Hello I'm a new member to this forum and would be appreciative if someone could help me out with my weak output volume on my 1966 Epiphone EA-600RVT Solid State 100 Watt guitar amp. The amp powers on everything works but I get very low output volume from the speakers they are 2 cabs of 2×12 I measured the ohms at just below 16 ohms so I think they're 16 ohms could be wrong though. I have basic electronic skills and can work the multimeter. I read it may be the output transformer, or output transistors, even electrolytic capacitors. Can anyone who has knowledge of this issue give me some insight on what I can do to repair it. Thanks fellow ssguitarist.
Hi billy, welcome to the Forum.
Wow, 1966!!!
A very early amplifier.
Maybe you or somebody else may google the schematic and post it here, so we can suggest some tests.
You might post a couple front and back pictures, plus opening it and showing a couple gut shots.
As of the speaker cabinets, if each of them is 16 ohms so total load is 8 ohms with 2 cabinets plugged, sounds quite reasonable to me.
Photos of Epiphone EA-600RVT Solid State guitar amp head
Anyone have any ideas why my volume is so weak sounding ??
Welcome, Billy. Have you tried checking the volume control? The reason a I ask is because I have experienced a similar problem with an old Sears amp and it turned out to be a very dirty volume control.
I haven't yet but I'm working on it if that don't fix the weak output volume would you suggest any other troubleshooting steps to take??? The amppowers on I get sound but even at ten it is very weak. Also the Reverb knob when I turn it past 2or 3 it start this horrible screeching sort of feedbacking sound. I will check that out as well may be potentiometer as well thanks for you replying to me I've been trying to get info from anyone who has knowledge of these things. I really appreciate it very much!!!!!!
Ok, let us read the schematics and get a mental picture first.
Are those *all* the schematics you have?
Can you use a mutimeter, identify parts on a PCB and read and post values we ask you about?
We'll have to start by putting images the right way (most are upside down ) before even *reading* it.
You will be asked to download a test tone, and make a test cable with an earphone plug in one end, and the other free (hot and ground) , so you can connect said audio test tone from a PC or notebook or MP3 player or Smartphone to different points in the amplifier, so we check whether the levels expect are actually there or not.
I have the whole schematic for this amp, set A which is for Gibson GSS-100 my Epiphone EA-600RVT amps brother , and set B which is my amps schematic. I know set B is my amps schematic because I checked the components on my amp and they matched the schematic and parts list.
I have a 15 range multimeter, I can identify the parts on the amp, take test measurements values and post them back to you on this forum in this topic.
I will post better photos of the amp and schematic.
I can download the test tone and make a earphone jack withe free end being a hot and ground I take it is positive and negative right? Place on different points of the amp and post results. I will do what you tell me so I can fix the amp u sound like you know a very great deal on the subject and I thank you very much. I been tryn to find the problem for a long time .
Just tell me what to do and I'll post the results.
I smacked the power supply PC board moved wires and that got it to produce the volume level i t should rattling the windows and pictures the way a hundred watter should. So it must be a short or need time to warm up the transistors a cold solder joint idk. But I'm glad it sounds loud like it should. It's a rare Epiphone EA-600RVT Solid State guitar amp I've never seen anyone else have this vsame amp they only ran this model from 66' to 67' I'm thinking about a hundred were made from the info I've gathered super rare SS amp. Reverb still needs work tho if I turn it past 2 I get the loud humming screeching noise any ideas guys???
i like the fact that you chose smack the PCB in your beloved very rare 50 year old amplifier, but i know the feeling when you start to think a "Phillips adjustment" is needed.
by the way transistors do not need to warm up, there is a great deal of work in removing the heat from the transistors, ideally they should not produce heat, but they do.
Sounds like you may have a few bad solder joints in there. I can relate to the smacking of the amp as I've done that several times to my Kasino amp. You should probably try to fix those before putting the amp to much use, as it can and will lead to one or more parts failing. Also, what type of reverb tank does your amp have? I've had similar problems with the reverb in my old Sears amp self oscillating and if yours has a similar tank you could try playing with the spring tension a little. Hope you get it sorted.
Smacking an amp is a perfectly valid troubleshooting technique. it exposes loose connections. However it is never intended as a REPAIR technique.
