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Post by christop on May 11, 2022 13:13:51 GMT -7
so I need to replace the power tubes on my amp finally, the previous owner told me that when he replaced them that he didn't bias it cause he read somewhere that you don't have to on these? is this true? my version is past 2013. but I feel like this isn't true. I see lots of threads about biasing on these amps, but I just thought ide ask to make sure.-thanks
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Post by Ridgeback on May 11, 2022 13:28:41 GMT -7
The EZG is an adjustable fixed bias amp so there is a bias pot. Whether the amp needs biasing is a different issue. If the rectifier is stock and if the power tubes have been replaced with similar rated tubes in the past, it ay not need to be re-biased. I'd be inclined to check the bias after replacing the power tubes.
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Post by christop on May 11, 2022 14:54:04 GMT -7
The EZG is an adjustable fixed bias amp so there is a bias pot. Whether the amp needs biasing is a different issue. If the rectifier is stock and if the power tubes have been replaced with similar rated tubes in the past, it ay not need to be re-biased. I'd be inclined to check the bias after replacing the power tubes. so if I replace the 5AR4 rectifier tube I would need to bias it regardless?
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Post by Ridgeback on May 11, 2022 16:04:56 GMT -7
Not necessarily, but a new rectifier could change the voltages enough to matter to you. Plug the new tubes in and if it sounds good and the tubes don't look strange when they have warmed up, you are probably fine. I just check the bias on my amps when I change rectifiers and\or power tubes for kicks. Most times they don't need adjusting or just a minor tweak. I always check the bias first thing if I purchase an adjustable fixed bias amp (new or used).
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Post by christop on May 11, 2022 16:22:43 GMT -7
Not necessarily, but a new rectifier could change the voltages enough to matter to you. Plug the new tubes in and if it sounds good and the tubes don't look strange when they have warmed up, you are probably fine. I just check the bias on my amps when I change rectifiers and\or power tubes for kicks. Most times they don't need adjusting or just a minor tweak. I always check the bias first thing if I purchase an adjustable fixed bias amp (new or used). ah ok that's good to know. so I can change out all my tubes including power and not bias it, if it sounds good and im happy then I don't have to worry about anything? no way it can damage the amp? I did buy the same brand of power tubes that are in it now, "winged c's" but I guess the previous owner never did a bias either like I said so i dont know how far off those are from the original tung sols, also keeping same type of rectifier tube, but I went crazy on all the preamps as far as different stuff
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Post by Chilly Gibbons (Todd T.) on May 11, 2022 16:44:23 GMT -7
Just make sure the power tubes do not red plate. Look at some examples of red plating online to get an idea of what it looks like. If you see it happening, shut her down and bias.
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Post by premiumplus (Dave) on May 11, 2022 18:17:49 GMT -7
Just a quick FYI, here's the recommended tube and bias information from Z amps website:
EZG 50
V1: 12AX7, V2: NOS 12AT7/6201, V3: 12AX7, V4: NOS 12AT7/6201, V5/6: Tung Sol 6L6GC STR(matched pair), V7: 5AR4
Recommended Bias Point: 28mA
Fuse Value: 2A 250V SLO 1.25″ x .25″
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Post by christop on May 11, 2022 18:52:17 GMT -7
Just a quick FYI, here's the recommended tube and bias information from Z amps website: EZG 50 V1: 12AX7, V2: NOS 12AT7/6201, V3: 12AX7, V4: NOS 12AT7/6201, V5/6: Tung Sol 6L6GC STR(matched pair), V7: 5AR4 Recommended Bias Point: 28mA Fuse Value: 2A 250V SLO 1.25″ x .25″ awesome, thank you, I had put a new Fuse in, this whole ordeal has started because my amp as of recently lost some headroom, its breaking up a little bit when it never has before, I could never get it dirty withought using pedals. so this has led me to buying all new tubes and replacing one at a time hoping to fix it woth the power tubes and a bias last.
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Post by jhen86 (jordan) on May 12, 2022 14:15:58 GMT -7
If you’re replacing the 5AR4 with another 5AR4 or GZ34, I wouldn’t bother with a rebias. Especially if that’s something you’re paying a tech to do.
If you’re replacing the power tubes though in a fixed bias amp, it is worth the trouble to at least check the bias. But even if you forgot that, likelihood of damage to the amp is very low. Worst case the power tubes are biased too hot and you cool the tubes prematurely.
