5E3 Build - B+ Issue

[Diablo1]

What is the wattage of the bulb in your light bulb limiter? You need to match the wattage to the amp's current draw to get understandable results. I think it's odd that you see 450 volts B+ with a 5E3 with the tubes installed, especially with a limiter. Seems awfully high.

[ChrisM]

The mini-watt has been out of the circuit - the symptoms I'm describing are without the mini-watt. I took it out as soon as I cooked that resistor. But I'll check out the diodes and ditch the bleeder - thanks!

BTW - the mini-watt is great for what it is; a small VVR-type circuit to reduce B+ for volume attenuation. I'm sure there's improvements that could be made, but there's nothing really wrong with it. I've gigged with one fairly heavily for a good 3 years or so and have installed them in a couple other amps. The fet is robust and the resistors look small but they are just 1-watt metal oxide resistors in a smaller form factor so the size of thing can be reduced - which is why I use that instead of a VVR; it fits perfectly where the power switch on a 5E3 goes. The pic on the website is a bit misleading.

Those diodes can often "go" so yeah I'd check them out carefully.

The 330K 1/2W resistor is dissipating 0.48 W. That's definitely an issue, that resistor should be 2W-3W. I usually use 220K 2W for my bleeder resistors.

Sorry didn't mean to diss the Mini-Watt. These voltage regulators are great in the cathode biased amps.

I use a voltage regulating module myself in my Tweed.

[Morgan]

Fixed!

I ended up disconnecting the OT primaries to test the diodes. They were fine. While I was in there, I tested the OT for shorts and it came up fine. Poked, prodded, cursed, and scratched my head for a while until I was satisfied nothing was hooked up incorrectly, and then went back through the start up procedures; this time with no questions from the limiter.

So, the limiter worked well, told me I had something wrong going on in there. The only thing I re-did after the last test was desolder & resolder the OT primary leads, so I'm guessing I had a cold joint on one of them or something.

I tested out the semi-conductors on the Mini-Watt, they all tested fine, replaced the burnt resistor, and all is as it should be.

BTW - I'm using Classic Tone transformers in this one with JJ 6V6's & JJ 5Y3, and the transformers are giving me 366vdc B+, unattenuated, with 122 vac from the wall. Pretty good!

Thanks to all that chipped in - I appreciate it! And thanks Chris for the tip on the bleeder; I'll swap it out for a beefier one.

- Morgan