Mesa Triple Rectifier Signal Cutoff

[Helmholtz]

Just for curiosity and statistics: Was it a bad orange drop? What is its voltage rating?
Seems Mesa amps frequently develop leaky coupling caps. Am I wrong?
Wondering how reliable orange drops are. Or is it the high temperature inside a Mesa?
E.g. I never saw a bad mustard cap in a Marshall or a bad blue molded cap in a BF Fender.

[Pedro Vecino]

On the Dual/Triple Rectifier, Roadster, and Roadking models, the orange drop are rated at 400 V. On older models, some are rated at 600 V. Leakage is not especially common, but it does occur. I assume heat plays a role.
They are also affected by problems with the anode resistors (noisy in the presence of high voltage), sometimes with some relays, and also with the power supply diodes for the first two tubes and the switching circuit. In some cases, this makes that area of the board conductive.

[g1]

Or is the high temperature inside a Mesa?
E.g. I never saw a bad mustard cap in a Marshall or a bad blue molded cap in a BF Fender.

I mentioned in another thread about Mesa basically using the board as a heatsink in some models. On one that I worked on, the plastic labels on many of the large electrolytics were shrunk, and hot to touch. I replaced them all and the new ones also got hot to the touch. And this was with the chassis out in the open air. The heat was all coming off the circuit board itself, transferring to the caps.
Agree that it is very rare to find leaky mustard or blue molded, but I have changed a few over the years.

[Helmholtz]

Thanks a lot g1!
I really appreciate first hand info from an experienced repair pro.

[misterc57]

400V dead short

[Helmholtz]

400V dead short

Thanks for the pic.
So it's a Sprague SBE715P polypropylene cap with an operating temperature limit of 85°C.
https://www.cde.com/resources/catalogs/715p.pdf
There are also other orange drop types.

Mustards (rated for 100°C but only available up to 400V) and blue moldeds are polyester/Mylar dielectric caps.