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Thread: Looking for a power transformer Hartke HA 4000

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    Looking for a power transformer Hartke HA 4000

    My power trannie is Bad on my Hartke HA 4000 Bass Head and I have already soaked a lot of work into it so i want to get it going. I called samson they no longer make the part and they have no NOS. I looked for people who rewind trannies and only found one that does small guitar amp types still waiting to hear back from them every body else is industrial.Anyways Im Kevin if you can help please let me know thanks.

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    Try to have a new one wound. I'm sure someone here will be willing to share the specs of it...
    It will be cheaper.

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    got a quote of 210 not including shipping this morning a little more than i am willing to pay.

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    I do HVAC professionally and i have dealt with a company that winds motors for years if someone on this forum can give the specs i would ask them they might give me a better price as a favor.

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    Old Timer J M Fahey's Avatar
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    Just curious, are you really sure the PT is bad?
    Have you checked it on its own, with all secondary taps disconnected and floating in the air?
    What kind of failure does it show?
    Open primary?
    Heavy short, blows fuses instantly?
    Shorted turn/compromised insulation: overheats on its own and maybe 30 minutes later starts smoking/becomes unbearably hot?

    In any case I guess it wont be hard to find an over the counter transformer, same or very close specs, for a reasonable price
    Antek is a good supplier, write them.
    So far this one looks close enough to work in your amp, maybe they have a closer one, price is very good:
    AN-8448 - 800VA 48V Transformer - AnTek Products Corp

    As I read the specs, they have 2 secondary windings for each voltage stated, so if Im not wrong, they have 2 x 48V secondaries which in series would be good for getting +/-67V rails , guess original Hartke must be very close to that.
    The lower voltage windings should be fine to power the preamp.

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    Juan Manuel Fahey

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    Supporting Member Jazz P Bass's Avatar
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    I think the HA4000 uses closer to 80 volt rails, if that helps.
    Schematic is here: Hartke HA4000

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    Wow thanks Fahley I have only been repairing and building amps for a couple of years and i have not gotten good with substitution yet. And yes the transformer insulation is about shot it measures about 1 ohm dc resistance on the primary and a little less on the secondary the low voltage taps one tap to ground gives me about 8 volts the other about 1.2 any kind of load on it and it instantly blows a fuse but no that I see you can fin substitions this is good.I have already replaced all the 8 shorted out npn and pnp power transistors and the ceramic bias resistors the voltage regulators I have put some work in im in too deep to quit.Thanks again I like this forum

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    Old Timer J M Fahey's Avatar
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    Thanks but I'm not sure yet you have a blown transformer.
    The low primary and secondary DC resistance do not look bad for such a big transformer.

    Reconnect primary to power switch, fuse, etc. , and DISCONNECT ALL SECONDARIES , by unplugging connectors, desoldering, whatever it takes.
    If you end up with some unterminated wires, tape ends individually for safety and insulation.

    Only after that, place the proper fuse in the holder (remember it's probably a slow blow or "T" type one) and give it one more try.

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    Juan Manuel Fahey

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    Quote Originally Posted by J M Fahey View Post
    Thanks but I'm not sure yet you have a blown transformer.
    The low primary and secondary DC resistance do not look bad for such a big transformer.

    Reconnect primary to power switch, fuse, etc. , and DISCONNECT ALL SECONDARIES , by unplugging connectors, desoldering, whatever it takes.
    If you end up with some unterminated wires, tape ends individually for safety and insulation.

    Only after that, place the proper fuse in the holder (remember it's probably a slow blow or "T" type one) and give it one more try.
    It does not blow a fuse disconnected but it is still bad it is putting out irratic voltages two taps that are supposed to be evenly center tapped yet one is like 8 volts to ct and the other 1.2 same with the main rail irratic voltages just enough insulation shorted on itself not to ground but when a load is applied pow!There is no substantial short or low ohms in any other part of the circuit the semiconductors are 7815 and 7915 15 volt regulators the old one were questionable so they were replaced the newer but compatible LM series but every thing is kosher the only bad apple in the bunch is that transformer. I contacted Hartke and he said he would email me the exact specs so I could match it up better.

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    Old Timer J M Fahey's Avatar
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    Quote Originally Posted by rkscott7 View Post
    It does not blow a fuse disconnected
    If it passes current (it does, you already confirmed the primary is not open) and does not blow fuses or quickly overheat on its own, Im still not convinced its bad.
    but it is still bad it is putting out irratic voltages two taps that are supposed to be evenly center tapped yet one is like 8 volts to ct and the other 1.2
    Shorted turns transformers do not do that, so I rather think bad measurement, poor probe contact, etc.
    Please draw a simple transformer schematic and write on it lead to lead voltages and lead to lead resistance.
    So far you might be measuring stray voltage between unconnected windings.
    same with the main rail irratic voltages
    Makes me think what I write above.
    just enough insulation shorted on itself not to ground but when a load is applied pow!
    That makes me think that the problem is not with internal insulation but with external load.

    There is no substantial short or low ohms in any other part of the circuit
    Maybe not with <1V that the multimetter applies for testing, nasty things might still happen with actual hairy voltages.

    the semiconductors are 7815 and 7915 15 volt regulators the old one were questionable so they were replaced the newer but compatible LM series
    but every thing is kosher the only bad apple in the bunch is that transformer.
    If things blow when applying load, there are still some pretty bad apples around there.
    I contacted Hartke and he said he would email me the exact specs so I could match it up better.
    Cool, but Id hate to read you bought an expensive new transformer and one day later you post the amp still has problems.
    Id test that transformer further until satisfied its shorted or open.
    Nothing yet confirms that.
    Good luck.
    PD: nothing fancy, a crude Paint drawing is fine

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    Juan Manuel Fahey

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    Master Destroyer nosaj's Avatar
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    If a ha 3500 pt will work I have one for sale $40 plus shipping from 32571.

    Thanks,
    nosaj

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    Supporting Member The Dude's Avatar
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    I'm with Juan on this one. Transformers almost always either blow fuses (short) or open. The type of failure mode you describe is EXTREMELY rare. I'm more inclined to attribute your readings to some sort of metering error.

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    Yeah, well, you know, thats just, like, your opinion, man.

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    Ok I took my measurements again your right this transformer is good the voltages are even and good i dont know if I was just frustrated or in a hurry but that is good news i did not want to sheel out that money anyway.

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    Lifetime Member Enzo's Avatar
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    So you are back to something in the circuits blows the fuse hard.

    As with any amp, isolate the problem. Check for shorted output transistors, check that main bridge rectifier for shorts, the lower voltage supplies seem to have individual fuses.

    If this is like I think, you have three wires from the main power winding and bridge, and then maybe a connector for all the lower voltage wires? Try plugging in the connector but not the three wires. Blows fuses?

    Got the three main wires from the bridge, leave them off, the three terminals are ground and V+ and V-. Check if V+ or V- is shorted to ground, then also check to see if V+ is shorted to V- directly.



    A top, when you are trying to measure voltage at the end of a bared wire, use clips. It is hard to maintain good contact with a held probe on a loose wire.

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    Old Timer J M Fahey's Avatar
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    Please build a bulb lamp limiter.
    It will let you measure *something* without constantly blowing fuses and stressing stuff.
    Try to get somewhere a 100/150W filament lamp, worst case a stick/pencil quartz lamp which I think still are sold.
    Light Bulb Limiter

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