DX-4D cuts out...

[rickb]

Prob been answered here before but could not find using the search function, so I would appreciate any opinions/comments offered.

DX-4D connected to a Tascam 22-4...works fine for about 30 seconds and then a faint "click" and all the encode/decode red LED's go out. Main power lamp stays illuminated. I'm pretty confident it's all conected correctly including the control cable to the 22-4.

Any thoughts/suggestions, again appreciated.

Thanks in advance...rickb

[Herm]

Do you have a wiring diagram for the rear of the dbx unit? And Did it work before and this is something new?
You might clean the pins on the plug and pull the top off of the unit and make sure there are not any jumpers loose or anything like that.
Its been a while since I have had the top off of mine so Im not sure if there is something in there that could be loose or not.
Good luck with your machine I love my 22-4,s

[krhall]

Hmm...

30 secconds sounds about the right ammount of time for a capacitor to reach full charge.

It is a remote possibility but you might want to take some meter readings from the internal capacitors to find out if any are leaking. (ie: unable to sustain full charge for long).

A Capacitor will only allow the current to flow until it reaches full charge, which hints me towards a possibility.

Also the input and output sockets as mensioned already is also a good place to start.

Hope this info helps
Keith

[rickb]

Got it off eBay for like $60...just got it hooked up to the 22-4. All looked good for a brief time and then the encode/decode lights just "clicked" off. I'll have to check when I get home on the manual...believe I just got the user manual and not the maintenance one (if there is one). I'll try cleaning the pins with some Caig and maybe pop it open to see if there is anytine obvious to me (I'm not much of a tech). Just was curious of this could be non-functioning unit (have had pretty good luck on eBay actually). Thanks for your thoughts Herm.

[MCI2424]

Originally Posted by krhall

Hmm...

30 secconds sounds about the right ammount of time for a capacitor to reach full charge.

It is a remote possibility but you might want to take some meter readings from the internal capacitors to find out if any are leaking. (ie: unable to sustain full charge for long).

A Capacitor will only allow the current to flow until it reaches full charge, which hints me towards a possibility.

Also the input and output sockets as mensioned already is also a good place to start.

Hope this info helps
Keith

I re-cap all old equipment period. Against the valued opinions of a few here, I have found many electrolytics with very high ESR. Every one of the caps on my 24 track MCI recorder is bad form high ESR to practically shorted. I am re-capping right now. The only reason the power supply still works fine is because it was re-capped a few years ago.All old equipment will work and sound better when it is re-capped. The single biggest market in the analog word at this time is in re-capping pro audio equipment. Home recordeing stuff gets unoticed because home recorders just don't know about it.

[evm1024]

As noted by MCI2424 recapping is not a bad idea. This is especially true of the power supply.

I would suggest that you open it up and measure the supply voltages (carefully) before and after it fails. Voltage rails should be in spec to start with (12 volts near 12 volts for example).

Electrolytics fail for a number or reasons. Supply electrolytics either open which allows more ripple or short which tends to plasma the cap if you supply has enough oomph. I doubt that it is a supply cap. But it will not hurt to recap.

You can also let it run for a little while and then unplug it and test the components for excessive heat with the back side of your finger. Remember to unplug it.....

You can find a schematic here: http://arafel.org/audio/manuals/dx4dsch.pdf

Remember that heat will cause mechanical changes which could open up a connector. I don't think that this is the case but don't be narrow sighted.

I don't see any relays in the schematic or remember any from when I last had mine apart. I would look and listen very carefully to try to locate where the click is coming from. That should put you in the right direction.

All the lamps are lit from their own winding and diodes (so as to not share this with the audio supply)

This leads me to think that it is in your deck (where the noise comes from?) or in the control PCB.

The more I think about it I think that you should measure the voltage on the control connector pin #1 (yellow) and see if that is changing when the click happens. If so the suspect your deck strongly.


--Ethan

[The Ghost of FM]

Originally Posted by evm1024

You can find a schematic here: http://arafel.org/audio/manuals/dx4dsch.pdf


--Ethan

That's a great web resource you've shared with us...thank you!

How did you come across that?

I also found, one level up a directory with documents to other TASCAM pieces including a full, decent quality manual for the M512/520 mixers with the full service manuals included!

http://arafel.org/audio/manuals/

Cheers!

[cjacek]

Ethan, Jeff, WOW!! Thanks for sharing those links with us! WOOOW!!

[evm1024]

Originally Posted by The Ghost of FM

That's a great web resource you've shared with us...thank you!

How did you come across that?

I also found, one level up a directory with documents to other TASCAM pieces including a full, decent quality manual for the M512/520 mixers with the full service manuals included!

http://arafel.org/audio/manuals/

Cheers!

Jeff and cjacek,

That is my server and manual collection... Send more manuals and I'll put them up.

--Ethan

[rickb]

Thanks for all of your input. Haven't opened it up yet but will do so soon. I'm no electronics "guru" by any means, but will give it a go. Cool links also...

[rickb]

Plugged it in to my recently purchased Tascam 38 and it lights up like a Christmas tree! So, evm your hunch is right...the 22-4 deck and not the DX unit itself. Haven't passed signal through yet so that's the next step. I'll clean the contacts of the 22-4 real good and see if that helps. Maybe a new control signal card for the 22-4??

[Rodger Hartlett]

I had the same problems with a Tascam desk.The problem was in the power supply board.
I re-soldered all the joints in the power supply area ( card/connectors) as the heat had cracked the solder over time and made the connections unreliable.
That fixed it well.

[rickb]

Thanks Rodger...will be taking a look.