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  • speaker protection relay issue

    I have a hartke HA5500 bass head here I'm trying to fix for a buddy and I'm having a heck of a time trying to figure this out. Mainly because it's so intermittant. problem is, the speaker protection relay clicks off at times but will start working perfectly other times and i can play the thing even loudly for 30 minutes and it won't happen. then another day I'll power it up and the relay will click on, then within 30 seconds it'll click off and will not click back on again till i turn it off and usually have to wait a bit. I thought if there was a shorted output or such wouldn't it always click off? Or a device thats heating up....if that were the case it sure as heck wouldn't allow me to play it loud w/o issues for 30 minutes.

    Of course the only thing i could think of given these details is a bas solder joint or connector. But i have chopsticked the entire amp, boards, components, wiring etc ad nausium and never triggers a thing. I can email a schematic to anyone who is willing to look at it. But I think it's possible a older revision. Anyways, even any thoughts off the top of your head would possibly help, as this is getting to be extremely time consuming and i DO have a life....well, I DID B4 this anyways.

  • #2
    My advise , on any amplifier that is acting stupid, is to look at the soldering job of the boards.
    If the largest components look like they did not pick up enough solder, bingo, a reflow is called for.
    Understand, I am just a picky SOB who does not want amps coming back.

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    • #3
      Originally posted by Jazz P Bass View Post
      My advise , on any amplifier that is acting stupid, is to look at the soldering job of the boards.
      If the largest components look like they did not pick up enough solder, bingo, a reflow is called for.
      Understand, I am just a picky SOB who does not want amps coming back.
      Already did that but nothing looked suspicious. It's actually one of the better boards i've seen in that respect.

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      • #4
        Have you tried monitoring the Vdc on the speaker output?
        Protection circuits can kick in with just ~+/-50mV there.
        Pete.
        My band:- http://www.youtube.com/user/RedwingBand

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        • #5
          Originally posted by pdf64 View Post
          Have you tried monitoring the Vdc on the speaker output?
          Protection circuits can kick in with just ~+/-50mV there.
          Pete.
          Just did. I turned it on with the meter leads on the speaker +&- on DCV and it didn't register even a single mV, even when i heard the relay kick off. (after having kicked on 20 seconds before when i turned the amp on) It's so bizzare because i can turn it on hot or cold and it may work for 30 minutes (never played longer but thats as long as I wanna sit there playing bass) w/o a hitch, or the relay may kick off 10 seconds after it first kicked on when i started the amp and never go back on till i shut it down. Or it may shut off then a while later back on. All of those for no rhyme or reason i can think of. I hate &^%$ like this !

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          • #6
            Oooooh ! This is interesting ! theres a diode in parallel with the relay coil, and it reads 24VDC as it' should being a 24VDC relay. That is, untill i hear it kick off at which time it reads 94 VDC! Could this be a intermittently bad PSU cap?

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            • #7
              Are you measuring the Vdc on the 'amp' side of the relay contacts, rather than the 'speaker / protected' side?
              If there's no Vdc on the amp side but the protection kicks in, then, if all else fails, a hardwire bypass across the relay contacts is an option.
              Not recommended, but...
              Pete.
              My band:- http://www.youtube.com/user/RedwingBand

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              • #8
                So the amp is going into protect.
                You need to find why.
                The TA3717 is a 'protect' IC. (Edit:" TA7317" Correct IC#)
                You need to find out if the ic itself is at fault (including the relay circuit) or is it doing what it is designed to do.
                Which is: drop out the relay if overcurrent (pin 1) or Vdc present (pin 2 & 3) is an actual fault input.
                Monitor those pins & document what is happening, on those pins, when the relay is energized & when it drops out.
                Last edited by Jazz P Bass; 04-27-2012, 11:51 PM.

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                • #9
                  Here is why, I will bet my lunch money on it.

