First post, my “new” 18W

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JMPGuitars
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Re: First post, my “new” 18W

Post by JMPGuitars »

Make sure no part of your ground bus bar contacts the chassis anywhere except at the single point it's supposed to.
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colossal
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Re: First post, my “new” 18W

Post by colossal »

Skydog6653 wrote:
Tue 06/25/19 12:09 pm
No leaking; it tested slightly under the rated 0.022 at 0.0197.
Ok, that's good. Carry on!
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geoff 1965
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Re: First post, my “new” 18W

Post by geoff 1965 »

you're getting there with the grounding and i've just been through the whole post from page one and one component we've overlooked is the dual can capacitor.if that is original then it's 16 years old and could be leaky which will cause hum so it might be worth considering?
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Re: First post, my “new” 18W

Post by Skydog6653 »

I found the dual can cap with no problem; looks like an exact match https://www.tubesandmore.com/products/c ... ectrolytic I can't find the 5W 1K4 resistor.
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Re: First post, my “new” 18W

Post by geoff 1965 »

the dual can looks good,in the same link click on resistors,power, then 5W wirewound, they have 1.5K which will be okay,
check the width of the can will fit your clamp.
what voltage rating are those 2 red/orange capacitors in the preamp skydog?
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Re: First post, my “new” 18W

Post by Skydog6653 »

geoff 1965 wrote:
Tue 06/25/19 8:31 pm
the dual can looks good,in the same link click on resistors,power, then 5W wirewound, they have 1.5K which will be okay,
check the width of the can will fit your clamp.
what voltage rating are those 2 red/orange capacitors in the preamp skydog?
Those are 0.01uf 200V Sprague. The width and height of the dual can match mine exactly.
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Re: First post, my “new” 18W

Post by JMPGuitars »

Skydog6653 wrote:
Tue 06/25/19 9:33 pm
Those are 0.01uf 200V Sprague. The width and height of the dual can match mine exactly.
Physical size doesn't matter as much as value/quality. They might be fine, I haven't used their caps. I usually use Sprague, JJ, or F&T.
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Re: First post, my “new” 18W

Post by geoff 1965 »

yeah quality counts most with filtering,i like the F&T's for the dual caps, the CE claims to be superior to any capacitor so if that's true it should be good!
i mentioned earlier that those 1K's were "overkill" skydog and to be honest just one of those will easily run both el84's with a jumper across the pin 9's,at the moment your bias resistor is laying against your 470uf.those bias resistors get hot "i know i grabbed one that had been on for about half an hour" and you might have problems with that,ideally you want a gap between so air can circulate around the resistor.
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Re: First post, my “new” 18W

Post by crgfrench »

geoff 1965 wrote:
Wed 06/26/19 8:16 am
yeah quality counts most with filtering...the CE claims to be superior to any capacitor so if that's true it should be good
I haven't tried CE but I like their approach. Didnt know about the washing machine thing before this!

https://youtu.be/yfSSIO2c_ak

https://youtu.be/ITYPYwc_GEo
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Re: First post, my “new” 18W

Post by JMPGuitars »

Don't forget about the dishwasher: https://youtu.be/HDcEZURxWOs

Pretty interesting videos.
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Re: First post, my “new” 18W

Post by Skydog6653 »

Are the 200v sprague caps sufficient?
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Re: First post, my “new” 18W

Post by geoff 1965 »

the one next to the sozo blocks your DC voltage from the V1 plates so if you've got 150-60 volts on your plates it's not much of a safety margin,i would be happier seeing a higher voltage rated cap like the sozo or mallory's then if you do any mods in future that raise your plate voltage you know it's safe. i.e. i had around 150 on my plates but then i did a cascade mod which brought the plate voltage up to over 200 volts.
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Re: First post, my “new” 18W

Post by colossal »

Yeah, you definitely want any coupling cap to be rated for at least the full B+ at no load condition.
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Re: First post, my “new” 18W

Post by Skydog6653 »

Hello again, everyone! Apologies for my absence, but I was presented an opportunity to come out of retirement briefly, and couldn't afford to say no! Unfortunately, it manifested into more than anyone ever expected. I still have about two weeks of wrapping things up, but just ordered the F&T dual can cap, the higher voltage caps, several resistors, a tube socket, and a few incidentals. I can't wait to get back to working on my amp. Any available free time I've had lately has had to go towards keeping my chops sharp (otherwise, what's the point)!
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Re: First post, my “new” 18W

Post by Skydog6653 »

I can't believe how the days turn to weeks to months! Last week, I finally made the time to solder in several more components. I replaced the two 5W 1K resistors with like cement ones and replaced the two caps with the Zosos. I reused one of the 1K resistors and replaced the old Dale one when I replaced the dual can cap. The amp is much quieter now. It still has a low hum, but so does our other two amps, the Siegmund MS, and a new SFDR. I believe this is a power issue. I'm going to look at power conditioners next. Anyway, here's the chassis as it looks now.
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