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Amazingly Original Pre-War OAHU Amp Gets a Tune-Up
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- Опубликовано: 28 фев 2022
- 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: dldcam@aol.com.
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 ;)
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 RUclips has to offer. Thank you for what you do.
Wow, thanks so much for your very nice comments, John. We really appreciate them :)
@@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 !!!
@@tomstiel7576 It's nice to be missed, Tom. We're already working on our next video, so stay tuned :)
@@tomstiel7576 And I will "thirdle" it! Ha!
@@UncleDoug . . I'll 4th that. If I were raised with teachers like you I would be a lot smarter today :)
Congrats on 100K, Doug. Your dry sense of humor was the draw for me. Your electronics acumen keeps me coming back!
Thanks so much, Orion.
@@UncleDoug somehow didn't see this when you first uploaded... Glad to see you finally got your Play button 😀👍👍👍.
@@stevem.1853 I hope you enjoy it, Steve :)
@@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 👍👍👍
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.
Cool, Brad!
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 :)
@@UncleDoug XD
@@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!
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.
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.
That's great to hear, Daniel. I hope you enjoy it :)
Congrats on a very well deserved Award. Hope to see you with many more.
Thanks so much, AZ.
Great as always. my world stops when a new uncle Doug video gets posted!
Thanks so much, MP :)
43:07 Oh my goodness, UD! The imagery. 😂😂😂
Congratulations on your plaque! Well deserved.
I'm shocked that anyone could misconstrue my accurate description of events as being salacious ;) Thanks !!
The award could not go to a nicer guy, and as always a very informative and top notch video thanks for everything!
Thanks so much, GS :)
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!
Thanks so much, Kort :)
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.
Thanks so much, y0 :)
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.
You're welcome, Tom. Since I started bitching (in videos) about the packing....it's gotten way, way better ;)
Congrats, Uncle Doug - you're the best. I came across your videos years ago and they helped me learn so much about tube amp repair and restoration. I'm so glad you're still producing great videos. Love that you passed 100,000 subscribers - Here's to 100,000 more!
Thanks so much, JC :)
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.
Thanks so much, Aaron, for your nice comments and observations :)
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!
Thanks for sharing, SC, and for your nice comments.
What a really interesting amp that is. As always, your videos are a great watch.
Congratulations on the RUclips award. The 100,000 is thoroughly deserved for your unique, fascinating content and your dry wit.
Thanks so much, Stub.
Congratulations Uncle Doug, you are well deserved for this award. Thank you for another great video, this amp sounds fabulous.
Thanks so much, Asaf :)
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
Glad you liked it, Big Dave. It will be home soon :)
That amp looks like it just came out of the factory! I've never seen one in such pristine condition! Superb!!!
Thanks, BC. I agree.....it's a true "survivor".
Congratulations uncle Doug love watching you repair amplifiers and leaning about them.
Thanks, Fred :)
Congratulations on your 100,000 subscribers award! So glad to see you get recognition for your well done and enjoyable work on your videos.
Thanks so much, Scott.
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.
Thanks for all your excellent observations and suggestions, GU.
So many, well deserved congrats to the Master of tube amps! As one of your loyal followers I found it took a lot longer for you to gather 100k subs. Should have been much sooner! I’ve viewed the channel since the beginning and it’s about time! Another amp brought up to today’s specs for another several years. The sound was so clean, almost like a Fender. I thought you covered every aspect of the repair I noticed as you went through the repair! Nothing this time to add to what you did! Love from your buddy in NW Colorado. Thanxz
Greetings, ATL, and thanks for the very nice comments. It's always good to hear from you :)
Congrats on the subs and finally receiving your plaque.
Totally unrelated - I was just thinking that it has been a while since I've seen a new video from you, and Boom! there it is. Good to hear you going through such a nice piece of history. Still amazes me how such early stuff can last so long and sound so good even after 70+ years.
Thank you for all you do.
Thanks, TV......glad you enjoyed it :)
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!
Thanks so much, Joseph. Glad to hear it :)
Congrats on 100k subs. Started watching you around 2016 and was coming back for your repairs but also for your personality. Always can hear you are talking about something you really like and that is so nice to watch and listen to. Cheers.
Thanks so much, Michael :)
Great persistence on your part - as is typical. I enjoyed the teaching sections of the video. What a nice sounding amp! Congrats on the 100k award too.
