Geloso G1.1110-A

[Andresound]

Also need to find a easier method of posting pics.

[Racing]

It is very common for old electrolytic capacitors to drift in value.
More the rule than anything if you ask me.

For shit n giggles try opening of of them oldies up. Use a cutter in your dremel and cut away at one end of it. Point here being that i believe it´d be educational to you to physically see how an electrolytic is put together.
There´s another point to it though and that is that most likely that old thing will be dried up. Ie;no fluid coming out of it as you cut it apart.
This is where most folk,techs,bum out. They measure and measure and fail to take not only the values to heart but more so simple logic. That the fluid within evaporates out of there over time,no matter how good a seal,is just plain logic.
The one brand that stands out as far as keeping together is Swedish Rifa. They cost accordingly... I´ve measured such e-lytes that date to the 60´s that still measured like new. Impressive! Rifa though IS what stands out. Rest of them,not so much.

Ergo.
We make good use of ESR meters and what not for REASONABLY "in doubt" capacitors. However,bare in mind that an e-lyte used on a regular basis can very well be used up within 5 yrs. Then do the math for an e-lyte 50yrs old.
In short it is simply bad practice to not have them replaced when going the full 9 yrds. Or...to be blunt it´s just plain folly. None the less it can always be a good lesson to have them measured. If nothing else to get a grip of HOW used up they are.

Be aware that size wise a LOT has happend as far as e-lytes since the late 60´s. When possible i find it convenient to replace mounted within axials with modern "can" e-lytes which are very often twin such in a given package. JJ high voltage ones comes to mind. Also Be aware that these can be mounted within. Often to the shortside walls of the chassis.

In turn,when so called for,making an "e-lyte" area within the chassis is certainly also doable. Just use common tag/solder strips for this.

I´ll be happy to assist best i can.
Yeah. The Dukane is one of my later circuits that even i find to perform well ,and that´s saying something. Be aware tho that that circuit takes the use of a tube or two.

[Andresound]

Thank you for the info. I will definitely do an autopsy on the e-lytes . BTW, it turns out, I have the series 2 version. The one with the extra circuitry feeding the 503 grids. What’s up with that? Some sort of solid state cathode follower?

[Racing]

You´re on the right track with the BC type transistors.
In a way it´s an attempt of a more reactive type gridleak really,and thereby freq response, and i presume the idea was to improve bass response.

If i were you i´d just scrap the entire system. Mainly as it has signal running through the transistors and seing this will be a guitar or bass amp,or a combination of the two,i have no idea how them transistors will take to distorted and/or increased signal. Might very well be way over the top destroying the transistors all said and done.
Nor do i really see the point of them,seing how well a regular/normal regulated and adjustable setup works. Resetting that there into a more conventional setup,preferably with with one trimpot per pair,will make for a less sensitive and just as well working setup. I´ll be happy to assist you doing so.

On that note if i were you i´d also replace them 503´s with regular EL-36´s. That quartett of EL-503´s will fetch a premium at any international ebay site and should be able to sponsor the entire project for you. An educated guesstemate would be around the 200 Euro mark and up easy.
EL-36´s are a dime a dozen and available everywhere. The 36´s will come out making the same power as the 503´s in this application,no doubt. You just need a set of ceramic top nipple sockets to pull it off (ebay),and of course replace the magnoval tube sockets with regular octal such (ebay). Certainly doable all of it and the only thing you need to keep in mind is that the 36 is an older design that needs more swing for full saturation than the 503. No biggie as you alter the bias setup anyways and thus are free to let amplitude out of the phaseinverter be what it needs to.

[Andresound]

Hi Racing,
I will first get this baby going, just to get a handle on the sound before doing a conversion as suggested. Just replacing the e-lytics at present. Will post pics and maybe a clip. Will be an interesting exercise. I am not in a hurry, so this should be a good learning curve.

[Racing]

In that case be wary and fire the thing up sans the powertubes.
Don´t recall which pin is g1 (control grid where the negative bias voltage is applied) for the EL-503 at the top of my head,but physically check to see that there´s negative voltage DC on said pin. (read-download data sheet and check)
If not,power down and take it from there.

As these transistors see signal it might be a good idea to check the integrity of them in this manner before trusting the setup seing the age of the thing.

As far as the sound out of it,don´t expect all that to much. The later era (read-last) Gelosos were more mainstream from that aspect than their earlier,and way earlier,brothers.
Compare for instance a 211 vs a 1020 in behavior in stock form. Like night and day for guitar use. Also be prepared that output power might not be what you expect with a guitar signal. Power´s there to be had though,trust me...

[Andresound]

Will do. Will bring up slowly with a variac and bulb limiter. Thinking about it, I will also remove the “transistor” shit off the grid.

[Racing]

That "transistor shit" needs to be there if you´re to run the thing in stock form first.
You HAVE to have negative control grid voltage or the powertubes will self destruct.

[Andresound]

Even if I wire it as per the series one? I have that schematic as well, which excludes the “transistor shit”. Otherwise the schematic is almost identical, with the exception of slightly lower filtering.

[Racing]

Nope.
It was you that said that you were gonna run it as is. Ie;as a series 2.

[Andresound]

Thanks racing. So to be clear.. it will be ok with series one wiring? Don’t want to f&$?!*% it up. I will make sure there is a negative bias, without tubes, before trying a set .

