# Epi Valve Junior Amps



## MarkM (May 23, 2019)

Over the summer I picked up two Epi VJ's, one off KIjiji that sounded crappy and another off a fine member here at a reasonable price with a Bit-Mo kit ready to install. I have bought a couple pair of JJ' for these amps and installed them last night. I will have to build a head cabinet as well.

I have them set up ready to test with my COVID cabinet build , haven't plugged anything in yet because I kinda over served myself last night and thought better than to play with exposed power.

One has a fuse and the holder is fubared , is it critical to have a fuse in this amp?


















I know you guys are thinking that's so 10 years ago and a simple undertaking, for me this is a big step for!


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## greco (Jul 15, 2007)

Personally, I would not want to omit the fuse.
Rather than an inline style fuse holder, you might want to consider this panel mount style...


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## Lincoln (Jun 2, 2008)

I agree with @greco , I don't think it would advisable to run a tube amp without a fuse. Picture of the messed up fuse holder maybe? There are a few different types. I can't remember where the fuse holder is on a Valve Jr.


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## BlueRocker (Jan 5, 2020)

A fuse is $0.79 well spent.


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## Guitar101 (Jan 19, 2011)

This cover song Hurts So Good was recorded circa 2010 by our band Rockin Horse at my place using an Epiphone Valve Jr and a 12" speaker cab played by GC's own Gene Machine. Gene also sang the song. I was pretty impressed with the sound and bought my own Valve Jr and built a 12 in speaker cab. The girl in the pic is my Grand Daughter Abbey with our dog Sally who had just been swimming in the pond.


__
https://soundcloud.com/guitar101-1%2Fhurtssogood


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## Latole (Aug 11, 2020)

"is it critical to have a fuse in this amp?"
-MarkM

Fuse is a must in any amp.


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## Budda (May 29, 2007)

If you want some fun, plug one into a 412 and dime it.


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## MarkM (May 23, 2019)

Well I fired these up yesterday, both worked good out of the gates. The one with the fuse sounded a little better so I cranked it to 11 and was having some fun and it cut out and the EL84 looked like it was on fire and that was the end of it! Fuse is not blown but the amp doesn't work anymore. Of course it's the one mounted in the head cabinet so I didn't have time to pull it apart to look inside. That was a brand new tube that Fried!


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## Latole (Aug 11, 2020)

"....and it cut out and the EL84 looked like it was on fire and that was the end of it! "
-MarkM

Amp' EL84 need right bias. Bias is a way to hot ; El84 red plating .
Check 220 ohms resistor at V2

Schematic here : 



http://mercurymagnetics.com/images/pdf/schematics/wiring/E-VJ-schem1a.pdf


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## Latole (Aug 11, 2020)

Rad here too : 

R14 Cathode Resistor
C5 Cathode Capacitor
The cathode resistor for the power tube interacts with the plate voltage to set the bias of the tube. The stock 220R is a little low, which means the tube is biased too hot. Higher values for R14 result in colder bias. This resistor should be replaced with a 250R or 270R 2W resistor to bias the tube more reasonably, which improves its tone and increases its life.

All here ; https://ashbass.com/AshBassGuitar/vjr/vj_kit_inst.pdf


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## MarkM (May 23, 2019)

Appreciate that advise, I will get assistance from my electrical buddy . I learnt my lessons about stored energy playing with big power in Asphalt plants when I shouldn't have been in there. Ah to be young and invincible again!


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## MarkM (May 23, 2019)

Lincoln said:


> I agree with @greco , I don't think it would advisable to run a tube amp without a fuse. Picture of the messed up fuse holder maybe? There are a few different types. I can't remember where the fuse holder is on a Valve Jr.


















Here is a picture with and without


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## Lincoln (Jun 2, 2008)

Are there fuses or a fuse on the circuit board?


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## greco (Jul 15, 2007)

Is that an ( somwhat/partially) uncovered solder joint? YIKES!


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## MarkM (May 23, 2019)

Why yes it is!

I am not sur I follow you Lincoln?


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## Lincoln (Jun 2, 2008)

MarkM said:


> I am not sur I follow you Lincoln?


Don't mind me, I'm just struggling with the lack of a visible fuse or fuse holder on that one amp.


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## Guitar101 (Jan 19, 2011)

Here a pic of mine. Pretty sure mine's original.


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## MarkM (May 23, 2019)

greco said:


> Personally, I would not want to omit the fuse.
> Rather than an inline style fuse holder, you might want to consider this panel mount style...
> 
> View attachment 332378


I like this setup,mi will be going this way.


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## MarkM (May 23, 2019)

Latole said:


> Rad here too :
> 
> R14 Cathode Resistor
> C5 Cathode Capacitor
> ...


Hi Latole
I thought it would be easy to source these resistors and capacitor. I would imagine that there is different quality and I would rather spend a couple more bucks for better quality. Where do you get your parts from?


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## MarkM (May 23, 2019)

Latole said:


> Rad here too :
> 
> R14 Cathode Resistor
> C5 Cathode Capacitor
> ...


