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Post by John H on Feb 3, 2023 8:00:06 GMT -7
Traded one of my Carmen Ghia's for a Z28 combo that had been "slowly dying" on the original owner. Tubes were all goofy.. 5751 in V2, unbranded 6V6's, and a Phillips rectifier tube that was not a 5ar4. I asked him if he had it biased after he changed the tubes and he said, "No, because I was told that I didn't have to." Anyway, 470 screen is obvioulsy toast. I don't own a bias probe, but I'm not opposed to buying one. That said, should I buy a bias probe, solder in 1 ohm resistors off of pin 8, or do this the old school way?
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Post by Seńor Verde on Feb 3, 2023 9:12:09 GMT -7
I have a bias probe, oscilloscope and signal generator. Checking/setting the bias on my Z28 using scope and checking with the bias probe, the idle current was 28mA, which is what the good Doctor recommends. Going forward I'll just use the bias probe as it is less hassle and yields the same result.
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Post by daddyelmis (Greg) on Feb 3, 2023 11:14:28 GMT -7
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Post by bubs42 on Feb 4, 2023 8:56:08 GMT -7
Traded one of my Carmen Ghia's for a Z28 combo that had been "slowly dying" on the original owner. Tubes were all goofy.. 5751 in V2, unbranded 6V6's, and a Phillips rectifier tube that was not a 5ar4. I asked him if he had it biased after he changed the tubes and he said, "No, because I was told that I didn't have to." Anyway, 470 screen is obvioulsy toast. I don't own a bias probe, but I'm not opposed to buying one. That said, should I buy a bias probe, solder in 1 ohm resistors off of pin 8, or do this the old school way? All you need is a multi meter for biasing a Z28. The 5751 is a great choice for V2 to slightly, very slightly cut the midrange. My personal choice in the Z28 and if you don’t like it I am willing to buy it from you. If the power tubes are unbranded and you didn’t buy them and don’t know what they are, I personally would just buy a “Matched” set. BUT when you bias your current set you will be able to check if they are reading the same or close enough. Watch DRZ’s Bias video, its makes it very easy. I learned the same method from Andy Fuchs, he also has a similar video. It’s easy and you don’t need a bias probe unless you want one.
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