Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Diverted on April 29, 2020, 11:00:13 am
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Hi,
I have been thinking about building Sluckey’s version of the Revibe. It looks great, documentation is amazing and the board is smaller which is one reason I’d like to go for it.
One question about the power transformer: On the schematic, it shows a Mojo 779PT. But in photos, he’s using the Weber Revibe transformer (WRVBPT). I’m wondering which would be better. Current capacity on the Weber is 20ma less according to specs, but 6.3v winding is 3A as opposed to the Mojo which is 1.5. That seems slightly undersized as with four 12A-7s, 6V6 and a pilot the 6.3V is going to be drawing 1.8A.
I’m sure either would work fine, but I’m wondering which one I should go for. I’m leaning toward the Weber because it’s half the cost and has more than enough 6.3v current handling. Anyone? Thanks Sluckey for putting your build online!
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power supply "magic" isn't a thing for a Revibe, specs and $'s should be the deciding factor
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One question about the power transformer: On the schematic, it shows a Mojo 779PT. But in photos, he’s using the Weber Revibe transformer (WRVBPT). I’m wondering which would be better. Current capacity on the Weber is 20ma less according to specs, but 6.3v winding is 3A as opposed to the Mojo which is 1.5. That seems slightly undersized as with four 12A-7s, 6V6 and a pilot the 6.3V is going to be drawing 1.8A.
Look closely at my documents and you will see that I referenced the Weber PT on all my pages. However, I also included Hoffman's original schematic and it shows the Mojo PT that he used.
There were three reasons that I used the Weber PT. You got two of them already... much better price and more filament current capacity. The third and most important reason is the Weber PT fits under the chassis which means I could use a smaller chassis. With my layout there is no room for a PT on the outside of the chassis. I think it looks better with the PT hidden. My Revive was designed from the gitgo to proudly display all the 'tronics. :icon_biggrin:
Have you seen this recent thread?
https://el34world.com/Forum/index.php?topic=25569.msg277241#msg277241
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No I haven’t, but thanks for that. Going to read through it this afternoon.
I’m definitely going to go with the Weber PT then. Mine’s going to be built on a bassman chassis which is a little bit bigger than yours was, but not as deep. So the power transformer’s going on top.
One other question (which I may have missed in your notes): Your third and fourth power filters are 100uf as opposed to Hoffman’s 47uf. I’m going to go with yours and I was happily surprised to see that those Weber 100/100 cans are pretty reasonably priced. One question: Weber does not list the dimensions of those cans; do you have any idea what the diameter of the hole should be? I’d like to punch out all the holes over the next few days while turrets, board etc etc etc are getting shipped. Thanks again for the layout/build pages and help.
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Going to read through it this afternoon
looks like if you print page 5 to scale you'll get real close guess :laugh:
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My Weber caps are 1-3/8" diameter. I like to punch a hole slightly less than the cap diameter. But, I caution you to wait until you have the caps in hand before punching the chassis. The pic on Weber's site looks a bit different than my caps that were bought in 2014.
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Shooter makes a good point ... DUH had not thought of that :laugh:. Caps are on order, I’ll wait until then. There’s going to be acres of room to the left of the board on this one since the chassis is a good 3” longer than Sluckey’s. It’ll be nice to have room, I tend to try to cram too much into small spaces.
Thanks again.