@Latole thanks for this, @Lincoln was good enough to send me this resistor and I soldered my first circuit board successfully!

Works great now, I will be doing this to the other amp as well. That resistor was black and smelled burnt.

Cheers!


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## MarkM (May 23, 2019)

greco said:


> Personally, I would not want to omit the fuse.
> Rather than an inline style fuse holder, you might want to consider this panel mount style...
> 
> View attachment 332378


@greco I took your advise and put this in both amps.


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## Lincoln (Jun 2, 2008)

very nice.


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## cboutilier (Jan 12, 2016)

Budda said:


> If you want some fun, plug one into a 412 and dime it.


Can confirm. 100% valid.

I've played a lot of bar/pub gigs with my 1x12 halfstack VJr.


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## MarkM (May 23, 2019)

I do have an old Marshall half stack that I will play these through. I have a Bit-mo trio mod kit I want to install when I get up the courage to take a project like that on.


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## MarkM (May 23, 2019)

Does anyone have a picture of the Bit-mo mod installed in the amp? I can find the outside but not how the mod ties into the amp. I checked with Bruce the guy that put it together and he said he didn't have anymore than the instructions.


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## MarkM (May 23, 2019)

Well I finally got around to finishing these up, both have the resistor that @Latole suggested change and one has a Bitmo kit that @Lincoln provided me. I was pretty excited when it worked after the Bitmo was installed, my first amp mod ever.

















Now this should provide incentive to complete the head and speaker cabinets I started six months ago maybe.


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## Tone Chaser (Mar 2, 2014)

I have an V1 combo version of this amp. The circuit looks untouched, original. There can be a lot of hum at idle. You don’t hear it while playing. I have read the update versions got quieter as versions progressed. I also read that upgrades or mods might quiet things down.

I mostly use the amp as a head, powering a 16 ohm Traynor DH 112 cab, with a Phaez 4:16 Brink attenuator for 75% dB reduction. The Brink is very useful, effective, with all of my 4 ohm out amps, and the 16 ohm cab. It retains the tone, and is still loud enough with the amp dimed. The hum is virtually gone at idle when using the Brink attenuator.

I was considering trying some mods to correct the hum, up until I determined that it isn’t an issue when using the Brink with the 16 ohm cab.

While researching mods, I came across many pictures of fuse holders off of the transformer. My V1 unit doesn’t have extra fuse holders or fuses that I can identify. The only fuse is the one where the power cord plugs into the back of the cab. That fuse is well camouflaged and hidden. The V1 amps have limited info for modding. The majority of modders, prefer V3, which seems to have a lot of documentation and support. If I want a little more zing, any of a host of fuzz, drive, distortion, or EQ pedals, tastefully applied, do a super job of tailoring tone, increasing volume.

Am I missing something? What are all these extra fuse holders for? Some of the amps have multiple fuse holders coming from the transformer.


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## MarkM (May 23, 2019)

These V3 fuse holders were external and I replaced them so I could access them easily from the back. One didn't have a working fuse holder and the other was cut out. It is not in the plug.

Hum was not bad in either amp and still isn't. I am looking forward to playing the Bitmo dimed into my Marshall 4x12. I have a gaggle of dirt pedals to drive it as well.


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## Latole (Aug 11, 2020)

Tone Chaser said:


> I have an V1 combo version of this amp. The circuit looks untouched, original. There can be a lot of hum at idle. You don’t hear it while playing. I have read the update versions got quieter as versions progressed.


Hum issue;  hum listening test must be done with nothing plug to the amp
Single end amps may have some hum, more than push-pull amps.
Check if 12AX7 is noisy
Check filter caps
Check rectifier diode D1 to D4
Check R10 and R11values and ground
Check AC cable to ground, both end and you wall outlet


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## jb welder (Sep 14, 2010)

One thing to keep in mind is that a single-ended power stage does not have the hum-cancelling feature like a push-pull power stage.
So the single ended type tends to hum more (Champ's have the same issue).
You can help reduce it by beefing up the supply filtering (PI filter or choke) but it is a design issue.
In a way it is like comparing single-coils to humbuckers.


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## MarkM (May 23, 2019)

@ jb welder, what the hey is pull push power?


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## jb welder (Sep 14, 2010)

MarkM said:


> @ jb welder, what the hey is pull push power?


Briefly, it's the most common set-up when you have more than one power tube. Usually class AB, whereas a 'single-ended' uses one power tube and is class A. Class AB is much more efficient and gives much greater output power.
Push-pull is just a way of describing the action of the 2 power tubes working in opposite phase into an output transformer. Because they are opposite phase they tend to cancel out hum, similar to humbucking pickups.


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## Paul Running (Apr 12, 2020)

Like sawing wood with a two man bucksaw.


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## MarkM (May 23, 2019)

Well I have one now working perfectly fine that I might try to mod, anyone had anything to do with the Billy Gibbons mod? I never have been able to quit while I'm ahead!


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