1965 Gibson GA-5T Skylark in Superb Original Condition

In this video we will closely examine an extremely nice, original Gibson GA-5T Skylark inside and out. Then we will trace the entire schematic, correlating it with the actual circuit, to assist those who are trying to learn how to read schematics. Next, we will make several basic alterations to the circuit to improve the tone of the amp. Finally we will hear the amp as it sounds, both before and after the circuit modifications.
Extra features include the unpacking (and cat scanning) of a big surprise package from a viewer, and another trip to the big hot rod show at the War Eagles Air Museum in Santa Teresa, NM.
If you enjoy instructional, advertising-free videos like this, please subscribe to our channel and consider becoming a Patreon patron at: / uncledougsvintageamps or make a PayPal donation to: [e-mail]. Also if you have any unused vintage tube gear or surplus components, please consider donating them for possible use in future videos. Thanks !!

[@PipeCat1965]

Looks like that amp sat in a box in a dry attic for 50+ years. Gorgeous.

[@UncleDoug]

Thanks, PC :)

[@freepress8451]

@@UncleDoug Hardly any oxidisation on any of the joints

[@chisbang53]

Lengthy session? It just flew by. Can't wait for the next one.

[@UncleDoug]

High praise indeed, Paul. Thanks !!

[@UncleDoug]

Menu: 0:00 to 10:00 Tour of the Amp 10:00 to 30:39 Detailed Schematic/Circuit Review and Correlation 30:39 to 44:00 Circuit Modifications w/ before and after audio demo 44:00 to 53:00 Car Show CORRECTION: At around 13:50 in the video I say that the interstage transformer phase inverter output is to the plates of the 6BQ5's.......Of course, it is actually to the grids. Sorry. I guess I was thinking of the OPT primary.

[@MitchelYoung]

Uncle Doug Thanks for another awesome video. I like the idea of your “table of contents”. I have a ga-5 skylark that I think is a 60 or 61, it’s the tan tolex style, all the tubes are from mid late 1960 and the screws look like they’ve never been out( this beauty even came with the original fitted clear vinyl cover) It’s tone seems good to me with hotter humbuckers but thin and ice-picky with a strat or horrible with a Telecaster. The schematic that was in the back of the amp shows some kind of weird voltage divider network for the tone control that I, frankly, don’t comprehend. Any chance of a video explaining the Gibson voltage divider tone control? Thanks again for all the awesome info. I wish I could give more to your Paterion but things are tight right now. I love the car show stuff too. I’m getting ready to sell my 1964 Oldsmobile Starfire convertible I’ve had forever then I’ll hopefully have more disposable income to invest in your awesome, informative, entertaining videos.

[@UncleDoug]

I discuss the unusual bass control in this video, Mitchel. I'm not sure about the tone control in yours......maybe I'll encounter one in the future. Yes, these amps are god-awful with anything but humbuckers. No problem on the Patreon contribution.....we appreciate any and all pledges. I hate that you have to sell your '64 Olds, but best of luck with whatever you decide.

[@rfostore]

Hi Uncle Doug. Another excellent video. When I saw the face plate for this amp I recognized it from somewhere. If you watch Back To The Future where Marty McFly plugs into the enormous amp that blows him across the room, It has that face plate on it. I know, useless trivia, but I thought you would enjoy that. Keep rockin'.

[@UncleDoug]

Thanks for that interesting connection, Ray. I will check out the movie scene.

[@TheGuitologist]

Sounds great! You get so much for your money with these.

[@UncleDoug]

Thanks, Brad. As you know, they are still affordable and very well made. With a few modifications, they can become excellent amps.

[@SkyscraperGuitars]

Great breakdown of the circuits in the amp. As always, I love the hotrods at the end.

[@UncleDoug]

Thanks, SS :)

[@Finom1]

Hi Uncle Doug, we love you amp videos!!! You manage to always surprise us with your finds. It's so exciting to see you work on vintage tube amps!!!

[@UncleDoug]

Thanks so much, F1 :)

[@jamesbracken4618]

Love that C47/DC3 in the background at the airport. I work on my own amps to, just converted a Precision 20 PA to a Princton tone circuit, No tremalo, great amp. Thank you. GOD BLESS YOU! GOD BLESS AMERICA!! GLORY BE TO GOD!!!

[@UncleDoug]

Thanks so much, James. Likewise :)

[@irusman62]

14:40 uncle Doug this is enormously helpful thank you so much. after watching over 100 of your videos im really starting to get it!

[@pyrotas]

Sir, your videos are always a nice little present. Excellent presentation, informative and highly valuable! Thank you :)

[@UncleDoug]

You're welcome, Fabio. Thanks !!!

