Tascam 38 track 6 not working!!!

[vivalastblues]

I bought a Tascam 38 recently and have been recording with it, but never used the 6th track (only needed up to 5 so far). I've come to use it and it's not working. I've checked all the connections etc. it's definitely something with the input on the 8-track.

what should I do? Can I fix something like this myself? I don't know of anyone in Sydney that knows how to fix these things.

[Jim Williams]

It's probably a stuck relay. Open the bottom and swap card 6 for card 5. If it comes back, it's probably the relay, or maybe a fried opamp. The relays are standard 16 pin dip sized so install a 16 pin machined socket so you can swap it if it fails again.

[vivalastblues]

It's pretty difficult to get my hand in there without taking out almost everything else, and it's all held together with wires soldered to circuit boards and whatnot, so I'm worried I'll accidentally tear something off and not know where to put it back.

Anyway I'll have another look and swap the two. I opened it yesterday and couldn't really figure out the order of the cards. They run in a sort of upwards line, but nothing's labelled or anything like that. It's hard to tell which is which. But I'll give it a shot.

thanks Jim.

[vivalastblues]

I opened it and took a few photos.

This is the underside (i assumed this is what you meant when you said open the bottom):



and this is from the side of the board that connects directly to the ins/outs.



What exactly am I looking for?

[Jim Williams]

Unscrew that bar that goes across those 8 pcb's, those are your record/play cards, one for each channel. I think channel 1 is towards the front, but it's been many years so I could be opposite of the order. Use 2 hands, gently pull straight up on the card and it will come out. Use care in reseating them so pins align. If you want to get into it, you can replace the opamps with National LME49720's or AD8599's and then pull out the cheesy step up transformer used to get cheap gain off the heads. Bridge it and the remove the resistor from pin 2 to ground on the opamp. Replace it with a 91 ohm or so, low enough to make up the lost gain to unity. That will open up the playback quality to no end. They can then sound like MCI -JH-24 or Studer A-800. It's also possible to replace a couple of parts in the bias circuit so you get more, enough for +6, maybe even enough for +9 levels with GP-9 type tape. The output trims can be elevated to get +4 unbalanced outputs and reducing the record trim allows +4 db inputs as well. Lots can be done to tweeze these machines, I made a few very good sounding records with one back in the early 80's on a heavily modified machine. Doug Sax at Mastering Lab was my mastering guy then and he always commented on the excellent sound I brought and was very suprised to hear they were recorded on a modified 38 and a custom console.

[vivalastblues]

Hmm they don't seem to just pop out. I feel like to get one of the cards out I'd be forcing it. I found someone in my area who services these machines, I think I'm just going to take it to him.