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Thread: Two Amps Died the Same Way HELP!!

  1. #41
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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by GoldenVulture View Post
    Not likely to cause any operational problems at all.

    Your using a step up transformer , not an inverter, it's a bit irrelevant. [ 1000W step-up transformer. ] Plenty big enough to handle the draw of the amp and other things you have plugged in.
    You are right. At no point is DC inverted to AC. AC to DC rectification only. The s/u transformer provides a corrected line supply... Understood. I'm referring to the amp itself. If line AC is dropping (due to faulty s/u transformer), theoretically the amplifier should be pulling excess amperes per demand. The AC to DC rectifier assembly is the first point of contact after the main supply. Is the bridge rectifier not the stress point? The mains and bridge are fused, but lets say the amp is pulling excess amperes, for whatever reason... Can the rectifier diodes become damaged without the fuse being blown?

    I once owned a Mojave "Dirty Boy" amp that had three transformers! One for line supply, one for a on-board variac, and one for heater supply. Line supply had to be maintained at 120VAC, as did the heaters at 6.3 volts.
    Last edited by 67Mopar; 07-10-2018 at 06:21 AM.

  2. #42
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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by 67Mopar View Post
    You are right. At no point is DC inverted to AC. AC to DC rectification only. The s/u transformer provides a corrected line supply... Understood. I'm referring to the amp itself. If line AC is dropping (due to faulty s/u transformer), theoretically the amplifier should be pulling excess amperes per demand. The AC to DC rectifier assembly is the first point of contact after the main supply. Is the bridge rectifier not the stress point? The mains and bridge are fused, but lets say the amp is pulling excess amperes, for whatever reason... Can the rectifier diodes become damaged without the fuse being blown?

    I once owned a Mojave "Dirty Boy" amp that had three transformers! One for line supply, one for a on-board variac, and one for heater supply. Line supply had to be maintained at 120VAC, as did the heaters at 6.3 volts.
    That is one possible scenario but based on his advice [OP] from Engl pointing towards the diodes, I'd say it's a common problem that they are aware of. At this point probably because they are under rated and probably better replaced with higher ampaerage diodes.

    Under rated diodes and resistors are a fairly common problem in power supplies of many devices I have serviced over the years.

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by GoldenVulture View Post
    That is one possible scenario but based on his advice [OP] from Engl pointing towards the diodes, I'd say it's a common problem that they are aware of. At this point probably because they are under rated and probably better replaced with higher ampaerage diodes.

    Under rated diodes and resistors are a fairly common problem in power supplies of many devices I have serviced over the years.
    Once again, thanks for all your help and feedback.

    Honestly, you're probably correct on all accounts. However, considering that multimeter readings from the outlet show my jury-rigged ground is not functioning properly, I figure it's in my best interest in any case to address that issue as well. At the very least it will make my surge protector actually capable of protecting against surges for a start, LOL.

    Also I believe I read something about amps using ground as a voltage reference? If that's the case, running a crapped out ground connection probably isn't doing my amp any good, even if it isn't the cause of the present failure.

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by 67Mopar View Post
    You are right. At no point is DC inverted to AC. AC to DC rectification only. The s/u transformer provides a corrected line supply... Understood. I'm referring to the amp itself. If line AC is dropping (due to faulty s/u transformer), theoretically the amplifier should be pulling excess amperes per demand. The AC to DC rectifier assembly is the first point of contact after the main supply. Is the bridge rectifier not the stress point? The mains and bridge are fused, but lets say the amp is pulling excess amperes, for whatever reason... Can the rectifier diodes become damaged without the fuse being blown?

    I once owned a Mojave "Dirty Boy" amp that had three transformers! One for line supply, one for a on-board variac, and one for heater supply. Line supply had to be maintained at 120VAC, as did the heaters at 6.3 volts.
    I'm sure that my step-up transformer is delivering adequate power — I've measured it myself (119V). The ground wire is definitely not doing what it's supposed to though. I opened up the socket panel today and found that the "ground screw" inside is connected to a plastic housing embedded in a sheet of drywall. It might as well be grounded to a Dixie Cup.

    There's a properly grounded three-pronger on the ceiling which supplies the air conditioner. In Japan, ground wires are safety grounds, so I'm thinking I'll just use an extension to piggyback the ground wire from the step-up transformer into the aircon jack.

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by GoldenVulture View Post
    That is one possible scenario but based on his advice [OP] from Engl pointing towards the diodes, I'd say it's a common problem that they are aware of. At this point probably because they are under rated and probably better replaced with higher ampaerage diodes.

