to be all punk rock about it.Use it as a pedal box or in a cab or something,lol! A lot of times,when watching a new channel (as one does occasionally) I’ll notice how established they are by seeing their plaque before I look at the number of subs they have. If they get that big, they’re usually doing SOMETHING right.

[@jdmccorful]

Congrats on the award! It is a tribute to your fine work. Thanks for the look.

[@UncleDoug]

Thanks, John :)

[@mamutcat]

That is a very handsome plaque. Richly deserved.

[@UncleDoug]

Thanks so much, Allan.

[@Bleats_Sinodai]

That amp looks like it just came out of the factory! I've never seen one in such pristine condition! Superb!!!

[@UncleDoug]

Thanks, BC. I agree.....it's a true "survivor".

[@goodun2974]

I am curious if the amp actually had shorting input jacks as shown on the schematic; amplifiers of this vintage often did not. Also note that a problem that can arise when the input stage has no grid-leak resistor is that a small voltage from the preamp tube grid can be fed backwards into the controls and pickups of the guitar, leading to crackling noises when the guitars volume is adjusted (which is the reason why you might see a capacitor between the input jack and the grid of the 1st preamp tube, to block DC from getting to the guitar's controls). The possibilities are legion for hum induction in an amplifier constructed like this. The 1st filter stage capacitor has its own ground ---- bolted, or riveted? ---- and the 2nd and 3rd stage filter caps have a separate ground several inches away through what looks to be a riveted-in-place terminal strip. Also the input jacks are bolted directly to the chassis without isolating launchers. All of this mechanical grounding was originally done to a heavily painted chassis without the factory taking pains to remove the paint around those holes, and 80 years later it can be pretty much guaranteed that there will be oxidation and galvanic corrosion underneath those bolts and input jacks, and especially at the riveted ground points for the terminal strips. Unfortunately it can be a big job to undo all those grounds and clean the metal and put them back together, and it's certainly not in everyone's budget, but it can be sonically rewarding (greatly lowering the hum and background noise floor) if one has the patience, or the budget, to do it. One pointed comment pertaining to safety; I would recommend attaching the ground wire from the power cord *directly to the chassis* and not to the frame of the filter choke because you are relying on the 80-year-old bolted connections holding the choke in place to connect to ground electrically through the frame of that choke ( the bolts and the chassis are probably oxidized underneath the monting tabs of the choke). This also might tend to induce eddy currents into the chassis, increasing hum.

[@UncleDoug]

Thanks for all your excellent observations and suggestions, GU.

[@thermionic1234567]

That debit card addition is brilliant!

[@UncleDoug]

Glad you liked it, Jeff.

[@bobparker4989]

Congratulations on your KZbin award you deserve it. Always enjoy your videos.

[@UncleDoug]

Thanks so much, Bob :)

[@jimcatanzaro7808]

That sounds really good

[@henrykpycha1637]

Hello First, congratulations on KZbin recognition for your fantastic broadcasts and lessons. You really deserve it. I am such an average listener very happy about it. With great respect Henry

[@UncleDoug]

Thanks so much, Henryk.

[@timothyandrews2157]

Congratulations Uncle Doug on your KZbin award! You must feel a bit proud to know you've reached the hearts and minds of so many of us. You have taught me so much with your no nonsense, thorough explanations of how amps work. I am sorry that I have not been able to support you monetarily as I'm on a somewhat fixed income (oddly named it seems) BUT I do have a collection of all sorts of vintage tubes! If you ever need a hard to find tube please contact me and I will see if I have one for you. Of course I don't have extra GZ34's 😢 but I have The tubes you are showing in this video and many of my tubes are NOS. Anyway, thanks for being you and taking the time to teach.

[@UncleDoug]

Thanks so much, Tim. I'll keep your offer in mind. Meanwhile, our best to you and yours.

[@nick1fenton]

Hey Uncle Doug. Congratulations on 100K. Now as for people that think the plaques are silly. Well there are over 100,000 people on this planet that don't think they're silly. 100,000 people who are interested in what you have to say, who's lives have been enriched by your knowledge. Mine certainly has. Well done.