[Andresound]

https://www.dropbox.com/s/c37eukci1whqy ... 1.jpg?dl=0
This is the schem. I will up the smoothing as shown. The amp I have, had 250uf as the first filter value. I am replacing with 1x 100uf/100uf can cap (JJ) in parallel (for first filter), and the another can cap feeding the next two stages with 100 and 100uf each. The last stage, I have replaced with a 22uf, because I didn’t have a 16uf on hand. All the bias e-lytes, were replaced with 1000uf/50v as in the original series 2.

[Racing]

Yes.
It will certainly be ok with series 1 wiring. As noted,just make sure you´ve got negative bias voltage present at all 4 powertube sockets.

That said.
Filtering.
Now. Be adviced that a guitar amp is an abnormality, What we´re basically trying to do is get midrange out of a topend circuit through bass speakers. Yes,it is THAT f-d up.
Seing that general assumptions as far as various "amplifier standards and truths" go out the friggin door. To make a guitar amp sound like a guitar amp,as we know them,takes a completely insane approach really.

One would think that a filtering designed to just about create a "flat line" deviation (ripple) is a good thing but not so. Due to the inherents of a push/pull amp we see phase cancelling to the degree where several volts of ripple within the B+ line basically amounts to nothing from a sonic perspective. Ie;what´s heard out the speakers.

So what DOES it all boil down to when it comes to picking capacitance values for filtering then,when we´re talking guitar amps that is.? In a word,behavior. Less capacitance makes for a more "pick prone" and alive amp,but at the same time an amp that will change face depending on load and what not to a MUCH greater extent.
An amp with greater amounts of capacitance?
Well,that turns into a stiffer amp that won´t budge to the same degree when leaned upon among other behavior features. Look a schematic up for a REALLY old amp and you´ll notice that it can for instance survive with a mere 8uF for the first two hits. Not uncommon at all. Lesson learned is that back in the really old days they had to suffice with what could be had why them old designs can teach us a LOT when it comes to design,to this day.

Alright?
So what´s the optimum capacitance then? Well,the correct answer to that is...none of the above. Picking "first hits" for capacitance is mainly a matter of two things.
Thought use/genre, and in turn taste.

There´s a fallacy going around that promotes the idea of that a larger amount of capacitance is what´s needed to make a push/pull amp more silent,as far as ills that is.
This is simply not true and the fact of the matter is that a mere few uF will suffice making said amp behave. Yes,when you know what you´re doing design wise a few mere uF will cope. Design the amp according to the book/rules and that will be net effect. Deviate the slightest..and you´re off and dead in the water.

So?
Why DO we opt for various/given amounts of capacitance then? Well,see above. A nu-metal amp for instance we WANT to be stiff upper lip. We WANT it to be almost insanely tight no matter what we throw at it. Distortion we set via the preamp and the powerstage is basically along for the ride and we anticipate it standing up to no matter what.
The other end of the spectre that would be a downright nightmare amp for the 18w blues guitarist amp. In short this is a matter of approach and should as such be considered.

Me,i guess i´m on the "less might be better" shelf here. I rarely hand the amps i build more than 50uF+50uF for the first hits,and this as what i MAINLY do is rokknroll amps. To my TASTE there´s no need for more filtering for the first two stages that control the plates and screens of the powertubes. None what so ever even,and when applicable supported by a 4-6H choke. (As a choke has an impact on ripple as well)
Be adviced though that i throw yet another trick or two at the powerstage when at it. Ie;behavior i get out of my amps is not only a matter of filtering capacitance.

200uF and up? Well,then you´re into numetal territory in my book. I even frown a tad at the Marshalls using 100uF for first hit,and this simply as i see no need as long as the amp is well designed and true to the world in general.

Further up the preamp in turn..take your pick. I normally end up using 22uF-47uF depending on which stage and application. When it comes to preamp design though take the following to heart if you want to be old school. Never load a given node with more than two gainstages. There´s good reasons for this and there´s designs out there that violate this in a MAJOR way and get away with it. The ones that really DO get away with it are few and long apart however.
There´s a ton of half assed factory designs out there,you can take that to the bank,they can still be worth a look from an educational point of view none the less.

[Racing]

Footnote.
What is said above holds true for push/pull configuration amps for guitar use.
Single end amps don´t have the "advantage" of the push/pull principle and thus completely lack phase cancelling. Thus the filtering of these amps need to be regarded in a completely different fashion.

Many of them use almost massively more capacitance to make the amp reasonably silent as far as ills. IMO designers should take a long hard look at the use of chokes in such an application instead.
Yes. The use of chokes will certainly up the cost of said amp and more than likely that´s the reason they ain´t used to greater extent than they are. Ie;these days it´s way cheaper with a "high" capacitance e-lyte than a choke and most SE amps are regarded as entry stage or level tube amps.

Might be.
The use of a sane sized choke would certainly,IMO,make for a way better sounding and working (read-to play) such amp. Seing the development of SE amps the ones these days that are actually willing to spend a penny or two on an SE amp is the harp players. For such an amp it would IMO be a wise move to check the qualitys of a choke that feeds the ENTIRE amp (hence amount of H needed and so forth) like in the old days. This would set the scene for an SE amp that wouldn´t necessarily have to sport hundreds of uF for filtering and thus become a more "live" amp to play. Yes,this would of course hold true for such a guitar amp as well.

Chokes are IMO an underrated tool used these days. Pity...

[Andresound]

Thank you for such an in-depth reply and taking the the time to do so!!! Once again, this is highly appreciated. I am gaining knowledge by the day.

So, I will start by using what I have on hand, just to fire her up. 100uf + 100uf respectfully for the first two hits (one can cap), and 32uf + 32uf for the next two (another can cap), and the last being a 22uf axial?

We can see how this sounds first and then strip it and built a “proper” guitar amp in this chassis.