Help! Problems with Tascam TSR-8 tape bias!

[pointillist]

OK, so I'm trying to be more consistent on my tape based work. I have a Tascam TSR-8 I got from the Texas school for the blind a while ago, which is in really nice shape. I want to rebias the machine for ATR tape. I've always used older Quantegy, so I want to be sure the machine plays well with the new tape. Here's what I have done:

1. I picked up a B+K 2707A multimeter (one of the suggested meters on the seventh circle site, has good reviews as well).
2. Put test probes to TP1 and TP7, loaded up tape, hit record
3. Meter shows almost nothing, just a little noise at the .001 v level. Per the Tascam manual, I should be looking for 35mv +/-2.

So from other posts (e.g. http://messageboard.tapeop.com/viewtopi ... c186ac8552) I can see that you need a multimeter capable of reading the bias tone, which is at 100khz.

So here is my problem solving, in order of what seems most to least likely:

1. Mutlimeter is not reading the bias tone. The manual for the 2707A looks like it goes up to 500Hz. However, when I look at the specs for some of the nicer flukes, they still don't go up to the 100khz level.
2. Multimeter is out of spec. Needs to be calibrated. This is possible, but it was just checked in the past 8 months, and tests on other AC voltages in the house look OK.
3. The cards in my TSR-8 look different than the cards in the manual (perhaps they are -01 or -02 rather than -00?). Are the test points different in different versions of the cards?
4. There is something I don't know (or missed) which is tripping me up.

Any ideas? I feel a little stumped at this point, and want to get the machine up and running again! Thanks much-

Andrew

[Matt C.]

well I don't know for sure, but here are some thoughts. I'm not familiar with that specific machine, but from the looks of my Tascam MS-16 manual, those test points are only used for Bias Tuning and Bias Trap Adjustment, of which they say realignment will not be necessary unless the heads, bias amplifier, master bias osc pcb card, or bias osc unit are replaced. basically if the machine is working properly, you should not need to make those measurements when re-biasing for a new sort of tape. you should only have to adjust the Bias Level.

[pointillist]

The manual I have for the TSR-8 specifies 1 and 7. It specifies 6 and 7 for the bias trap. I'm just going after the tape bias, not head adjustments- they've never been a problem before, and all of my recording/mixing will be on this machine so I'm not worried if they are a little off. More worried about bias, which I think explains some minor drop out problems on the ATR that persisted after degaussing the heads/tape path... I'm going to try to hunt down a Fluke 87 III (anyone want to sell one?) since it looks like that reads the higher Hz.

[Matt C.]

sorry, when i said "realignment" i was referring to adjustments to Bias Tuning and Bias Trap, not head alignment.

like i said, i'm not sure without looking at the machine and the manual for it, but generally speaking you don't need to take any measurements from any test points to re-bias a machine for new tape.