epiphone valve junior, jr? build help....pls.

[dizmaloner]

hello all, im new to the board, and of course im here because i seek the divine wisdom of the sages here.

 

I recently acquired a "marshallized" board for an epiphone valve junior, i already had a power transformer and output transformer from an old roberts (akai) 770 reel to reel, i feel like a rookie all of the sudden. i have rewired and modified many tube preamps and such (generally with much frustration and cussing) but have never wired a board. so im lost. i have 260v running to t1/t2, 6.3 running to t5/t6, and output transformer to t3/t4. im getting no tube warming at all, i wired the power switch in the middle of the line run from outlet to transformer and it shocked the #$%@ out of me (stupid me) and i dont have the proper connectors to hook up my volume pot or my 1/4" jack..

i hate modern tech... someone who is familiar please help. i need to know where hot/cold go on 260v and 6.3v and where you recommend placing my power switch and any other help would be appreciated as well

[Cheeks]

I kinda don't understand what you're saying but:

 

The power switch should go on the MAINS side... so it turns off

the PRIMARY SIDE of the transformer.

 

IF you wired it anywhere else, only part of the circuit would

be switched off and the rest still in the ON position when the

unit is plugged into the mains (120VAC/USA).

 

Now, listen to this...

 

INSTALL A FUSE in that same PRIMARY SIDE of that transformer.

 

If you don't, and you get a short somewhere downstream in the

circuit, or a capacitor shorts out... you will probably FRY

(burnout as in a OPEN secondary winding) the transformer

on the secondary sides of that transformer.

PUT A FUSE in there. Even if a factory unit comes

WITHOUT a fuse, be smart and install one on the PRI SIDE

of that xmfr. Not to mention, the fuse could PREVENT A FIRE

from starting should a part go ape on you...

 

CHEEKS

[Eracer_Team]

been a while since I worked on my VJ... The points you reference are terminals on the pcb built by epiphone..

 

here is the layout for VJ in Rev2b wiring.. some values have changed but the circuit is close.

 

Make sure your heaters are 6.3VDC.. A/C heater wiring requires a slightly different wiring.

Can't say I ever measured the voltage on T1/T2 (probably have but don't remember) but you need at least 330vdc at the R10-C6 junction too

I know the schematic shows 340vdc at R10/c9 but that's too high there.. really need about 320 max at that location

 

[fuse]

I have to say, I am confused as to what problems you are having, and also by some of your terms. The power switch is about the most basic connection in the amp. If you do not know how to properly install that, you may want to reconsider this project.

As for the 260 and 6.3 taps on the PT secondary....again, I am confused with your terminology. There is no HOT or COLD on that side of the PT. It is all hot. If I misunderstand your questions, no problem, my fault. But again, if you are under the impression there is a "cold" side of the PT secondary, you may want to reconsider this.

It is a pretty simple circuit. Do you understand the schematic that has been posted?

[dizmaloner]

Sorry about all of the confusion. This is my first board build. I always wire from point to point. I was taking instructions from the person who I bought the board from, who was born apparently half retarded. He said to connect 250 and ground to T1 and T2 which caused most of my problems. Also, I have a center tapped transformer which confused him even further thus throwing me off even further. The power switch problem was because I did not have the center tapped transformer grounded properly per his instructions. I have since gotten the amp working, but now would like to unmod/mod the board to get cleaner tones and add a tone pot and change the output wattage. Can anyone point me in the right direction of mods that may fit those criteria? Thanks in advance.

[fuse]

Sorry about all of the confusion. This is my first board build. I always wire from point to point. I was taking instructions from the person who I bought the board from, who was born apparently half retarded. He said to connect 250 and ground to T1 and T2 which caused most of my problems. Also, I have a center tapped transformer which confused him even further thus throwing me off even further. The power switch problem was because I did not have the center tapped transformer grounded properly per his instructions. I have since gotten the amp working, but now would like to unmod/mod the board to get cleaner tones and add a tone pot and change the output wattage. Can anyone point me in the right direction of mods that may fit those criteria? Thanks in advance.

 

I guess the first thing I would do is make sure you are running numbers that are close to the schematic on this page. I would try to get your amp as close to stock as possible. I would not worry about a tone pot right at the moment. Just see if you can get your Valve Jr. working "properly".

I do not have a whole lot of experience with these amps, but a OT from Hammond makes for a big improvement. Their 125CSE is all you need. An efficient speaker will also aid you in your quest. Make sure you have enough filtering in the B+. Play around with some of the coupling cap values to make sure you are not getting too much bass response and "mud". Make sure your heaters have a decent CT or (sometimes even better) a virtual CT via a pair of 100 ohm resistors. I guess what I am suggesting, is to make sure you have all the basics done right. Before you start "modding", make sure your amp is working "correctly" and quietly....to the best of your ability is all anybody can ask.

Good Luck