Thanks so much, Stephen :)
Greetings uncle doug! Is so nice see a brand new video of yours. Thank you so much!
I hope you enjoyed it, Demian :)
Big fan for many years here, thank you for sharing your knowledge & preserving these pieces of history so carefully. Bravo!
You're welcome, GM :)
Wow, that's a fab specimen of an old amp..! Love the repair and excellent valve and circuit explanation. Congrats' on your plaque Doug, so well deserved..Well done you... More knowledge absorbed... Thanks for sharing..Ed..UK..😁
Thanks so much for the very nice comments, Ed :)
100K and more to come Uncle Doug! Thanks and well done to you :)
Cheers Good Sir!
We appreciate it, Rick :) Likewise.
Congratulations on the 100k subscribers. You Rock! We Roll with Uncle Doug!
Thanks so much, Curtis.
Keep the vids. coming they are "the best", and greatly enjoyed !
Thanks, RD. Will do :)
Congratulations on your RUclips Plaque!! Another great and informative video, thanks UD
Thanks for sending me the amp, Big Dave. It will be on the way home quite soon :)
Congrats on your 100k plaque! And thank you for another very well put together video on tube amp repair.
Thanks, Robert. Glad you enjoyed it :)
Congratulations, Uncle Doug. We absolutely love the passion you share with us.
Thanks so much, Kelli. That's great to hear :)
Congratulations for your RUclips channel...... thanks for all your hard and enjoyable work. 🙏👍
Thanks, Mr. McGee :)
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.
Thanks so much, Andrew. Yes, they are doing well.....although often up to no good :)
Your channel is an absolute jewel! Congrats Doug and friends!
Thanks, Han :)
Great to see you back Uncle Doug, another great job on that gorgeous little amp, I just love watching your videos.
You are “the man” uncle Doug, many thanks.
Congratulations on your award it’s well deserved.
Thanks so much, Steven :)
Uncle doug new video!!! time to take a coffee, relax and enjoy. Again, another great video and amazing teachting skills!
Thanks so much, GT. I hope you enjoy it :)
Congrats on your milestone. And thank you for what you share here. Your's was one of the first channels I looked at when I decided to learn to build tube hi fi amps.
Thanks, Joseph. Glad to hear that :)
Congratulations Uncle Doug on your You tube accomplishments! The information you give the world is invaluable, and thankfully immortalized in the interwebs. Glad to see you could wrangle that Oahu into shape, she turned out to be a pretty warm singer.
Thanks, Butch. Glad you enjoyed the video :)
Congrats! This channel has been a great education for me, thanks for sharing your knowledge.
That's good to hear, Kevin :)
Awesome and congratulations! You’re doing an absolutely great job for the community on your YT video channel. I have liked and truly subscribed. 👍
Wow, GD. Thanks so much for commenting and subscribing :)
It's easy to see how you got to 100K and I'm so pleased you're chuffed with the recognition. You're the best Uncle Doug and thanks for your informative approach.
You're welcome, Mark. Thanks !!!
Congrats on hitting 100,000 subscribers! I'm glad to account for at least one of those subscriptions. This amp is an absolute beauty.
Thanks so much, Greg :)
Very nice range of tones. Enjoyed this one and the very good explanations of the technical circuitry...
Glad you enjoyed it, Dave :)
Congratulations on your subscribers award Uncle Doug!! and thanks for another video treasure :)
Thanks, Shawn.....glad you enjoyed it :)
Congrats on the Silver Creator Award, Uncle Doug! Your channel is an awesome resource, and you are a wonderful human!
Wow.....thanks so much, Bela :)
Congratulations on 100k adoring fans! It's always worth the wait for an Uncle Doug video, and it always makes a nice end to the day.
Thanks so much, NN :)
Congratulations on the subscriber goalpost! Hopefully the same high quality of educational material just keeps coming. What a lovely channel.
Wow....thanks so much, Yup :)
Congratulations on your RUclips award you deserve it. Always enjoy your videos.
Thanks so much, Bob :)
The dinner+flowers got me good 🤣 Many well-deserved congrats on 100k! Cheers!
Glad you enjoyed it, S :) Thanks !!
