Members CountGrishnackh Posted August 15, 2009 Members Share Posted August 15, 2009 Got it in this little shop while visiting my aunt this weekend. Talked him down to 250. Speaker seems to date at '63, so one of the earlier ones. Powers up fine, sounds pretty good, pots are real scratchy though. Not the cleanest, but certainly very good condition for it's age. Got some real oddball tubes. Now, I'm looking for a little more info on it, but getting bounced around on the sites with the info. 14-17 watts? What the hell does that mean? Anyone got any info on the amp? I got it for a rockabilly recording amp, which I think will suit it fine. NICE tremolo. Now, i've only played it maybe 15 minutes since i've bought it due to the coming and going of noise, dirty pots and vague burning smell. Reverb seems iffy, turn the knob a bit here and get a nice strong reverb then it dissipates. Could be because it's got a layer of dust all over and whatnot. I pulled a tube out and it said "made in the USA", so i'm guessing it must have the original or next to original tubes in it, can't think of the last time they made tubes in the US. Bottom line, I like the amp, think it will work, but don't want to go frying anything. This would be the first true vintage amp i've used. Should I just open the sucker up, hit it all with contact cleaner, retube and see where she stands from there? I know I'm kinda all over the place in this post, but any advice would be great. Link to comment Share on other sites More sharing options...
Members imgooley Posted August 15, 2009 Members Share Posted August 15, 2009 You got pics of it? I've not been able to play any old Epi's, but if they're anything like Gibson amps, I'd probably like them. Link to comment Share on other sites More sharing options...
Members CountGrishnackh Posted August 16, 2009 Author Members Share Posted August 16, 2009 Howdy neighbor. I'm in Colfax. I'll get a pic of it up soon. I realized that it has a grill cloth over the original grill cloth, it's a gold cloth, looks boss. Shined up the plate today, still a pretty clean amp. It's exactly like a gibson apparently. Made in Kalamazoo. Believe this model is the exact same as a GA-17 scout, at least I read that somewhere online. I'd like someone to clarify why there were two brands if they are the same amp. Sounds incredible, but I only have it turned on for a few minutes at a time due to the faint burning smell and those scratchy pots. I think it needs new tubes, hope that's the extent of it. I'm this close to opening it up and spraying it down with contact cleaner, I just want a little more info before I do so. Link to comment Share on other sites More sharing options...
Members CountGrishnackh Posted August 16, 2009 Author Members Share Posted August 16, 2009 Found the amp on some amp bluebook thing, "Wattage output unknown". Classic. HA! Link to comment Share on other sites More sharing options...
Members guitarcapo Posted August 16, 2009 Members Share Posted August 16, 2009 here's a schematic link (pdf... sorry) It seems to utilize two power tubes in push/pull. A very weird 6AQ5 I'm hearing this described as a "7 pin minature version of a 6V6" The following spec sheet confirms this Here's a spec sheet on the tube I would guess that the power output would be around 15 watts if that was the case...similar to a Princeton Reverb's output? BTW I would highly recommend sending that sucker to an amp tech for an overhaul. If you fry out the transformer you would be seriously {censored}ed finding a replacement. It most certainly needs new filter caps by now. The reverb is tube driven so the preamp tubes are probably why it's coming and going. You think they might need replacing after 40+ years? You can find replacements for sale on the internet Ebay etc...surprisingly cheap sometimes. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted August 16, 2009 Members Share Posted August 16, 2009 The 6AQ5 is a very sweet sounding little tube. They put out around 4 watts in class A - probably double that for a push-pull, but not certain. I have an old Takt amp with 2x6AV6's [a 12AX7 is 2x6AV6's in a single bottle] and 6AR5 I swapped out for the 6AQ5. Not much to the amp but it sounds great. I found a guy in Florida that will make a 6AQ5 to 6V6 adapter, which is next on my list to try. Get some contact cleaner for the pots and replace the caps and you should be golden. Burning smell usually comes from dirt that's accumulated on the tubes that burns off when they heat up. A good cleaning should take care of it. Link to comment Share on other sites More sharing options...
Members guitarcapo Posted August 17, 2009 Members Share Posted August 17, 2009 I don't know how to read a spec sheet but the one I posted did say that within it's maximum ratings it matched the performance of a 6V6GT...so I figured it could in theory be as high as the 22 watts that a Deluxe Reverb puts out...since it uses two 6V6 tubes in push/pull....but probably more like a Princeton Reverb would seem more likely because of the preamp tubes being different and the transformers being less beefy...I guess it's impossible to know exactly unless an electrical engineer is on here and can tell from the schematic...i dunno. Link to comment Share on other sites More sharing options...
Members CountGrishnackh Posted August 17, 2009 Author Members Share Posted August 17, 2009 Well I played with her a bit tonight, one sweet, sweet sounding amp, and I know it could sound better, so i'm pretty ecstatic about it. Pretty damn touch responsive. Got a real nice surf tone with one of my strats. I dimed the sucker and it wasn't overly loud. It would be loud enough for a controlled drummer, but certainly mic'd live. A good studio amp. Putting a OCD in front of it really changed things. Thanks for the advice and the schematic. I find myself wanting to do the work on it myself, but I know the amp tech is the correct answer. My electronic knowledge is not very large, even after two classes (of course that was years back in high school). When I mess with the reverb knob while playing, I get a slap back echo effect for a second or two. Found a guy on ebay selling full sets of NOS/high life tubes for the amp for $89, which seems reasonable. Also, what is this push pull business? Link to comment Share on other sites More sharing options...
