Ceriatone Chupacabra 50W: contemplating PT (power transformer) swap. What would I need to take into account?

TheTrueZoltan! said:
I imagine a collaborative rendition of "Ride the Lightning" by the remaining forum members. Would that be to your liking?
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Even better :headbang

Well, bad part:
- can't find my box of fuses; had a bunch of them in a box, always in the way - now when I need them, can't find the damn thing.

Good part:
- if it's just the fuse, amps' gonna be up & running after I put a new one in
- PT seems to put out 346/0/345 even if rated at 325/0/325 so I guess I'll look at the V1A plate resistor first; maybe get it lower to something like 330K first
 
TheTrueZoltan! said:
I imagine a collaborative rendition of "Ride the Lightning" by the remaining forum members. Would that be to your liking?
Click to expand...

It’s our most modestly priced receptacle.

1710254465438.jpeg
 
Got my HT fuse replaced today - amp's back up and operational :pickle

Came across these folks (Piemme Elektra) in the EU (Italy), they make a drop-in JTM45 replacement power trannie that fits the Chupacabra 50W and Yeti 50W (confirmed sizes with Nik from Ceriatone). They also do custom orders so I could get a PT with higher secondary voltages.

My PT puts out 345/0/345 (690 VCT) measured even though it's rated at 325/0/325 (650 VCT). My B+ is 432 VDC with EH EL34 tubes in.
Thinking of getting a 370/0/370 (740 VCT) PT which could bump B+ with tubes in to 450 ~ 460 V.

Not sure yet - gonna try a pair of E34L tubes before I order a PT; see how those behave.

I also have a bunch of resistors on order; planning on putting a 1Mohm in parallel with the V1a plate resistor (470K) first as Jason and other folks seem to recommend. That should get me a 320K value to see if it gets the amp to be slightly more punchier.
 
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V1a plate resistor didn’t make too much of a difference (had a 1Mohm in parallel with the 470K). It is ever so slightly less hairier but I think it would be the same spot you'd end up in if lowering the Pussy Trimmer.

As far as tubes are concerned, I like the EH EL34 better compared to the JJ E34L at the same bias voltage (36mV).

I'll look at toying around with the first two cathode resistors and get those to 2.7K/.68 from the 820 /.68 values they're at right now.

Possibly going to try another NFB resistor too and maybe even a different slope resistor.

The PT is here and it looks like the screw spacing is right for a drop-in swap.


Going to eventually put it in but first I want to get a feel if these preamp tweaks do.
 

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2dor said:
As far as tubes are concerned, I like the EH EL34 better compared to the JJ E34L at the same bias voltage (36mV).
Click to expand...
Did you measure using the external bias test points? I experienced a significant difference between my testing with a bias probe (41 mA, perfect for 423V plate voltage) and the test points (45 mV, which would be too high).

Biasing the amp hotter than 36 mV could also help you to get it a little bit less hairy.
 
TheTrueZoltan! said:
Did you measure using the external bias test points? I experienced a significant difference between my testing with a bias probe (41 mA, perfect for 423V plate voltage) and the test points (45 mV, which would be too high).

Biasing the amp hotter than 36 mV could also help you to get it a little bit less hairy.
Click to expand...
I just used the external bias points.
Did the same for my Molecular and King Kong when biasing.
My Chupacabra has 432 V plate voltage with tubes in.
 
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