    Under rated diodes and resistors are a fairly common problem in power supplies of many devices I have serviced over the years.
    I mentioned this, because he said that he experienced the same issue with two amplifier brands. I hope he gets this sorted out.

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by Punkrot View Post
    I'm sure that my step-up transformer is delivering adequate power — I've measured it myself (119V). The ground wire is definitely not doing what it's supposed to though. I opened up the socket panel today and found that the "ground screw" inside is connected to a plastic housing embedded in a sheet of drywall. It might as well be grounded to a Dixie Cup.

    There's a properly grounded three-pronger on the ceiling which supplies the air conditioner. In Japan, ground wires are safety grounds, so I'm thinking I'll just use an extension to piggyback the ground wire from the step-up transformer into the aircon jack.
    Have you checked to see if there is voltage on the ground? Are you in a house or an apartment?

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by 67Mopar View Post
    I mentioned this, because he said that he experienced the same issue with two amplifier brands. I hope he gets this sorted out.
    Personally, I don't see these as mutually exclusive conclusions.

    It's absolutely possible that the rectifier diodes have a tendency to blow out to the extent that Engl is well aware of the issue.

    It's also possible that what caused them to blow out is some kind of stress caused by my ghetto-fabulous power supply situation.

    As my original post suggests, I'm likewise very suspicious of the fact that both amps died in the same way. It may be merely a coincidence, but Occam's Razor seems to suggest a common link: A) some factor capable of affecting both amps during operation caused an identical failure in both vs. B) both amps randomly failed in an arbitrarily identical way due to common problems in their designs despite being made by different manufacturers at an interval of 40 years.

    Which scenario appears to require less assumptions?

    Where there's smoke, there's fire and all that.
    Last edited by Punkrot; 07-10-2018 at 07:43 AM.

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by 67Mopar View Post
    Have you checked to see if there is voltage on the ground? Are you in a house or an apartment?
    Apartment.

    I listed my multimeter readings in the original post, but no worries if you missed it — it was pretty deep into TL;DR territory at that point.

    Out of the surge protector (which is hooked into the transformer), I get:
    Line to Neutral = 119V
    Line to Ground = 59V
    Neutral to Ground = 33V

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by 67Mopar View Post
    Have you checked to see if there is voltage on the ground? Are you in a house or an apartment?
    I just realized you meant is there voltage on the aircon jack's ground. Sorry about that.

    It's a split phase 200V outlet.

    Line to Neutral = 200V
    Line to Ground = 100V
    Neutral to Ground = 100V

    Not sure if there's a special way to test for voltage on the ground wire. Maybe measure the ground to something else? But if so, what would I measure it to?

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    Default Re: Two Amps Died the Same Way HELP!!

    Dude, my status just changed to "Senior Member," and now I feel old…

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by Punkrot View Post
    I just realized you meant is there voltage on the aircon jack's ground. Sorry about that.

    It's a split phase 200V outlet.

    Line to Neutral = 200V
    Line to Ground = 100V
    Neutral to Ground = 100V

    Not sure if there's a special way to test for voltage on the ground wire. Maybe measure the ground to something else? But if so, what would I measure it to?
    https://www.hunker.com/12339178/how-...-for-a-current

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    Default Re: Two Amps Died the Same Way HELP!!

    Sorry I cannot help you with your amp problem...but I wanted to say: You have a B-42X! Awesome! I have the 4x12 cab for that head, and I have always wanted the matching head.
    Quote Originally Posted by LesStrat View Post
    Yogi Berra was correct.
    Quote Originally Posted by JOLLY View Post
    I do a few chord things, some crappy lead stuff, and then some rhythm stuff.

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    Default Re: Two Amps Died the Same Way HELP!!

    Quote Originally Posted by ItsaBass View Post
    Sorry I cannot help you with your amp problem...but I wanted to say: You have a B-42X! Awesome! I have the 4x12 cab for that head, and I have always wanted the matching head.
    Dude, I love that amp! It's delivers this huge, warm, buttery tone that just blows my mind. Since it's a two channel amp with two identical channels, I had an amp tech add a footswitch and hotrod one of the channels by converting the broken tremolo pot into a master volume. It's such a great amp! They're quite rare, but they go for pretty cheap when you find them. And it works great for guitar or bass, so long as you don't mind the 55W output.

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    Default Re: Two Amps Died the Same Way HELP!!

    Thanks!

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