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Thread: Help and ideas for repairs to Ampeg B2r

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    Unhappy Help and ideas for repairs to Ampeg B2r

    I'm the bassist in a Nashville band with a lot of shows coming up, and I'm flat broke having just moved into a new place. My amp works for a while, then begins to cut in volume and becomes dirty. I have noticed when I tap it (specifically in the center) it comes back. So my thoughts are that something is loss, or going out. I have checked the fuse, replaced all cables, plugged my bass into multiple other amps, and all of the other basic stuff. What would be bad, but still allow a distorted signal?

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    what amp?

    make and model would help.

    in general first thing comes to mind is the tube sockets need cleaned/ retentioned

    Ray

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    Lifetime Member Enzo's Avatar
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    Look at the thread title.

    First suspects are jacks - FX loop jacks, powr amp in jacks, headphones jacks, etc. RUn contact cleaner through them

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    Education is what you're left with after you have forgotten what you have learned.

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    The model is the Ampeg B2R E. And it's solid state. Wish it where tube...

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    oops

    I should use my glasses when I'm on the computer. I thought I read "help and Ideas for repair to AMPLIFIER"
    Mia Culpa

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    Yeah day three I've got it out on my table again. I guess I'm going to start the reverse engineering process. I have found that if I tap the main board ( stamped JB9 ) this makes it come back in... Wish me luck. I need to find a chat-room for this sort of thing so that I can have technicians talking to me like I'm defusing a bomb screaming at the top of their lungs that I'm removing the wrong line...

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    Supporting Member Jazz P Bass's Avatar
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    Ampeg B2

    Just my 2 cents worth. Look at the soldering of the biggest components.
    If the joints look flat, you really should attempt to resolder the board.
    The solder should flow up the component lead. Miniscus is the word, I think.
    Well over half of my repair jobs call for resoldering.

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    Last edited by Jazz P Bass; 10-09-2009 at 04:31 PM. Reason: misspelling

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    You mean on the bottom of the board (side facing down )?

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    Supporting Member Jazz P Bass's Avatar
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    Miniscus

    Yeah, look on the bottom & the top. Obviously you cannot see under the big capacitors. Look around. If tapping changes the amp, I would surely suspect bad soldering.

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    There is a gel like goo around a lot of the resistors and capacitors. I know techs use it to hold electronics in place, but if used in excess should I be concerned about the amp being ''jerry'' rigged?

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    So I have completely removed the big board without disconnecting the wire harnesses, and have started to check all of the soldering points. They all appear to be fine, but then again I'm not really sure what to look for other than a stem.

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    Someone actually just suggested checking the "Bias resistors" and asked me if my output buttons where set correctly? I'm assuming that they mean the buttons that say -20 db / 0 db and pre/ post. All I use with this head is a r.m. compressor and a r.m. tuner. So what should those buttons be set to, and could that affect anything?

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    Here are some examples of some solder joint cracking in various stages from advanced to subtle (not in an Ampeg but indicative of what you are looking for) - having had experience with Ampegs made over the last couple decades or so I would bet there are solder cracking issues in a few places - especially at the multipin headers which the ribbon cables plug onto.

    Use magnification & lots of light when inspecting.

    http://amp8.com/tr-amp/hitachi/etc/jpeg/8500-u.jpg

    http://www.jamma-nation-x.com/jammax...oldercrack.jpg

    http://home.comcast.net/~tatng/Auto/MainRelay-5-cracked-joint.JPG

    http://www.rangerovers.net/repairdet...rackjoint1.jpg

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    Lifetime Member Enzo's Avatar
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    Please humor an old tired man, check your loop jacks.

    You have not only the FX loop jacks, but also the preamp out and power amp in which work the same as a loop. if the return jack on either pair gets electrically dirty at all, it can cause exactly what you complain of. Take a spare cord and plug it from send to return at the FX loop. Take another cord and plug preamp out right back to power amp in. Does that stop the problem?

    or from the inside, look at the row of loop jacks across the rear - four of them in a group. Unless these are the ones with the white plactic cover - which can be peeled off - you can see the contacts. They are metal strips crosswise to the plug. As the amp is doing its bad thing, gently press down on each strip - the ones that touch the tip of a plug if one were in them. Does that make a difference?

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    Last edited by Enzo; 10-10-2009 at 07:06 AM. Reason: spelign problum
    Education is what you're left with after you have forgotten what you have learned.

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    Quote Originally Posted by Enzo View Post
    Please humor an old tired man, check your loop jacks.
    Oh yeah - and what Enzo said (twice).

