Ceriatone Chupacabra mods

  • Thread starter Thread starter peterc52
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peterc52 said:
Do you know what the stock values are for the diodes in a chupa 50? :)
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I'm going by memory but I think 12v for the "modern" setting and 20v for the '80s.

peterc52 said:
Also. Does it matter if I use carbon resistors?
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It can matter. Just depends on your goals. For lower noise, I'd stick with modern metal film. For mojo, carbon comp. But yeah, it will increase noise and the values will drift over time from heat.
 
Noob question. How does I tell a 1 watt resistor and a 2 watt resistor apart?
 
peterc52 said:
Noob question. How does I tell a 1 watt resistor and a 2 watt resistor apart?
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Like if they're just sitting on your desk in front of you? It's hard to tell. Physical size would be an indicator. If they are the same exact resistor, but one has a higher wattage rating, it will probably be larger. But if they are just different types of random resistors from unknown manufacturers, then you can't tell.

If you know the part numbers, you can look 'em up.
 
B+ is 420 volts now. If I wanted to increase that what do I need to change?

I have JJ EL34L in it btw
 
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peterc52 said:
B+ is 420 volts now. If I wanted to increase that what do I need to change?

I have JJ EL34L in it btw
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What was B+ before?
What did you change?
What is plate voltage on V1a? I like at least 160v.
420v B+ is low. I like something at least 450v, if not 480v.

If all of your B+ droppers are 10K, then the only other thing you can do is change your PT. Ceriatone's Chupacabra power transformer puts out low secondary voltage. At least on all the 50-watt amps I've seen.
 
FourT6and2 said:
What was B+ before?
What did you change?
What is plate voltage on V1a? I like at least 160v.
420v B+ is low. I like something at least 450v, if not 480v.

If all of your B+ droppers are 10K, then the only other thing you can do is change your PT. Ceriatone's Chupacabra power transformer puts out low secondary voltage. At least on all the 50-watt amps I've seen.
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Turns out the 10k was already in there. I think they changed the layout a couple of years back.

It’s the 50 I have :/ What replacement transformer could work?
 
FourT6and2 said:
Any 1202-55 clone (JTM45). Marstran is a great option: http://marstran.com/JTM45-100-JMP100 TRANSFORMERS.html
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+1

I grabbed a JTM45 style Mercury Magnetics transformer with 520V on the secondaries to bump my 74 up. It’s sitting currently at 440V biased up and out of standby, too low for my preference. In standby and no tubes installed it sits around 480V, so that’s a 40V drop due to tube load. With that assumption I’m expecting post transformer change to be around 480V all biased up. It will also take some gain out of my design and improve dynamics - all things it could use IMO.
 
Does it also have the 3,15 volts out?

D17540B1-3AA5-454F-AE58-46F858204F0A.jpeg
 
350-0-350 is your best bet. That's the most common for this type of amp. Will get you around 460v - 480v depending on the specific transformer and your mains voltage.
 
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