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#1 2010-02-04 06:25:07

zarr
Member
Registered: 2009-01-03
Posts: 38

eliminating campactron ?

okay, so while i've been told by numerous people 6k11 and such will be around for a while, the fact looms they will one day dry up.
i've been reading various bits of scattered info here and there concerning what a 6k11 is, and i wonder (and i am ignorant), if it is different parts of different tubes, can a dongle be made?  like it plugs into the 6k11 slot, breaks out into a few different tube sockets and maybe some sort of circuit, then mounts on the chassis?
part of the design would be to make it so it just unplugs from the original circuit so a 6k11 can be used if so desired.
so, pipe dream?  an enthusiasts' project?  simple curiosity!!!!


don't panic!

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#2 2010-02-04 06:40:30

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

the short answer is yes.

there are a number of ways to do it also.

it would be quite easy to just make a circuit board with similar layout but using two dual triodes instead of one triple triode.  The fact that the 12ax7 on that board is not even using one of the triodes makes it seem even more likely that one could simply replace the 6k11 with a dual triode and make use of that second triode in that 12ax7. 

in that case it might even be possible to remove the tube socket for the 6k11, drill a hole for a Chassis mount 12ax7 and do a little clever wiring. 

ultimately there are many ways of doing it.
-steve

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#3 2010-02-04 07:06:32

zarr
Member
Registered: 2009-01-03
Posts: 38

Re: eliminating campactron ?

hmm...so it's not crazy really.  i suppose the convenience of a 'plug and play' sort of device whot allows a 6k11 to be used or a combo of tubes is kinda ridiculous tho?  wouldn't this device also allow for more tonal experiments?  ie one could swap many different tubes out where they could only swap three(?) different makes of 6k11s beforehand?
so, what i imagine, is something that plugs into the compactron slot, but terminates on the other end into two(?) different sockets for two 12ax7s?  then one could swap out 12ax7s in that midrange circuit until they were blue in the face....far more tonal option than the three(?) manufacturers of NOS 6k11s?  or are old ampegs too picky with their tubes to even dream of such madness?!


don't panic!

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#4 2011-01-04 02:00:49

Steelyman
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From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

I too would like to find a way to replace the 6K11. So I decided to draw a new schematic and possibly create a new PCB to replace the old one. I knew that to replace the 6K11, I would need 1 triode stage with an amplification factor of 17, and 2 triodes with Af of 100. So I created a schematic that replaces the 6K11 with a 12DW7 and uses the previously un-used triode in V203 12AX7 (pins 6,7,8). The 1st triode stage of the 12DW7 (pins 1,2,3) has an Af of 100, and the 2nd stage (pins 6,7,8) has an Af of 17. PLUS, factors such as Plate Resistance, Transconductance, and Plate Current of the 12DW7 are identical to the 6K11, and according to NJ7P.org, other factors such as the Input, Output and Grid-to-Plate Direct Interelectrode Capacitances are damned close...and only approximations at that. So I'm running with it. I tried to draw a layout from the new schematic with pencil and paper, and killed several trees in the process. Can anyone here recommend some tube preamp layout software? - Thanks

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#5 2011-01-04 19:45:41

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

you just need to know the specs of the tube socket you're going to use. 

If you have the specs you can use any layout software to create the tube socket,  then you add the socket you created to your library.
anytime you need another socket you go to the library and there it is! 

a little work up front,  but from then on,  its cake.

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#6 2011-01-05 18:05:55

Liquids
Member
From: CT
Registered: 2010-08-01
Posts: 491

Re: eliminating campactron ?

I would love to see high quality V4 PC boards made available - if for nothing else than the 'reverb' / 6k11 board. 

I mean, why not? If someone was good with layouts, you could make it all line up with the stock panel.  I'd buy one simply as insurance for the future, even thought I have 2x 6K11s on hand. I want my kids to use my V4 and a 'simple' new PC board layout could make that highly likely, and make V4s that much more maintainable. I'm sure fliptops would offer them if someone submitted a layout in a reasonable format. Not that I've ever drawn a PC board in my life.


Matthew

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#7 2011-01-06 05:36:43

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

I never thought it would need to happen.  I remember 6k11s being like 6 bucks 10 years ago.
but lately the prices are crazy... I've certainly been entertaining the idea.

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#8 2011-01-06 14:33:01

Steelyman
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From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

I have a schematic for a replacement board, but I don't have the time to download every free layout software on the web to find one that works. I really need someone's help in pointing out something that has worked for them, and will work to create a 3-tube, 3.25"x 6.75" layout with the same screw-holes, socket placement, and will allow the use of the original cover plate without having to replace it or punch another hole in it. Socket placement could also be mirrored so that the original cover plate could be used by simply flipping it. I imagine the reason the 6CG7 wasn't centered on the brd was because more room was needed for components related to the 6K11, and not as much for the un-used half of V203. Maybe someone here know a better forum to take this question? Is there a PCB Layout Forum? - Thanks

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#9 2011-05-31 01:05:17

jay42
Member
Registered: 2011-05-02
Posts: 34

Re: eliminating campactron ?

If I was doing this, I would use only 12ax7 and 12au7 tubes -- skip the 12dw7.  The low budget approach is ExpressPCB.  I would kiss off the existing sheilds.  Backwards compatibility is a tempting, yet unfortunate goal.

Last edited by jay42 (2011-05-31 01:07:19)

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#10 2011-05-31 01:10:50

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

The 12DW7 is on the other circuit board. 

the new board would end up using a 12ax7, 12dw7 and 6cg7.

