Serviced Teac 80-8 with Incessant Intermittent Volume Drop on All Channels-No Rhyme or Reason

[xynox]

Let me start out by saying that I know this is an old machine and maybe someday I'll get something else, but this is what I have to work with ATM.

Recently purchased a Teac 80-8 from a reputable reel to reel dealer that had been serviced and bench tested and even came with frequency diagrams for each head(or maybe for each channel, can't quite remember).
Pretty much ever since I got it I've been having the insanely frustrating issue of when tracking, upon playback or using the monitor head there are sudden volume drops-then sometimes it'll return, then maybe slowly fade, then maybe come back full force, then maybe cut out all together, then come back slightly, then maybe come back all the way on EVERY channel.
There is no rhyme or reason. Sometimes I think I've got a channel that's working and then it cuts out.
Input and Norm settings sound great- so the machine is getting good signal, but it won't lay track properly.
I've tried swapping cards and it actually seemed to help on one of the swapped channels...but then I was unable to monitor the channel during recording-like it was totally silent- but then on playback the channel had tracked and I was able to listen to it on both record head and monitor head. How is that physically possible?wtf
Knocking on the cards and/or relays seems to have no effect on the volume drop issue.
I've cleaned all the RCA connectors on each card with deoxit as well as the edges that plug into the machine.
Here's a video of one input feeding all 8 channels at a time so you can get an idea of what I'm talking about.

guitars a bit loud-might want to turn it down some

another one

here's one of just two channels playing the same input


and then after using it for a frustrating period of time it seems to start to get better and the channels want to work but they seem to revert back to their old ways once I've given the machine a break for a while.

Now I'm concerned I'm pushing my 40 year old transport too hard trying to diagnose with ridiculous issue.

 

[sweetbeats]

Hi.

Don’t discredit the machine because it’s not working right and it’s “old.” Yes the 80-8 is a less “sophisticated” machine, but that also means it’s potentially easier to fix and keep operating long-term than a machine with, for instance, a complex full servo transport. The 80-8 was a home-run for Teac because of its reliability and good sound…and price at the time. It’s a solid machine. Question: this diminished level issue…are you saying the level changes identically and simultaneously across all tracks, or would you instead describe it as random in nature, no rhyme or reason and dissimilar between tracks? Like you think you have something figured out with some manner of consistency swapping cards or whatever and then it curve-balls you again and you’re left saying WTH…is it like that?

 

[xynox]

Yes, its the no rhyme no reason thing. Here's a video first showing levels on input mode and then monitor of one input feeding all 8 channels:

You can see how out of whack thing get. There are more videos in the OP
he's never seen anything like it before and is going to send me 8 new cards when he can but I'm not convinced its the cards.
I do love this machine and really just want it to work properly.

 

[sweetbeats]

First thing I would do is replace all the relays. I’m surprised your tech has not experienced anything like this before. I’ve experienced this exact symptom set on multiple machines. The problem was faulty relays. That’s where I would start if it was me. I may be completely wrong.

 

[Slouching Raymond]

I'm not a tape man, but is the power rail to the channels fluctuating?

 

[xynox]

my boy is sending me 8 new tested hard cards and looking into relay alternatives. Will update.

 

[Jimi Shelter]

Let me start out by saying that I know this is an old machine and maybe someday I'll get something else, but this is what I have to work with ATM.

