I bought a tube combo amp.

Discussion in 'The Squawk Box' started by kevinpaul, Nov 2, 2015.

  1. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    fwiw, mine had been making a bit of an "arc"ing sound from the get go, particularly on the distortion channel.

    also.. beware the trs plug for the footswitch. mine went bad, and the amp won't work right if it shorts inside. i had both channels going at once and the reverb was like a master volume. quite amusing. ;)

    ok... all that said, i AM gonna mess with the circuit some i think. the dirt channel is ok, but unuseable above about 8 on the pre gain. sounds like ass.

    but thats for another day. i got fuzzboxes i gotta build, or mama don't eat. talk soon. keep on silkyn'n!
     
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  2. kevinpaul

    kevinpaul Premium Member

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    I am in awe of you.
     
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  3. DavGrape

    DavGrape Silver Supporter

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    The descriptions by jimiphoton are just what I needed.
    Language I unnerstan.
    Special thanks for "roach clip" as opposed to "alligator clip."

    I wish he lived next door.
    It would get loud.
     
    Last edited: Aug 22, 2017
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  4. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    kev....
    i'm not worthy, believe me.

    dave...
    it might get REAL loud.

    i am nothing but a 3rd rate mostly white blues rock guitar slinger from the fertile muddy waters of the willimantic delta

    and i gotta roach clip and know how to use it. ;)

    ya know its funny, back when we all called roach clips roach clips, even my parents didn't call 'em alligator clips. ;) strange planet.

    so anyways... i ordered new tubes last nite. i've cheaped out and gone "russian equivalent" cuz they are cheap enough for me to afford being a pseudo retired crip (and not the street gang kind) and they kick total ass and seem to last forever. i love kommies on ebay. one guy i could get a matched sex tet (sounds like something from a steven king dark tower story gone 50 shades of lame) for 39 bux!! )

    look for 6p3s, russkie military grade 5881s designed for high impact... perfect for an old geeze like me who tends to drop stuff... and 6n2p's which are parallel heatered 12ax7's, also military grade.
    they have to be run at 6.3vv only, you can't run them at 12.6 like some dual triodes and they draw a tiny bit more current... but i gotta 10 pack for like, 30 bux. i like prices like that.

    i shouldn't post this shit to the interwebs, cuz they'll all be gone, but what the fuck. in the spirit of glasnost and all... nasvidanya

    the str's that were in it at the pt meltdown survived fine. but i changed 'em out anyways and put 'em aside for future tests if needed.
     
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  5. jep1210

    jep1210 Senior Member

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    I'm a bit confused, the "Silkyn Super 50 Power Transformer.pdf" document in this post (2242) is different than the "Silkyn Super 50 Power Transformer.pdf" in posts 2120 and 2202. Looking closer, it seems one PDF has Lead 13 listed as "copper foil ground/noise section", the other has "copper foil ground/noise section" listed as Lead 15.

    Not sure how much this matters but I just wanted to make sure I have all the right information for the guy who is going to install my PT.
     
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  6. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    i love it , no more no more... used to do that song when it was current. toys in the attic was a great album. i forget if my brother dick (wagner) was on that one too... very likely. joe perry was a mess back then.

    never tried a partial capo, i never really use capos.

    dave, this is me playing with an oldies band called ricky and the rockets a few months back, during our soundcheck at a benefit for the vietnam vets MC, an ancient crazy elephant song called "gimme gimme some lovin" and one of my brother Ed's songs, "recipe". if ya get really bored brave or stupid, there's a ton of pedal demos and shit, some old live things etc. heavy on the dumb where possible.



    sounds pretty much like me. expect some clams. this was like, the second time i played with them.

    the color code of the new transformer is identical to the original one bro so ya can just wire 'em up the same..

    attached is the actual silkyn super 50 onetics doc

    the yellow and green ground wire from the pcb to ground is not part of the transformer. the red and white and black and white leads go to ground as well. the two red wires go to the switch, you must
    combine leads 1 and 3 in parallel and 2 and 4 in parallel for a 120v amp. just print the pic and take it to your tech. this doc is right and the only one ya really need.

    onetic silkyn.png
     
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  7. jtcnj

    jtcnj Member

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    The diagram in the above post 2267 is the same as mine.
     
  8. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    that's the proper diagram for the onetics replacement. it matches the original xformer's color codes etc. works great. just mind your p's and q's and read the instructions, its pretty straight forward.
     
  9. jep1210

    jep1210 Senior Member

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    Thanks bro, I'm not trying to be a nudge, just want to fully understand.
     
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  10. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    no worries bro! in this kind of situation, there are NO dumb questions, so ask ANYTHING. seriously. take your time, do it right. you can't rush this kinda gig, so set aside some time to do it in. should only really take a couple hours if ya don't get all anal like i did ;)
     
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  11. les a paul

    les a paul Member

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    anybody know what the negative voltage spec is on this amp? For the bias ?
     
