Modifying a 1964 Gibson GA-17RVT Scout

In this video we will look at a super clean example of a vintage 1960s 'Crestline era' Gibson Scout GA17RVT guitar amplifier. We will examine the stock tone with both a Gibson SG and a Fender Telecaster and find out why a lot of people agree these amps are far too thin-sounding, and quite useless with a Fender guitar. Then we will look at a schematic and talk about modifications which can vastly improve the amp. Mods include removing the infamous Sprague tone sucking network and a couple other minor changes. The result is an amp with more balls, more character, more gain and breakup, and a more useful all around tone with both a single coil and humbucker equipped guitar.

[@randallissimo]

I have the same amp in my shop with the exact same complaint, so for me this video is pure gold. I did what you suggested with excellent results. My blues harp playing client is going to love it. I've been doing this for over 30 years, but today I learned something. Thank you.

[@dwightbehm2886]

Hi Guitologist. I know of your amp repair videos. I'v seen some. But I would skip them because you were some what back and forth in your explanations of what you were doing alittle confusing. But in this video you were precise very good and explained things one step at a time much better. Very good. I'll look you up more now. You are a very good Guitar player as well. I hope you are doing well in all. Between you- Uncle Doug- Terry D lab-and Chris the amp tech in Australia you are all very Good. Dwight.

[@francesnieznay6623]

Great you did it again fantastic sounds.brought that amp to life.

[@TheGuitologist]

Thanks. I believe there's more bass we could coax out of it with some other tweaks, but for now, I am convinced the 3 minor mods we did were the most bang for the buck mods you can do on one of these.

[@telecasterman18]

This is a beautiful vintage! I have this exact amp. I also play all Strat’s, Tele’s and other single coil/p90 pickup guitars and it was too trebly. I found that a simple speaker change did the trick. I went with a Weber AlNiCo 10A150P which is a heavy magnet speaker that is a blend of American and British tone. It works very well with this amp!

[@Zelleram55]

Nice job. I like that you went over the schematic and which components( capacitors and resistors ) that should be ok to leave and what ones to change. You seem to know just what to change values to in your conversions to get really nice tones out of all sorts of amps. I'm trying to pick tips on that. Thanks.

[@TheGuitologist]

Thanks for watching. Be sure to subscribe, I have a lot of videos where I do minor mods and explain my reasoning behind them.

[@GuitarWorXFiji]

Fantastic !!! Keeps me watching. Don't forget the trem effect along with the reverb when testing the overdrive next time !! I was looking forward..

[@TheGuitologist]

will do. It sounded great also.

[@ElektroCuration]

I’ve got one of these! Such a fun little amp

[@redfishbum]

Great video, Brad!

[@TheGuitologist]

thanks!

[@ottolohr]

Another nice and informative video. I am enjoying the 1965 Epiphone Zephyr amp that I got from you that had some of the same mods done. With OD pedal gets very very tweedy with stout bottom. Those stock CTS speaker are nice. On the three prong debate; I am not an amp builder/service tech but nearly ever one I have talked with have said the same thing... its your call to go to three prong but its cheaper than replacing transformers. On a safety note the I had seen stars while playing a old 5 watt Champ that had two prong; so from my experience change it to three prong.

[@kaneo67]

wow this is amazing

[@telecasterman18]

Hey @Guitologist, I’m finding that I’d like a bit more bass response out of my amp. I want to start with a simple sprague removal. I simply snipped it out, and the amp is almost non existent.. do I need to reconnect the poles where it was? Thank you for any help!

[@catlord357]

hey!!, im in the process of swapping out a speaker in a ga-17, unfortunately i can’t seem to get the from baffle off. i’ve taken all the screws out that i can see( besides chassis screws) and can’t seem to get the top two screw to come out, wondering if u have any insight on this?

[@michaelwebb4082]

Also I have one of these amps and someone replaced the two prong plug with a three prong but left the death cap. Can I just clip that death cap out or do I have to put something in its place?

[@waynegram8907]

How do you know by looking at the schematic the bypass cap values and the decouple cap values the "Cut off points"? You mention its going to roll off bass or shift the frequencies from left to right depending on the cap value, but how do you know by the cap value if its going to shift the frequencies spectrum from Left ( more bass ) to the Right ( high freq ) ?

[@LordWellfleet]

Any recommendations for the 6AQ5 tubes? Will any do?

[@michaelwebb4082]

Is that an electrolytic you used for the bypass cap?

