Guitar Gear Forum

Quite a bit of Mr Handyman this time out but...i mainly bought this one for the transformers. Vortexion is an old British brand that was highly reknown for their studio stuff. Very much like the German made Klein&Hummel.
This though..came to strike me as an earlier piece...
Radiomuseum claims these as "1950 ? "...and i for one would state that..and then some. That atop it is a portable tube amp. Ie;it could be run off of a 12V car battery via a so called vibrator.



Uhu. Usable output impedances even with todays standards,which of course made my decision simpler. TBH i was clear on the need for a chassis swap already from the start so..



I by NO means claim to be any sorts of expert on this but..i´ve had my mittens into an old tuber or two by now and..the parts this one´s made of simply weren´t used in the -50s to my knowledge. Hence i believe these to be just a tad older. Old wax capacitors and what not...



That´s the entire preamp. The bypass caps for the cathode resistors are of the variety that bolts to the chassis. Odd to be sure..



Reeeeight. Mr Handyman. So.
These bricks are supposed to sport a pair of 5881´s in push/pull right. Then it´s of no use that Mr Handyman shoved a 6V6 in there is it. All of the capacitors were shot and..Mr Handyman had solved that by replacing the first hit one with one of 350VDC voltage capacity. Seing that the PT hands us approx 370VAC between tap and chassis...yeah well...



Primary taps are easy to swap atop the endbell of the PT.



As you can gather the transformers of this thing are on the hefty side. OT on top,a choke of 20H in the middle and the PT ...out of pic.



A 6J7 and a 6C5 makes for the entire preamp and this heads into an interstage transformer as PI.



The vibrator in turn...yeeeeeees...that´s what they´re called. A Motorola one no less.



Wiring is dry rotted and/or chafed it isn´t even funny. Like an old Italian made Binson approx.

Well,i got the thing going in as much that i could determin that the transformer and choke were still in the game. For the better i guess.



Couldn´t contain myself so i took to making the thing come alive in its most crude form on the bench. Didn´t sound worth a damn but..it was alive at least.
The 20H choke? What´s up with that?
Well,back in the day several manufacturers opted to sport a choke between the hightension centertap and chassis ground to minimize ripple. I´ve hotroded several Gelosos so equipped for instance,where the setup works rather well.
In this case tho...nah. Just nah. DC resistance of that thing is like 1000 Ohms so just..HELL no.



All said and done ALL of the wiring was dryrotted and needed replacing. Down to the bundles coming off the various transformers.



Right. No words needed.



Endbell got a tad of paint and the voltage selector i picked apart and cleaned.



Yes i´m a nerd and yes i´m a moron. It´s just that i find it kind of neat keeping at least a few things of the stocker. Ergo them octal sockets have been completely picked apart and cleaned,retensioned and are now ready for business as usual again.



Now we´re getting an idea where this is headed i guess. That smaller "transformer" there is a different choke i opted to use of 5H. Way more appropriate for the task as being installed inline with the voltage rail.



The wiring for the OT. As it turned out it had become damaged to the point where the one wire off of the one side of the OT had come lose. Not the end of the world tho.



Uhu. Added saver diodes for the rectifier tube,taps for a bias board..fuseholders...IEC jack...you know the drill by now.

As of right now i have no idea what to make out of this one. Time will tell i guess.

Bit by bit gents. Important thing here isn´t that all that much gets done at the drop of a hat but more so that something happens every day.



Yep. The outside of the chassis is getting crowded alright. For better for worse. The OT came out just fine by the way,having all of its usable taps replaced with fresh wires too.



Right. Preamp and at least parts of the PI. Have since elongated the board a bit to take all what´s needed. Yes,there´s components in there to take a tube powered loop as well,yep..a noval has been added.

The entire heater winding setup is...a tad different. Stock this thing is to be run off of a 12 volt car battery,too. That brings that there´s a couple of heavy duty windings on the PT that really isn´t used for anything that hands me approx 8VAC a pop. Stock these are wired in series.