  12. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    mine is right around -50v give or take with about 504v on the plates.
    there's a bias tap on the transformer which i assume you've already connected.
    there's a bunch of ways to set the bias, all have plus and minuses. usually peeps say use an oscope, others maintain that shunting the OT with one meter so you can read the current with another.
    personally, and i know its sacrilige, i do it by ear. i watch the amp while i do it, and if the plates begin to glow i back 'em off. i tend to bias a little cold by ear to what i did when i did the current method years ago. i figure FOR ME ONLY of course that running it slightly cold is a bit easier on the circuit, and often a bit cleaner output as i'm relying more on the pedals i build for distortion than the amp a lot of the time.
    i know it sounds crazy, but i know a lot of guys who do the same thing. use an oscope to look at the wave and get it "right" then tweak a little til it sounds good.
    here's the thing.. the bias point shifts a bit with fluctuations in voltage, temperature, maybe even humidity. phases of the moon. too many kemzars in the old antipasto. all i know is every time i biased an amp with any "approved" method if i checked 5 minutes later it would be slightly different.
    there is no exact current, or exact voltage really in my humble and rather limited experience that is "right".
    i'd suggest googling as much info as possible.

    but i'd say around -50 to 60volts should be around the ballpark depending on the tubes. the voltage doesn't matter quite as much as the current draw. too much math for my widdle bwain, personally ;)
     
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  13. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    and please be careful, the bias adjust pot is right near some of the highest exposed voltage points in the amp... power tube sockets. why they used a side mount trim pot is beyond me. <smh>
     
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  14. Harold Purvine

    Harold Purvine Junior Member

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  15. jep1210

    jep1210 Senior Member

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    Thank you Harold, you're a gentleman and a scholar.
     
  16. ultra80096

    ultra80096 Senior Member

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    Just want to plug in a Big Thank you to Harold (Bud) Purvine & Luithien1 (John) for the availability to keep these amps running.

    I have one of my transformers removed & plan on install of the new one tomorrow. Shouldn't be too big of a deal. Got my grommets, & step drill on hand. I haven't had any of my four amps shut down yet, but thought I'd put one in for sure. Geez, I put one, & sometimes two of my amps through the paces at our monthly bar jams. I keep an eye, expecting one to go silent, but they both keep going, no problems.

    I just have a question that's been nagging me since I've bought these amps about the speaker outs.. I do know the output transformer is good & up to snuff, but being the main speaker out is 16 ohms, & the other two speaker outs being 8, what is the proper way to plug in another cab or speakers? On what I've read, I'm a little anxious to just plug in another one or two 8 ohm cabs or speakers just willy-nilly & the transformer & tubes can handle it. I need to study the schem more, but as the 1 page manual instructs, just plug in & go.. any ideas or knowledge?
     
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  17. Harold Purvine

    Harold Purvine Junior Member

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    The scondary windings are additive, outside of the coil. This means that so long as you are adding things together, in series or parallel, you need to use an appropriate tap. That's if you want to have the designed for reflected load line presented to the tubes.
    So, means just two connections to the output transformer, one to black, one to another color, no matter how many speakers you are connecting. You can experiment with misloading the tubes. The ouput transformer will not care. The tubes will not fall into oscillation unless you are truly foolish in your mismatch, because these outputs are constructed to avoid that condition. However those tubes will not last as long as properly loaded tubes will.
     
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  18. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    for all intents, the two 8 ohm taps look to me like you could add either one 8 or 16 ohm cab, or run two 16 ohm cabs... say, a full marshall style stack with two 16 ohm 4x12's. the two 8 ohm taps are in parallel. so 16 ohms x 2 in parallel is 8 ohms. i wouldn't go below an 8 ohm load. as long as you are 1 8 ohm box or two 16 ohm ones you should be fine.

    on a side note, before i took mine out for her maiden flight, i replaced all the preamp tubes too, and rechecked the bias.
    must have had a good day for electrictity, as now it appeared to be running 485vdc on the plates. the amp was a little overbiased at -50v.... in the dark, the plates were just beginning to glow. so i backed it down a smidge to about -53 volts and it seemed much happier.
    this thing has balls for days now.

    again, thanks john and bud and ultra8008 for all ya have done to make this a reality.
    bud, if ya still want the old transformer, let me know.
    rock on!
     
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  19. ultra80096

    ultra80096 Senior Member

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    Got one of mine installed. It went well, & pretty easy excepting .. I forgot to connect one wire on the star ground. One of the 22uf 100v caps started to smoke. Darnit! Found my mistake, the amp still works fine, biases up great, & it's quiet believe it or not, but I'm for sure going to be replacing those caps pronto, at least. I should have triple-checked my work. Dang, one gound wire..

    I do believe I have 5-10 more plate voltage than before, around 500 previous, now 508-509, biased with the same wattage dissipation. I'm running fresh JJ 6L6GC's so they should take it.
     
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  20. pinkjimiphoton

    pinkjimiphoton Silver Supporter

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    yeah bro surprises suck lol
     
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