martin manning wrote:Screw terminals are pretty solid, and I have to believe quicker than soldering unless the flying leads are soldered from the top side. No reason you couldn’t preserve either option. I wouldn’t goop them up with thread lock.
You could put a small dab of clear nail polish on them. Would keep them in place and not hard break the seal.
Good news first: Amp powered up and sounds very good. Got it biased at about 45mA per tube with 410v on plates. Damn thing is so quiet at idle I thought it wasn't on! Major props to @jazzguitargimp for excellent PCB layout--no hum at all, and extremely low white noise.
Bad news: the switching system is drawing too much current, and burned out my Zener when all four relays were engaged. So I'm not able to test the Overdrive channel. But we'll get there!
IMPORTANT PSA: Did you know the metal bodies of radial caps (at least these Nichicons) are HOT? I mean live with DC? I got a gentle reminder when I brushed the chassis and caps with my hand.
IMG_1789.jpg
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I build and repair tube amps. http://amps.monkeymatic.com
xtian wrote: ↑Sat Feb 23, 2019 5:10 am
Good news first: Amp powered up and sounds very good. Got it biased at about 45mA per tube with 410v on plates. Damn thing is so quiet at idle I thought it wasn't on! Major props to @jazzguitargimp for excellent PCB layout--no hum at all, and extremely low white noise.
Bad news: the switching system is drawing too much current, and burned out my Zener when all four relays were engaged. So I'm not able to test the Overdrive channel. But we'll get there!
IMPORTANT PSA: Did you know the metal bodies of radial caps (at least these Nichicons) are HOT? I mean live with DC? I got a gentle reminder when I brushed the chassis and caps with my hand.
IMG_1789.jpg
Thanks for the info regarding the Nichicon radial caps body being live with DC. I bought a few a while back and have not used them yet. I will be extra careful when I do!
Why did you use a voltage converter to power the relay? Could it be easier to use low-voltage relays and power them with a low-drop voltage regulators by connecting it to the filament winding. I've done this a few times and it works fine
And another question - Using the top layer of the board as a shield protects work well in low-voltage devices. But I think there may be problems with high voltage. The distance between the contact pad and the edge of the shield seems too small to me.
alkuz1961 wrote: ↑Sat Feb 23, 2019 6:04 am
Why did you use a voltage converter to power the relay? Could it be easier to use low-voltage relays and power them with a low-drop voltage regulators by connecting it to the filament winding. I've done this a few times and it works fine
And another question - Using the top layer of the board as a shield protects work well in low-voltage devices. But I think there may be problems with high voltage. The distance between the contact pad and the edge of the shield seems too small to me.
Hi alkuz,
I have done what you suggest (lower voltage relays fed from the heater supply) with great success. The problem with this amp, is that the heater winding has no center tap, which would necessitate tying one end of the heater winding to GND, thus unbalancing the GND reference, and possibly contributing to 60Hz hum. So I decided to design a switching power supply that is fed from the bias winding. Same idea as Fender, sans the heat (and fried pc boards).
As for creepage, I am using 2.5mm from the GND planes to everything except the high voltage AC lines from the HT winding. For those I am using 3mm to the GND plane. These spacings are in-line with IPC Standard 2221B.
xtian wrote: ↑Sat Feb 23, 2019 5:10 am
Bad news: the switching system is drawing too much current, and burned out my Zener when all four relays were engaged. So I'm not able to test the Overdrive channel. But we'll get there!
Given that clever turn using switch-mode power supply one should be able to use relays with higher-voltage low-current coils. A minor belated thought.
