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TWANG

el34 vj

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Hey Twang,

 

That's real pretty amp there... Check in from time to time but haven't posted for a while as my Gil inspired Voxy/Marshall caps on a switch mod has been serving me well, several full on band shows, recording an album with some old college buddies and hanging well tonewise with the St. Louis and Victoria amps that the other cats at the dad jam... but fate has is bringing another stock head into my hot little hands any day now and I'm thinking of doing the octal EL34 and and wondering if you did this mod with a stock board or if you've attempted it - would love not to spend the add. money for a new pcb or turret but don't want to end up killing the guts I can use by trying something that's not gonna work out... any help, as always, would be appreciated..

 

Thanks!

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You can do it to the stock board. Or rather, OFF the stock board. ;) Gotta mount the new socket to the side and run jumpers to it is all. You could always just do that to the amp you've got, and do a BabyWill or 5E3 pcb conversion to the new one. Use most any Heyboer 18watt OT for either one and you'll have those Victoria players drooling like crazy!

 

Gil...

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If you check turretboards marshall board.. and swap the values to m theorys. ta da!

so since that can be done on a stock board.. so can this.

except you have to run the tube hole off to the side..

I'm going with the Weber OT since I have one..

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Heyboer huh? Is this the OT of choice now over the Hammond? Well I just got the head and it's a V2 with 7.5 OT so that's gonna have to go - really psyched about the octal but need to do more research to figure out what I'm doing - meanwhile I'm already looking at what I have left form the last 2 mods....hmmm a mallory .022 and a mallory .01 for C1 and C2 maybe... a couple 4.7uf electrolytic caps for C3 n 4 and a mess of resistors - not quite the marshall thing I think I'm after but it might be enough get me into toneland while I start shopping for the tranny and stuff so why not have some fun : )

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I'm going with the Weber OT since I have one..

 

Is that the WSE15 or 25 TWANG?

 

I noticed the prices are a bit cheaper on the webers - anybody getting big tone dif between the Heyoer, Weber and Hammond?

I feel like the Edcor I used on my 1st mod may have been a bit less improvement than is hyped for some of the others...

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WSE15.. M theory uses one and gets good results.. I've got a hammond12ese I've been saving for something.. but a Weber onhand, too.

I tried the WSE15 and it seems to me to be very close to the 125ESE so.. nice price great sound..

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Ok' date=' from left to right across the board:

 

* I went w/the UFs for diodes, but I can't imagine it would possibly matter either way.

R11 = 220k

C6 and C9 = 47uf/450v

C7 and C8 = 22uf/450v

C11 = .1 (this looks like Mallory)

R10 = jumper

R12 = 1k/5 watt

 

___________

THIS BIT:

R13 = 1k/2 watt (might as well use 5w here, too)

 

KEN has 15K 2W there...seems quite a jump but I'm assuming this is a spot you tweaked for a little more stuff!

_______________

 

* Resistor from red wire on rail to pin #4 of el34 = 1k/5watt

C5 = 100uf/100v (experiment with uf rating here, but there's no reason for 1000uf, and 25v is pretty marginal on v rating)

R14 = 220R/5w

R5 = 470k (it looks like I used 1/2w here)

R15 = 1.5k/.5w

 

____________

 

THIS BIT:

 

* resistors from ground to pins 2 and 7 = 100r/5w

 

5w? I had 1W in.. ?

____________

 

C1 and C2 = .01 (sozo)

R3/R4/R7 = 100k/.5w

R2 = 10k/.5w

R1 = 1m/.5w

R8/R9 = 1.5k/.5w

C4 = 3.3uf/63v

C3 = 22uf/63v

 

 

The reason I ended up increasing the wattage ratings of the resistor to pins 2, 4, and 7 on the octal socket is because I had slightly smaller rated resistors in there before, and they went up in smoke with a KT77 tube. Bear in mind that the values that I have on this amp were only tested with an EL34 output tube. I'd caution about using a KT77, frankly, although I will admit that it sounded VERY nice for about a month, until it literally smoked those resistors.

 

Build it with these values for an EL34, match it with a single 12" Celestion g12h, and it'll breathe fire. VERY touch responsive, VERY gainy, bold, aggressive, and impressive. I continually get rave compliments on this amp, every Sunday night at the jam. [/quote']

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Well I found out that I should have 5W resistors there.. because they both just fried.

 

I have these as from pins to ground...

 

I thought my problem was the tube, so checked around and improved a couple solder joints, etc..

and left 'em in.

lasted about ten minutes.

