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Topic: amp-6L6 converted to 6V6. how to go back? |
Bob Carlucci
From:
Candor, New York, USA
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Posted 10 Feb 2023 4:36 pm |
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Plush all tube head- These were originally equipped with 4 6L6 output tubes, and were based closely on the Fender Dual Showman circuit...
Not sure why, but at some point this amp was converted to 6V6 output tubes..
It sounds pretty good, and is loud and clean, but the overall tone just does not sound to my ears the way a proper 6L6 amp should.... It just responds different.. Guy that sold it to me[at a great price] is a shop owner that repairs amps and guitars, and is a pretty good guy. He told me all that is needed to return it to 6L6 tubes is a re bias... any thoughts on that?.. Also hums a bit when first turned on, but quiets down a lot after the amp warms in a few minutes... Power supply caps?.. bob
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I'm over the hill and hittin'rocks on the way down!
no gear list for me.. you don't have the time...... |
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Dave Mudgett
From:
Central Pennsylvania and Gallatin, Tennessee
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Posted 10 Feb 2023 5:20 pm
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If the only change made to convert to 6V6 was to re-bias, then re-biasing should work.
However, most 6V6 tubes do not like the significantly higher plate voltages that a typical Dual Showman amp would put on the plates. Nominally, 460 VDC, and possibly a bit higher these days due to a bit higher AC line voltages. I mean, even Deluxe Reverbs stress a 6V6 out some at, nominally, 420-430 VDC.
To deal with this, someone might have used one or more ballast resistors to bring the voltage down and possibly made more circuit changes. But if everything is stock, re-biasing probably would probably be enough.
I would want to difference what's in the amp with a schematic. Not sure whether you have the guitar version P1000S, which is intended as a guitar amp and has reverb and trem, and is very close to a Dual Showman Reverb; and the P1060TPS, which is a bass amp. Those are the two I've seen, for the most part.
I see some schematics -
P1000S - https://images.reverb.com/image/upload/s--__Lfr8kL--/f_auto,t_supersize/v1625874012/hzweamzrjork4ra2rr4i.jpg
P1060TPS - http://www.prowessamplifiers.com/schematics/images/Plush_1060S0001.pdf
As far as hum goes - well, certainly I'd look at the power supply caps for sure. If it hums without anything being plugged in, I think that would be likely. But there are so many potential sources of hum that it's hard to be sure. Grounding on these is sometimes an issue. If you google Plush P1000S schematic or Plush P1060TPS schematic and look at the google images, you'll see some gut shots. And you can see that these are not exactly the stout, relatively precise build of an old Fender. |
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Bob Carlucci
From:
Candor, New York, USA
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Posted 11 Feb 2023 4:02 am
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its the 1060.. bass amp. The hum is not bad,and its transitory,, Pretty much gone after a minute or so.
_________________
I'm over the hill and hittin'rocks on the way down!
no gear list for me.. you don't have the time...... |
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Jim Kennedy
From:
Brentwood California, USA
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Posted 11 Feb 2023 11:18 am
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Make sure all your ground connections, knobs, jacks, are tight. Heat expansion might be "correcting" a loose gtound.
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ShoBud Pro 1, 75 Tele, 85 Yamaha SA 2000, Fender Cybertwin, |
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Bob Carlucci
From:
Candor, New York, USA
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Posted 11 Feb 2023 4:44 pm
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No, its a pretty quick
"resolution".. Starts as soon as tubes start to glow, and is more or less gone within a minute, and is never very loud. Does not sound to me like a ground noise..Dealt with those before.
_________________
I'm over the hill and hittin'rocks on the way down!
no gear list for me.. you don't have the time...... |
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Michael Brebes
From:
Northridge CA
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Posted 12 Feb 2023 11:53 am
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If no resistors have been changed in the power supply section, it should be as simple as switching the tubes and resetting the bias.
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Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Dave Meis
From:
Olympic Peninsula, Washington, USA
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Posted 12 Feb 2023 8:54 pm
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| The hum you describe sounds like it's just the power tubes coming up to operating temperature... since they they don't heat up precisely in unison, there's an unbalanced moment until the tubes get up to operational heat. My twin does that, but if I use the standby switch, I don't hear it. |
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Raybob Bowman
From:
S. Lake Tahoe, CA, USA
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Posted 13 Feb 2023 12:11 am Re: amp-6L6 converted to 6V6. how to go back?
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| Bob Carlucci wrote: |
Not sure why, but at some point this amp was converted to 6V6 output tubes.. |
If it was properly converted, the output transformer should have been changed.
Check numbers on the OT and look up that OT. If it's for 4x6L6s no problem.
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Sierra U12 4+5 / 1933 Dobro / homemade Tele B-bender |
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