[@AdmiralQuality]

Awesome, Doug, thanks! You know your magic tutelage is working when us young grasshoppers are mouthing the words you're about to say before you say them. (But you couldn't give us 2 seconds on a jet? LOL!)

[@UncleDoug]

You're welcome, AQ. The next time the USAF Thunderbirds come to the Air Museum, I'll ask for a ride-along :)

[@Kilovolver]

OMG! I was just thinking... how cool would be to have some UD videos for this easter! Thanks so much UD, you read my mind!

[@UncleDoug]

We took some time out from hiding Easter eggs to prepare an Easter surprise for our viewers, K........glad you enjoyed it :)

[@sworgan1]

always great to see a new Uncle Doug Video even when I am on Holiday on the other side of the world and miles from my own workshop LOL

[@UncleDoug]

That's good to hear, Steve. Have a great vacation !!

[@jamescarter4175]

Another great video! Thanks for the circuit-schematic comparisons. Things are coming into focus.

[@UncleDoug]

That's good, James. You're welcome.

[@michaelbutler2312]

very well done. thanks for tracing the circuit.

[@UncleDoug]

You're welcome, Michael. I hope it was helpful.

[@jamesbruno5896]

Love the mods you did to that gorgeous original amp! I'm a big car guy so I appreciate the car show footage! Thanks UD!

[@UncleDoug]

You're welcome, James.

[@jeffreywinter2450]

A week ago I picked up and old white panel Skylark, identical to this one. It was inoperable and in rough shape. It was a thrift store find and couldn't resist. I want to thank you for this comprehensive tutorial, which helped me get the amp up and running. Much appreciated. I have yet to lift the cap off the bass pot, but after playing the amp it seems like a good idea.

[@UncleDoug]

We're glad the video was helpful, Jeff. Good luck with the Skylark.

[@jeffreywinter2450]

@@UncleDoug I'm wondering about the values of the rectifier diodes. My Skylark also had a burnt 1K resistor in the same location as the one in your video. When I replaced it one of the diode leads broke. I repaired the solder joints where the two diodes are connected, but would like to eventually replace them. I didn't find anything identical when checking suppliers. What would you suggest as replacements? Would a 1N4007, 1 amp diode be sufficient?

[@UncleDoug]

Yes, but since diodes are so inexpensive, you could increase the amperage rating to 2A or 5A if you wish.@@jeffreywinter2450

[@lamppostwillie]

Thanks Doug for the excellent translation between layout and schematic- that has been my main hurdle trying to learn this stuff.

[@UncleDoug]

You're welcome, William. I hope it helps :)

[@troyprosser4890]

Absolutely awesome way to help us new guys get some real world understanding of schematics. It's easy enough to do but having the clarification we are reading them correctly and can use this video to help if we ever want to clone an amp for layouts etc. Cheers for this format of video. Been waiting for someone to do this.

[@UncleDoug]

You're welcome, Troy. I'm glad it was helpful :)

[@stevelacombe5291]

Uncle Doug has such a soothing voice. Nice tour of the amp and hot rod bonus was great too.

[@UncleDoug]

Thanks, Steve. Glad you liked it.

[@jimdawes7261]

UD, I appreciate the schematic/circuit review and correlation part of your videos, very helpful when you're learning electronics, thumbs up!

[@UncleDoug]

Thanks, Jim. I'm glad it was helpful.

[@tonysplace8009]

Thank you for the circuit analysis! I think this can be an excellent teaching tool for anyone who wants to learn to use a schematic in relation to the actual circuit itself.

[@UncleDoug]

You're welcome, Tony. I sure hope so. Lots of viewers have requested this, so I thought the Gibson circuit would be a good teaching tool.

[@spencerfreed6947]

Wow!!! I've been on the hunt for one of these for a bit. They do pop up now and then at a much more attainable price than it's fender vintage cousins. Absolutely inspired by your work, thank you for sharing!!

[@UncleDoug]

You're welcome, Spencer. Glad you enjoyed it :)

[@Bigjoedo66]

Great Video Uncle Doug!!

[@UncleDoug]

Thanks, BJ :)

[@petercornell2002]

Thanks Uncle Doug, another great vid.

[@UncleDoug]

You're welcome, Peter :)

[@butchlauer]

Man where would I be without you uncle Doug. You never disappoint me your patience and knowledge that keep me learning all that I can. You are a treasure trove of info and I have to say, THANK YOU SIR!

