Help me, before I throw my 80-8 into the street!

[Chris Meck]

Yipes!

A couple of problems, and I've got 1 record in mid-stream and 3 (from folks who want to pay, no less, after hearing some raw tracks) in the wings, and I'm stumped.

First of all, the machine drifted some after the first few sessions, no doubt due to seeing a bunch of voltage after sitting for years (almost dead mint recorder, wasn't used much at all). So I got some De-oxit, I got a 3 tone MRL (100, 1k, 10k) and a multi-meter and went to work.

Quandary no.1: when I got to the EQ adjustments, the manual states that I'm supposed to set 16k to -10db on the machine's meters. Then later in the manual (in the sort of tabled out adjustment checkpoint pages) it says to set 18k to -10db. To add to the confusion, my test tape has only a 10k high frequency tone. So what do I do?

Quandary no.2: Channel 3 is showing proper voltage from the console (Allen & Heath System 8 stepped down to -10 via a patchbay) to the machine; yet the machine is only showing about a 1/3 of the proper voltage at input. Yet it's playback registers perfect on both the 'normal' and 'monitor' heads. This was fine the other day; just started acting up today. Card's properly seated, connections are all fine, tested voltage... Any ideas? Considering cannabalizing another 80-8 with bad heads. Or taking a sledgehammer to it all...

any ideas?

Thanks in advance!!

Chris

well, not really. But I'm close.

 

[The Ghost of FM]

For problem one;

Just use the 10Khz tone on your tape and adjust the eq trim for the same measurement as 16Khz or 18Hkz.

For problem two;

No clue. Sorry.

Cheers!

 

[Chris Meck]

Well, problem 1 solved. Between using the 10k on the tape and an oscillator kicking out 18k, we've got it pretty well set.

Problem 2 is still there...looks like something involving the input voltage on the card itself is bad. I'm going to swap it out with a card from another 80-8.

Thanks!

Chris

 

[Uli_the_Grasso]

See the other thread about the Teac 80-8 in this forum! The problem are FETs gone bad. There are four ones used per channel, three for the input/sync/repro switching and one for play amp mute. The latter is rather unimportant, but the former three are not. After you have made up your mind about to what signal you want the output fixed to (input, sync or repro), you can shortcut Drain and Source (marked D and S on the PCB) of the right one. I chose sync. (The 80-8 uses the same type of head for rec and play, therefore the sound is exactly the same for repro and sync, except for different head wear or Sinister Foot Wear.) If you want to fully repair the machine, you can get new FETs. (For a raised lifespan, Gate voltage should be lowered, and the reduced off resistance should be made up by applying another three FETs as shortcutters, driven by inverters).