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Geloso G.221

Posted: Tue Nov 14, 2017 7:30 pm
by Racing
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There was two of them in the bundle right and this is the other one. A model G.221 and truth be told i´ve had half an eye open for one of these for quite a while.
Not that there´s all that much different with them,just wanted to handle one in the flesh so to say. As you can see this 221 sure has seen better days too.

Seller,Diego,is a standup guy tho. Should be said.

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For a few years there in the early/mid -60´s Geloso had this idea to install sorts of an aluminium plate "sticker" ontop. No idea as to why. As it´s a piece of aluminium sheetmetal tho it came right off with a little help from a heat gun. Glues and heat don´t mix all that well see so..

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Yep. Basic,and see that´s the idea of mine with BOTH these amps when done. Have done a few of these Geloso "piccolos" by now and know what to expect so..one channel does it all. "Four doors no waiting",but..FOR a channel OTOH.
No frills,no bullshit. Just simple and balls to the wall tubeamps for rocknroll use.

Difference them between is that the 1020 uses EL-84´s out back and this 221 uses a pair of 6V6´s. Gonna toss yet a few differences at them but..one thing at a time.

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Uhu. See,the socket to the far right is supposed to hold one of them "vibrator" jobbies that convert car DC voltage to AC voltage to run the tubeamp. Well,noone uses that anymore and the vibrator is long gone in turn. No harm no foul as far as i´m concerned.
That style of tube chart to is VERY Geloso.

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After a thorough check i fired the thing up and sure enough. Presto,we had sound. Had to replace a few electrolytics in a kind of hip-hap manner but that done we were all good to go.

Now. As the vibrator is missing this means that i´ve got a winding on the PT that will HAND me AC voltage that isn´t used (stock it is the INPUT from the vibrator).
As it turns out this winding was of approx 18 volts and doing the math that made me end up a tad short as far as negative bias voltage. See,stock these things are cathode biased and...we´re done with that crap already.

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So what i did was a so called voltage doubler. By installing diodes and e-capacitors in a certain manner i use the half periods in such a manner that the net effect is double what i´d normally see.
Whole thing works like a charm which means that i see a tad over 50VDC. Way enough to control the amp in its new setting when the time comes.

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Right. As you saw above this one was about just as bad from a rust POW so...bare to the metal it is. Just as with the 1020 i cut the holes i saw needed before handing the chassis some primer.
Fabbed a block-off plate for the rear facia. Don´t want all them holes that people can stick their fingers into.

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As the vibrator was missing and the chassis in turn is half roomy on the outside i decided to run a couple of JJ cans. Them two there will cater to what i need which leaves for a more sano impression within.

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Uhu. Of COURSE an IEC jack. That and i recessed the voltage selector socket,gonna fab a "lid" for it too. In turn a mains fuse holder of way more contemporary design than the stockers.

Re: Geloso G.221

Posted: Wed Nov 15, 2017 9:16 pm
by Racing
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Sure enough. The 221 got the treatment too.

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Out back,apart from the modern jack n fuseholder,i came to fab a block-off plate as mentioned. Didn´t really melt into the surrounding tho but hey..can´t win ´em all!

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Uhu. Coming together.

Again. I want to boost the quality of these old PA amps. Geloso really IS the real McCoy. No BS. Like in this case,you can grab an old rustbucket and with a minimum of effort turn it into a small screamer.

Re: Geloso G.221

Posted: Wed Nov 15, 2017 10:47 pm
by ajaxlepinski
A bit of paint does wonders! :thu:

Re: Geloso G.221

Posted: Wed Nov 15, 2017 11:26 pm
by jgreenwd
Is that spray enamel paint?

Re: Geloso G.221

Posted: Thu Nov 16, 2017 4:39 am
by Racing
Yep.
Carpaint in a spraybomb

Re: Geloso G.221

Posted: Thu Nov 16, 2017 11:25 am
by jgreenwd
Awesome! Looks great!

Re: Geloso G.221

Posted: Thu Nov 16, 2017 3:29 pm
by Racing
Thanx!

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Started wiring the thing. Goes more into that than most believe i think.
Yep. Even a "discharge" resistor installed,atop the rectifier bridge. Choke is the stocker,just relocated.

Re: Geloso G.221

Posted: Fri Nov 17, 2017 3:49 pm
by Racing
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Yes ma´m. We´ve got liftoff. After a couple of tweaks tossed at the thing i´d say we´re on par. Sounds the part.

Re: Geloso G.221

Posted: Mon Nov 20, 2017 7:28 am
by Racing
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Getting there. Still needs more clearcoat and what´s more i need to adress the bottom plate too.

That said the amp plays great. Going to try yet a few tweaks tossed at it and see where that takes me. All in all though already a really great little rocknroll amp with plenty volume ontap and does what it´s supposed to.

Rocknroll.

Re: Geloso G.221

Posted: Mon Nov 20, 2017 12:31 pm
by ajaxlepinski
Looks awesome! :fap:

Re: Geloso G.221

Posted: Wed Nov 22, 2017 4:33 pm
by Racing
Thx.

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Yeah. These somewhat simpler amps turn out rather tidy within too. Simple enough that someone in the know should have no issues what so ever to get the logic behind what´s what and why.

Re: Geloso G.221

Posted: Wed Nov 29, 2017 6:26 am
by Racing
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Ok. So done deal,this is the net result. Happy? Yeah,happy.
Tossed a highpass filter at the circuit to make the thing more overtone prone as gain increases and i´d say that had exactly the result i was asking for.

These smaller amps,the thing is about on size with a Tiny Terror and weighs a mere 6kg,are real screamers when called upon. Powerwise they come to deliver around the 25watt mark when going balls to the wall and for most that suffices and then some.
Many are those that miscalculate their power needs in my experience.

Why this amp,and it´s soon to be sybling the 1020,comes to life. Simple,rugged,well performing small amps with one intention in mind. Dirty rocknroll.

Again. For those of you out there capable of building yourself...these smaller Gelosos are a no-brainer in my book. Transformers and hardparts in general are from the absolute top shelf.