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Post by doctorice on Jul 15, 2011 14:09:59 GMT -7
The Tube Store website sells sets of tubes as used by Z for the amps. There are notes as to which amps need biasing and which don't.
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Post by benttop (Steve) on Jul 15, 2011 16:56:51 GMT -7
I have that info captured on my spreadsheet too - click the Amp Specs link in my sig and check it out.
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Post by doctorice on Jul 15, 2011 16:58:47 GMT -7
^^^ Even better
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Post by Jan on Jul 15, 2011 17:13:02 GMT -7
Dear Steve, please add Plate Voltages to your specs. Thanks Oh, and you know what else would be fab? How about a note * about which tubes need to have balanced triodes. btw, what happened to the * note? You have the Z-28 5751 *'d sans note. Kidding ... not really, because it would make an excellent resource even better. Truly excellent.
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Post by benttop (Steve) on Jul 15, 2011 17:34:34 GMT -7
Dear Steve, please add Plate Voltages to your specs. Thanks Oh, and you know what else would be fab? How about a note * about which tubes need to have balanced triodes. btw, what happened to the * note? You have the Z-28 5751 *'d sans note. Kidding ... not really, because it would make an excellent resource even better. Truly excellent. No problemo - just send the list of plate voltages (taken at 120 VAC line) and I'll add them right in there.
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Post by Deleted on Jul 15, 2011 23:02:34 GMT -7
hehe!!
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Post by doctorice on Jul 16, 2011 4:19:07 GMT -7
Z-28 plate voltage is 375 per the biasing notes on Z website. Measured same during my re-biasing.
One down....
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Post by Deleted on Jul 16, 2011 5:31:56 GMT -7
I often saw 450VDC using a NOS RCA 5AR4/GZ-34 rectifier on my 2004 Route 66.
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Post by doctorice on Jul 16, 2011 12:03:05 GMT -7
So tell us how it sounds! Mighty nice. I was getting a breathy overtone/overhang on certain notes, and that's gone. Plus there's a little more sparkle up on top. The old power tubes were definitely tired: there was about a 3 ma difference between them on the current measurement. The new tubes -- matched JJs -- showed essentially identical current and power from both tubes. The Compu-Bias is neat: reads plate voltage, bias current and power for two tubes simultaneously. Pricey, but neat
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Post by benttop (Steve) on Jul 16, 2011 14:38:01 GMT -7
Sounds like it was worth the investment. Thanks for the report!
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Post by doctorice on Jul 17, 2011 7:31:38 GMT -7
^^^
Certainly seems worth it. I can't imagine I'd get out for less than $50 taking this to a tech. Four more tube replacements and re-biases and I break even on the doohickey.
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Post by benttop (Steve) on Jul 17, 2011 7:47:36 GMT -7
^^^ Certainly seems worth it. I can't imagine I'd get out for less than $50 taking this to a tech. Four more tube replacements and re-biases and I break even on the doohickey. Plus, if you happen to buy another amp that requires biasing you already have the doohickey and the knowledge of how to use it.
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Post by doctorice on Jul 17, 2011 7:59:51 GMT -7
Plus, if you happen to buy another amp that requires biasing you already have the doohickey and the knowledge of how to use it. Yup. I have a Galaxie, which will need new tubes one of these days plus some non-Z amps that likely need biasing also. I would have bought the Compu-Bias anyway for the Z-28, but its cost probably will get paid back pretty quickly.
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Post by Albert on Jul 17, 2011 16:02:43 GMT -7
Good Luck... you should do well .. I took these last time I did mine notice the last pic where the amp has a speaker plugged in for the load... Here is the bias pot (the Blue trim pot on the right) Here is the amp before I turned it on And my reading... mine is the old weber Bias tool reads out in Millivolts
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Post by Jan on Jul 18, 2011 17:51:15 GMT -7
Sorry Steve, lately I am idea man. My doing is on holiday.
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Post by benttop (Steve) on Jul 18, 2011 20:37:53 GMT -7
Sorry Steve, lately I am idea man. My doing is on holiday. That's ok - if I had five bucks for every idea I ever had (that ended up being Google, or Microsoft, or some other giant corp.) then I would probably be able to afford that Ghia combo I've been lusting after...
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