[@UncleDoug]

Wow.....very nicely said, Nick......and I agree 100%.

[@bullthrush]

Congratulations! Your willingness to share your knowledge in a relaxed and humorous manner certainly deserve recognition. A beautiful vintage amp with great sound. I hope the kitties are well and not up to shenanigans.

[@UncleDoug]

Thanks so much, Andrew. Yes, they are doing well.....although often up to no good :)

[@amoruzz]

Awesome! Sweet tones.

[@UncleDoug]

Thanks, Amo :)

[@richardwissing954]

Congrats! Well deserved.

[@UncleDoug]

Thanks, Richard :)

[@Yupppi]

Congratulations on the subscriber goalpost! Hopefully the same high quality of educational material just keeps coming. What a lovely channel.

[@UncleDoug]

Wow....thanks so much, Yup :)

[@robertdodge8587]

Congratulations!!

[@UncleDoug]

Thank you!!

[@abelincoln95]

You earned it Unc!!! You lay down some sweet videos and so many teachable moments. Shame you haven't cobbled together a DVD collection to educate the young ones. Who knows, maybe that's forthcoming. Love you, Bro!!!

[@UncleDoug]

Thanks so much, Abe. Likewise :)

[@irusman62]

UD Rusty, Jack, Casey and Ollie congratulations on getting over 100,000 subscribers, thats a remarkable achievement. im glad to see Google/KZbin are not the evil dark side and recognized you all even though you dont allow them to profit from your content. the amp sounds fantastic! im sure glad in this day of consumption and throw away after a few years of use, that you keep this great historic equipment alive and useful.

[@UncleDoug]

Thanks, Russell. Apparently they do make money from my channel but simply don't share it with me. To be honest, I don't care.

[@69mercurycyclone44]

Congratulations! Well deserved 👏

[@UncleDoug]

Thanks, MC :)

[@shannonharris2816]

You are still, the man, Uncle Doug.

[@UncleDoug]

Thanks, Shannon :)

[@JohnCarey1963Jag]

Congratulations!

[@UncleDoug]

Thanks, John :)

[@andy2538]

Nice, always great information. Thanks

[@UncleDoug]

Thanks, Andy :)

[@kwsailer1]

Another great video! Congratulations on your milestone!

[@UncleDoug]

Thanks twice, K1 :)

[@nparbs]

Congrats Doug!

[@UncleDoug]

Thanks, Nick.

[@davidsimpson3380]

Congratulations Uncle Doug! And thank-you for the wonderful videos!

[@UncleDoug]

Thanks, David. It was our pleasure.

[@alvarofalcon7136]

Congratulations Uncle Doug !!

[@UncleDoug]

Thanks, Alvaro :)

[@dinofond]

Congratulations Doug!

[@UncleDoug]

Thanks, Dino :)

[@thelonetwangster]

'...Had to take it out to dinner and buy it flowers...' You sir, are a wag. I learn ever more watching your content. Congratulations on the 100k - fully merited.

[@UncleDoug]

Thanks so much, Phil :)

[@DrHumbertoable]

Dear uncle Doug, congratulations to your 100K. You definitely deserve it 🙂 if not more . For me you and your videos belonging to the kind of content that made KZbin so famous and unique and is the reason I still have it. It is honest, educational, non profit, and with a lovely sense of humour. You are one big influence that brought me into electronics and I hope you ll stay on air many years.

[@UncleDoug]

Wow....Thanks so much for the very nice comments, Doc. We really appreciate them :)

[@mikeroadblock]

Kind sir, YOU ARE THE BEST! Thank you.

[@UncleDoug]

Thanks, Mike :)

[@fredgrove7886]

Congratulations Uncle Doug!

[@UncleDoug]

Thanks, Fred.

[@GeorgeKamps]

Congrats! Love your channel.

[@UncleDoug]

Thanks, George :)

[@ronnewby3196]

GREAT AMP AND VIDEO GLAD YOUR BACK!

