Two Amps Died the Same Way — HELP!!
Hello Everyone,
I have a rather mysterious problem, and I'm hoping some of the good folks on here — especially those of you who are versed in amp repair and/or electrical systems — can help me out.
As the title says, I have two amps that stopped working in exactly the same way, and I have no idea why.
The Amps
Amp #1: Ampeg 1969 55W Jupiter B-42X (tube rectified)
Amp #2: Engl Fireball 100 (diode rectified)
The Problem
The problem started as a periodic volume fluctuation (like someone slowly turning the volume down and then back up again). This became more frequent, and then eventually the amp stopped making sound altogether — as in, one day I turned it on and no sound came out.
This problem first occurred with the Ampeg. I figured the power tubes were going bad, and I've been wanting to make the jump from distortion pedal to tube distortion, so I sprung for the Engl (bought it used off eBay). I put new power tubes in it myself.
Everything was fine for about 9 months or so, but then the Engl started doing the volume fluctuation thing exactly the same way. Recently, I turned it on and it took a really long time to start making sound — but it did start working normally after awhile. A week went by during which I didn't get to play, and when I finally fired up the amp it didn't make any sound, even after waiting for more than 10 minutes for it to warm up.
I emailed Engl Tech Support, and they had me check to see if the first three (out of four total) preamp tubes were heating up. They weren't. Engl's best guess is that "the rectifier diodes may have been damaged," and that the amp will work once they're replaced. They're probably right, and I fully intend to bring the amp to a tech for repairs.
However, what I want to know is why this problem happened to two different amps so I can stop it from happening again.
Also, and here's one of the truly mind-bending parts of the mystery — I decided to plug in the Ampeg to see if its preamp tubes were cold too. Not only were they warm and working, so was the amp. The Ampeg, after sitting on a shelf for 10 months, magically fixed itself. (WTF?!)
If any of you shredders can give me a lead, I'm all ears.
Additional Information (which may or may not be relevant)
1. I played both amps at very low volumes since I'm in an apartment (working to get my chops up before starting a band).
2. I'm in Japan where it often gets humid as all hell, and both amps failed during the soggy months.
3. I always let both amps sit on standby for a minute or so after powering up, and before powering down.
4. I ran both amps off a surge protector plugged into a 1000W step-up transformer. (Both amps are configured for 120V US power, but Japanese sockets provide 100V.)
5. Because Japanese sockets are two prong, I used a "cheater plug" with a protruding ground wire, and hooked the ground wire to the screw inside the socket panel.
6. I kept both amps plugged in, even when not in use.
7. Multimeter test of the socket:
Line to Neutral = 119V
Line to Ground = 59V (I believe half voltage readings from line to ground are normal in Japan, but I'm not clear as to why — something about phase?)
Neutral to Ground = 33V (I think this is due to the diodes in the surge protector, but…?)
8. Multimeter test of the step-up transformer:
Line to Neutral = 119V
Line to Ground = 76V (???)
Neutral to Ground = 9V (???)
9. Multimeter test of wall socket (cheater plug with ground wire hooked to panel screw):
Line to Neutral = 102V
Line to Ground = 67V (???)
Neutral to Ground = 1V (???)
10. The surge protector also supplies a solid state analog stereo, and my rig's tuner pedal (also both requiring US voltage).
11. A few other notes about the Engl's current status — power tubes light up and get hot, power tube monitor lights read normal, fourth preamp tube (the PI) gets hot, first three preamp tubes stone cold, no sound at all from the speakers except for a faint hiss when cranked, plugging into the FX return makes no difference, changing channels makes no difference.
12. Both amps are now sitting unplugged in hopes that the Engl just might magically fix itself too (not holding my breath…)
Sorry for the mile-long post. And thanks in advance for any help!
Hello Everyone,
I have a rather mysterious problem, and I'm hoping some of the good folks on here — especially those of you who are versed in amp repair and/or electrical systems — can help me out.
As the title says, I have two amps that stopped working in exactly the same way, and I have no idea why.
The Amps
Amp #1: Ampeg 1969 55W Jupiter B-42X (tube rectified)
Amp #2: Engl Fireball 100 (diode rectified)
The Problem
The problem started as a periodic volume fluctuation (like someone slowly turning the volume down and then back up again). This became more frequent, and then eventually the amp stopped making sound altogether — as in, one day I turned it on and no sound came out.
This problem first occurred with the Ampeg. I figured the power tubes were going bad, and I've been wanting to make the jump from distortion pedal to tube distortion, so I sprung for the Engl (bought it used off eBay). I put new power tubes in it myself.
Everything was fine for about 9 months or so, but then the Engl started doing the volume fluctuation thing exactly the same way. Recently, I turned it on and it took a really long time to start making sound — but it did start working normally after awhile. A week went by during which I didn't get to play, and when I finally fired up the amp it didn't make any sound, even after waiting for more than 10 minutes for it to warm up.
I emailed Engl Tech Support, and they had me check to see if the first three (out of four total) preamp tubes were heating up. They weren't. Engl's best guess is that "the rectifier diodes may have been damaged," and that the amp will work once they're replaced. They're probably right, and I fully intend to bring the amp to a tech for repairs.
However, what I want to know is why this problem happened to two different amps so I can stop it from happening again.
Also, and here's one of the truly mind-bending parts of the mystery — I decided to plug in the Ampeg to see if its preamp tubes were cold too. Not only were they warm and working, so was the amp. The Ampeg, after sitting on a shelf for 10 months, magically fixed itself. (WTF?!)
If any of you shredders can give me a lead, I'm all ears.
Additional Information (which may or may not be relevant)
1. I played both amps at very low volumes since I'm in an apartment (working to get my chops up before starting a band).
2. I'm in Japan where it often gets humid as all hell, and both amps failed during the soggy months.
3. I always let both amps sit on standby for a minute or so after powering up, and before powering down.
4. I ran both amps off a surge protector plugged into a 1000W step-up transformer. (Both amps are configured for 120V US power, but Japanese sockets provide 100V.)
5. Because Japanese sockets are two prong, I used a "cheater plug" with a protruding ground wire, and hooked the ground wire to the screw inside the socket panel.
6. I kept both amps plugged in, even when not in use.
7. Multimeter test of the socket:
Line to Neutral = 119V
Line to Ground = 59V (I believe half voltage readings from line to ground are normal in Japan, but I'm not clear as to why — something about phase?)
Neutral to Ground = 33V (I think this is due to the diodes in the surge protector, but…?)
8. Multimeter test of the step-up transformer:
Line to Neutral = 119V
Line to Ground = 76V (???)
Neutral to Ground = 9V (???)
9. Multimeter test of wall socket (cheater plug with ground wire hooked to panel screw):
Line to Neutral = 102V
Line to Ground = 67V (???)
Neutral to Ground = 1V (???)
10. The surge protector also supplies a solid state analog stereo, and my rig's tuner pedal (also both requiring US voltage).
11. A few other notes about the Engl's current status — power tubes light up and get hot, power tube monitor lights read normal, fourth preamp tube (the PI) gets hot, first three preamp tubes stone cold, no sound at all from the speakers except for a faint hiss when cranked, plugging into the FX return makes no difference, changing channels makes no difference.
12. Both amps are now sitting unplugged in hopes that the Engl just might magically fix itself too (not holding my breath…)
Sorry for the mile-long post. And thanks in advance for any help!
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