Weber Copper Cap Module

For those building and repairing amps on their own. Learna and share ideas.

Weber Copper Cap Module

Postby reguera on Fri Jun 26, 2015 5:10 pm

Hi! Newbie here, did a search for amp forums and this one seemed the right one for my needs.

I have an Ampeg GVT5-110, supposed to be based on the blackface champ with baxandall tone circuit and solid state rectifier. The problem is the difficult to get natural breackup so I thought about a less efficient speaker (weber DT-10) and a tube rectifier (not a real tube, just a simulator). I'd like to install a weber copper cap module to replace my solid state rectifier but weber sells two kind of mudules, one for full wave and one for bridge rectifier:

"In the case of a full wave rectifier supply, simply connect the two orange wires from the Copper Cap module to the high voltage winding from the power transformer. Next, find the point where the full wave diodes connect to a wire that feeds the high voltage to the filter capacitors and the rest of the B+ circuit. Disconnect that wire from the two diodes and connect it to the red wire from the Copper Cap module. It is not necessary to remove the original diodes from the circuit.

For the bridge type Copper Cap module, connect the orange wires to the high voltage winding wires coming from the power transformer. Connect the red wire from the Copper Cap module to the wire in the circuit going to the filters and B+ circuit. Connect the black wire from the Copper Cap module to a convenient power ground point. It is not necessary to remove the bridge diodes from the circuit, but you must disconnect the wire feeding the B+ circuit from the diodes so it can be connected to the red wire from the Copper Cap module."

I posted this before in the telecaster forum, but Im not totally sure about the repplies I got: http://www.tdpri.com/forum/amp-tech-cen ... ridge.html
In that post you can see the schematics and an image of the amp guts. I wasnt able to load those archives in this post, sorry.

Could you tell me wich one should I buy? Thank you!
Last edited by reguera on Fri Jun 26, 2015 5:26 pm, edited 1 time in total.
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Re: Weber Copper Cap Module

Postby PeterS on Fri Jun 26, 2015 5:23 pm

This may not help as much as you think - if it's a class A amp with only one power tube, the current draw is more or less the same regardless of output power, so there's no sag effect. All you're doing is lowering the power supply voltage a little (which might help).

Can't tell which one you need without seeing a schematic for the amplifier.
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Re: Weber Copper Cap Module

Postby reguera on Fri Jun 26, 2015 5:28 pm

Sorry, was editing my first post while you where writing your repply. Thank you, great info!
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Re: Weber Copper Cap Module

Postby PeterS on Fri Jun 26, 2015 8:43 pm

OK, now we're getting somewhere. Look at D3, D4, D5 and D6 on the schematic. They are in pairs in series just for safety (i.e. to increase the voltage rating). This is what is called a full-wave rectifier. (Just to confuse things, a bridge is also a full wave rectifier but the circuit is a little different - you can see an example just below, in the heater circuit). Look to the right of those diodes (3 4 5 6) and you'll see a 250 ohm resistor, R16. That resistor reduces the power supply voltage in exactly the same way you are trying to achieve with the copper cap module. So I would forget the copper cap and instead try increasing the value of that resistor. Try 500 ohms (or 470 which might be easier to find). Watch out for the power rating, the new resistor will dissipate more power than the old one (which is 5 watts) so I'd try to fit a 10 watt resistor in there...
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Re: Weber Copper Cap Module

Postby reguera on Sat Jun 27, 2015 8:11 am

Wow! You've relly impressed me. It seems a very good way to go so will give it a try. Thanks!!!
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Re: Weber Copper Cap Module

Postby pdf64 on Sat Jun 27, 2015 9:24 am

Reducing the VB+ (in accordance with the excellent guidance from PeterS) / use of less efficient speaker will reduce the max sound pressure level that the amp can produce; this may reduce the annoyance caused to housemates / neighbours when the amp is cranked.

But if you want more 'break up', you may need to increase the gain level, in order to push the amp into a higher degree of overdrive.
The Baxandall type tone control circuit will reduce the amp's mid range gain by about 20dB; if the ground link to the tone controls is disconnected, most of the loss may be recovered, giving a big boost.

But the simplest way to increase the gain level is to use a 'clean boost' type pedal between the guitar and amp.

Bear in mind that vintage amps, especially BF Fenders / Ampeg were designed to sound cleaner than previous amp designs, eg tweeds.
That they sound great when overdriven is a happy bonus, which may not have been part of the design remit.

Note that post #6 from dsutton24 on the linked tdpi thread is incorrect; your amp's power transformer appears to have all necessary windings to run a tube rectifier.
My band:-http://www.youtube.com/user/RedwingBand
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Re: Weber Copper Cap Module

Postby reguera on Sat Jun 27, 2015 10:39 am

Thank you pdf64! I agree about the booster, already have a radial pb1, but the amp isn't working properly. I like BF cleans, just want a litle breakup, something like this one in the following video:

https://www.youtube.com/watch?v=RuzBj2vEHes

My main guitar is a Epi es-339 Pro, so it should work: humbuckers+clean boost+low wattage amp = verge of breakup. Saddly, It's not working like it should.

One more thing I'm not sure about, I changed my preamp tube for a 5751, just for experiment, but dont know if I'm doing right or might get back its previous 7025 / 12AX7 ...
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Re: Weber Copper Cap Module

Postby PeterS on Sat Jun 27, 2015 12:25 pm

5751 has less gain than 12ax7...
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Re: Weber Copper Cap Module

Postby reguera on Sat Jun 27, 2015 2:12 pm

I wasn't sure about what would happen. I wondered It would breakup easier.. That's the kind of things that happens when you don't know what are you doing and misunderstand forums info... I did it because I've read that SRV did so.
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