No output on Tascam 48 channel

[lo.fi.love]

So, this is weird. I feel like I've been this route before.

Remember when I lost output on several channels of my 48, and a relay replacement brought them all back to life?

Now, one of the channel cards has no output, either unbalanced or balanced. It follows the card when I move it around. The VU meter shows the card is amplifying the signal, but it's just not being output.

I'm guessing this may be an issue with the other relay on the card. Before, when I replaced relays, output on the unbalanced outputs wasn't happening, but I was getting a clear signal on the balanced outputs.

Does this sound right to anyone? Any insight?

 

[lo.fi.love]

Oh yeah, and I lost a VU lamp. Dang it.

 

[The Ghost of FM]

If you have any remaining original relays in there, then they would be on the prime suspect list but without signal tracing where the signal stops traveling, it's only a guess.

Cheers!

 

[lo.fi.love]

Thanks for the input. I just wish I had a card extender.

 

[sweetbeats]

Jeff, which relay did you replace on the cards? K003? K004?

 

[sweetbeats]

And my next suspect is U001...that's the line driver amp. Its output feeds the unbalanced line out of the card (which I believe goes straight to the RCA output jack) as well as the balance amp. So if there was some problem with U001 or with something that supports U001 both the unbalanced AND balanced out will be effected.

U001 is a 2043 opamp which is an updated version of the 4558.

Check for continuity between pin 4 of U001 and pin 1 of J006 on the card...should be 100ohms...and also check pin 8 of U001 to pin 2 of J006. Likewise should be 100ohms of resistance. You are checking to make sure that power can at least get to the V+ and V- inputs of U001.

The meter is driven by a totally different circuit on the board so it is not surprising that the meter still reflects signal. This could actually be helpful. Can you still record? I understand you won't be able to monitor the input nor hear the playback, but can you record something that you can identify via the meter balistics to confirm whether or not audio still makes to tape through that amp card?

You could always replace C021 just for poops and giggles. Can you hear anything via any of the outputs from the card (balanced or unbalanced) when you overload the input? IOW set the 48 to monitor the input and send a signal to the faulty card like you thumping on an SM57 and listen to that output...crackles? Anything? Get that peak LED a-lighting. Anything?