Weber Copper Cap Replacement for 5Y3GT Rectifier Tube in LSS

[axman53]

So, after those resistors are clipped, than I can safely use 5Y3s without fear of them blowing? Or would you recommend I continue to use the 5V4?

I can tell you this: After I had this mod done, I've been running a MESA 5Y3 in there probably going on 20 hours or so by now and NO PROBLEM. Before the mod, that would not have been possible. YMMV, but that's my experience so far.

 

[ricardo loma vista]

So, after those resistors are clipped, than I can safely use 5Y3s without fear of them blowing?

Or would you recommend I continue to use the 5V4?

I'm using the NOS JAN Philips 5Y3, just because it's been more reliable with or without the mod, and it's only a few bucks more than a Mesa russian tube. As far as the 5V4, the whole point of having a 5Y3 is to get major sag. A 5V4 will not deliver the same response as a 5Y3. I think I'd use the copper cap before the 5V4, or just stick with the 30 watt setting and its SS rectifier.

 

[Thundersteel]

Does the modification alter the tone or affect the amp in any negative way?

 

[Thundersteel]

the two resistors clipped are R101 and R103 immediately on either side of the ribbon cable.

OK--which ribbon cable? There are three of them! And which end of which cable are they located?

I wanted to do the mod today, but I couldn't find the resistors. They are labeled, but most of the resistors lie directly on top of the label, making identifying them impossible.

Is there any way for someone to circle the correct resistors on the picture?

 

[ricardo loma vista]

Please don't take this the wrong way, because I mean no offense, but it seems as if you are not too familiar with basic electronics. If you don't know how to properly discharge capacitors or recognize components, you should not be inside the amp. You can be seriously injured or killed if you don't know what you are doing.

 

[Thundersteel]

Please don't take this the wrong way, because I mean no offense, but it seems as if you are not too familiar with basic electronics. If you don't know how to properly discharge capacitors or recognize components, you should not be inside the amp. You can be seriously injured or killed if you don't know what you are doing.

I meant to say in my previous post that I couldn't find the correct resistors.

It's kind of hard to tell which resistor is which, since they are laying directly on the circuit board, covering up their respective desingations.

Oh, and I've been an electronics technician for > 20 years, and also have a degree in electronics, so I think I know what I'm talking about--no offense taken!

 

[Thundersteel]

two resistors, one each on either side of the ribbon cable

the numbers should be stenciled on the board

OK, I figured it out last night. They are immediately adjacent to the middle ribbon cable, one on each side. Each one is a 470-ohm resistor, in parallel with a 100-ohm resistor.
Each resistor pair value is about 82.5 ohms; pulling the 470-ohm resistor brings it up to 100-ohms, effectively increasing the voltage drop across each resistor. More ohms = more voltage drop = less current flow through each resistor.