Congrats on such a wonderful achievement. I am rather shocked the subscriber figure isn't 10x that amount by now! I only discovered your videos a few months back and I am ingesting your catalog like Cujo on a killing spree. Excellent detective work on this little Oahu. Witnessing your ability to intuit a schematic through logic and contrast is like having a front row seat to Bach inverting a fugue. Masterpiece!
Wow.....thanks so much, Dwayne. We're glad you found us :)
Such interesting material for tons of people. I don't know diddly about old tube amps other than I like them. I really like to hear and see you talk about them.
Thankyou Doug.
You're welcome, Roger :)
Thanks for another great video and especially the rectifier tutorial. I love little vintage tube amps that I can actually lift. I rescue them from disrepair using similar approaches as you, and so I love your videos. Your videos have all of the fun of amp repair, but none of the frustration (you fast forward through the hair pulling parts, that is very kind), so thank you again for sharing your hobby and knowledge. The Oahu owner really has a great amp now!
Thanks so much, George :)
Two thumbs up Doug. Going to be late getting into my own shop this morning, Got a Uncle Doug vid to watch. That's almost like Christmas morning.
Thanks, Martin. I hope you enjoy it :)
Embarking on a journey of vintage gear is truly a step back in history .You have a gift of presenting an overview of how things were done and do so in such an educational and informative manner.Always a treat watching your videos.Cheers from Canada.
Thanks so much, FB. We appreciate it :)
glad to see you back. congrats
Thanks, SC :)
Congrats on the 100K milestone. You deserve more subscribers with your insightful channel. Thanks for all the great content.
Thanks so much, MR :)
Congratulations from 1/100K! Really enjoyed this one as I just experienced the same issues on my same Oahu amp about 5 weeks ago. Updated all caps, some resistors, a lot of head scratching on how it is wired. Same 60 cycle hum with V1, replaced V1, same results you had. It was fun and quite a learning experience. Great sounding amp IMO.
Thanks so much, Mr. C, both for the kind words and confirmation of the issues I encountered.
Congratulations on reaching 100k subs. Your channel has been very entertaining and informative. I have learnt so much from you over the years.
Thanks, Mark. That's good to hear.
Congratulations Uncle Doug! And thank-you for the wonderful videos!
Thanks, David. It was our pleasure.
Congrats Doug! I always watch your videos and love the sense of humor, especially when it pertains to Juarez.
Thanks so much, Scott. It was a big part of my youth and I guess it shows in my comments ;)
Congratulations for 100 000 subscribers, trust you will go for the next 100k. Great video with lots of useful information. Regards from Germany, Thomas
Thanks, Thomas. We are indeed :)
43:09 and just when you were hoping for a cheap date Uncle Doug :) Congrats on the 100K viewers and many more to come
So true......Thanks, Pedro :)
Hello
First, congratulations on RUclips 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
Thanks so much, Henryk.
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 RUclips 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.
Wow....Thanks so much for the very nice comments, Doc. We really appreciate them :)
Great video! Thanks for posting. Congratulations on the 100k.
Thank you, too, Ryan for helping to make it happen.
highly deserved, well done uncle Doug , its been well worth the wait,
thanks for another awesome video, 🙂👍👍
Thanks, William. Glad you enjoyed it :)
Congratulations, Uncle Doug.
What a great project to celebrate the milestone !
Thanks, SP :)
Congrats on the award! It is a tribute to your fine work. Thanks for the look.
Thanks, John :)
Congrats on the milestone of 100,000 subscribers and thanks for this very interesting video !!
(I'm gonna watch it again, and again.)
Thanks so much, Mr. CC.
Congratulations Unlce Doug! Your a wealth of knowledge for Us! Thank you greatly for sharing it!
Thanks, Anthony :)
Congrats U D on 100,000+ subscribers ... Great vid as usual ... Thx ...
Thank you very much, Ed :)
Congratulations on the 100 thousand subs Doug. This is well deserved and it is nice to see a really good, informative, amusing channel achieving success and recognition. Well done my friend.
Thanks so much, GP. We really appreciate your kind words :)
Congratulations! I love your channel because I used to repair a lot of vintage gear but back then it wasn't vintage.
Thanks, Mr. Pile :)
Sounds super clean. A simple design from the past but still sounds good. Wow you made someone happy for sure. All the best UD .
Thanks, J&B :)
Another great video! Congratulations on your milestone!
Thanks twice, K1 :)
Congrats on 100k! Well deserved. Been watching you for many years. Keep up the great work!
