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Epiphone EA-600RVT Solid State amp weak output volume problem

Started by Billythekid, March 13, 2016, 02:15:01 PM

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Billythekid

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.

J M Fahey

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.

Billythekid

Photos of Epiphone EA-600RVT Solid State guitar amp head

Billythekid

Anyone have any ideas why my volume is so weak sounding ??

LJN

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.
If it sounds good, USE IT!

Epiphone Les Paul, Kasino U100- P, Sears 125-XL

Billythekid

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!!!!!!

J M Fahey

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.

Billythekid

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.

Billythekid

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???

Vitrolin

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.

LJN

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.
If it sounds good, USE IT!

Epiphone Les Paul, Kasino U100- P, Sears 125-XL

Enzo

Smacking an amp is a perfectly valid troubleshooting technique.  it exposes loose connections.  However it is never intended as a REPAIR technique.

LJN

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.
If it sounds good, USE IT!

Epiphone Les Paul, Kasino U100- P, Sears 125-XL

Vitrolin

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.

LJN

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.
If it sounds good, USE IT!

Epiphone Les Paul, Kasino U100- P, Sears 125-XL