Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: BrianS on March 10, 2014, 03:02:55 pm
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Well, I'm in the process of rebuilding the power supply of my Maestro GA-1RT. I purchased some new filter caps of almost the same value as the originals, but they are SMALL.
The caps are Ruby Gold electrolytics in 10uf@450V and 16uf@450V. So, the specs are good, but the caps are only about an inch long by about a 1/2 inch in diameter...I'd say they are less than half the size of the ones that were in there (20uf@500V, not original).
There was no reference for physical size when I ordered them, so I went on specs alone, and I know Ruby is a tube "brand", so felt okay about purchasing them.
The GA-1RT is a low wattage amp, and I'm getting a new Classic Tone PT for it that will be able to deliver a B+ voltage that is close to the original specs, so in theory, the caps should be fine...I've just never seen filter caps that small.
Should I be concerned?
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Should I be concerned?
I would say no, not because of the size.
Modern e-caps are made differently, are much smaller and less $$, mainly driven by use in computers and switching power supplies. I have been using Panasonic EE radial series, 105c, hi ripple current and so far no problems. Less than $1.50 each but they often don't fit in old amps unless you rig up something to keep them in place.
Sluckey(?) posted a picture here a while back of a Sprague Atom e-cap he cut open and the cap itself inside was much smaller than the can's size. I've cut a few open also and it was the same, cap smaller than the can size. However the modern caps I cut open the cap was very close in size to the can it was in.
What I would worry about is if the Ruby cap, which is just a relabeled cap is a good 1 or a cheapo? You would think at least they would re-label a good 1.
If there's more ripple voltage than the cap(s) is rated for the ripple voltage heats up the cap(s) and helps cut the cap(s) life short, so getting a e-cap with as high a ripple and hi temp 105c ratings is what I look for.
It's the 1st B+ filter cap(s) that take the brunt of ripple as you go down the B+ rail the ripple gets smaller and smaller. I've read some say you need the 1st filter cap(s) to be rated at least 2x the amps total B+ current. Others say at least 4x to 5x in that position. :dontknow:
Brad :icon_biggrin:
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Re-post below of the Sprague picture previously posted on this forum.
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^That's funny!
It's nice that the caps are so small, as I don't have a lot of room. Now I can do a proper mounting of the caps.
Thanks for the info.
Brian
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I've used those "small" Ruby e caps in several amps, never a problem.
I used them a lot for replacing expensive can caps because the small size and 500V rating is ideal.
Price is good if you call for dealer discount.
A few amps have been going for a few years, played a lot and no problems.
al
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Good to know, dude. Thanks. Now I just have to wait for my PT to arrive.
Funny story, I ordered a PT for a 5watt SE amp. They somehow mistakenly send me a PT for a 100watt Marshall! Now I have to wait for the correct transformer to arrive...
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Sluckey(?) posted a picture here a while back of a Sprague Atom e-cap he cut open and the cap itself inside was much smaller than the can's size. I've cut a few open also and it was the same, cap smaller than the can size.
Brad :icon_biggrin:
If you open the small Ruby Gold , is there a smaller cap inside too ? :laugh: :laugh:
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Good to know, dude. Thanks. Now I just have to wait for my PT to arrive.
Funny story, I ordered a PT for a 5watt SE amp. They somehow mistakenly send me a PT for a 100watt Marshall! Now I have to wait for the correct transformer to arrive...
Did you keep the Marshall PT?
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^No. They paid to have it shipped back to them. They screwed up, but took care of the problem very quickly and to my great satisfaction.
I'm well on the way to getting the little Maestro up and running now!