Thanks, WwM :)
Good to see you again, Uncle Doug! I saw a Patreon payment sent, got exited so checked and there ya go! Another Uncle Doug video! WooHoo!
Thanks, Maurice. I hope you enjoyed it :)
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.
Thanks, Dana.......glad you enjoyed it :)
Quick note to congratulate you on 100k, and to thank you again for all these consistently hilarious, broad and yet deep technical videos.
Thanks, M. Glad you enjoy our videos :)
Mega dittos Uncle Doug you deserve it and we are glad to be here to have a part!
Thanks so much, John.
Congratulations! Yet another nice video as well...
Thanks, Stirling :)
Congratulations on the big milestone and another stellar episode! Keep up the good work!
Thanks, Ravi. Will do :)
So glad you're back, 2 months was too long! Congratulations on 100K.
Thanks twice, VTA :)
Uncle Doug, you are my Rock, when it comes to working on Amplifiers. As you know, it's been a few years now, since I became inspired to learn this stuff.
There's a couple other channels I watch.
But when I am looking for die hard, bottom line, correct information. I ALWAYS go back to see what you have to say on a given subject.
Thank you, for keeping me and many others inspired!
Wow, thanks so much for the very kind words, DW. It's always great to hear from you :)
WOW! Congrats for the 100k+ subscribers, Maestro!
Thanks so much, FW :)
Uncle Doug - welcome back. Congrats on your RUclips plague. I've been playing bass guitar for 51 years and have gone from all tube amplifiers to all transistor and now have a hybrid model. I would normally have bypassed your section on the various tube types but I found it interesting, and your detailed descriptions so engaging that I watched the entire segment. Thank you.
Thanks for your nice comments, Paul. We're glad you enjoyed the video :)
That debit card addition is brilliant!
Glad you liked it, Jeff.
Another fantastic video to brighten my day. Congratulations on the YT plaque. Thoroughly deserved!!
There are some great amp channel's on here but Uncle Doug is the go to and best!!
I eagerly await the next episode 🙂
Wow....thanks so much, Richard :)
@@UncleDoug no thank you!!
Congrats Uncle Doug,much desrved award,its a testament to your excellent and straightforward teaching skills that even an electrocutional hazard old mechanic can understand! cheers!
Thanks so much, Ted. Be careful :)
Congratulations Uncle Doug. And thanks for another great video. A great way to start the month.
Thanks, Kim :)
Very Good Video Uncle Doug!
I Grew Up learning on circuits similar to the Oahu amp.
I had an old ValveCo amp I played through practically the same circuit as your Oahu.
Greetings, MP. Thanks for sharing :)
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)
That's great to hear, Pete. I'm glad the videos are bolstering your confidence.
You are a true historian Uncle Doug. We need more of you to stop history repeating itself.
Beautiful amp wonderful restoration work. Joy.
Thanks so much, IL.
Congrats on reaching 100 000 tube twiddling maniacs around the globe Uncle Doug. Could you ever imagine reaching this milestone when you began this channel..! Kudos to your warm humour, steadfast principles and the helpful contribution of ole Rusty, Jack and the rest of the 4 legged furry crew, thanks for all the joy you have given us. .. greetings from South Africa.
Thanks so much for your very kind comments, Alex. Honestly, no, we never dreamed of reaching 100K. Early on, I was glad to have ANY subscribers :)
WOW! UD, I remember when I started watching your wonderful channel, that you had like 50,000 subs! I am thrilled and very happy that you have crossed the 100,000 sub mark! That is a very monuments occasion indeed! I must now offer my thanks and deepest gratitude for starting me personally along the path of tube amp repair! I was interested in amps before I found your channel and found most of the information to be confusing and contradictory, your channel however, was and is clear and concise and I personally am forever indebted to you for sharing your vast knowledge of tube amps with us mere mortals, lol. Thanks for all you do and if anyone reads this and is interested in going on to work on tube amps I HIGHLY recommend UD's how a tube amplifier works videos to get you started!! Again, words cannot describe how grateful I am for the knowledge I have learned from watching your videos!! Peace! And greetings from Oklahoma!!
Wow....thanks so much for the wonderful comments, Jack. Viewers like you make it all worthwhile :)
Congratulations for the 100k subs. Amazing video as always. Keep it on!
Thanks so much, O. Will do :)