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Discussion in 'Amps and Cabs [BG]' started by i_got_a_mohawk, Aug 12, 2005.

  1. I was in town today, went into the music shop to check with the guys about getting my amp re-bias'd

    one guy thought that meant i wanted to buy a new one . . . but, gtf, ****ing salesmen :eyebrow:

    Anyway, they call up the tech that they deal with, and he says that you only ever need to do the bias when you put new tubes in, if the bias is off there has to be something else screwin up in the amp

    Im pretty sure its a good idea to have amps rebias'd every year (Beats the hell out of buying a new set of valves)

    Anyway, it doesnt seem like hes going to rebias is :eyebrow:

    I may have another source, but i think he could rebias it, but wouldnt give the whole amp the once over, hmm, choices eh
  2. Hawkeye

    Hawkeye Canuck Amateur

    You're right Mohawk. Bias can drift over time.
  3. cheers, i was pretty sure (99%) of it from what PBG and Jerrold T had said it in the thread about my 6550's

    i think the guys just wanting an excuse to try and rip me off, through the teeth
  4. Passinwind

    Passinwind I Know Nothing Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Maybe, but it sounds like he told you he didn't want to take your money for doing something he doesn't think is necessary. Tubes can shift in their operating curves over time, but biasing is done so inconsistently by many techs that you might well do better just to leave it alone if you don't have someone you really trust to do the work. Are you unhappy with how your amp sounds at the moment?
  5. Eric Moesle

    Eric Moesle

    Sep 21, 2001
    Columbus OH
    I don't get it. How is he trying to rip you off if he turned you and your money away?

    Frankly, I'd find a more reputable tech if the guy didn't understand that biasing can drift over time. I wouldn't want him working on my gear anyway.
  6. im going on the advice of other TB'ers that my amp is burning up, or moreso that one valve in particular is

    its burnt out some of the getter on one of the tube, and it could also explain the loud hum i get in the background
  7. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    I am with Passinwind.....

    Yes it can drift, No, there probably isn't a reason to have it rebiased on any particular schedule.

    There is "checking" and there is "re-setting". No need to "re-set" if it "checks" OK.

    There isn't anything unreasonable about checking it, and I personally might do that, simply because I have the equipment to check it handy and it doesn't cost me anything......

    If you are paying, I question the need for a yearly check, let alone a re-bias (re-set).

    It isn't so much the bias drifting, as it is the tubes drifting in "gain", which can affect bias. But of course the setting can move, too. But it might do that a month after you get it checked, instead before...........

    It also depends on the circuit..... many/most cathode biased amps never need any biasing, its automatic.

    If the amp gets used a lot, and is moved a lot, and the consequences of a mess-up are higher because there are a lot of expensive power tubes, maybe.....

    I WOULD have it checked as part of any actual servicing, just because you already know of a problem to fix, and the techs are already "into" it. Shouldn't add much if anything to the bill........if they are any good, they'll *check* it anyway.

    I WOULD have it re-set when power tubes are changed.

    Some people do bring their equipment in on a regular basis for checking over, and a "check" of bias would be part of that.....

    BTW, I am assuming its a tube amp..... SS also have bias, but it is better left alone unless known to be messed up.
  8. No, he said that biasing only needs to be done when you get new tubes, i think he was hinting at getting new power valves

    Aswell as the fact he was adamant it had to be something else = more bench time, more "problems" that get fixed

    He didnt turn away my money, i turned away my buisness
  9. Yeah, as i really should have had it checked out when i first got it, it was a real workhorse before i got it, used at big festivals and stuff over here, im not sure if the guy rented it out or what, but its definatly been around

    Im looking into the guy i know who may do it, just got to get him to give it a going over
  10. Funkengrooven

    Funkengrooven Turn it down? You gotta be nuts!!