I have no idea why ampeg decided to use a 6K11 when they were leaving one section of the 12ax7 unused.

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#11 2011-05-31 14:32:11

Steelyman
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From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

I will have a kit available soon, that consists of a new PCB which uses a 12DW7 for 2 of the 6K11 triodes and the unused half of the 12AX7. To do this I swapped the positions of the 12AX7 and the 6CG7. The new PCB is .080 inches thick so it doesn't flex easily like some of the original brds. The original shield can go right back on also. Check out the pic of the new PCB installed in my V4. I've been testing it out for 2 weeks now and it works great. I'm still waiting on some components, but I should have 10 kits available soon. They will have the new PCB, all the caps, resistors, 3 tube sockets, and buss wire for the jumpers, but won't include the 12DW7 tube. I'm still putting the installation instructions together and will probably make them available as a download. Installation should only take an hour once you have the amp opened up. There are only about 15 wires to unsolder from the original brd and resolder onto the new PCB. Also, I should have some exact replacement aluminum standoffs coming soon.

http://i292.photobucket.com/albums/mm31/Neal82852/Neals%20Retro%20PCB/AmpegSmallPCB1.jpg

Last edited by Steelyman (2011-08-08 12:25:25)

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#12 2011-05-31 16:27:22

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

Not too shabby Steelyman!

what kind of price you gonna charge?

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#13 2011-05-31 16:42:43

Steelyman
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From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

Not 'zackly sure yet hangman. My business partner in this venture is supposed to have a price for it soon. Should be less than $75 tho. Standoffs will be considerably less hahaha.

hangman...you think there would be interest in an .080" thick re-pop of the V4 main brd for replacement? How about the control pot brd re-pop?

Last edited by Steelyman (2011-06-01 00:07:31)

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#14 2011-05-31 18:32:08

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

if there would be interest,  it would probably be mainly for people who have damaged boards.  so there may be demand,  but the reverb board replacement has more draw since the 6K11 is becoming increasingly harder to find and more expensive,  while JJ and EH both make 12DW7s.   
There might be a draw in making a control board with the toroidal inductor for people who have the discrete inductors.... but the cost of the toroidal from Mercury magnetics is rather high.  so hard to say if many people would go that route.

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#15 2011-05-31 19:08:58

Steelyman
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From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

Thanks hangman. I'm considering doing a version of the control pot brd with discrete inductors. I was also thinking of a shorter version of the main brd without all the components that are V4 specific from R37/R35 to the end of the board, but would include D5. Used with the 2 other brds, it would be the basis for a custom home built amp of any wattage. The pwr xfmr would have to be chosen carefully and the pwr supply would have to be modified somewhat, but it might make for a great 20-50W 1-12" combo with all the tone selectability of a V series amp....and alot less weight. I'd probably go with an aluminum chassis. But, gotta get the retro brd out first....see how that goes.

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#16 2011-05-31 22:52:29

Steelyman
VIP
From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

Here's a pic of my new PCB installed in my amp.....

http://i292.photobucket.com/albums/mm31/Neal82852/Neals%20Retro%20PCB/AmpegSmallPCB1.jpg

Last edited by Steelyman (2011-08-08 12:29:10)

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#17 2011-06-01 04:56:55

jay42
Member
Registered: 2011-05-02
Posts: 34

Re: eliminating campactron ?

I'd like a bare board, if you end up with any stranded.

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#18 2011-06-01 14:53:01

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

that is really something else!   you might need to put me down for one!

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#19 2011-06-01 17:21:13

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

I know its a bit late for rev 1.   But the board seems to have enough space that you might be able to put an axial filter cap on there.  f&t 47uf @ 500V.
eliminating the need for a 40x40x40. 

also,  if you're still considering the control board.  you could then eliminate the wafer tone stack and put all discrete components.  it also wouldn't be too hard to make it work for discrete inductors or the toroidal.

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#20 2011-06-01 17:57:52

Steelyman
VIP
From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

Jay42..in regards to selling the bare brd...let me check that out with my partner in crime. I don't see why not.

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#21 2011-06-01 18:17:14

Steelyman
VIP
From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

Hangman....I see your point, but I don't think I want that cap on there. Besides, I already have a REV 2 in the works that addresses a minor layout issue. Nothing operational. I'm pretty sure that will be the end of tweaking this product as I'm onto other things...possibly a mod kit for the Fender HotRod Deluxe. Good platform, but I think there's room for improvement. Yeah I know...wrong forum.

Last edited by Steelyman (2011-06-01 18:17:41)

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#22 2011-06-02 06:01:23

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

yeah... I guess i was just dreaming.   would make recapping the V4 a little easier.

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#23 2011-06-02 14:09:50

teledeluxe
Member
From: Chicago, IL
Registered: 2008-09-24
Posts: 467

Re: eliminating campactron ?

hangman wrote:

yeah... I guess i was just dreaming.   would make recapping the V4 a little easier.

Don't people typically just suspend the extra axial cap atop the 2x50uF cans?


2 wrongs don't make a right, but 3 lefts do!

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#24 2011-06-02 14:31:39

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: eliminating campactron ?

yeah,  it is a subtle issue.   I just think it would be cleaner if it were on the board.

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#25 2011-06-02 15:22:53

Steelyman
VIP
From: Massachusetts
Registered: 2010-11-17
Posts: 107

Re: eliminating campactron ?

Teledeluxe...I just install a terminal strip using one of the screws for the new cap clamp. I prefer the 3x40uf can, but the terminal strip method is pretty easy and ALOT cheaper. I think I got the idea from this forum......might have been Rytetone...can't remember.

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