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Post by mickey on Jul 7, 2018 3:27:57 GMT -7
Last night my 2015 Maz Jr reverb head lost power with no sound, luckily right at the end of the gig. I thought it was sounding kind of thin and gutless, then after we finished playing I saw the pilot light was out, with the power switch still on, and the standby off, ie there should have been sound but now there wasn't. But the power tubes were still glowing, and as far as I could see so was the rectifier. I switched the amp off, then a few minutes later switched it on again. As before, the pilot did not light but the power tubes started glowing again. Still no sound.
Today I decided to work through Doc's troubleshooting guide. First, though, I removed the chassis and inspected it, nothing obvious that I could see in the way of damaged components, so I reinstalled it in the head cab. I tested the plug fuse (I'm in the UK), which was OK, then I checked the amp fuse, which was also OK. That surprised me, so I fired the amp up, and guess what, it worked, with the pilot lit and sound as normal. Now this worries me, as I don't want to risk the amp breaking down again at my next gig.
I fully expected the rectifier to be at fault, but it's working at present. I'm thinking I'll change it anyway, but other than that I'm out of ideas!
Any suggestions gratefully received, thanks!
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Post by purpletele on Jul 7, 2018 5:07:42 GMT -7
Mickey,
It sounds a lot like the rectifier is on its way out to me.
It seems I have had similar reactions that turned out to be the rectifier as suggested.
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Post by mickey on Jul 7, 2018 13:37:39 GMT -7
Mickey, It sounds a lot like the rectifier is on its way out to me. It seems I have had similar reactions that turned out to be the rectifier as suggested. You're probably right, but I always thought rectifiers either work or they don't?
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Post by purpletele on Jul 7, 2018 13:42:54 GMT -7
Mickey, It sounds a lot like the rectifier is on its way out to me. It seems I have had similar reactions that turned out to be the rectifier as suggested. You're probably right, but I always thought rectifiers either work or they don't? Good point, then under those similar symptoms something will go out soon. Maybe it’s the power tubes that act like that. I recall a few different instances where that occurred and something went out shortly thereafter.
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Post by bgkyt1 on Jul 7, 2018 20:41:38 GMT -7
is it a maz mk II? if not, is it possible that the venue had a voltage drop? was the amp plugged into the same circuit as any other equipment?
it seems odd that the tubes were lit but the pilot wasn't, unless the amp had enough voltage for the filaments but not the pilot (if the pilot was a higher voltage type).
and would the pilot light go out just b/c a tube was going bad but not blow a fuse?
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Post by mickey on Jul 8, 2018 2:00:09 GMT -7
is it a maz mk II? if not, is it possible that the venue had a voltage drop? was the amp plugged into the same circuit as any other equipment? it seems odd that the tubes were lit but the pilot wasn't, unless the amp had enough voltage for the filaments but not the pilot (if the pilot was a higher voltage type). and would the pilot light go out just b/c a tube was going bad but not blow a fuse? It's a 2015 Maz, so Mk 1, and yes the amp was in the same circuit as other equipment which was fine. Yes all very odd. Unless anyone has any other suggestions I think I will replace the EL84s and the rectifier, and probably V1 and V5 at the same time, then hope for the best.
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Post by BritInvasion on Jul 8, 2018 5:00:03 GMT -7
I strongly suspect it's the rectifier Mick , it may have an internal connection that is opening intermittently. I've had similar happen- no sound , indicator light out but tube glowing.
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Post by mickey on Jul 8, 2018 5:24:44 GMT -7
I strongly suspect it's the rectifier Mick , it may have an internal connection that is opening intermittently. I've had similar happen- no sound , indicator light out but tube glowing. Thanks for this Frank, it makes sense, and reassuring to know you've experienced the same thing. I'll order a new Sovtek, but also I'm looking for a decent NOS Mullard like I have in my Maz Sr, that one must have lasted ten years now, and I expect it to last another ten.
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Post by mickey on Jul 8, 2018 7:43:37 GMT -7
Quick update....installed new V1, V5, EL84 pair and a Sovtek 5AR4 I had kept as a spare. All good so far, but I'm also a bit poorer having ordered a new Sovtek as a spare and a NOS Mullard which I hope will be totally dependable....early 60's Blackburn, double ring getter, 4 notch plates, not that I know much about these but it should hopefully do the job!
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