    Hey Mohawk,
    too bad you ain't in the states on the east coast, I would hook up and teach you how to do it.
    not too tough, but easier shown than explained.

    what say Jerrold?
  11. Passinwind

    Passinwind I Know Nothing Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    So, you've diagnosed your hum problem as bias related, and ruled out the possible need for new tubes, even though a tube that's gone out of gain match with the rest can potentially create hum? But you're still gonna pay some other tech to check things out anyway? Or will the other guy do it for free? :eyebrow:

    There's a very good chance that the tech was right on in this case, IMHO. Troubleshooting over the phone or on a web forum is a crapshoot at best. If that rubs you the wrong way, you have every right to deal with someone who tells you what you want to hear, or who you trust more for whatever reason. Hope that works out for you. :cool:
  12. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Oh, yeah, its YOU, and you're talking about THAT amp............... Well, that changes my attitude a bit.....

    Must have been my day not to notice........sorry... tried to fall down the stairs too....

    With the stuff you have been remarking on, there is likely every reason to get it checked out. You got it used, and it came up with problems fairly shortly..... which would be a pretty good clue that it may need some work....

    IIRC, you had hum, and at least one funky-looking tube, some other noises, mebbe something else too, right?

    Not to be harsh here, but what's the issue with getting it checked out in detail? Then bias seems to fall under the "check when doing other repairs" category.

    You presumably have no idea what the previous owner did, really. And maybe the P.O. didn't do anything....as in never had it looked at and just sold it when he got tired of those noises.....?

    Or maybe he has another one, and stuck in all his old bad tubes before you got it.

    (hopefully you didn't buy it from a TB member, who I have just thoroughly dissed.....)

    The downside to "having it checked" is that it is almost impossible to check for everything that COULD be wrong......and after the tech does check it, some folks feel the tech should cover any problems for free...... making some techs a tad bit shy about that sort of thing.
  13. cheezewiz

    cheezewiz Supporting Member

    Mar 27, 2002
    Here's a suggestion. Go to a tech, buy new tubes if they are needed, have the tech bias the amp for the new tubes.

    Thank you. That is all.
  14. Shop tech = alot of money

    friend of the family tech = cheap

    big consideration into this, and i dont want to have killed off a set of sylvania 6550A's :bag:

    I know from what the previous owner said it was used alot, not something to really boast about is it ? theres also a sticker saying it was checked out (you know the kind right) and tested fine in september (i think) last year, altho, i know that problems could have come up since then and that yeah bad tubes may have been swapped in

    either way, hopefully get it checked out without having to pay too much, i can but hope
  15. cheezewiz

    cheezewiz Supporting Member

    Mar 27, 2002
    If you trust your friend of the family tech, then great. Have him look at it, get some new tubes if you need them, and have him bias the amp. You seem to want to make something simple, complicated.
  16. You got me right on that note + im a cheap bastard :D
  17. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    Remaining a cheap bastard will end up doing this amp no good. At the very least, you should be looking at replacing at least SOME of the tubes...you've got at least one that is problematic.

    You could find a tech that might be able to 'match' to the useable tubes in your amp right now, and check your bias...but if the condition of the tubes or the bias are not the real problem, then you're gonna end up wasting the $$$ you spend on that 'bargain' fix. You're just gonna ruin another bunch of tubes and have to take it in for a real fix.

    I second the notion that you should have the amp gone over and spend the money. Do it now, make the amp sound good, build your peace of mind that the amp will keep running and be playable when you need it.

    What's the point of buying this amp, having it in barely playable condition that could deteriorate to unplayable and then complain about it all the time?
  18. Its going to get a good going over, i just want the cheaper tech to give it a going over

    Aswell as the one in the shop will now be on holiday for 2 weeks, buggery

    I'll sort something out when im not on the brink of psychosis :D
  19. That's a VERY BAD idea. Good techs charge more; you're paying for their experience. Anybody can eventually figure out how to fix a car, but when it breaks, you look for a good mechanic, one who won't waste time and money or hunting down a problem that an experinced mechanic can find in five minutes.

    BTW, I don't think you necessarily NEED new tubes.
  20. Nothing wrong with paying for experience, but why have to pay the excess that'll be taken from the shop and especially when this is someone i know and and probably has as much if not more experience (25+ years)

    i'll get it sorted out at some point, and i really hope i dont need the new tubes, but when in need i guess