I wasn't suggesting it as a repair technique. I was simply stating what you just said in your last post. My suggestion is that he should find those loose solder joints and fix them before continuing to use his amp.
maybe is just me but to smack something sounds hard, guess i mixed with punch...
I usually go for something like a light pad or lifting the amp a few cm at one end and let it fall... and somethines with the lights out, or low you can see the spark at the loose connection.
Okay, maybe using the word "smack" is making it sound a bit more harsh than was intended. Firstly, I wouldn't advise anyone to do anything that would damage their prized amplifier. Secondly, I would not advise anyone to go banging on an amplifier's internals as it can cause severe damage and electrocution (something I'm sure nobody wants) . I was only referring to hitting the rear panel of my own amp, which only happened because I was very frustrated with it. If it had been a spot that would actually cause any harm to my amp or myself, I wouldn't have smacked the rear panel. I apologize for the misunderstanding this has caused.
Not to worry, I often suggest people "ball up their fist and whack" their amp. If you want to be more official about it, use a rubber mallet - I have a couple of those by my bench too. Certainly it won't hurt the amp. If the amp cannot withstand a good whacking, it will never hold up to transport in the trunk of a car gig to gig.
Fist or mallet, I will hit a complete amp - in the cab - on the top and ends and front and back. If the chassis is on the bench, I will whack the end of the chassis with my palm, no wires there. And of course the rubber mallet can hit the ends of the chassis or the top edges or the transformer or even a flat area between parts.
it is a reasonable way to expose loose connections. Such looseness can be a cracked solder joint, a cracked or broken copper trace, even cracked connections within components. A lead coming loose inside a filter cap for example.
And sure, lifting an amp up a couple inches at one end and letting it drop back to the table top is not really any different from whacking, it just sends a mechanical shock through it a different direction than a mallet. I used to make that a regular part of keyboard service, because aside from loose connections, it also sometimes exposed key contact problems.
I was not accusing anyone of amp abuse, just pointing out to all who read the thread that there is nothing wrong with whacking the amp to find out what is wrong with it. But there are people who honestly think it is OK to just smack an amp to get it running every time, and considers it a fix.
i understand what your getn at. i just want to get 100% again, but for now the amp is workn, i also could of had the speakers wrong series with one cab 2 10s plugged in instead of both cabs 2 10s time 2 paralell may have been a impedence mismatch idk. but i have a good time talkn to everybody bout our gear we use and want to repair etc. i feel like people my age dont care bout rock and jammin making music being a band. its all rap cars and money
Quote from: Enzo on March 16, 2016, 08:29:56 PM
Not to worry, I often suggest people "ball up their fist and whack" their amp. If you want to be more official about it, use a rubber mallet - I have a couple of those by my bench too. Certainly it won't hurt the amp. If the amp cannot withstand a good whacking, it will never hold up to transport in the trunk of a car gig to gig.
Fist or mallet, I will hit a complete amp - in the cab - on the top and ends and front and back. If the chassis is on the bench, I will whack the end of the chassis with my palm, no wires there. And of course the rubber mallet can hit the ends of the chassis or the top edges or the transformer or even a flat area between parts.
it is a reasonable way to expose loose connections. Such looseness can be a cracked solder joint, a cracked or broken copper trace, even cracked connections within components. A lead coming loose inside a filter cap for example.
And sure, lifting an amp up a couple inches at one end and letting it drop back to the table top is not really any different from whacking, it just sends a mechanical shock through it a different direction than a mallet. I used to make that a regular part of keyboard service, because aside from loose connections, it also sometimes exposed key contact problems.
I was not accusing anyone of amp abuse, just pointing out to all who read the thread that there is nothing wrong with whacking the amp to find out what is wrong with it. But there are people who honestly think it is OK to just smack an amp to get it running every time, and considers it a fix.
It seems that sometimes it's easy to misinterpret the meaning of some posts. Thanks, Enzo.
Quote from: Billythekid i feel like people my age dont care bout rock and jammin making music being a band. its all rap cars and money
/quote]
Yes, I have run into the same problems quite a bit. It seems that nobody's wanting to start a band these days. I've met people who will say they want to start a band, but they're usually just all talk.
Oh, and very glad to hear your amp is finally working, Billy! :tu:
I expect your neighbors are really enjoying it, too. Haha
Oh, and my apologies for the way the above post turned out. Not sure what happened there.