TAD-1000 bias help, please!

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TAD-1000 bias help, please!
« on: 30 Dec 2020, 05:42 pm »
I have a pair of the late Paul Gryzbyk's TAD-1000 monoblocks, which have been dark for a couple of years.  I want to power them up.  I have bought a kit to place between the power tubes and the sockets, with leads to permit bias reading/setting on a multimeter.  My amp pair was from the later-run, with LED lights to guide in setting the bias , but I don't know what bias values should be as measured by a meter, and since the amps were supplied with EL34s, I don't know if the built-in set-up will correctly guide me to correctly bias the KT88s currently installed, or what a proper bias would be on kt77s (which I might like to try)

Can anyone help? I found the instructions for his smaller amps on the web, I have a copy of the instructions for using the built-in light system, but I can't find the instructions for the earlier version that used a multimeter.

(I can't do a search here, because I haven't had the requisite posting history.)

Thanks for any help you can provide!

Bill in Green Oak


Re: TAD-1000 bias help, please!
« Reply #1 on: 30 Dec 2020, 08:09 pm »
Welcome to AudioCircle wabonii!

Whenever you replace power tubes, especially if it's a different type or same type but different tube mfg, but also even if they are same brand and type it's a good idea to turn the bias pots all the way down to zero current and give them a fresh new bias job. Easy to burn up a new tube with too high bias.

Bias pots are not always clockwise = more current. Sometimes it's the opposite, so you have to find out for sure before making changes. Within the same mfg product line the bias procedure is often similar to their other products.  This thread has some links:
Implies that the TAD-60 bias procedure worked on his TAD-1000.