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Post by freakboy on Oct 13, 2018 2:06:31 GMT -7
I've been having an issue with my Maz 8 for a little while. I hear a sound like broken glass rattling or perhaps the sound of an old fashioned telephone ringing far off in the distance as a note dies away. From what I've read on the web, I suspect that one of my tubes (or valves as we Brits like to call them) is on the way out. Is there a way of testing this or finding out which one it is without buying a whole set and replacing them one at a time? Any tips would be much appreciated.
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Post by Chilly Gibbons (Todd T.) on Oct 13, 2018 6:29:43 GMT -7
One of them has gone microphonic. Take the back off of the amp, the tube covers off, and tap on each tube with the power on and standby off. You’ll find it pretty quickly.
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Post by mudman on Oct 13, 2018 7:44:46 GMT -7
Don’t tap hard however, as you can break a tube in that manner. The safest way to go about it is to sub in one good tube one by one until you find the culprit.
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Post by gbowman on Oct 15, 2018 11:58:11 GMT -7
I tap gently with a chopstick or pencil (eraser end). You'll know...
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Post by zpilot on Oct 15, 2018 22:56:01 GMT -7
The most likely culprit is V1. That is the tube on the far right looking at the back. I find the next likely tube to be the power amp tube which is the EL84/6p14p.
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Post by dcarver on Oct 16, 2018 0:24:02 GMT -7
Hi Freakboy. Haven't seen you around for a while. Welcome back. Could be tube rattle. What you're describing sounds like what I noticed with my Maz 8 several months ago. It sounded like something rattling against glass. It was very faint, and I only noticed it as a note tailed off. Also, some notes produced the faint rattle, and some didn't. I figured it was tube rattle. The metal structure inside the tube was rattling against the wall of the glass envelope. Since it was so faint, it didn't bother me much. I had the original EL84/6p14p in my amp for over 2 years. Probably had over 2500 hours on the output tube. One day a couple months ago, I decided to replace it, even though it still sounded good (except for the faint rattle). I put in a new 6p14p from forum member Perry R. I replaced the red rubber tube dampers at the same time. The original ones had gotten kind of hard. One broke while removing it from the tube. Problem solved. No more rattle, and the amp sounds a little livelier in pentode mode. I think the original EL84 was getting a little tired. If you need a new stock 6p14p, Perry R.sells them here : reverb.com/item/3404159-nos-russian-6n14n-el84-power-tubes-quad-for-your-dr-z-trainwreck-1980-sHe grades them by a transconductance number. If you want early breakup and great output tube overdrive, order one with a Tc # of 15, or less. If you want more clean headroom and little or no output tube breakup, get a Tc # of 25 or higher. Good luck.
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Post by zpilot on Oct 17, 2018 2:55:40 GMT -7
It is so difficult to diagnose amp woes without actually hearing the amp. Descriptions are subjective.
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Post by freakboy on Oct 19, 2018 13:23:41 GMT -7
Thanks guys. It is the power amp tube which is a Russian 6n14n. It seems to be a vibration issue. No noise when I tapped it but the noise stopped when I pinched it with a tea towel. I'm going to try a tube dampener ring first as it seems to work OK, apart from the rattle noise. I hope that works because I can't really afford an expensive replacement at the moment.
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Post by mudman on Oct 19, 2018 13:43:38 GMT -7
Thanks guys. It is the power amp tube which is a Russian 6n14n. It seems to be a vibration issue. No noise when I tapped it but the noise stopped when I pinched it with a tea towel. I'm going to try a tube dampener ring first as it seems to work OK, apart from the rattle noise. I hope that works because I can't really afford an expensive replacement at the moment. Those tubes are only $25 from Perry R. Any el84 will work in the circuit though.
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Post by freakboy on Oct 22, 2018 13:36:18 GMT -7
Well the damper ring seems to have done the trick. I got one made of Viton which is supposed to be able to cope well with extra high temperatures. There's still some vibration with the amp cranked right up but I rarely get the opportunity to play that loud for very long. I hope I don't sound like a cheapskate but I'm in the UK and NOS usually = expensive! My next task will be to try to tame the treble when playing with single coils equipped guitars.
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Post by Chilly Gibbons (Todd T.) on Oct 22, 2018 14:29:50 GMT -7
A simple JJ will work great as well. Should be readily available in the UK, and inexpensive.
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