[wabonii]

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

[richidoo]

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:
https://forum.audiogon.com/discussions/manuals-for-tad-1000-and-tad-150
Implies that the TAD-60 bias procedure worked on his TAD-1000.

[phook68]

Bill, I have a pair of Tad-1000 monoblocks that have the bias pot lights. I too need biasing instructions. Would you be willing to send me an email with the instructions that you have? Thanks in advance.

Patrick

[wabonii]

Patrick, I'll try to dig them up, now a hard copy print-out., I think.  I just ordered new tubes, and a search led me back to this forum...sorry I didn't see you inquiry until just now!

[wabonii]

This is what I've got:

From Paul, for the later amps with the led's, for initial startup.  Power up 20 min. + Idling, no music playing, flick switches one at at time, adjust to fully light the second LED, with a hint of the third beginning to light.  repeat checking till all read "2-1/2". Check after 1 month w/ new tubes, then every 6 mo.

I don't have and cannot find the instructions for the older version.

 A survey of forums finds 350-370 on all four;  another writes 650 mv for 6550 or KT88 and 350mv for EL-34.

I bought a bias meter kit for use between tubes and sockets, but I haven't tried it out.  I intend to get a reading when the lights are consistent with the instructions, and if there seems to be consistency, I'll try to set to the values listed.

Other than the TAD instructions, all of this is a result of sleuthing, and I have no way to know if the information is acccurate or not!