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Post by christop on May 12, 2022 14:44:21 GMT -7
If you’re replacing the 5AR4 with another 5AR4 or GZ34, I wouldn’t bother with a rebias. Especially if that’s something you’re paying a tech to do. If you’re replacing the power tubes though in a fixed bias amp, it is worth the trouble to at least check the bias. But even if you forgot that, likelihood of damage to the amp is very low. Worst case the power tubes are biased too hot and you cool the tubes prematurely. so what if im replacing the power tibes with the same brand as the ones in there now? does that mean even less likelihood I need to do a bias?
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Post by headshrinker (Marc) on May 12, 2022 16:43:00 GMT -7
The brand has nothing to do with whether you need to bias or not. It's the rating or characteristic of the tube set you have. The same manufacturer can have hot medium and cool sets. If you ask for a medium rated set, you will be in better shape. If the amp sounds good after you change them, as someone said above, play it for an hour or so with the tubes facing you. If they don't start to red plate, you are likely fine.
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Post by jhen86 (jordan) on May 12, 2022 17:39:01 GMT -7
What Marc said ^^^
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Post by doctorice on May 16, 2022 4:37:14 GMT -7
Biasing an amp is not hard if you have the right equipment AND follow safety procedures. I have several Z amps that have user-adjustable bias pots, so I invested in the equipment to save $$ on tech visits.
And, to be clear, some Z amps -- the MAZ series, for example -- are effectively self biasing, so you can replace tubes without any need to fiddle with the bias.
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Post by christop on May 16, 2022 21:47:37 GMT -7
Biasing an amp is not hard if you have the right equipment AND follow safety procedures. I have several Z amps that have user-adjustable bias pots, so I invested in the equipment to save $$ on tech visits.
And, to be clear, some Z amps -- the MAZ series, for example -- are effectively self biasing, so you can replace tubes without any need to fiddle with the bias.
how similar do you think the ezg 50 is to bias? I'm just nervous because I've never done it before and I love this amp and don't wanna mess anything up, with there was a video online working woth this exact amp but there's not. i dont know what to even look for
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Post by jhen86 (jordan) on May 18, 2022 13:44:10 GMT -7
The Maz series and the ezg 50 couldn’t be farther apart from biasing procedure. The Maz series is cathode biased (or self-biasing). The ezg is what is called adjustable fixed bias (misleading term). It just means measurements need to be taken and the bias be adjusted to a fixed amount of resistance with the biasing resistor network. It really doesn’t sound like you’re ready to tackle this yourself, aside from another ezg50 owner making a tutorial on this exact amp. Even then you’d need to purchase a multimeter, and proceed knowing the risks. More so to you, electrocuting yourself. Less so to the amp. I don’t say that to discourage you. I was where you are and decided to read a ton and learn. I’m still an amateur but after building and repairing a few amps I’ve learned a ton. This would be helpful reading to start with. carlscustomamps.com/cathode-vs-fixed-biasBiasing any adjustable fixed bias amp is pretty much the same process: - Take voltage readings on power tube plates - Measure resistance across output transformer (there are calculators and other tools online) - Calculate plate dissipation based on those numbers - Adjust bias with bias trim pot - repeat process until bias/plate dissipation is set Edit..... Here is another link on HOW to do the above procedure. I’m not suggesting you do this, just want you to be informed of what it entails. robrobinette.com/How_to_Bias_a_Tube_Amp.htmSometimes, builders will put components in place to make the measurement process quick and easy in a fixed bias amp. Usually this is in the form of a 1 ohm resistor tied between Pin 8 of the power tube and ground. Not sure if the EZG has this though. I suspect it does not.
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Post by christop on May 18, 2022 15:57:47 GMT -7
Biasing an amp is not hard if you have the right equipment AND follow safety procedures. I have several Z amps that have user-adjustable bias pots, so I invested in the equipment to save $$ on tech visits.
And, to be clear, some Z amps -- the MAZ series, for example -- are effectively self biasing, so you can replace tubes without any need to fiddle with the bias.
how similar do you think the ezg 50 is to bias? I'm just nervous because I've never done it before and I love this amp and don't wanna mess anything up, with there was a video online working woth this exact amp but there's not. i dont know what to even look for thank you for taking the time to explain all that in such good detail, luckily I have found someone that knows what they are doing and they are gonna teach me in person so hopefully ill be able to do this in the future. Safely for both my amp and I.
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Post by Chilly Gibbons (Todd T.) on May 18, 2022 17:14:54 GMT -7
You’ll be very happy knowing how to do it. It will save much trouble down the road.
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Post by doctorice on May 19, 2022 9:51:43 GMT -7
It's great that you found someone who can work on the issue and educate you at the same time.
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