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Thread: 6505+ with EL34?

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    Old Timer tedmich's Avatar
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    6505+ with EL34?

    I know the 6534+ is Peavey's take on the older 5150II with EL34s but looking at the PCB for the 6505+/5150II power amp board the only problem seems to be the lack of a connection between pin 1-8 for V8, which is present in every other power tube. By connecting the V8 pins 1-8 (and modifying the bias circuit and SGRs) this amp should work fine with EL34's right?

    see here

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    Old Timer soundguruman's Avatar
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    Quote Originally Posted by tedmich View Post
    I know the 6534+ is Peavey's take on the older 5150II with EL34s but looking at the PCB for the 6505+/5150II power amp board the only problem seems to be the lack of a connection between pin 1-8 for V8, which is present in every other power tube. By connecting the V8 pins 1-8 (and modifying the bias circuit and SGRs) this amp should work fine with EL34's right?

    see here
    Theoretically it will work with 220 K bias splitters, 1K screen grid resistors, and pins 1,8 tied to ground, as long as you bias it...
    but sometimes those boards burn, i suppose when the output impedance is mismatched.
    you can tie pin ones to bias and it will draw less current, but I don't know if it sounds as good...

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    Lifetime Member Enzo's Avatar
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    Well, if yo0u did that, you would then have to lift the other three pin 1s to similarly connect them.



    Yes, jumpering to that one lonesome pin 1 will do it, as long as you make the other changes.

    And the stock power transformer has more than enough oomph for the additional heater draw. Remember EL34 draws 1.5A heater, while the 6L6 draws 0.9A.


    Meanwhile, where did you get that layout drawing? It is not the same as my 6505+/5150-2 layouts.

    Look at the layout for the 6534. It is the same drawing as yours, but with the link from pin 8 to pin 1 included. If you look close, you can see the link is added to the basic drawing. On both side views.

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    Old Timer tedmich's Avatar
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    Quote Originally Posted by Enzo View Post
    Well, if yo0u did that, you would then have to lift the other three pin 1s to similarly connect them.



    Yes, jumpering to that one lonesome pin 1 will do it, as long as you make the other changes.

    And the stock power transformer has more than enough oomph for the additional heater draw. Remember EL34 draws 1.5A heater, while the 6L6 draws 0.9A.


    Meanwhile, where did you get that layout drawing? It is not the same as my 6505+/5150-2 layouts.

    Look at the layout for the 6534. It is the same drawing as yours, but with the link from pin 8 to pin 1 included. If you look close, you can see the link is added to the basic drawing. On both side views.

    this is just the PCB from the 5150 II schematic I have, although the traces were very faint and I needed to up the contrast in Photoshop, I have never seen or found the 6534 schematic/PCB layout, it would be useful...

    To be clear the "other changes" you mention include "lifting other pin 1 to similarly connect them" meaning what exactly? It should just look like the 6534; with the V8 pin 1 and pin 8 connected right?

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    Lifetime Member Enzo's Avatar
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    SGM suggested connecting that loose pin 1 to bias. I countered that if you did that, you would then have to isolate the other three and similarly wire them. My comment was only meant as a reply to him, NOT a suggestion.

    You can get any PV schematic from PV by asking customer service, you don't have to "find" them.. Your image is exactly that from the 6534 set except the 6534 has the added jumper.

    Does that layout drawing look exactly like your 5150-2? If it does, great. MY only question was where did you get that drawing. My factory copies for the 5150-2 do not look like that. The 5150 and 5150-2 used the same 6L6 board, at least originally. I must presume that they may have changed production and are using a different power tube board in the 5150-2 now. For example, in your drawing there are two screen resistors crosswise in the center, while on the old 5150 board there are four of them all lined up along one edge of the board.

    As long as you get where you need to be, we are fine. I am asking all this as an acedemic interest.


    Here, I attached the 6534 set, and for reference the 5150-2 set. See how my 5150-2 differs from yours?
    Attached Files Attached Files

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    Old Timer tedmich's Avatar
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    Enzo thanks as always!, my 5150 II pdf is 1.8Mb and has quite a bit more PCB detail, can't remember where I got it.

    The schematic 1st page is identical to yours, but higher res. The pdf I have was created 3/17/2004 at 2:13:15 PM, if that helps...

    https://docs.google.com/open?id=0Bx4...2V6ZWJNVW9yTm8

    wonder how to attach here....oh well

    Have an extra big PT/OT so I might turn a 6505+ 112 cheapy into a 120w 6505/34+ 112

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    Last edited by tedmich; 07-06-2012 at 01:43 AM.

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    Supporting Member Jazz P Bass's Avatar
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    A 'Vega' funny car!
    Holy Sh*t.

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  8. #8
    Old Timer tedmich's Avatar
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    Vega

    other one is a Pinto!

    (both are silly)

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  9. #9
    ToneOholic! big_teee's Avatar
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    Here is the file in the link.
    I downloaded then attached it.
    T
    peavey-5150-ii.pdf

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    “When you find yourself in a hole, quit digging.” WILL ROGERS

    Keep Rockin! B_T
    Terry

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    Lifetime Member Enzo's Avatar
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    Oh, well there you go. Your drawing set includes both versions of the power tube board. The newer on is dates 2001. I've never seen that until now. Thanks.

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  11. #11
    Supporting Member Jazz P Bass's Avatar
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    Repost of the 6534 schematic:

    PV 6534.zip

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  12. #12
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    Careful, you've exhumed SGM

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  13. #13
    Old Timer tedmich's Avatar
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    Quote Originally Posted by Dave H View Post
    Careful, you've exhumed SGM
    Custom ceramic caps in a Marshall!!!! The owner of Tennis.coms house! Every 5150 blows up like that!!


    (spooky!)

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    Quote Originally Posted by tedmich View Post
    Custom ceramic caps in a Marshall!!!! The owner of Tennis.coms house! Every 5150 blows up like that!! CRATEPEG! CRATEPEG! CRATEPEG! CRATEPEG! GO BUY A REAL AMPEG! Bias your amp with a hammer!
    Jusrin

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    "... If an older Boogie and classic Marshall had a (clearly illegitimate) child and you baked it in an oven set to clown shit crazy." - Chuck H. -
    "When receiving a shock I emit a strange loud high pitched girlish squeak." - Alex R -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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