[@UncleDoug]

You're welcome, Philip :)

[@butchlauer]

The skylark walk thru inspired me to re open a newly purchased 66 Gibson explorer of said same vintage. My explorer was a recent Ebay purchase that arrived doa. I reached out to the previous owner for some back story on the amp as I could tell it had some hot rodding already accomplished on it. I assured the guy that my communications were not monetary shakedowns just curiosity. Anywho, I am 3rd generation in my family in the vast electrical industry, amp tech just not part of my field of expertise, that said I went back to my 5 senses. Double checking my cap draining skills I dove back in with the trusty chop stick to finally unearth the shipping problem. The small transformer that acts as the power supply choke seems to have had a not so up to par solder job on one of its legs. There is a terminal strip in this location that has numerous connections and luckily I spotted that loose lead that was only an inch of wire at most.....phew. Well she sprang back to life and I haven't looked back as the Chattanoogas amp techs mods turned out to be spot on and she sounds fantastic. Thanks again uncle doug!!!

[@SciPunk215]

This is one of your best vids, Uncle Doug. And that's saying a lot.

[@UncleDoug]

Wow....thanks, SP :)

[@gkwall]

You know you've trained me well Uncle Doug because I almost screamed aloud "Don't touch the capacitors". Good job and thanks for all your education and humor over the years.

[@UncleDoug]

You're welcome, GK. Safety first :)

[@OldRichieBoy]

Thanks for this great video. Tonight I did some repairs on my GA-5T, replaced a resistor, got the three 20uf caps installed correctly (it had 4 of them and a 220 uf cap connected in with them} that were super glued together and glued to the chassis, put a 3 way grounded cord on it. When I turned it on to test it, like WOW!!! It worked nice. No noticable buzz until volume 7.5 with treble and bass at 10., but still quiet and acceptable to me. And I don't get a shock from touching anything metal on my guitar or jacks. This project has been one of my best Christmas presents ever! This video to me is like video Gold!

[@UncleDoug]

Your very nice comments made our day, Richie. We're really glad the video was so helpful :)

[@russellesimonetta3835]

Five to ten minute videos are entertainment uncle doug teaches .worth every minute. His series on how tube amps work is great i,m on my third and fourth times watching those.

[@UncleDoug]

Thanks so much, Russell :)

[@TheFreddyfloyd]

Great video Unc. Really enjoyed the schematic to board section.

[@UncleDoug]

That's good to hear, FF. Thanks !!

[@robertcalkjr.8325]

Thanks Doug! Great lesson! I got my stuff cat-scanned this morning by Mr. Binx!

[@UncleDoug]

You're welcome, Robert. Regards to Dr. Binx.

[@robertcalkjr.8325]

He's still a kitten about 5 months old so he doesn't have a doctorate in sniffing yet. lol

[@jonpardue]

The bass control fix is really worth while! Great car show and location.

[@UncleDoug]

Thanks twice, Jon :)

[@mechanoid5739]

Hi Doug. Thanks for the very informative comparison of the schematic to the hardware. Makes following the circuit through the amp so much clearer. I have learnt a lot from you on repairing tube amps. (We call them valve amps here in the UK but hey! ) :)

[@UncleDoug]

You're quite welcome, M57. We're glad the videos are helpful :)

[@alanhoggard4554]

Great vid and I really appreciate the comparison of the schem. to the actual amp!

[@UncleDoug]

Thanks, Alan. I'm glad it was helpful.

[@williamscaliarini8201]

Another gem uncle Doug !

[@UncleDoug]

Thanks, William :)

[@mastertigh-8617]

Very groovy amp, thanks Doug!

[@UncleDoug]

You're welcome, MT.

[@barbaracooper6496]

wow Uncle Doug those guitar lessons really paid off.great video i have several Gibson amps and really like them

[@UncleDoug]

It's all due to Ollie & Jack, Barbara. They are my feline strummers :)

[@Ideal1980]

That’s just tremolicious, Uncle Doug! Thanks for the videos

[@UncleDoug]

You're welcome, Ideal......good to hear from a fellow trem-hound :)

[@timka880057]

Uncle Doug! good to see you again. I remember this amp. A cousin I used to play music with had one. I played an Aria Pro 2 guitar through it back in the early 80's. It had a nice warm sound to it. I saw this video on my alerts and I was eager to take a look...as usual. Enjoy your videos! Thanks man!

[@UncleDoug]

You're welcome, CT. It's good to hear from you :)

[@timka880057]

@@UncleDoug 😎 🎸🎵 🔊

[@Bbendfender]

Nice work. You turned this little Gibson from "tinny" tone to a solid, satisfying tone.

[@UncleDoug]

Thanks so much, Arch. That was our exact intention :)

[@geemac7267]

Thanks for the great car show footage. I did want to see that Studebaker truck too. Also, the tutorial from schematic to amp innards was helpful, so thanks for that too.

[@UncleDoug]

You're welcome, GM. Lots of viewers liked the Studebaker. Maybe I need to hunt one down for the driveway.

[@bobgausman1127]

Love your videos Uncle Doug. Keep the kitty and hot rod segments coming!!!

