Ran into this one on the Danish "Craig list" (sort of) out of all places. The 3298..220. 220 for it being setup for 220VAC inbound voltage only. Ie;no voltage selector.
Up until recently i had no idea that Geloso was actually imported to Denmark,but i stand to be corrected.
Basically stock. The two axials each side of the x-former is by me. Measured the stock ones and they were shot. I picked this one up DOA. Reason is simple,this one´s odd even for a Geloso see..
It uses 6146 powertubes..run at approx 800VDC
! Rendering that a 3298 puts out inxs of 100watts with ease.
DOA alright. I installed an IEC jack and a panel mount mains fuse first thing. Mainly as the stock mains cord was a phase n zero jobbie...and running sans safetyground is a no-no with ANY tubeamp in my book. Checked various vitals and...well,the one powertube was shot to kingdom come for starters.
Not the end of the world as NOS 6146´s ain´t an arm and a leg. So i ordered a pair over gerry e-bay and done deal.
As i replaced them e-lytes,which there´s three "stairs" of all in all,and fired the thing up sans the preamp and what not...i got a mere 560VDC. That gave me the creeps... Not a shot PT again! Now,please have in mind that this thing stacks two windings for HT.
Well,no fret. It turned out to be a set of shot diodes and done deal. So i in a rather coarse manner installed a set of regular 4A rectifier bridges and let it rip. That made me end up with 880VDC running on that LONE powertube that was still alive. All good and a sigh of relief.
If you look at the print on the farther tube you´ll notice it´s been run hard. Look deeper yet and you see how the plate has been discolored within its "corners". Sure enough,as bias voltage was applied ONLY it took a serious dive as it hit that tube. In short that tube is dead but..i´m just as happy no matter as it turns out the x-formers and choke all are good to go. In short the expensive stuff.
Did i mention it weighs a friggin ton (for a Geloso that is)? It sure as hell wasn´t a cheap alternative when new. That there is the add-on x-former that runs negative bias voltage and the rectified voltage for the preamp heaters. The can in turn is the first one i´ve even seen with the text Geloso on it.
Yep. The plates gets fed from the top. The connectors even sports the Geloso insignia and are of course ceramic
No wonder the thing weighs approx 20kg... That there is a couple of chokes. One for the "lower" HT winding and the other is for the bias setup. Ripple control gents. Ripple control..
Danish importer? Yeah. The stock instructions for speaker out impedance had a sticker..which said the same thing in Danish.
That´s the pair of e-lytes for the lower winding. Dead as doornails. Bin time...
The powertubes sport a minor cathode resistor of 15 Ohms stock. That one was burnt to crap.. The common 15 Ohmer for various reasons i guess (noooooo..the amp is still fixed bias). As i checked the coupling caps between the PI and powertubes they were leaked like crazy so..i guess what has happend is that bias for that one tube was simply first out. Shot screen resistor,burnt cathode resistor and burnt tube. Done deal.
As that took effect it went on into the bias circuitry and thus yelled fire in the hole to the entire rectified heater voltage for the preamp. Hence the looks above.. cause you see...
Entry tube sure as hell wasn´t any better off.
As i now knew that all the transformers were ok i said to hell with it and started cleaning the SOB both out and up. Washing acetone and some elbow grease made all the soot within vanish at least. Soot,if you didn´t know,is imperative to get rid of within an amp as it is conductive.
Have to say that the stock ceramic octals cleaned up real nice! That hookup there tho..no idea why Geloso opted to do it that way (that in the pic is by me tho) as pin 1-4-6 is supposed to be internally connected for the 6146?.
Well. A crapload of work to go before i fire this one up again (read-before the new powertubes show up). Needs to be done tho.
As the amps is as heavy as it is i´m giving thought to that there this time out. Imagine a sort of Marshall JMP look if you wish. Cab is an old transistor one that i scrapped a while back. Amp is rather low profile so..it juuuuuuuuuuuuust fits height wise.