Recently purchased a Teac 80-8 from a reputable reel to reel dealer that had been serviced and bench tested and even came with frequency diagrams for each head(or maybe for each channel, can't quite remember).
Pretty much ever since I got it I've been having the insanely frustrating issue of when tracking, upon playback or using the monitor head there are sudden volume drops-then sometimes it'll return, then maybe slowly fade, then maybe come back full force, then maybe cut out all together, then come back slightly, then maybe come back all the way on EVERY channel.
There is no rhyme or reason. Sometimes I think I've got a channel that's working and then it cuts out.
Input and Norm settings sound great- so the machine is getting good signal, but it won't lay track properly.
I've tried swapping cards and it actually seemed to help on one of the swapped channels...but then I was unable to monitor the channel during recording-like it was totally silent- but then on playback the channel had tracked and I was able to listen to it on both record head and monitor head. How is that physically possible?wtf
Knocking on the cards and/or relays seems to have no effect on the volume drop issue.
I've cleaned all the RCA connectors on each card with deoxit as well as the edges that plug into the machine.
Here's a video of one input feeding all 8 channels at a time so you can get an idea of what I'm talking about.

guitars a bit loud-might want to turn it down some

another one

here's one of just two channels playing the same input


and then after using it for a frustrating period of time it seems to start to get better and the channels want to work but they seem to revert back to their old ways once I've given the machine a break for a while.

Now I'm concerned I'm pushing my 40 year old transport too hard trying to diagnose with ridiculous issue.

Hello, there. I got my 80-8 about a year ago. Traded my 388 for it. It was supposedly gone through. I immediately had issues. I hadn't been in studios since the nineties, and the studio I owned with two others, I had to experienced Hyde Street/Automatt engineers to insulate me from the hassle. First problem was I didn't even get the my Model 520 mixer was missing all the jumpers, so I thought everything was broken. Duh... But the tape machine.... Channel 1 won't record but I use it for routing and recording. The preamps in Chans 1&2 are great. Electric guitar straight in... Sounds great. Just remember not to go into those preamp XLR inputs with a Phantom Powered condenser mic. unless you want to hear the people down the street snoring... So, channel one won't record. Channels 2 & 3 somehow got internally cross-wired. Channel 2 on the tape machine goes to channel 3 and vicey versy. The snakes are hard to get wrong. Color coded. It's not that. the connections in the back of the cards must've been f*cked around with and done wrong. The sound drops out, drops down, comes back, disappears... Whatever. It's random. I'm hereing some sort of relay clicking and then the sound problem. The fact that the thing came mounted in this nice wooden rolling cabinet makes it look cool but in order to do real work on it, it needs to come out of the cabinet and that could take two or three people to do it safely. Oof. I'm considering selling all this stuff and just sticky with my little TASCAM Model 12 SD-Card recording interface thing... I just use that to mix down onto so I have the analog digital so I can share it instead of mailing cassette tapes. That's great but it's a funny way to use a multi-track recorder but it does that job nicely. I'm gonna try to investigate but I'm not taking this thing out of the cabinet quite yet but may need to in order to bring it to someone. I don't want to pay TEAC experts for that drudgery... Clean the heads constantly and vigorously. Gonna give it a degauss. Got the machine for that. Gotta be careful. I could accidently erase stuff...

 

[sweetbeats]

If the problems are intermittent and “move around” it’s likely a relay issue. And keep in mind there may be anti-thump muting relays located elsewhere than the r/p amp cards…they are usually mounted to the motherboard in a machine like this. Sometimes relays are used, sometimes it’s a transistor-based timing circuit…it prevents there from being “thump” in the outputs during power up and power down. If it’s relay-based then this is another area that can cause intermittent audio.

 

[rob aylestone]

You seem to have the usual reel to reel choices. Put up with weird operation that wrecks your music making, or get it repaired by an expert. Paying Teac experts is not drudgery, it’s normal. Shipping is a killer too. It’s expensive, but vibration is a killer. What was a perfect machine in the workshop might be bad again when it gets to you, so you need an expert who you can deliver to and collect from. Or, you get a new hobby and learn how to fix them yourself, buying lots of test gear. It is always like that. My Tascam 34 has been broken for a year, because I have not had the time or energy to fix it, yet again since it went up in smoke. It too has a similar issue to yours in that ch1 is fine, 2 seems linked to 3, and meters move on record, but sometimes not on replay. If it were perfect, I’d still not use the thing, so it stays broken.