[@UncleDoug]

Thanks, Bob. We will :)

[@tomk1tl]

Evert time I watch your videos, I learn another aspect on amplifiers...many thanks for sharing all of this Doug ! KC sounds like my Sylvia when she is hungry, wants more attention or shows her presence in a room ;-))

[@UncleDoug]

You're welcome, Tom. Regards to Sylvia :)

[@UBOOFTB]

A Beauty UD! Keep them coming!

[@UncleDoug]

Thanks, UB. We will :)

[@bassiclogic]

Genius! Very major improvements! The Gibson amp model I played back in the sixty's had a dark low deep bass tone!

[@UncleDoug]

Thanks, Michael. The Gibson you played in the 60's was probably from the late 40's or 50's.....when Gibson amps were as good as any being made in the world. All that changed in the 60's, unfortunately, thus the need for modifications in the circuit of this amp.

[@rowdyyates3801]

Great show UncleDoug . Thanks fer sharin'

[@UncleDoug]

You're welcome, Rowdy.

[@ConspiratorElec]

I have a ‘65 Gibson GA-17rvt. I think he Gibson’s of this era are really underrated. Killer tremolo on my unit. Love the video as always Doug!

[@UncleDoug]

Thanks, Aaron :)

[@bullthrush]

Very clean amp, and a nice sound after the tweaks. Beautiful details on the yellow pickup.

[@UncleDoug]

Thanks, Andrew......glad you liked it :)

[@jonnybeck6723]

Thanx to you my knowledge of amps and their workings steadily improves... and all I hafta do is listen (!) Dyin' ta know what your guitars look like... Always appreciate your auto commentary... what a fabulous bunch 'a sleds. Thanx matey... Zachery sends along a nice loud "hello" (which he's learned to say with frightening clarity) to Jack and Casey. cheers all

[@UncleDoug]

You're welcome, Jonny. In this case, it's my workshop guitar (1980 Vantage V-695 Performer) with humbuckers. Single coils are awful through these old Gibson amps. Regards to Zachery :)

[@michaelogden5958]

For the past few days, I've been considering writing to you to ask for a video demonstrating schematic vs physical layout. This video helps me a lot. Thanks!

[@UncleDoug]

Great minds must think alike, Michael :) I hope it was helpful.

[@jaymichaels5187]

Another great video, Uncle Doug. You improved the sound of that amp like nobody's business. Strange to see a transformer as the phase inverter, see them more on 1930s amps and on some 1960s Japanese made amps and on the 1970s Fender Bronco amp. Good stuff !

[@UncleDoug]

Thanks, Jay. I agree. It is a high-quality, old-fashioned PI method.....that I wish we could see more often.

[@Finom1]

Great educational videos!!!

[@UncleDoug]

Thanks, F1. We try to respond to viewer requests.

[@henryhunter5026]

Your direct comparison between the schematic and the actual circuit layout was a great idea, I always do that sort of thing myself when working on a chassis because, as you found, schematics don’t always match what’s actually there. I’ve only come across the phase inverter transformer idea once before in a guitar amp , that was in a small Fender bass amp that I was fixing . The amp sounded very good after your circuit mods. Love your videos, I’m even beginning to take an interest in hot rods.

[@UncleDoug]

Thanks for your nice comments, Henry. Welcome to our channel and hot rodding :)

[@hpelisr]

Yes, Its always good to see Uncle Doug with a video. I would love to take that red Chevy pick-up for a run, Ha. on the open road.

[@UncleDoug]

Thanks, Hack. So would I :)

[@bradleysmith4409]

Yeah!!! A new Uncle Doug Video!

[@UncleDoug]

Yep. I hope you like it, Brad.

[@bradleysmith4409]

Well done, as per usual! Taking time to walk through the circuit is VERY cool. I'm beginning to actually believe that SOMEDAY I could do some sort of DIY amp hack...THANKS! Great BUNNY roast weekend to you! @@UncleDoug

[@paulcargo4233]

UD, on a side note from old school to new school, take a gander at yesterdays Spacex falcon heavy launch. It is 15 minutes of remarkable high tech. Not only did they launch a satellite but they recovered all 3 boosters, two of which returned to Florida and softly touched down at the center of their targets and the third booster landed on remote controlled drone barge 500 miles off the coast. 90% of the techs and engineers are under the age of 30...

[@UncleDoug]

Thank heavens there are young engineers arriving on the scene to advance our space and science capabilities. I would like to think that my years as a math and science teacher might have contributed somewhat to this fresh pool of creativity. We tend to dismiss the younger generation somewhat unfairly......probably much like old-timers dismissed ours. I am aware of the Spacex achievements and was impressed by the precision of their recovery capabilities.....and the economy provided by reuse of equipment. Leave it to the private sector to dramatically improve upon wasteful government practices.