Members Verne Andru Posted August 17, 2009 Members Share Posted August 17, 2009 Also, what is this push pull business?Analog output is in the form of an oscillating sine wave - a Class A [single tube] handles amplification on both positive and negative parts of the cycle. A Push-Pull design [and I realize this is an over generalization but for the sake of simplicity] one tube handles the positive and the other the negative parts of the wave. Link to comment Share on other sites More sharing options...
Members guitarcapo Posted August 18, 2009 Members Share Posted August 18, 2009 Push/pull means that one tube is powering half of the wave form and the other tube is powering the lower half of the waveform. Basically it's a way to wring more power and headroom out of the power tubes. Some people classify push/pull as the opposite of class A but that isn't always true. A general rule of thumb is that you can double the maximum output of the tubes when the design is push/pull and that's the output of the amp. So it sounds like your amp has a pair of roughly 5 watt tubes in push/pull generating 10 watts of power. And yea you are getting hosed on those replacement tubes If your amp hums when you turn it on, you can probably fix that with new filter caps. They're the bigger capacitors in the amp. They dry up and fail after decades. A typical symptom would be a hum at 60 hz heard through the amp when you turn it on. Here's that GE spec sheet again...it's weird how they say it's equal to a 6V6 and then at the bottom say it peaks at 10 watts in class A...you can get 22 watts out of a pair of 6V6 in class A Link to comment Share on other sites More sharing options...
Members CountGrishnackh Posted August 18, 2009 Author Members Share Posted August 18, 2009 Hey, thanks again for all the great info. Yeah, 10 watts sounds just about right. I'll go with that link for the tubes. And yeah, it does have some hum issues. It also has some ground issue somewhere, it hummed bad when I put my foot on the reverb switch, but then went away. I emailed a guy in Sacramento who does amp work for an estimate on a recap and bias, pending other issues it may have. A new speaker probably wouldn't be out of the question either. Thanks again for the help guys. Link to comment Share on other sites More sharing options...
Members guitarcapo Posted August 18, 2009 Members Share Posted August 18, 2009 Does it have a 3 prong grounded power cord? If not you might have the tech do that while he's doing the recap. Replacing pots and tubes would probably be a simple job too. I usually keep the original speaker in a safe place if you ever want to sell the amp. It seems to add value even if it sounds worse. just pull out the new speaker and keep it.... and install the old one when you want to sell the amp. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted August 18, 2009 Members Share Posted August 18, 2009 Yeah, those old amps usually have 2-prong plugs. A good way to test if grounding is an issue is to take your hands off the guitar - if there's noise/hum, touch something on the amp that makes contact with the chassis [a screw, face-plate, etc.] and see if that has the same effect as touching the strings. If you go to a 3-prong, consider getting a 3-prong plug put in the amp then use a cable like the ones used for computers and monitors. The reason for this is that I've found quite a few places that don't have properly grounded outlets and if the wiring is reversed, you'll find the hum/noise is even worse. With a 2 prong I can just flip the plug, which reverses the polarity. Can't do that with a 3-pronger. But with a jack, you can easily have a couple of cables wired to different polarities. There will be a level of hum regardless of what you do. But replacing the old caps should clean up the sound considerably. Many of the old Jap amps used oil caps that go bad with time and should be replaced. There are probably not more than a couple dozen caps in the whole amp so get them all replaced and be done with it. I echo GC on the speaker. It probably came with a pretty sweet alnico speaker that adds quite a bit to the tone. You can easily add an extension speaker jack [with a switch to turn off the internal speaker] and run it to a different cab. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted August 18, 2009 Members Share Posted August 18, 2009 Pictures? Link to comment Share on other sites More sharing options...
Members blackwaterdan Posted December 11, 2013 Members Share Posted December 11, 2013 One of these Epiphone EA-33RVT ' s showed up at my place. My brother found it at a garage sale. This thing must have been in storage. Not a scratch on it. Had a nasty hum. Got rid of most of it after cleaning but not all. Found 3 bad tubes. The 6CA4 rectifier (short), Both 6AQ5 power tubes, one doa the other very weak. New tubes ordered. Pre-amps test good ! Does anyone know what ohm speaker this is ? Nothing stamped on it. Are the filter caps the two very large one's ?dob Link to comment Share on other sites More sharing options...
Members Mr.scary96 Posted December 14, 2013 Members Share Posted December 14, 2013 Though its not the exact era your Epi was built its from the same decade and made in Kalamazoo like yours likely was built. A 66 Gibson GA-15RVT that at the moment will need a recap and possibly a power transformer.http://s1331.photobucket.com/user/Mrguitarman96/media/Mobile%20Uploads/image_zpsed662427.jpg.html?sort=3&o=1 Link to comment Share on other sites More sharing options...
Members Mr.scary96 Posted January 28, 2014 Members Share Posted January 28, 2014 I don't know but how much did that cost you in the end? As my amp could use the recap and the 3 prong plug. Link to comment Share on other sites More sharing options...
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