80-8 issues....

[Chris Meck]

So...

I'm recording my band, and I'm having problems with previous takes 'ghosting' on some tracks. Not all of 'em; just a few, and you can tell that they're partially erased, just not completely.

So I'm freaking out and calling everyone I can think of, and I finally get a suggestion besides "well, the machine's almost 30 years old."

To keep the session going, I rebiased the erase trim on the offending channels essentially by ear and got them functioning. Later, I detected one of them drifting again a bit, so I pulled the front plate and tinkered again until it was working. So...it's working.

My questions are these: Is this likely just a product of the fact that this machine was used VERY little and not at all in the last several years, so it's just reacting to sudden usage when it hadn't had any for a long time? i.e. voltage drifting a bit? Or is this symptomatic of a bigger problem further up the chain? Extender card (?) issue maybe? caps? relays?

This machine registers the 1k test tone from my board pretty much dead on for all 8 channels, and is pretty much dead on from the last 80-8 I started this project on that I retired due to head wear problems. However, I'm sure a re-bias is in order at the very least, since it sat for so long. Can I do sort of a ballpark bias adjust for the channels using the 1k test tone supplied by my console, or should I wait to get a test-tape? Would it hurt more than it would help? I'm not noticing any weirdness in sound other than the aforementioned erase bias issues. Should I just go ahead as I am until I get the tape?

Thanks,

chris

 

[The Ghost of FM]

I'm sure we've all heard the term; Rust Never Sleeps.

You machine is just experiencing a bit of oxidation on the pots and switched and probably all need a decent cleaning with a good cleaner like Caig Laboratories Deox-it while you are doing a fresh calibration.

Not having the MRL calibration tape will be a bit of a handicap but it is not impossible to do a decent and fairly accurate calibration without it.

Get you meters on the deck calibrated first, monitoring input, inject a 1Khz tone at .316 volts, A.C. and set them to read 0vu. Prior to each calibration step, clean the pots with the spray and hopefully the setting will hold longer if the contacts are clean.

Beyond that, following the rest of the alignment regime, as per the service manual, you should find that your 30 year old deck is just fine.

Cheers!