A ceramic highpower resistor each and..ta-da! We´ve got us 6,3VAC on the money. Nevermind the "zero" wire of the PT,that´s just put there temporarily.



As a matter of fact the entire thing is coming together. Yeah. I like fuses. For a good reason . Now for a biasboard and firing this thing up. Off to pick up spares in an hr or so...so...

As is though i´m giving thought to replacing the 5881/6L6´s with regular EL-34´s. Partly as i think it´d fit the amps character better and partly as i´ve got a crapload of them laying around.

Pots. Pots are good,we need pots.



High n low jack. All good.



For better for worse them amps of mine are starting to look a bit crowded. Comes with the territory i guess. Sure enough,this one´s up and running again.



Now for the looks of it. Dunno about that ATM...considering selling it as a "done" chassis to someone that knows his way around a scroll saw. Mainly as..homefront of mine went belly up as one of my two closest friends died saturday. There´s simply more important things to handle ATM.



Uhu. Them irons there are most likely late -40s British made ones. Rather cool after all... B+ is all in @420VDC with a GZ-34 rectifier in place. Not all that bad after all.



That in turn then the 6L6´s and the GZ rectifier.

It needs a bit of tweaking though and has me stomped ATM. Power simply isn´t there as it should be. Don´t get me wrong,it´s loud alright...just that it should be even more so.
Have looked into it and something is loading the PI it isn´t sane. As i run the thing sans the capacitors outbound of the PPIMV i see like 85VAC...as i let them capacitors hit the wiring heading for g1 of the powertubes i see 40VAC. In other words a swing (positive wave) of approx 20 volts..and that simply doesn´t suffice.
At the moment i have no idea why.

Well. Figured it out. Issue was that signal amplitude took a serious dive as soon as i hooked the phaseinverter to the powertubes. As it turned out it was a matter of a faulty PI tube.

That said this thing is roaring along happily ever after. Power is about on par and..it´s doing what it does like it was going out of style.

Giving thought to asking a friend to be in charge of that powersaw to fab a cab for it. We´ll see where it all ends up.

Amazing! Love your build threads!

Thanx.

Idea of mine with these threads is to turn the drama queen and black arts of it off so to say. Heraton thread for instance,i´m all to happy to answer any questions that might arise if i´m able to.

With any luck..one or two guitarist might turn a little wiser *LOL*

All said and done it got a home of its own...and that there cab has a just as interesting story in a way...

Clad in fake croc skin..it is the cab of an old so called "Yugo Marshall".
Say wut?
Well. Back in the day,back in the early -70´s,people heard artists like Hendrix and what not on for instance radio free Europe..
They found out that Marshall was the hot thing,but such couldn´t very well be had behind the infamous iron curtain.
So down in former Yugoslavia they made their own Plexi rip-offs. In a manner.. I´ve had a few of these through the shop and have scrapped them all as they in a word are friggin lethal. Moronic DIY builds of the time.
Be that as it may the cabs still hold up and..that above is a cab of one of these Yugo Marshalls.
They where often Plexi copies meaning that they sported plexi face and rear plates too...and i believe i´ve got a few pictures of one somewhere where they tried a bit farther... At the rear it states "Marchall"...

These builds surface from time to time for instance on German e-bay and what not. From the outside they might look like...close enough but no cigar,while on the inside they´re anything but. Stay away is the best advice i can muster on the subject.

Anyways.
A build based on old Vortexion -xformers finished off with a Yugoslavian cab. That´s history for ya,right there.

Excellent work dude!

F n' A AWESOME!!!


Noob question.... You mentioned a temporary "zero" wire on the PT... what's that all about? Is it a temporary ground for testing?

Thanx guys!

Ah. Yes. The "zero" wire simply goes to the PT´s core. Nothing more involved than that. IOW it is perfectly fine to leave it out wish be.
Various older PT´s sport them. Dynacord ones come to mind for instance.

Very nice. I wish I could find the time to build at the moment

Thanx.
I hear ya. ATM i´m knee deep in preparing for northern Europes largest guitar fair coming up...