[@johnnymojo666]

This is amazing, I have the same exact amp. I've had it for about 4 years...As I was watching this, I tried out all of my guitars again, and yeah, I need that mod desperately. I am a bit too amateur to do this myself (especially if there are things called "death caps", then I'll be the one to accidentally catch death) So, realistically in 2020, during this pandemic, what would be the going rate for an amp tech to do this mod? I was thinking I can just save this video and show it to a tech and say, "do this"...anyhooooo, thank you so much for this...this is fantastic

[@mike60510]

It's amazing the difference in tone without the Sprague 102C84 network.

[@TheGuitologist]

Yeah, there's a ton of shaping going on in those things, bleeds off a lot of signal.

[@genekloszewski5484]

good job on Gibson scout, we would build small guitar amps, 1970, ,,old Magnavox stereos, can't beat small tube amps, they clip real nice, gene

[@OFR]

Nice work, and good explanations of this set of changes. Very clear and informative! Hope you can keep on doing these. At the end, the amp sounds a little "splatty" - maybe another type of speaker would soften that, keeping the original for those who want it...

[@TheGuitologist]

I do agree on the speaker. The voice coil is tiny. ...and I could have bled off some highs with a 500pf cap to ground from the plate of the first stage, like you see in a Supro Thunderbolt, for instance, but I chose to keep that signal content so the player can use the tone knob on the guitar to cut highs instead.

[@DeadKoby]

I agree with this technique too... you can bleed off the highs with a knob.... but ya can't add the bass. I'd rather have a guitar amp who's tone stack is "Too much to Too Little" on each knob... meaning there's a medium in there that's just right. That's gonna vary from instrument to instrument.

[@TheGuitologist]

Most of the demo was done with guitar tone knobs maxed. That's out of habit on my part really, but leaving some of those highs in at least gives the player (on an amp with no tone knob) the ability to leave them in or cut them at the guitar's output.

[@mike60510]

Thanks again for making the video about the Gibson GA17RVT. Glad you pointed out the difference between real life (12AX7) and schematic (6EU7) for the V1 tube. It would be bad news for your amp if you decided to plug-in the 6EU7 into the V1 connector since the pin-outs between that tube and the 12AX7 are different. In watching the video, I noticed a similarity between the amp you were working on and the one I have. The schematic for the reverb section shows that pin 8 of the V1 tube has a 1k ohm resistor and a 20 uF cap; however, my amp and from what I can see in your video (at around 32 minutes), the amp you worked also has a value smaller cap. The cap in my amp is a 0.1uF. I discovered this trying to track down some hum and distortion when the reverb circuit is engaged. Like you and Uncle Doug have suggested, I have look at other schematic to see what has been done in the past and as you will probably agree, Gibson seemed to be all over the board with a cap on this leg. Any thoughts to the benefit of removing the 0.1 uF cap and increasing it to a 20 uF as the schematic shows? Thanks again

[@TheGuitologist]

The recent Kalamazoo I serviced had very weak reverb. It ended up coming back to me for that reason. Upping that cap GREATLY increased the reverb output. As for the hum in Gibson reverbs, that one had it also. It was tow issues, one was a reverb pedal wire running too close to high voltage and 6V wires, so I moved that wire up and around away from high voltage and 6V stuff. Helped a lot. And also grounding. The ground schemes for these is HORRIBLE. You'll need to experiment with some different grounds. Trace out all the places where things are grounded to the chassis. The preamp stuff should be grounded to the chassis at a separate spot than the power section, and the reverb should be grounded at its own spot too. Lifting a few grounds and experimenting with gator clips might be helpful. Good luck!

[@mike60510]

Thanks, I'll rewatch those videos.

[@christopherschmitt9924]

TF-8A-P I have the same amp only difference you say the 20th week for your or your clients amp mine says 50 otherwise the same exact numbers God bless and thank you for your post

[@steverish944]

Not sure where your located, (hopefully near ohio?) I sure would like you to perform some upgrades on my 61 Ga18T. Appears you have a awesome collection of Gibson amps!

[@kevoDwebo]

I did exactly this mod to it and it sounded awesome with either my strat or Es-175 until the TF-8A-P Power Transformer was getting Super hot and smells like notebook paper burning, Could that have been something i did wrong or do the Power transformers run their course? Also the reverb when turned on makes a hum and when turned up will go into a continuous feedback. Any thoughts? Or just chunk it in the trash back where i found it and go buy a new Chinese amp....

[@kevoDwebo]

Oh well..

[@Fnortner01]

You beefed that thing right up. I like it. I don't know if purists want to see a vintage amp modded much but I would be happy with the end result here.

[@johnsherwood9260]

you rock thank you

[@TheGuitologist]

No prob. Good luck, and please report back with how it turned out!

[@johnsherwood9260]

Im going to mod myGA17 scout Rvt how did you complet the circut after removing the sprag tone sucker? John S

[@TheGuitologist]

The two legs of the component need to be removed and the connections they were going to need to be connected together. The center leg just goes to ground, so you can either leave it attached inside the amp or clip it out.

