Resurrecting an 80-8

[Thermionicist]

Hello all,

Well, I've decided to resurrect my original recording system, which includes the TEAC/TASCAM 80-8, TEAC A3440, Model 5 mixer, Crown D75 amplifier, Revox A77-HS, Pioneer CT-F9191 cassette and Klipsch La Scala monitors. (Hey,I wanted all TEAC/TASCAM recorders -- but the day I went to buy the system, the dealer was out of stock on the 25-2 and a high-end TEAC cassette deck, so I bought the Revox and Pioneer. I was on a deadline and couldn't put off the purchase.)

Everything checks out in working order -- EXCEPT the TASCAM 80-8.

It won't record. None of the 8 channels will record, either singly or with all-8 selected.

PLAY and SYNC work fine on every track. It reads input levels perfectly, and I get output in REC mode. It just won't record. I'm unsure if it erases, I have no tapes with anything recorded onto them.

Any tips on how to get it recording again? Could the fault be the bias oscillator? Is it likely that all 8 relays would be defective?

Any help would be greatly appreciated! I really enjoy the 80-8 and am anxious to have it making music again!

Thanks!

 

[SkywaveTDR]

First, I would place a scope probe to the erase head leads- just near them and see if the erase oscillator is coming up. If not then look into why the bias control is not being given. The deck uses TTL IC's so it should be able to be fixed. I can remember repairing a number of them at Tascam in Arlington Heights and then in home studios. The relays were not known to be all that trouble free and in fact are the most likely cause of failures in the unit. I changed a lot of them out. The supply of new ones these days may be a problem.

 

[Don Hennig]

Would love to purchase a Tascam 25-2 to transfer some old masters to CD. Any leads on where to find one? South Central Ohio.

 

[SkywaveTDR]

I am puzzled by the need to go after older units to get a job done when more new and advanced units exist for the job. The 25-2 as well as the 35-2 which I have here for work are going to take a lot more work than a basic 32-42-54 decks and the BR20 is a favorite of many people. In my post Prod studio I used a 52. Now that is as good as any Studer I think. I also have a 62 as well.
If you do find the 25-2 make sure the interconnecting cables are there. The 35-2 I have here has them good thing.

 

[Don Hennig]

That was what we used to master to when we had the studio. We also had a Revox 1/2 track.

 

[Lou Anschuetz]

Hunh. In *exactly* the same boat. Have an 80-8 in good shape. Have the variable speed and the Dolby unit. Signals get to the unit. Existing tapes play back. But the bias control has no effect on any channel. Was being used a couple of years ago. Sort of frustrating and, to me at least, seems odd that all 8 channels would fail to show any value on the bias adjustment. Very big bummer and hence may be looking for someone to take the whole thing who can make it work. Color me sad.

 

[SkywaveTDR]

If all channels fail at the same time one must consider the master oscillator that controls all cards slave oscillators. For one to have no Master Oscillator and to try and do adjustments the person is missing a large problem that is not addressed. I have three units here now to fix. Also a few 40-4 which is the same kind of design.

 

[Lou Anschuetz]

Thanks SkywaveTDR. I suspect you are right. There is, in fact, in the original manual a note showing that oscillator having been replaced in the 1980's (a note that says "mine"). Trying to work out how to test without owning an oscilloscope. If it's dead it would be disappointing since everything else - other than the counter - work quite well.

 

[SkywaveTDR]

This is one of the bad things about having older stuff but these block RF oscillators which were made for Teac are not something that are easy just to make up. I talked to Alex Nikitin in the UK about it and also some Ham people who say they can make them but no results yet. I could experiment with equipment here but the time is the issue. I have some other bias oscillator modules for decks that might not be the right frequency but these are not frequency agile so they have to be redesigned to make them work. I have now a X2000 deck that has a burned out Osc block. Same condition as yours- I am trying to find one. The question is does your deck erase tapes? If it does then the oscillator is working. If not then there is no easy way to test or diagnose these decks without a scope. I have 4 of them at my shop. Once I get to work on the 80-8 unit here, I will have some better insight. I have worked on these since the mid 80's so they had one there before or at the time I started at Teac in Chicago. That was in 1982 I think.

 

[Lou Anschuetz]

You've mentioned something really important here. It does erase, but nothing new will record and there is no needle movement using the bias control on any channel. Input signals are definitely present when metering is set to Input or Normal. Is there somewhere else I should be looking? Thanks!

 

[SkywaveTDR]

Good that it is erasing. I have had units come in from people that adjust them themselves and they would not record. The problem in some of these cases is that the erase current was not set and the bias was wrong. These decks have such a wide range of bias that they can be adjusted to not record. They expect the person who adjusts this to know what they are doing and often times this is a guy with a scope. The adjustments of bias traps say to use a meter but for all my experience I have always used a scope and had no problem doing that. If you have no equipment like AC Millivolt meter and scope, then you may not be able to fix the unit but then neither can I. This is why I have two benches and plenty of spare equipment.

 

[wkrbee]

Relaya

 

[SkywaveTDR]

If Bias and erase are going to the heads, the audio process in the record section might have to be traced. You can find anything from relay problems which are very common or even an op amp or bad cap in these old boards. Often times the repair might require an extender card to work on these. I did have some a while back.