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    Just a word of caution. When you start to solder/re-solder, work as quickly as possible with the smallest, lowest wattage tip you can. It is so easy to lift a trace or pad, and then you are back pedaling with jumper wires.
    Good Luck

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    Wow... I get home and have a few good ideas from friends, on top of all of these suggestions. I will let you guys know how it goes... Thanks!

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    Sorry about the delay in response guys. I tried "Enzo's" idea: "Take a spare cord and plug it from send to return at the FX loop. Take another cord and plug pre-amp out right back to power amp in." I also tried the other suggestions, including the loop jacks, and all connect points. I am exactly where I started. Thanks for your help guys but it looks like I might just need to save up some more cash over time and give it to the pro's. If any other suggestions, please feel free to hit my email (but I will definitely recommend the forum to some friends of mine. It has got me back in tech mode with everything around my house that need fixing. Thanks, Chris~ An Ariatic Silence

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    Last edited by cscarpenter; 10-21-2009 at 06:04 PM. Reason: html removed

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    Supporting Member rf7's Avatar
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    You need to chop stick the board. Put it back in the chassis with everything hooked up. Feed a constant signal or play through it, and move stuff around on the board with a chopstick (non-conducting, of course) and see if moving or touching anything makes the sound cut in and out. You might be able to identify the problem that way. Be very careful and don't touch the electronics with anything but the stick. That is your next step.

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    I'll try that first thing. Thanks

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    Nope. Well it works, but on to big of an area. Can't really figure out what area it's coming from. So now I'm just lost on this...

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    Well after all of that, I took it to Marc Ferguson of Fergs Amp Shop in Nashville. I can't remember what he said it was, but apparently one of the components had come apart. He actually had another one just chillin on his desk and didn't even charge me to fix the amp. Just the bench fee of like $40 and it works way better than the day I bought it! Just wanted to say thanks to this site, and I have kept my word. I have told all the guys I know to come to this site for any help. You guys have been awesome. So thanks again... cscarpenter

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    Supporting Member TomCarlos's Avatar
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    Can I reopen this thread? I am curious if cscarpenter found out "which" component failed.

    I too am working on a B2R for a friend. It has an intermittent "crackle" sound. I am checking and resoldering the main power board. One thing I noticed, R54A and R54B, both 270 ohm, 5 watt resistors, in series with one another. Instead of having a dedicated spot on the PC board for each resistor and using a trace to connect them, they are connected in free air by having the leads soldered to one another. Does that seem right? Must be a fix after the PC board was designed?

    Yes, I used jumpers on the Effects Loop and Power Amp In/Out jacks. So I am hoping that we have a solder problem on the board. Will report back.

    Tom

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    Last edited by TomCarlos; 08-02-2011 at 06:52 AM.

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    Lifetime Member Enzo's Avatar
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    It would be simply a HUGE coincidence if the exact same component was making the noise on yours. You just need to get in there and isolate the problem. Ball up your fist and whack the top of the amp. If the amp reacts with a noise, then there is a loose connection somewhere.

    Plug a cord into the preamp out jack and feed the signal to some other amp. Is the noise on that feed? And same with the FX send, is the noise on that? Hook up the DI out to some amp or mixer, is the noise on that? Does the pre/post switch change anything? Plug a shorting plug into the power amp in jack, does that kill the noise, or does it remain?

    And that ribbon cable from preamp to power amp board? Wiggle either end of that - make noises?

    Those two resistors are intended to be that way. The layout pictorial shows them there, and even has a note about soldering them together before installing.

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    Supporting Member TomCarlos's Avatar
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    As always, my appreciation to Enzo and others for sharing.

    I think the problem has been fixed- a soldering issue in the Power Amp.

    I was able to get a clean signal out of the Effects Send and Power Amp out jacks. So that meant the problem was in the Power Amp section. With a signal through the amp (an ipod and some music), I gently pushed down on the Power Amp board and could hear the crackling sound. So I knew this is there the problem was.

    I carefully examined each solder joint and did some touch up soldering. As for R54A and R54B (270 ohm, 5W resistors), I had to do something with those puppies. So I changed them out- BUT- as you can see from the attached photo, I drilled a small hole in the PC board and brought the two leads together, through that hole, and then soldered above the board. I believe that doing this puts less stress on the leads. The resistors were not the problem. But I wanted to clean this up before turning the amp back over to the owner.

    Anyway... 1 hour of playing and things seem to be back to normal.

    Click image for larger version. 

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  26. #26
    Supporting Member Jazz P Bass's Avatar
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    I like the drilled hole.
    #1 on that.
    You would think some of these amp manufacturers would catch on when it comes to laying these boards out.
    Sheesh.

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