 

TWANG

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I have to look up the weber details.. but I know there are three wires.. B+ and plate.. and different ohms. so

whatever it is.. 5K I assume since I have the WSE15 in my el84.. and 7K?

 

point is.. which is better for the EL34.

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well... no response on the ot ohms..??

 

I put in the Weber after running a ground to pin one as gil suggested.

now it wont work.

 

can't be the ot.. maybe I smushed something.

 

ordered the MPS020 OT to compare to the Weber .. when I get it working.

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el34.. was working fine.

put in weber ot.

wired ok.. just like my other..

*but it's el84 so.. that difference*

 

325 325 312 to 304 at pin 4

 

but.

now.

ax7

pin 1 164.2

pin 3 2.37

pin 6 129.7 and no pop.

pin 8 1.3

 

el34

pin 1 160

pin 2 2.36

pin 6 161.9

pin 8 1.8

 

I think I've got my notes wrong on which pins on the el34

 

but what the heck happened to my signal?

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still no pop when testing with meter.

I can't figure out what the heck is wrong.

 

I took out the gain pot.

I took out the R9 crunch switch.

I pulled the tone vol and went over them and reinstalled..

 

the only time I get any sound at all out of it is when I dime the volume.. then turn up the tone..

I get a real high pitched but not very loud squeal.

 

I guess I'll pull the tone off, and try another pot for the volume.

 

If that fails, I'll pull the Weber out and put the old OT back in. but it's brand new WSE15. and wired in correctly.

 

I went over everything. it's all solid.. besides.. it was sounding very nice with the tiny stock OT.

 

The only thing that changed was connecting pin 1 El34 to ground.. which I now have as per the layout connected to pin 8.

I don't think that's a problem though.

And yes, I swapped out both tubes.. and all four were new ones.

 

The only other thing I can think of... maybe some solder dropped to the chassis through an eyelet somewhere in the pre or input section.

So.. may as well pull the board off and check that, too.

 

so near

and yet so Twang.

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I don't mind at all that you guys get a laugh..

and I'd rather have you laughing than doing the usual internet stuff.

This amp worked beauty.. with a couple of mistakes!

Then got a new OT and it wont work. and there's no clue I can find so far.

I notice nobody's exactly jumping in with any clue of theirs either.

 

I still average ok. usually one out of three gives me some kind of fit.

Like a perfectly working modded green board I have right now..

and the tone pot wont do a thing, no effect whatsoever.

too bad, too I wanted to put up a pic.

 

TWANG

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I went back in tonight a bit.

and I still can't figure the signal loss.

I was getting 224mv at pin 6 preamp which is the highest I've seen.

otherwise it's typical test results.

 

I reflowed solder.

can't find anyplace where anything could be running to ground.

 

can the center tap resisitors be run to a pin, cathode, instead of to ground on this?

just asking.

 

would this do the job

http://cgi.ebay.com/AMPLIFIER-RADIO-SIGNAL-TRACER-INJECTOR-REPAIR-K7000-KIT-/350350557544?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item5192854168

 

seems a lot easier than any directions or schematics I've found considering shipping and parts not a bad price I guess.

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the preamp heaters. pins 4/5 give me a continuity beep to ground.

they dont on the other amp.

so did I fry a tranny?

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it gives me 320 at pin 6 and you push on it a bit and it gives 217

but still no noise.

I chasing gremlins again.

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What's pin 6 got to do with pins 4/5? If pins 4/5 are shorting to ground, you've got to find that, don't you?

 

Also, something is making the voltage change when you "push on" pin 6, right? Obviously, you're causing some sort of shorted path there when you push down. Bad socket? Is this something that you rescued from some other project, by any chance?

 

Hard to say what the culprit will ulitmately be, but I'd definitely be looking very closely at that socket, and in particular pins 4, 5, and 6. Most certainly, 4 and 5 shouldn't be shorted to ground. Those two pins should be tied to pins 4/5 on the octal socket, and those should have transformer leads connected to them. Check your continuity from pin 4 of the 12ax7 to pin 4 of the EL34, and then do the same for pin 5 to pin 5. You've got a short there somewhere.

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yep. it was just an odd thing I thought I'd mention.

it's a new socket. ceramic.

 

I don't like them. The others never give me a problem with stability, but the ceramics are hard to seat solid everytime.

That is, they tend to move just a little, about half the time, after installed.

I don't know.. maybe it's the metal on the frame that's too thin or something.

 

Anyway, yeah I'm gonna have to pull the socket I think as that just isn't right.

 

I had to put the peavey on the bench but the el34 will be back today.

thanks

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