[@UncleDoug]

Thanks twice, Ron :)

[@soundcityec]

Congrats Uncle Doug!! I love your videos, you are my role model :)

[@UncleDoug]

Thanks so much, Daniel :)

[@jonbutcher5593]

Congratulations Doug : )

[@UncleDoug]

Thanks, Jon :)

[@trevorclarey3336]

great stuff , Uncle Doug.

[@UncleDoug]

Thanks, Trevor :)

[@wmk0100]

Congratulations, and another great learning experience.

[@UncleDoug]

Thanks, Bill :)

[@brendanlindsaywebb4932]

Congratulaions, Doug!

[@UncleDoug]

Thanks, Brendan.

[@davebollinger8863]

Congratulations Uncle Doug

[@UncleDoug]

Thanks, Dave :)

[@georgeescaped6035]

yay your back thanks! hope is all well! made my day!

[@UncleDoug]

Thanks, George. We missed you :)

[@carltosten7875]

Love your videos, I've learned so much!

[@UncleDoug]

That's great to hear, Carl.

[@theoloutlaw]

100K and more to come Uncle Doug! Thanks and well done to you :) Cheers Good Sir!

[@UncleDoug]

We appreciate it, Rick :) Likewise.

[@drjoephd]

Great to see you back!

[@UncleDoug]

Thanks, Doc.

[@williamgombert7710]

Congratualations with the +100.000 subscribers and with the recognition you received for this event from You Tube. If there is one thing positive at the covid pandemic is that I discovered You tube, and more particular your channel. I graduated in Electronics in the mid eighties (for some reason we never learned about vacuumtubes, although all TV's in that era worked on vacuum tubes ...), but I never ended up working in electronics. It was by seeing your videos that my intrest in analoge electronics got a wake up. I digged up my old studybooks and looked for hours at your videos. Now am I building my first tube amp and I am very glad I rediscovered my intrest in electronics. Thank you!!

[@UncleDoug]

Thanks so much, William. It's great to hear that you are pursuing your interest in tube circuitry. We hope our videos continue to provide inspiration and information :)

[@fibberscloset498]

Congratulations, Uncle Doug.

[@UncleDoug]

Thanks, Mr. McGee :)

[@danielpirone8028]

Congrats on 100k - well deserved.

[@UncleDoug]

Thank you, Daniel :)

[@curtismuma1931]

Awesome work! You are the master.

[@UncleDoug]

Thanks so much, Curtis.

[@bradrebar101]

Thank you Doug for the very fine video's.

[@UncleDoug]

We're glad you enjoy them, Brad.

[@han36solo]

Your channel is an absolute jewel! Congrats Doug and friends!

[@UncleDoug]

Thanks, Han :)

[@kimmassey6596]

Congratulations Uncle Doug. And thanks for another great video. A great way to start the month.

[@UncleDoug]

Thanks, Kim :)

[@akdenyer]

Thanks again, very educational, your teaching skills really shine through. The paint is an inspection mark, we do that to indicate screws have been torqued and checked.

[@UncleDoug]

Glad you enjoyed the video, AK. Thanks for your input.

[@MegaTubescreamer]

highly deserved, well done uncle Doug , its been well worth the wait, thanks for another awesome video, 🙂👍👍

[@UncleDoug]

Thanks, William. Glad you enjoyed it :)

[@davidshutt2273]

Thanks, Uncle D

[@UncleDoug]

You are very welcome, David.

[@davidshutt2273]

@@UncleDoug Yay Rusty

[@richardfranklinmorse]

I just bought one of these, thanks for the info!

[@UncleDoug]

You're welcome, Richard. Good luck with it :)

[@Fnortner01]

Congratulations. Well deserved reward.

[@UncleDoug]

Thanks :)

[@SC-gu4pd]

glad to see you back. congrats

[@UncleDoug]

Thanks, SC :)

[@zyghom]

amazing piece of hardware and amazing approach ;-)

[@UncleDoug]

Thanks twice, ZH.

[@OSHomestead]

Congratulations, Uncle Doug. We absolutely love the passion you share with us.

