Epiphone Valve Junior rebuilds?

[Yoda]

Has anybody here ripped the guts out of their Epiphone Valve Jr. and put something totally different in it, rather than mod the VJr itself?

[ChopSauce]

Why that question / what do you have in mind?

Possibilities are (almost) endless and you might end with something interesting.

It all depends on what you're after.

[Stevem]

If your learning how to work on amps and or mod them and have one of these you can afford to make mistakes on then the changes are near endless that can be done!

Is this just the head you speak of,or the combo amp?

I like turning the combo amp into a head because you can mount the power transformer on the floor of the amp which makes the amp very fee of 60 HZ noise injection!

[Phil_S]

Well, you can do whatever you want within the limits of the existing transformers. Or, if you discard those, also, then whatever will fit in the chassis. You can enlarge the power tube socket hole and install an octal socket for a 6V6 or 6K6. The possibilities are endless and you don't say what you might have in mind. I suggest your question has been asked and answered elsewhere by people who have a specific interest in using the Epi VJ as a platform.

There is a forum http://www.sewatt.com/forum with a section dedicated to the Epi VJ. I suggest you register so you can read several existing threads that should address your question. http://www.sewatt.com/vj-mods
This is a recent thread that seems to be either very close or exactly your question. http://www.sewatt.com/node/22096

[brewdude]

http://www.wattkins.com/projects/universal-pcb
The Watkins family of forums (includes sewatt.com and peaty.com) has a “Universal PCB” which is designed to fit the EVJ chassis.
There are many amp circuits which have been designed to use with the UPCB.

[ChopSauce]

Not sure the power transformer produces enough voltage for an octal tube...

I wouldn't bother with a new PCB for just two tubes, firstly. Secondly having just two tubes is limiting so I'd be tempted to just tune it to taste.

[brewdude]

The Watkins uPCB is two 9 pin pre/PI tubes and two 8 pin PA tubes.

It would require new iron for many of the amps documented, but the uPCB is designed to utilize the EVJ chassis and cab.

http://www.ppwatt.com/universal-pcb

[Phil_S]

Not sure the power transformer produces enough voltage for an octal tube...

There is enough voltage and current, see below. The Epi VJ uses one EL84 for the power tube. Either a 6V6 or 6K6 would require less current. For that matter, you might consider changing to a 7 pin and use a 6AQ5, and you might consider sneaking in another triode with a 6MB8.

117VAC 50/60Hz primary; 260-0-260v rms @ 90ma; 6.3V @ 3.5A filament secondaries.

[pompeiisneaks]

For one of my buddies, I just swapped out the second gain stages cathode resistor from 1.5k to 1k I believe to give it a bit more gain, and it sounded a ton better in the overdrive sounds. The 1.5 imo made it sound a bit harsh and trebly, but biasing the tube a bit differently gave it a bit more oompf and it sounded way better with that one mod. I'd think quite a few simple component changes like this could do a lot with the Valve Jr.

~Phil

[ChopSauce]

Not sure the power transformer produces enough voltage for an octal tube...

There is enough voltage and current, see below. The Epi VJ uses one EL84 for the power tube. Either a 6V6 or 6K6 would require less current. For that matter, you might consider changing to a 7 pin and use a 6AQ5, and you might consider sneaking in another triode with a 6MB8.

117VAC 50/60Hz primary; 260-0-260v rms @ 90ma; 6.3V @ 3.5A filament secondaries.

By voltage, I was truely meaning voltage, not current. I thought I could read that the 6V6 sounds better with higher voltages.

So maybe the transformer would allow for a second pre-amp tube, and hence much wider possibilities?

[brewdude]

I used the stock PT for a Lite2B—essentially double the tube compliment. It’s probably not within spec, but it still works... in fact, I’m planning on give it a little exercise tonight.

[drew]

valvejrbeast1.jpg

link

[Phil_S]

By voltage, I was truely meaning voltage, not current. I thought I could read that the 6V6 sounds better with higher voltages.

Sorry, I missed your point about tone and its effect due to voltage. Here is a schematic. It says B+ at the power tube is 305VDC. I'd think that is high enough for a 6V6.

[ChopSauce]

By voltage, I was truely meaning voltage, not current. I thought I could read that the 6V6 sounds better with higher voltages.

Sorry, I missed your point about tone and its effect due to voltage. Here is a schematic. It says B+ at the power tube is 305VDC. I'd think that is high enough for a 6V6.

Sorry too. I was taking the silverface champ for reference & didn't noticed that the tweed Champ seems to have lower voltages - at least in its 5E1 version.

So you're right, around 305VDC at the plate of the 6V6 looks good, thanks!

[Yoda]

I guess my original question is very vague and has infinite answers as you guys noted but I started this thread because I picked up a VJr head and a bunch of components off a guy on my local Craigslist and decided to try building my own little amp from scratch so here I did a 5F1 circuit:



This has really helped me learn and visualize what’s going on in the entire amp as a whole versus when I first started learning about this stuff years ago it was very confusing but this has been a fun project.

I know you guys are going to ask how does it sound? Well I don’t know yet because unfortunately I fried the power transformer and when I made a silly mistake that I’m too embarrassed to talk about but as soon as I get a Hammond 269AX I think it should be up and running.

I just think the Valve Junior really has a lot of potential and I see that there are already countless mods on the internet but it seems there are plenty of people who still believe the amp leaves a lot to be desired no matter what so it’s this second group of more ambitious people who I wanted to hear from.