DCC730 Channel Error

Morning all, Working on yet another 730 I have come across a strange issue and wonder if anyone could assist. When I first fitted the DDU to the chassis tapes played with a few dropouts so I switched out the pinch rollers/cleaned the head etc. When I tried to play again there was no audio at all, I put the machine in service mode and the first page of the DDU test showed errors, the channel error rate was 20 on all channels. I then just left the machine playing whilst I did something else, when I came back to it it was playing just fine! I have found this is repeatable - if I turn the machine off and later come back to it, it will not play, however leaving it to play over a long period the audio will return! Has anyone had something similar happen or have any suggestions as to what could be the cause? I have just added some images, in service mode the machine started with “Error 11111111” and every channel was on 20, with no intervention, just leaving the machine to play you can see from the images "Error 00000100 (the sixth bit alternating between 1 and 0 and the individual channels showing zero apart from CH6 and CH9 as pictured.


Thanks in advance. :slight_smile:

Wild guess, capacitors or the read amplifier.

It’s a know fact that capacitors get less value in time. But when they are in a warmed up environment, issues can disappear. It could cause the problem you are having after switching on the power.

If you have a freeze spray can or dust spray can, try to cool down the capacitors, 1 by 1, on the read / write board. Use the spray with caution. When you spray too much coolant at the same time, it becomes fluid and will cause other issues, like leaking current, or shorts with other components on the PCB. In that case you’d better try frosting a cotton schwab and then cool the capacitors.
Also check the power supply capacitors.

If that doesn’t work, try cooling the chips on the r/w board.

Good luck!
-Henrie-

Hi, great replies thanks, that seems to make sense. I do have another read/write board but am I right in thinking that these boards are matched to the head - this would be unfortunate as the head that goes with my spare board has broken ribbon cable :unamused:
Forgot to mention in original post, I used an analogue tape just to test and the machine has no issues playing that!

I remember someone posting some success fixing that, but I can’t find it right now.

For recording only and this should be adjustable, we could help you with that.

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My money is on the read amp capacitor(s).
If this proves to be right… well than all 3rd generation recorders will need replacement in time :sleepy:

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Hi @Fretlessfender , that would be bad news for a lot of people! It looks like they are all of the same value, but there is eleven of them :cry:

Holy smokes!!!

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Just done some in circuit testing on my spare board , I know measuring in circuit is not always accurate but I just thought this would give me a set of values to compare against my suspect faulty board when it is cold. Of course this may fall flat if both boards are faulty!
Don’t really have the heart to turn it off at the moment, listening to some Vangelis on it :heart: and its not missing a beat! :notes: :musical_note: :notes:
Farnell have Nichicon 10uf 16v smd caps in UK for around £0.27 each if I buy 10+

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