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Topic: Tube weirdness.. 6L6 to 6V6 and back to 6L6 again.. help!. |
Bob Carlucci
From:
Candor, New York, USA
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Posted 6 Sep 2014 4:31 pm |
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So I swapped a nice little Music Man RP 65 112 for a battered old Plush 1060S all tube 100 watt head.. yeah I know, I got the worst of the deal, but that MM was unsellable for whatever reason.. Could not give it away, here or on CL.. Never again will I buy a "hybrid" unless I get it for nothing.
Anyway, This old Plush is basically a direct copy of an old Fender Showman.. The amp can be repaired with the Fender Showman schematic from what I have read...
In any case, this head has had all the 6L6 tubes removed and replaced with a lovely new looking set of Tube Amp Doctor 6V6GT-STR tubes.. the amp seems to work fine and I was told these tubes were "super premium" tubes that could handle the higher plate voltage with no issues.. I dunno.. I would like to put 6L6 tubes back in.. Not sure if thats possible.. I am not sure if any changes were made to facilitate the 1st changeover from 6L6 to 6V6, however, from what I understand, any changes that WERE made should cause no problems with a 6L6 tube... any insight from guys that know tube amps a LOT better than I do??. Will I have to change the grid resistors?, or was that only needed with the initial "changeover" that I want to reverse? 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......
Last edited by Bob Carlucci on 7 Sep 2014 3:35 am; edited 1 time in total |
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Scott Duckworth
From:
Etowah, TN Western Foothills of the Smokies
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Posted 6 Sep 2014 4:42 pm
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Google "6L6 to 6V6". There quite a bit of info about them. In some instances, a one way swap can be done, in others, no swap. Sometimes parts have been changed to accommodate one or the other.
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Amateur Radio Operator NA4IT (Extra)
http://www.qsl.net/na4it
I may, in fact, be nuts. However, I am screwed onto the right bolt... Jesus! |
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Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
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Posted 6 Sep 2014 6:02 pm
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Bob,
Depending on the present plate voltage on the 6V6s (pin 3) you may want to check the bias voltage on the grids, (pin 5). It may be higher than normally required for 6L6s thus reducing the output power available.
Sincerely,
Craig Baker 706-485-8792
cmbakerelectronics@gmail.com
C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024
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"Make America Great Again". . . The Only Country With Dream After Its Name. |
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Bill Hatcher
From:
Atlanta Ga. USA
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Posted 7 Sep 2014 2:06 am
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| some folks are using JJ 6V6 even with the high plate voltage. does the amp have a bias voltage pot? if so, adjust it. |
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Bob Carlucci
From:
Candor, New York, USA
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Posted 7 Sep 2014 3:34 am
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I believe the amp is self biasing[cathode resistor]... The guy I made the deal with is a tube amp tech... 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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Tim Marcus
From:
San Francisco, CA
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Posted 7 Sep 2014 11:15 am
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The impedance of 6V6 and 6L6 is very different
also, a 100W amp will not play well with 6V6 - you'll likely see arcing or short the tubes out when you try to push them hard
If you want to go back to 6L6, and don't understand basic tube operating principles, I'd take it to a tech so that you don't burn money. There's a lot more to swapping tubes than there is to swapping light bulbs.
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Milkmansound.com |
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Dave Grafe
From:
Hudson River Valley NY
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Posted 7 Sep 2014 1:04 pm
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| What Tim just said. |
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Kevin Raymer
From:
Chalybeate, Kentucky, USA
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Posted 7 Sep 2014 6:12 pm
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Seek a qualified techs help.
Unless they changed the transformers the swap back should not be to costly.
Tubes should be your biggest material costs.
But.. If you don't know what you're doing you can hurt yourself BAD with the voltages involved in tube amps.
Find a Tech...
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Kevin Raymer
Zum / Knaggs / Breedlove
Fractal Audio |
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Bill Hatcher
From:
Atlanta Ga. USA
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Posted 8 Sep 2014 6:09 am
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| Bob Carlucci wrote: |
| I believe the amp is self biasing[cathode resistor]... The guy I made the deal with is a tube amp tech... bob |
the schematic shows a bias adjustment, so it is not self biasing. the output is similar to fender with the 1500ohm bias and 470ohm 1 watt resisters there.
this amp is listed as a bass amp and there was a slave amp made that you could link it to for driving more cabs.
485VDC on the plates....thats pretty hot for even the JJ 6V6. you need to get the voltage down a bit. there is no rectifier tube so that option of a 5U4 is out.
i would get a set of 5881 tubes. install and rebias. |
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