[@UncleDoug]

Thanks so much, Kelli. That's great to hear :)

[@mobicus1]

Congratulations Uncle Doug! Woohoo!!

[@UncleDoug]

Thank you, Rick :)

[@pda041376]

Awesome, display your award with pride, you have earned it.

[@UncleDoug]

Thanks, Pat. Will do :)

[@scott729]

Thanks U.D.

[@UncleDoug]

You're welcome, Scott.

[@tom4786]

Congratulations on the milestone.

[@UncleDoug]

Thanks, Tom :)

[@Kilovolver]

UD Time! This fandom will never let you down UD! congrats on the 100k. Now the way to 1 M subs starts!

[@UncleDoug]

Thanks so much, K. I'm not sure if we'll still be here if and when the 1 M sub level is reached......but we'll try :)

[@RaviNewfarm]

Congratulations on the big milestone and another stellar episode! Keep up the good work!

[@UncleDoug]

Thanks, Ravi. Will do :)

[@fredgarvin4482]

congrats on the 100k and nice video as always.

[@UncleDoug]

Thanks, Fred :)

[@stirlingschmidt6325]

Congratulations! Yet another nice video as well...

[@UncleDoug]

Thanks, Stirling :)

[@bertrodriguez3087]

Congratulation Doug. You very well deserve it and much more. Thank you for all you have shared.

[@UncleDoug]

Thanks so much, Bert :)

[@fredberthiaume6883]

Congratulations uncle Doug love watching you repair amplifiers and leaning about them.

[@UncleDoug]

Thanks, Fred :)

[@AsafSmilan]

Congratulations Uncle Doug, you are well deserved for this award. Thank you for another great video, this amp sounds fabulous.

[@UncleDoug]

Thanks so much, Asaf :)

[@BenState]

congrats on the milestone mate!

[@UncleDoug]

Thanks, Ben :)

[@R3TR0R4V3]

Congrats on 100k! Well deserved. Been watching you for many years. Keep up the great work!

[@UncleDoug]

Thanks, WwM :)

[@oldguy5381]

Very deserving award, congratulations

[@UncleDoug]

Thanks, OG :)

[@justinellison4214]

Good work ! Salute

[@UncleDoug]

Thanks, Justin :)

[@jjnicola]

Congratulations for the 100k. I really love your videos. I have learned a lot. Thank you very much for sharing your knowledge.

[@UncleDoug]

Thanks so much, Juan :)

[@tomw9875]

Thanks for another great video Uncle Doug. What a fantastic amp find. It must have been a great relief for you to find it so well packed for shipping.

[@UncleDoug]

You're welcome, Tom. Since I started bitching (in videos) about the packing....it's gotten way, way better ;)

[@olipito]

Congratulations for the 100k subs. Amazing video as always. Keep it on!

[@UncleDoug]

Thanks so much, O. Will do :)

[@toolmanchris]

Nice content as usual Doug and well done on the 100k subscribers it’s well deserved 👍

[@UncleDoug]

Thanks twice, Chris :)

[@marcuscarrozza732]

🎉Congrats Uncle Doug 🎊 that's awesome. I am happy for you! 🎸

[@UncleDoug]

Thanks, Marcus :)

[@gandichild]

Congratulations on the 100k Doug .What a beautiful amp . Excellent video thank you for the time you spend to explain these older amplifier circuits I've learned a lot from you.

[@UncleDoug]

Thanks, Dana.......glad you enjoyed it :)

[@robp9444]

Congratulations Doug, 'keep on rockin'...

[@UncleDoug]

Thanks, Rob. Will do :)

[@mickwilson127]

Glad to see you back Doug! Missed your vids

[@UncleDoug]

Thanks, Mick :)

[@ernestschultz5065]

oh man! I really needed my Uncle Doug fix!

[@UncleDoug]

Glad to hear it, Ernest :)

[@josephmagedanz4070]

Congrats on 100K! I always enjoy and learn from your videos and feel that I certainly get my money's worth from Patreon. Thanks for everything!

[@UncleDoug]

Thanks so much, Joseph. Glad to hear it :)