[@buddyweiser1288]

Tube amps & hotrods, what a great combination!

[@UncleDoug]

I agree, Bud :) Let's toast to both !!

[@buddyweiser1288]

Cheers! This amp inspires me to dig out my '66 Epiphone Comet that is in need of a little TLC on the inside. I'm a Fender guy like yourself, but these old Gibson amps aren't half bad either. Lifting that cap from the bass pot made a world of difference!

[@thijsruis]

Wow, this one is superb! Great!

[@UncleDoug]

Thanks, Thijs :)

[@renegade44040]

Finally someone is showing me the corresponding wires to the schematic!!!

[@UncleDoug]

We listen and respond to our viewers, JJ. Glad you liked it :)

[@alanhoggard4554]

That thing sounds fantastic!

[@UncleDoug]

Thanks, Alan. I was pleased with the outcome also.

[@CoquiAudio]

nice pleasant video Uncle Doug 🎶✌

[@UncleDoug]

Thanks, VM. That is our goal :)

[@outthereassociates7155]

Well done!

[@UncleDoug]

Thanks, Dan :)

[@angryshoebox]

Cool video. At 50:35, reminded me of the John Milner car from American Graffiti. Made me think of that movie, one of my faves. “Milner, you didn’t happen to be around the corner of 12th and G around eight-thirty tonight, did ya?” “Hey, we’ve been talking’ about you.” Yeah?!” “Yeah, there’s a very wicked ‘55 Chevy lookin’ for you.” “Yeah, I know.”

[@UncleDoug]

You may be right, ASB. That would explain the strange stance and rear "fenders". Homage or not......it's definitely not to my taste.

[@jackallen6261]

Yet another great video Uncle Doug! I have a Epiphone Pacemaker amp I picked up off of ebay a little while ago with loudness and Frequency controls only for the trem and volume control. It also has the chicken head on off control knob. two inputs and an on off indicator light. I haven't even put the tubes in it yet. The P.O. said it was an estate sale find but he had no way to test it...we shall see what it turns out to be. Wish me luck!! Thanks for sharing this wonderful amp with us!! Have a blessed day!

[@UncleDoug]

You're welcome, Jack. Best of luck with your Pacemaker......the amp, I mean :)

[@jackallen6261]

@@UncleDoug Thanks UD! I just got around to finishing watching the video and I'm guessing the rear fenders and the stance on the Deuce were an homage to Milner's car in American Graffiti, I could be wrong of course but it is very similar especially considering its the same color.

[@WillyMcCoy50]

Yes those cats can rock! That amp is about the cleanest Gibson of that era I have ever seen. Your rebuild really makes it live up to it's good looks! Dropping the car low really makes those rides look and handle exceptionally. I would always raise them up. I have gone through too many oil pans. Nothing like repairing an oil pan on forty miles of bad road! Used to carry a stick of J.B. Weld gas tank putty in my glove box.

[@UncleDoug]

Thanks so much for all your nice comments, KM. Usually the steering arms hang lower than the oil pan, so when you hit an obstacle, you can lose control of the car......but at least the oil pan is OK ;) Amen on the epoxy putty.....and a can of compressed air with Never-Leak.

[@whocares.20]

Another great video Uncle Doug, love the precise instruction, helps so much in figuring things out on my own project, a Monarch MA-620 amp. Was my first amp I used for my guitar, and now trying to revive it. It has a similar circuit as that bass control, only on the volume, with that 4th pot tap wire, have not really dissected the tone stack and volume setup in depth, but this will surely give some pointers, thanks. May have to report you, to the rehab centers.. they will need a new program, the addicted to Uncle Doug videos ward, ok, come this way... :)

[@UncleDoug]

Thanks so much, Sean. We really hope the video is helpful.....that was definitely our intent. It's nice to present great old amps for examination, but they are also quite suitable for teaching purposes.

[@rodrigog2686]

Thanks for share all the your knowledge and for the excellent explanation, hi from argentina

[@UncleDoug]

You're welcome, Rodrigo. Regards to all our viewers in Argentina :)

[@ThePreyMantas]

Wow! That is a great looking amp & pulling a cap, changing a resistor there on the bass and wallah!, really work very well! Good catch! You are a regular Merlin of amps! :) (bowing down in reverence) Another nice haul from another great viewer, Lewis! and please FEED our little girl! :) You need some sort bins now!

[@UncleDoug]

Thanks, PM. It was a good haul, indeed. The viewers often surprise me with their generosity. Trust me, KC eats about 9 times a day.....and even that isn't enough, if you ask her :)

[@mspysu79]

That little amp was transformed by the modification to the bass circuit, it sounds quite nice now. Some very nice cars and trucks at that show hope there is a part 3 where we get to see that Studebaker in all its glory!

