Really hot B+!

[adragndragn]

New TMB trinity completed! Started with Mecury Magnetics transformers , oversized power supply caps , mecury choke ,and cheap new tubes.My B+ was 395 with tubes! replaced bias resistor with 220 ohm. Disapating
27 ma each.My screens were still glowing! Tested different screen resistors and at 10k shared they did not glow and the sound was exellent!

[chabby]

Does Trinity have a TMB with Mercury transformers as an option? Or did you just arbitrariliy substitute mercury iron? Anyway, 395 is very high, where is it at now? Usually it takes the combination of a couple zeners and resistors to get it down enough to not be too hot.

Normal is somewhere between 325 and 345 at pins 7. But you have a choke which probably makes some difference. I used a 200r resistor between the rectifier and cap can, then 2 zeners after the first cap to finally arrive at about 335 from 395-400. But that was with a PT designed more for 4xEL84's or a couple 6V6's and being stuck with a 5u4GB rectifier.

I don't get the oversized caps...why? What's the rectifier? When you say oversized, do you mean in uf or VDC or what? You must have a solid state rectifier huh?

[krx]

You cannot run a B+ of 400V with only a choke dropping voltage to the screens and not expect the tubes to melt. The only way you can run the plates that high is if you get the screens way down (but that will affect the sound).

Your B+ should not be that high in the first place. What specific PT and rectifier did you use?

[zaphod_phil]

Yeah, just use some zeners to knock down the B+ to what it needs to be for an 18W. A choke doesn't belong in an 18W and will change the sound. I recommend selling the choke on eBay.

[goattech]

remember to place your zeners after the first filter cap like this http://www.18watt.com/files/b__zener.jpg. Also make sure they are 5watters and run in true series. On a side note.... thanks to zaphod_phil I was able to tame my 18 watt down even though i ws using 7189s, the voltage was too much and i had way too much clean out of my amp.now she sounds like a true 18 watt. Thanks again zp.

[chabby]

And make sure the anode point towards the rectifier! Or back toward the cap whichever the case may be usually accomplished both.

[adragndragn]

I put the choke before the main cap ,kept the circuit the same other than 50uf caps.They are tone clone series transformers, and it runs very hot! The 10k screen resistor tamed it down to a good point, seems the sound is more effected around 15k.My screens run around 300 which seems to be o k .Would the zeners make it sound better?I tried the choke between the plates and grids, but it was way too hot! So I moved it to the input side.

[zaphod_phil]

Yes, your amp will sound much better, and more like a real 18W if you put in the zeners, and also get rid of those huge screen resistors and that choke. Also that choke wasn't designed to to handle the main B+ current that you're putting through it.

And make sure the anode point towards the rectifier! Or back toward the cap whichever the case may be usually accomplished both.

The zeners will dissipate less power and drop closer to their spec voltage, if they're placed somewhere in the B+ line between the first filter cap and the OT connection.

[adragndragn]

I cant make that link for the zener schematic to work.What am I doing wrong?

[adragndragn]

With the extra money spent on transformers, I think I will just convert the circuit to 6v6s with the circuit for them on the output side.I will still have the correct preamp and not have hotrodded it just to tame it with zeners or vvrs, so I dont melt down el84s.

[adragndragn]

I bailed on you guys Thank you all for the awesome help
I went with real 6l6gc rcas, old 6l6gc iron and output, all cathode biased to stay close to original circuit, and no negative feedback
Thanks again!

[adragndragn]

I had two hot 18 watt transformers laying around with no use.I also had a 5e3 with a burnt output transformer.I put the two together and even though I had mercury's in it also, my plate voltage and bias went up from where it was! With the choke and output(wich is twice the size, probably because of multiple taps) the old school sylvania 6v6's sound wayyyy better.You have to remember my 5e3 already blues'd way out, now it rocks!
It also weighs more , and is louder!