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Geloso G.221

Discussion in 'Ampage Area' started by Racing, Dec 7, 2017.

  1. Racing

    Racing Synchromatic

    520
    Aug 30, 2014
    Sweden
    [​IMG]

    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 bull****. 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.
     
    G DynaTron likes this.
  2. Racing

    Racing Synchromatic

    520
    Aug 30, 2014
    Sweden
    [​IMG]

    Sure enough. The 221 got the treatment too.

    [​IMG]

    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.
     
    G DynaTron likes this.
  3. Racing

    Racing Synchromatic

    520
    Aug 30, 2014
    Sweden
    [​IMG]

    [​IMG]

    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.
     
  4. Racing

    Racing Synchromatic

    520
    Aug 30, 2014
    Sweden
    [​IMG]

    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.
     
    G DynaTron likes this.
  5. Racing

    Racing Synchromatic

    520
    Aug 30, 2014
    Sweden
    [​IMG]

    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.
     
    G DynaTron likes this.
  6. Racing

    Racing Synchromatic

    520
    Aug 30, 2014
    Sweden
    [​IMG]

    For the sake of argument. This is the finished amp within (sans the two wires heading for the pilot light). Clean,tidy and to the point. I bet a hobbyist could figure this out need be.

    Two 6V6´s at approx 370VDC and then a pair of small signal tubes,just used way different then in the 5E9 in case. Thus,more tailored vs rocknroll (read-distortion) at will.
    Way smaller too. This little amp weighs in at a mere 6kg or so. Ergo an amp so small that it can tag along anywhere by it´s carrying handle to come.
     
    G DynaTron likes this.
  7. Racing

    Racing Synchromatic

    520
    Aug 30, 2014
    Sweden
    [​IMG]

    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.
     
    G DynaTron likes this.
  8. thunder58

    thunder58 Gretschified

    Age:
    59
    Dec 23, 2010
    tappan ny
    you have the coolest stuff
     
  9. Racing

    Racing Synchromatic

    520
    Aug 30, 2014
    Sweden