[@UncleDoug]

Thanks so much, M79. I'm not sure if I was able to find it again :( It was a beaut, however !!! Hopefully there will be some more on it.

[@therugburnz]

That model was my first tube amp. A the Paul and a muff fuzz. Kinda sounded cool at one two settings. Not exactly what I thought a Gibson through a Gibson would be but it taught me about muffs and overdriven noise boxes.

[@UncleDoug]

It's a good, basic amp, RB. Thanks for your input.

[@dpatrick5164]

Excellent video Uncle Doug, and what memories looking at that amp brings back. The first amp i ever owned was a Gibson of probably a very close vintage to that one. I bought it used in 1969 for i think $90. It was in good shape so my guess was early to mid 60s version. I don't remember the model #, but if i remember correctly the animal association was a jaguar. I got it so I would be able to hear what the used strat I had located a few months earlier actually sounded like. It was $175, and as you probably recall $265 total was a mid size fortune for a teenager to come up with back then. I think i sacked several mountain loads of groceries after school over the course of a couple of years to be able to swing that purchase. But it was a mega step up from trying to learn on the old bow necked Harmony acoustic i was trying to learn on. Thanks for the memory, and keep the great videos coming. Very informative and (but don't tell the cats) quite entertaining too.

[@UncleDoug]

Thanks so much for all your comments and recollections, DP. I think a lot of us have very similar experiences, which is probably why we gather together around this topic :)

[@kevinwilkins9926]

Great way to bring in the long weekend. Awesome break down of the schematic. Should be of great benefit to those who are getting started to learn this stuff. I wish I had you as a teacher or get teachers to take lessons from you on presenting material. Another excellent video. There is one of those amps close to me for sale and he is asking $325. Looks to quite mint too. Except I think that one has reverb and no tremolo I believe.

[@UncleDoug]

Thanks, Kevin. The smaller amps rarely have reverb. If it does, and it sounds good, it might be worth getting.

[@kevinwilkins9926]

@@UncleDoug it is actually a GA-35 RVT. I remembered wrong.

[@GuitarSmith.]

Watching this excellent video during my lunch break from my home based guitar repair shop. One of our cats (Riley) decide to occupy my lap and just about had a freak out when Casey kitty meowed. Jumped up real fast looking for that strange cat in his house. :)

[@UncleDoug]

Since KC is always begging for food, your kitty may have thought there was a starving cat in your house :)

[@GuitarSmith.]

@@UncleDoug Good job showing people how to follow a circuit from the schematic. Thanks Doug.

[@UncleDoug]

You're welcome, Martin.

[@davidstuckey102]

Well Doug, you have done it again. This is the fourth time you have done an amp just like one in my collection. I got my 1965 ga-5t off the shelf and fired it up after watching. A slight hum which I can't hear with a guitar playing, but there is noise when I bump the front panel. I will work on that later. My amp is just about as tidy as yours except for my very worn handle. That must be tough tolex. Thanks for the inspiration.

[@UncleDoug]

I guess great minds think......and collect.......alike, David :) You may have a microphonic tube or a cold solder joint. Best of luck with it.

[@peterjennings7183]

Love your videos, Uncle Doug! I have learned so much from you. Thanks! It may have been mentioned earlier, but the Fender Musicmaster Bass amp of the '70s is almost an exact copy of this circuit - minus the tremolo and separate bass/treble controls. It also uses a 12AX7 instead of 6EU7, and the power tubes were 6AQ5 - later changed to 6V6. But, when you look at the schematics side by side, there is no doubt that the CBS designers were looking at this amp when laying out the MMB. The Fender amp is kind of lousy as a bass amp, but it can sound quite good with a guitar. I have enjoyed mine:)

[@UncleDoug]

Thanks for your input, Peter.

[@rockabillycat1954]

Used to have one of these mid 60s Gibson GA5Ts, it had a great tone, maybe someone did work to it like you did yours. It had a 3 wire cord, a different power switch, and no pedal. Sold it and a funky 70s Japanese made National semi-hollow with slider controls to make rent years ago.

[@UncleDoug]

I remember painting the wood trim on a 3-story apartment building, without a ladder, to pay my rent back in the good old days. We've all been there, RC. Thanks :)

[@murratosmani6517]

Wow what a beauty!

[@UncleDoug]

Thanks, MO. It's not a tweed Bassman......but it has its own charm :)

[@JuanHoya]

Such an educational video, thanks a bunch. If anything, adding more rectifier diodes in series may better protect such a jewel. Again thanks for the full walkthrough and voicing lesson.

[@UncleDoug]

You're welcome, Juan. Glad you liked it.

