Epiphone Valve Standard - needs help

[Noodler]

Just picked up an Epiphone Valve Standard... and it needs some help! Has a distinct HUM when MV is about 12:00 (kind of like a loud flourescant bulb), somewhat on the muddy side and the tone controls seem to be a bit limited. I was starting to get some help on the 18Watt forum but it closed down today! Figures... anyways, all I have so far is that when I pull V3 the hum goes away. Does anyone have some BASIC mods to get it to sound better? I'm not looking to turn this thing into the Holy Grail of amps... just trying to see if a few tweeks can make it a keeper. I'm just about ready to pack it up and send it back... any help would be appreciated. I attached the schematic for anyone that's interested in taking a look.

[StandardPaul]

I had exactly same mistake.

PCB is designed so that it can be assembled with or without DSP. The main mistake is, that signal wires on PCB are too long. I mean wire from preamp to DSP and wire from master volume potentiometer to end amplifier. High impedance signal wires can not be so open and so long. Real PCB wiring is done not 100% by schematic, what you have in attachment. Some components are not in use and some are additional. Please look carefully, what figures are on your master volume potentiometer. In my amplifier it was 1M and that is bad if DSP is in use. If DSP is in use, master volume potentiometer must be about 30-75k and linear. 1M master volume potentiometer can be used, if signal comes directly from preamp to end stage. Wiring must be done by shortest way.

I made some easy modifications: 1) I broke long signal wires (3 or 4 wires if I remember correctly) on PCB from both sides and replaced them with coaxial cables. 2) I replaced 1M master volume potentiometer to 50k potentiometer. 3) I changed place for some components: example C27 must be mounted closely to V3A, not closely to VR6. Because wire from VR6 to C27 is low impedance and after C27 it is high impedance. High impedance wire is antenna for hum and noises.

These investigations and changes took from me about 5 hours. I really wondered Epiphones quality and PCB design. That is really bad. Minimum you must check/change master volume potentiometer and replace C27 closer to VR6.

After these little modifications is my Epiphone Valve Standard now much better. Sorry my bad English and long story …

[Noodler]

Thanks for the info... really makes me wonder what Epiphone was thinking when they put this on the market (didin't they even turn one of these on?)!

[paddy]

Hi there,

I just had the same problem and this is how iI fixed it.
Firstly,remove the chassis from the cab.With the chassis on the bench,speaker plugged in and
controls facing away,you should see a piece of metallic tape close to the
master volume pot.Hook an alligator clip onto the main star ground and then
touch the other end to the metallic tape.If this cures your problem,you can
solder a wire to the metallic tape and connect a lug to the other and bolt it
down to the star ground.
I hope this works for you,it certainly did for me.

Cheers
Paddy

[mrtravesty]

paddy,
Could you describe where the star ground is located? I have the same hum and thought putting a balanced jj 12ax7 in the v3 position would get rid of the hum as it cleared it when I put one in my Hot Rod Deluxe. The hum still exists and I want to try your fix.
Thanks!,
Brett

[paddy]

Hi Brett,

on the rear of the amp you should see a bolt and nut near the mains input receptacle with a few green wires terminating there.That is the ground point.

Good luck

[mrtravesty]

Paddy,
Thanks again for the info....tried it but it didn't work. I'm gonna be using this amp for stage so I want to run the MV pretty much full out. When I push the gain past 12 o'clock the hum gets progressively louder. Great sounding amp though. I'll still use it out.
Brett

[mrtravesty]

Oh yeah....almost forgot....Celestion Vintage 30 and JJ tubes give it a little more bite

[AlexGold]

hey all I got one of these in a trade...it was ok better than what I traded for it ....
After playing with it for awhile I decided the gain was a little on the not enough side so i opened her up...while upping the gain and tone structure....makes her a real tone monster...way better...(more on that if you are interested later...)...any way I noticed as I removed the board those little fiber washers they used to isolate traces from the screw head fell off as I removed the board...also there is one of the fiber washers that is just sitting on the stand off with no screw through the board to it...make sure you put this one back....also the sta-kon wire connectors that connect the tranny taps and etc..are soldered to the board and are connected to the traces with thermals if you arent carefull when you remove them ( rock them side to side not forward backwards) they will break the pads they are attached to off the board giving a poor or in a worst case scenario no connection at all this can be fixed but its a pain.

making a real playable amp out of her....
C1 and R8 need to be changed to C1 470 MF 50v (or 35v if you do the next change as well) and R8 around 790 to 820 ohms 1/2 watt
I removed the jumper connecting C1 and R8 to pin 8 and added another 470mf 820ohm combination to drive that side of the plate independantly..this way you can vary either side of the tube as much or little as you want by varying the R C combination....
the last one is only if you want to open up the bass a little (or a lot more)...take out C2 and use anything from a .047 to a .1 mf...really booms it up

be carefull i noticed a few cold original solder joints and the wire lengths were a little excessive but wow an AC30 on stearoids when you mod it sweet...add better tubes and a better speaker...now for under 600 bucks these little babies are strong.
side note...I put some old RCA AX7s and some brittish old 60's 6bQ5/EL84 wow!!!!Do these mods or contact me and I will do it for you

Alex
Martian Technologies
exitmusicmusic@aol.com
http//www.myspace.com/exitmusicmusictoexitby

[jar0ahr]

Is the bias on this amp adjustable or is it fixed//self biasing? If fixed, can someone recommend a mod to make it adjustable?

[TheDriller]

Originally Posted by AlexGold

hey all I got one of these in a trade...it was ok better than what I traded for it ....
After playing with it for awhile I decided the gain was a little on the not enough side so i opened her up...while upping the gain and tone structure....makes her a real tone monster...way better...(more on that if you are interested later...)...any way I noticed as I removed the board those little fiber washers they used to isolate traces from the screw head fell off as I removed the board...also there is one of the fiber washers that is just sitting on the stand off with no screw through the board to it...make sure you put this one back....also the sta-kon wire connectors that connect the tranny taps and etc..are soldered to the board and are connected to the traces with thermals if you arent carefull when you remove them ( rock them side to side not forward backwards) they will break the pads they are attached to off the board giving a poor or in a worst case scenario no connection at all this can be fixed but its a pain.

making a real playable amp out of her....
C1 and R8 need to be changed to C1 470 MF 50v (or 35v if you do the next change as well) and R8 around 790 to 820 ohms 1/2 watt
I removed the jumper connecting C1 and R8 to pin 8 and added another 470mf 820ohm combination to drive that side of the plate independantly..this way you can vary either side of the tube as much or little as you want by varying the R C combination....
the last one is only if you want to open up the bass a little (or a lot more)...take out C2 and use anything from a .047 to a .1 mf...really booms it up

be carefull i noticed a few cold original solder joints and the wire lengths were a little excessive but wow an AC30 on stearoids when you mod it sweet...add better tubes and a better speaker...now for under 600 bucks these little babies are strong.
side note...I put some old RCA AX7s and some brittish old 60's 6bQ5/EL84 wow!!!!Do these mods or contact me and I will do it for you

Alex
Martian Technologies
exitmusicmusic@aol.com
http//www.myspace.com/exitmusicmusictoexitby

dude, you seem to know your stuff,
i want to ask, is this amp basically an AC15?
i ask because there is an even cheaper by Harley Benton which is a clone of this Valve Standard and im thinking of using that as a basis for building an Orange Tiny Terror clone, seeing as the Tiny Terror is basically an AC15 with an extra gain stage it would work out well.

[jsevy]

I have a valve standard which needs a replacement power transformer, any ideas where to get parts?