[@amdelux1]

The Guitologist s

[@artysanmobile]

The error with V1 is actually in the tube chart rather than the schematic. Clearly this amp operates with 6 volt filaments throughout.

[@meesterprofe007]

I really enjoy seeing and hearing the changes you make in the circuitry to open up the expression in these old low watt Gibson amps......big sound from a small amp😏

[@tobyk_8045]

Did I read 470K plate resistor!?

[@joesimon2018]

Everybody has their own philosophy about modding a vintage amp. Personally I have no problem replacing the power cord with grounded regardless. The amp does sound slightly tinny but they were made for humbucking pickups more. My next course would be to play the amp through a beefier more efficient speaker. If that solves the problem I would go that route before modding anything internal. Save the old speaker and go from there. BTW playing overdriven with the reverb on is a huge sin.

[@TheGuitologist]

I don't agree on the sin part. No such thing. But yes, I should have spent more time demonstrating the reverb with a clean tone at the end.

[@amdelux1]

It's kinda goofy that Gibson would make an amp to sound good with Gibson only guitars doesn't seem to make business sense. I own one of these in clean condition like this one ,some of the tubes are oddball and can be expensive. It's very well built , I wonder how it would sound with an eq pedal to bring some of the treble down.Maybe thats why Fender won the amp wars of the 60s. It's still a beautiful historic and unique amp 👍

[@TheGuitologist]

EQ pedal might be an improvement, but you're really just putting lipstick on a pig doing that. You'd be cutting a lot of highs and that's also cutting a lot of signal and definition from your pickups, not to mention introducing noise. And to top it off, the amp still won't be breaking up.

[@andrewdangelo2466]

Gibson did design their amps to bring out the sounds of a humbucker guitar. These amps are a bit too bright for single coil guitars. Also, the amps at this time were not designed to play on "ten". Both Gibson and Fender never thought that an amp clipping was considered a good sound.

[@douro20]

Three different sources of transformers- that's a bit odd. 549 is Midwest Coil & Transformer. 996 is Grand Coil Winders.

[@yqwgjsg]

Looks like these amps were tuned more for humbucker pickups.

[@Joejoe-nt3gc]

Do you accept repair? How to contact?

[@umajunkcollector]

when something old is mint / like new, I can't open it, keep the tools away, total original. Don

[@TheGuitologist]

I understand that philosophy. It's a judgment call. First though, it had already been serviced before with new power caps, so it wasn't 100% virgin. Second, the amp simply did not produce an acceptable output level for its watt rating. With anything other than a Gibson, it was so thin and uninspiring even a Line 6 Spider would sound better. No point in keeping something stock if you can't stand the sound of it.

[@GtrPknMama]

I have a Scout cabinet w Jensen speaker, but no guts...... anybody have some guts for me?

[@chokkan7]

Just curious...who manufactured the speakers for these? That speaker (and its Gibson sticker) looks just like one I've got in an old Lancer...

[@TheGuitologist]

Can't read the codes under the sticker, but I'm pretty sure this one is a CTS.

[@chokkan7]

Like to mods you implemented...this little jewel rocks out now, but probably sounds better in all ways as well.

[@Foxonian]

I used to have a 1964 Gibson Discoverer amp that was in similar condition. Great amp. Stupidly ended up trading in for a late 60's Gibson solid state amp that was piece of junk.

[@whynotme5926]

Nice job. Give me an S G, A tele,A les paul jr., And a strat And of coarse an old 10 to 30 watt tube amp with some gain and I am in hog heaven.

[@mesasavage]

Nothing about those new filter caps are OK. Floating a bit? FIX THAT SHIT!

[@itspat7285]

Wish I would have seen this before I traded mine, had one just as clean but was way too thin and not loud. Check out my video of it.

[@TheGuitologist]

You know exactly what I mean then. :D

[@itspat7285]

The Guitologist thinking about getting a 2x10 hawk, do they have that same tone sucker in there?

[@TheGuitologist]

Yes. I have one of those right now for sale. It isn't serviced yet, but could be relatively quickly, if interested.

[@itspat7285]

The Guitologist how much you looking for and where are you located?

[@TheGuitologist]

Louisville,KY. I do ship with paypal. $550 plus shipping. It will come fully serviced and with the tone sucking network removed.

[@Bbendfender]

I have one of these and it needs a tech.

[@TheGuitologist]

It deserves an amp spa day.

[@jman1428]

Even a humbucker guitar sounds terrible, with out mods.

[@christopherschmitt9924]

Not p it's an F

[@jman1428]

These amps sound like crap with out these mods.