[@drsproc]

World class production! Puts cable programming to shame and this is just one guy compared to the hords of knob heads it takes to pump out what passes for tv these days. The amp customization is purrfect engineering. And I luv those paint jobs, chromed power houses, upholsterred interiors, raised asses and fat takkies on those buff hot rods. Ampgasmic!

[@UncleDoug]

Thanks, Doc. Glad you liked it :)

[@tbonebruce]

The speaker looks like an Eminence 1028k; they're a very good speaker, one of my favourites. The earlier blue frame with a paper voice coil former are even better, and were used in the Bassman RI and early Fender Pro Juniors but are no longer available new. Thanks for another informative and entertaining video Uncle Doug.

[@UncleDoug]

That's great news, Bruce. Thanks so much :)

[@dale1956ties]

Just another great video as always Uncle Doug. I'm so jealous at the way you manage to consistently surface with yet another very cool vintage amp. I don't exactly know why but my experience has been that Gibson amps seem to deteriorate faster and in greater numbers than Fenders say, or even many other brands. I was a little surprised to see solid wood for the cabinet material. I was really beginning to believe that the reason Gibson amps seem to go to pot is that they used crap for cabinet materials. Honestly, I've seen a lot of them made out of particle board and worse. That one is easily the cleanest specimen I've ever seen. Thanks for sharing it with us.

[@UncleDoug]

You're welcome, DE, and thanks for your nice comments. I agree that later Gibson amps were hampered by cost-cutting, but (just like Fender amps) during the mid-60's they had not yet succumbed to this unfortunate marketing practice.

[@dale1956ties]

@@UncleDoug Ah...I see. So what seems to have happened in my case is that the maybe 4 or 5 Gibson combos I've crossed paths with just happened to fall into the "made of pressed paper board and Beeman's chewing gum" era.

[@Kris-P343]

Thanks Uncle Doug, I know this has been out for a few years but it came in handy since I picked up one of these in really nice shape recently. I got it for decent price due to one output tube having issues with red plating. I just placed my order from AES and plan on taking your advice on some of the modifications. Best regards!

[@UncleDoug]

I'm glad the video was helpful, Kris.

[@bucyruserie1211]

Hi Uncle Doug & Gang, a great day when a new video arrives from Texas! I have to stop watching to take our dog TT, one of the few remaining Chihuahua's that survived the fleeing from Mexico, braving the mighty Rio Grande, crossing the border, miraculously getting through El Paso while hunted by low riding pickups, t buckets, 30's Fords driven by grey haired men to the Vet.. I am enjoying the schematic breakdown thus far, and will have some questions when I return.. Tom

[@UncleDoug]

I remember that little guy, Tom.......he was too fast for me to catch :) We hope you enjoy the video.

[@allanpennington]

Hi Doug, loved the back and forth comparison between diagram and amp, just brilliant. We have discussed tremolo before, and this trem differs from Fenders. It is similar to an early Vox arrangement where the bias of the output tubes is varied to achieve the trem output. You have concluded that this is not the cleanest way to achieve tremolo as the cathode bias is fighting against the bias change introduced by the changing tremolo signal. On the Vox it enters after the phase inverter tube directly into the grid resister network then onto the grids of the EL84's.

[@UncleDoug]

Thanks so much, Allan. Bias modulating tremolos do work best in grid-biased circuits, for the reason you cited.

[@freepress8451]

A dropping free video, speechless

[@UncleDoug]

I was tempted to soil it myself, Nic......but my wife talked me out of it :)

[@freepress8451]

@@UncleDoug Naughty, I have only watched the first 20 mins and the condition is almost like new with little if any corrosion.

[@UncleDoug]

I know.....what a shame :)

[@rabidpb]

Trivia: this little amp was the heart of the rig in Doc Brown's lab, that Marty blows up at the start of BTTF.

[@UncleDoug]

Really?? I'll have to check out a YT video of that scene. Thanks !!!

[@UncleDoug]

I watched the video and you're right. He does plug into a Gibson GA-5T amp just before blowing up the speaker......and room.

[@danielthomas3057]

Thank you, Uncle Doug, a very good explanation of the schematic and relating it to the physical chassis. I like to know what each tube's function is. Death capacitor should be replaced with an XY rated safety cap. The original cap, although disconnected at one end, should be physically removed so no one in the future will be tempted to reconnect it and possibly shock themselves. As far as vintage vehicles go, it may seem odd, but my favorite car is a 1963 full size Pontiac. My dad had one, a Canadian base model Strato Chief. I always loved the overall look of the 60's Pontiacs regardless what model level they were. US models too.

[@UncleDoug]

You're welcome, Daniel. Thanks for the tips.

