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Winston GA-200

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Offline Racing

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Winston GA-200
« am: 12.09.2015 13:10 »




As some of you are aware i have a weakspot for the old Winston amps. Being Echolettes in reality that brings that a Winstons amp is simply a machine that´s been relabeled.

I ran into this piece of kit over "kleinanzeigen" and came to know the seller bit,one thing led to another so..at the moment i´m helping him out with his first "build" of his  own.

But..Winston was on the agenda.
As is clearly visible the stock cab is long gone,for whatever reason,and someone had replaced that with this steel sheetmetal setup. Judging by the pictures i thought to myself that i can always replica the cab of the GA-200 i already got but as the amp touched down with me..that decision wasn´t as clear cut anymore.
What from the pictures looked like a swift job to just cover the amp was in reality not. Someone had done their homework on this one,and the only thing the cab lacks really is a normal sized handle.





What unraveled itself as i unpacked the thing was...a stocker. A rather well preserved stocker. It was all there so to say.
Dirty...but that was about it and old amps being dirty is usually a good thing as that means they´ve been left alone.





Yep. Even the old Telefunken brown base EL-34´s were present.



As stated. That sheetmetal homebrew cab is certainly no hack job. Someone´s done their homework.



´N this is what a Winston GA looks like "under the hood". German engineering for you. What that means in plain text is that the amp per se is the size of a JMP...it´s just that German engineering has been the goal underneath which basically leaves an amp where the components have to friggin SHOUT to each other,they´re that far apart.



Well. This is a vintage amp,no matter how you regard it,and someone HAD been at it. That there hackjob...someone should be ashamed. Solderblobs like that for the amps main smoothing caps is NOT ok.
What´s more them there two electrolytes are hooked in series which means that the one closest with the oranga wiring running for it is what hits ground.
Well. That e-lyte SHOULD have an insulating washer vs the chassis,and thus handing us the option to determin where it should hit chassis ground..which it did not.
In short someone´s been at it that hadn´t taken tubeamp class 101.



What seems to be the part they different Winston amps share,apart from the transformers and EL-34´s,is the main PSU (power supply unit) card. A rather sturdy designed PCB.
However...notice the colour of the fuse holder closest to us. It´s the one for the heaters of the EL-34´s. That dark to the colour is usually not a good thing..

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As we just touched on in another thread these amps are sort of hybrids,then again not. The BA-200,the bass version,is all tube. The PA-200 and the GA-200 however uses transistors for entry stages,the followed by that there in the picture. To the left one of the ECC-808´s and to the right the ECC-82 that runs the onboard tremolo.
The ECC-808´s two triodes are used as independent gainstages for respective channel and the output of those are in turn mixed via a pair of 220k resistors.
Why i mention that these are hybrid amps and then again not is because all we ask the transistors to do for both stages is produce a meek 160mVAC out. In other words not all that much more signal then your guitar will hand you. Just that...we use the amplified signal of the transistor setup to run a tonestack  in  the case of the GA-200.
That why i think that these amps  are hybrids...then again not.



The phaseinverter of the Winston amps is a longtailed pair setup to the standards of what you´ll find in most Fender and Marshall amps out there. In the case of the GA with a twist though as it ends in a rather elaborate presence control.



Ditto for this. All in all 4 100nF coupling caps ,and we need four of them as bias is individually adjustable for each tube. Something they all have in common too.



O tempera,o mores. The old standard DIN jack was replaced by a modern day IEC one. In turnt he empty hole to the right is for a "mains out" jack stock. As i see no  reason what so ever to run anything from this amp...out,for safety reasons.



The IEC jack brings that safety ground needs a solderlug at the chassis of its own. The stock jack had that happen by its metal chassis. Ie; safetyground hits the chassis via the old jacks chassis.
Please also notice that them solderblobs at the main electrolytes are gone...



Well. Something had gone into orbit at some point in this amps life. That much is for sure. The fuseholder for the powertube heaters had certainly seen some action.
I therefore took the solderwick to it and cleaned it out completely,checked that everything was ok and so forth before putting the pieces back.



So. Previous owner told me that "amp hums more then it should". Well...as it turns out this amps ground reference for the powertube heaters was via a wire running for a solderlug attached by one of the rivets for the powertube sockets.
No good if that rivet has come lose.
At the same time the preamp heaters had been handed groundreference in the same manner. So i took to installing a pair of 500 Ohms balance pots,which made for all the difference.
Then...being well aware of the peculiars of the Winston amps i checked integrity of the one of four nuts holding the main PSU to the chassis as the farthest of them is what hands the chassis ground....indeed this nut was nothing more then finger tight. Torqued it down with an "8" metric key and....presto. Amp was now dead silent in idle again.
All that could be heard out of the speakers at wide open throttle was a slight hiss.. :topjob:



As much as the amp seemed intact that there little can was not. It was both ruptured and cracked so..a few dabs of superglue followed by som electricians tape.....
It is the "holder" for the tremolo photoresistor and it´s bulb to activate it. Then it sure helps if the inside of that can is dark..when so called for.