                  The TA 3717, and shouldn;t that be a TA7317?, has a few small electrolytic caps around it. They dry out from the heat. Just replace the lot of them. There4 is a 1uf/50v and a 0.47uf/50v (typically) that are probably responsible. But I go ahead and replace the 100uf and teh 470uf while I am at it.

                  Your relay coil does not have 94 volts across it. The relay coil runs off the V+ rail, the TA7317 drawsw current from there through the coil to energize it. The important concern in the voltage ACROSS the coil, the voltage from the coil to ground is irrelevant. The diode is in parallel with the coil, so it is a convenient place to measure. When the relay is on, and the amp making sound, there shoud be about 24v across the diode/coil. When the coil drops out - is not energized - there will be zero across the diode/coil. It may be sitting at +94v, but there is no complete circuit and so no current.
                  Education is what you're left with after you have forgotten what you have learned.

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                  • #10
                    Here is why, I will bet my lunch money on it.

                    The TA 3717, and shouldn;t that be a TA7317?, has a few small electrolytic caps around it. They dry out from the heat. Just replace the lot of them. There4 is a 1uf/50v and a 0.47uf/50v (typically) that are probably responsible. But I go ahead and replace the 100uf and teh 470uf while I am at it.

                    Your relay coil does not have 94 volts across it. The relay coil runs off the V+ rail, the TA7317 drawsw current from there through the coil to energize it. The important concern in the voltage ACROSS the coil, the voltage from the coil to ground is irrelevant. The diode is in parallel with the coil, so it is a convenient place to measure. When the relay is on, and the amp making sound, there shoud be about 24v across the diode/coil. When the coil drops out - is not energized - there will be zero across the diode/coil. It may be sitting at +94v, but there is no complete circuit and so no current.
                    Education is what you're left with after you have forgotten what you have learned.

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                    • #11
                      Originally posted by Jazz P Bass View Post
                      So the amp is going into protect.
                      You need to find why.
                      The TA3717 is a 'protrect' IC.
                      You need to find out if the ic itself is at fault (including the relay circuit) or is it doing what it is designed to do.
                      Which is: drop out the relay if overcurrent (pin 1) or Vdc present (pin 2 & 3) is an actual fault input.
                      Monitor those pins & document what is happening, on those pins, when the relay is energized & when it drops out.
                      I'm going to be gone for the weekend, but when i get back to it i'll see what i can do. I am going to have a heck of a time measuring at the pins the way this thing is put together, but i'll see when i look at it next what i can do.

                      Are you measuring the Vdc on the 'amp' side of the relay contacts, rather than the 'speaker / protected' side?
                      yep, and I realize now that i have to do it at the relay as both you and JPB said.

                      I keep thinking the symptoms should eliminate some things, probably DC to the speaker or any transistor. I mean, besides a shorted trace or other mechanical short or a intermittent connection/joint, what could make it work fine for a 1/2 hour and then other times the relay goes open 10 seconds after the amp was started and the relay had already gone closed ?

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                      • #12
                        You don't need to get to the physical pins of the IC, every pin on it is wired to some resistor or other thing. If pin 1 is wired to resistor R12345, then measure the voltage on R12345's lead.
                        Education is what you're left with after you have forgotten what you have learned.

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                        • #13
                          Originally posted by Enzo View Post
                          You don't need to get to the physical pins of the IC, every pin on it is wired to some resistor or other thing. If pin 1 is wired to resistor R12345, then measure the voltage on R12345's lead.
                          I do that all the time. It's just the way this thing is laid out makes it hard to get to anything. Not saying i can't, but it will be a pain 2 b sure.

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                          • #14
                            Just shotgun the caps like Enzo said. If you're not detecting an offset and the detection IC is good. That's probably the cause. If they are surface mounted caps, it goes double.

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                            • #15
                              Through hole, but there are a couple hot resistors right by there.

                              Not rare in Hartkes, common enough in Samson amps, even found the same thing in a TOA the other day.

                              And if it turns out to be something weird, well, we are only out a handful of cheap caps.
                              Education is what you're left with after you have forgotten what you have learned.

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