[@donaldknee6815]

Thankyou very much for the circuit tracing on the amp it helped me out a lot and showing how to mod the tone circuit that was incredible thanks so much im tring to figure out the mods on a crate 30 club combo its a bit dark and the reverb doesn't work really well if you ever do a hotroded club 30 ill be watching with bated breath thankyou so much for your knowledge and willingness to help my God bless your endeavors and pet the critters for me

[@UncleDoug]

You're welcome, Donald. Best of luck with your project.

[@AMStationEngineer]

I viewed this yesterday morning, and got to thinking, "what would Les Paul do"?? Last night, I remember reading, that while Les and Mary experimented in/with circuits of complexity, he once stated that "simpler can at times, be better", as is this 'Bass-circuitry' modification. Great depth from such a little box!!

[@UncleDoug]

I doubt that Les had much input on the amplifiers, SE, especially this one, but we all agree that "simpler is generally better"........a mantra that Gibson seemed to forget with their amp designs in the mid to late-60's.

[@jutukka]

Nice little amp. Like in case of many other budget amps, no grid stoppers or screen resistors added to the circuit. I would add 1k grid stoppers and 470R-1k screen resistors to output tubes to increase reliability and tube life. The transformer phase splitter is not so often seen in guitar amps. Perhaps that transformer brings some mojo to the sound! I very much enjoyed watching this video, as I always do. Thanks again Uncle Doug. 👍 P.S. It is important to check that the trem intensity pot wiper contact is OK because the output tube grids are connected to ground only through that pot.

[@UncleDoug]

You're welcome, J. We appreciate your helpful and kind comments.

[@paulcargo4233]

Good morning UD, the Gibby now sounds better than 90% of any that I have ever heard. I caught a glimpse of A Z28 that I would have liked to see more of. Finally, back in the world we had a term to describe all the limo tint that apparently is a necessity in your area we called it "probable cause".

[@UncleDoug]

Greetings, PC. Thanks !! Yes, I have a feeling that's why police around here always approach a stopped car from the rear......with weapons drawn.

[@kendavis8046]

Tape residue on a foot switch. If the only "foot-button" you have at a gig, you tend to tape it down. And though gaffer tape leaves less residue, most of us just used "Duck" (Yeah, I know "duct") tape. Thanks as always. You're not my real uncle, but your videos make me wish you were. Thumbs up, and another great day when there is a new video from Uncle Doug!

[@UncleDoug]

You're welcome, Ken. Thanks for the nice comments :)

[@SeanKerns]

I nearly bought a '50 Studebaker pickup two different times. Very cool, and different looking.

[@UncleDoug]

No kidding, Sean. I love the one in the video.

[@BillySoundFarm]

I inherited one of these from my late uncle. With my Les Paul or P90’s, sounds awesome. With my strat strung with pure nickel strings, I can’t get a good sound out of it no matter what I do. If Gibson was trying to make amps that would make Fender guitars sound like garbage under any and all circumstances, it worked.

[@UncleDoug]

Their amps seemed to work well with the (relatively "warm") humbucker pickups found in Gibson guitars......but were awful with most single coils, especially Telecasters. Way too shrill......ugh !!

[@BillySoundFarm]

@@UncleDoug What replacement speaker would you recommend? (I don't like speaker fizz)

[@UncleDoug]

I would think any speaker, i.e. Jensen, which can handle at least 15W of output power, which provides a nice safety margin.@@BillySoundFarm

[@BillySoundFarm]

@@UncleDoug Thanks!

[@dkruitz]

Thanks so much for sharing your knowledge and insights. On the death cap, what was the purpose originally?

[@UncleDoug]

To filter out any noise in the incoming AC supply.

[@TeleCustom72]

Cool amp (and video). Its crazy how Gibson put a 1w resistor in the PI filter. That resistor is badly underrated.

[@UncleDoug]

Thanks, HTH :)

[@TeleCustom72]

@@UncleDoug Have you ever tried changing the mids knob for a push/pull type and using it to lift the tonestack ground connection? Its a rough and ready way to bypass the tonestack, and thereby get a gain boost as you don't get the insertion loss from the tonestack.

[@Corporations8MyBaby]

Great video! Yeah..this series of amps was better for clean jazz playing at volume than was the blackface fender... they never break up. The Deluxe size/type "Minuteman" is MUCH HEAVIER than a 65 Fender though. Very thick construction using MDF instead of solid or plywood. They are really cool. They just need to stay put in your studio.

[@UncleDoug]

Thanks, C8 :)

[@jorgemellooliveira9611]

ótimo domingo mestre um grande abraço Sul do Brasil

[@dhpbear2]

Uncle Doug. What did you use to record the audio for this video?

[@UncleDoug]

I record all audio with my Sony camera stereo microphones, David.