Let it be know. I like my amps clean. Ergo i took some regular windex (window cleaner) and a stiff brush tot he amp followed by large amounts of compressed air.
Clean. Period.



Well. Having set bias and what not i played the amp for a bit and...it was in essence working the full 9 yards. In short it was doing its job.
Now me..i´m not about stock amps so...one thing i knew right off the bat.
A PPIMV install IS to be part of the amp,so took to installing one and thus...i was now able,for the first time,to experience what a GA-200 sound like with all the pots at wide open...just with sane levels of output volume.

TBH? Not all that hot. It WILL distort..it will,but for a god awful distortion it is...


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Re: Winston GA-200
« Antwort #1 am: 12.09.2015 13:16 »
Gave the whole concept some thinking and i arrived on that a "combination amp" was the ticket.

Ie;one that handles guitar really well and in turn handles bass at a rate where bassist at least don´t shy away from it.

At that time i also considered how to handle this from a tech point of view. Gave Tubetowns turretboards a moment...but..nah. Got a few of them stock ceramic soldersupports laying around since previous Winstons so...let´s keep this one all Winston shall we.





So. By rethinking how the stock setup was done i freed that soldersupport installed by me up...and thus we have the materials needed to make this thing go full circle.



The amp was at this  stage well behaved to say the least. No matter..new is new and hence i replaced the resistors of the PI with modern day n era metalfilm ones.
The idea of mine is to put an amp together for pro USE...



Yep. Tremolo is out. Cleaned the entire preamp out and rewired the heaters. Now with way more stringent twist to the heater wiring.
Idea here is simple.
Going to make this thing turn all tube...


...one Winstons GA-200 for modern day n era rocknroll coming up boys!

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Re: Winston GA-200
« Antwort #2 am: 13.09.2015 01:20 »
Nah.
Vorwärts. Immer vorwärts... ;D



Going hardwire has a tendancy to look like a snakepit in heat. Keeping it this "short" though...nah. We´re good. At least in my book. Anyone that opens this amp up eventually and knows a thing or two will know what´s he´s looking at,which is good enough for me.



You live and learn. The transistor preamps has been deleted and kept intact. Been replaced by a couple of pieces of cut to fit aluminium sheet metal.



Amp had been worked on before. That brought that the insulating washer for the last of the two electrolytes in series was missing. Someone had obviously missed out on what it does. So..one was installed...aaaaaaaaaaand....



Headed right here. As stated these amps do NOT comply to "the golden rule" stock,and as we´re to push amplification factor up...like into orbit,it friggin needs to.
Might be that the boys at Klemt thought-"to hell with it"-seing the rather limited amplification factor. I have a hard time seing that they didn´t know what they were doing,and indeed the stock amp is silent as they come in idle.
However..that is with a real limited amount of amplification...and as i´m to turn this into a roaring rocknroll amp..that reasoning simply won´t do. Hence...time to make "the golden rule" apply.

The whole thing works as such that the bridge negative runs for the standby switch. A solution that carries tech merit but..lacks out from a practical point of view as no tech these days gives the mere thought of a negative standby cut a second thought.
What?
Well. What such a setup brings is that IF you cut power via the standby...and then pick the amp apart it is possible that the circuit within still retains hundreds of volts...and you´ll get zapped as you won´t give this a second thought.
Anyways.
From the bridge negative to the standby switch and that switched is "looped" by a 10k ceramic resistor. From there the whole thing runs for the PSU card "stud" that heads the whole thing into the chassis. To act as chassis ground.
Well.
Before it hits that stud there´s a fuse... So what i did was head the grounding of the first in series pair of electrolytes for that point. The "off" side of the fuse.
Mission accomplished.



These two in turn serves the rest of the preamp. The tangs of their grounding washers are tied together,so separated those and ran groundwiring from each stage to the e-lyte that serves it. THEN tied the two e-lytes together,to head for main chassis ground.

Well.
Next up is drilling a hole for yet another noval socket. The socket that´ll form the preamp for the "bass" side of the amp. Rail voltage has already been headed where it needs to be so...a solder support and i´d say we´re in business.

What´s more i plan to implement dual PPIMV´s. These will be controlled by an LDR...as most guitarist ask for a "solo boos"..well,this is it.

In short?
Well gentlemen...to be continued.. ;D