DCC600 Digital audio failure

Hi, after much work I have now finally got my DCC600 tape drive mechanism to stop chewing tapes and work as it should however I now have an issue with playback.
The Analogue tape playback is fine but I am getting no playback audio from DCC tapes, I have checked connectors 1701 & 1702 on the Read/Write board and they appear fine (as 1702 carries the analogue signal I rather suspected that to be the case).
Have I inadvertently damaged the highly sensitive head??
Anyone got any thoughts on this??
Richard.

Does analog playback have wow and flutter? Did you replace the gears? I suggest reading Dcc300 does not play DCC cassettes only ACC

Thanks for the input. There is no wow or flutter on analogue playback, all is fine there.
Yes I replaced the larger gear (one that makes contact with the tape drive motor).
I will follow the service mode checks you linked to and report back, thanks.
Richard

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Hi Max,
I have done the service mode check you linked me to and the results are:
Head 1/2 95 95 0000
Head 3/4 95 00 0000
Head 5/6 10 45 0000
Head 7/8 30 20 0000
I will go through the proposed cleaning method next, unless the results above show that all is lost!
Again thanks for your help
Richard.

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Seems definitely worth a try despite some looking pretty bad. Is the azimuth screw still sealed?

HI Max, Again thank you for your help and support.
I have carefully cleaned the head face with Isopropanol cleaning solvent on the end of a cotton bud and did get some brown crud off and retested the unit.
I am now getting some sound but very broken up, the bit error figures are now:
1/2 0 (jumping to 5) 50 (jumping to 95)
3/4 00 00
5/6 00 00 (jumping to 5)
7/8 00 (jumping to 10) 0 (jumping to 50
In all cases the last 4 digits are 0000 (jumping to 0001)
At least I am now getting some noise!
Azimuth screw? I have studied the exploded view of the tape transport mechanism and cannot find a screw with that name, please can you point to it for me. Note I have not made and adjustments about the head mechanics.
Richard.

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These are the screws holding the head block. If the red or black seal is still intact, don not Touch them.

Next could be changing the pinch rollers.

Ralf

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Great, definitely a big improvement and a sign that the head is not dead!

You can try harder cleaning the head, to my knowledge no head was ever damaged using isopropanol on a cotton swab. Did you also clean the pinch rollers, if no try it, if you tried it and it did not help I agree with @drdcc to get new pinch rollers.

Don’t give up!

Hi Max & drdcc, thanks for the feedback.
I took the mechanism apart again (must be the 100th time!) and cleaned the head more thoroughly and also the pinch rollers (which don’t look that bad) and capstans but that no difference what-so-ever.
the two screws you refer too are 1-2mm projecting from the top of the head block but there is no visible sealant on them. I have not touched them.
I have got a new set of pinch roller rubbers but found it difficult to get the old ones out to change so gave up before I caused serious damage, do you have a video of the procedure to change the rubbers I can see?
Note the analogue playback is fine - now wow or flutter - so somehow I don’t think the pinch rollers are at fault.
I still have it in mind that at least one channel on the head (channel 2) is damaged.
Richard.

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O-dear my typing is getting worse…
…but that I found no difference…
…fine - No wow or flutter - so…
Richard

Here is the video regarding pinch rollers:

I hope for the best!

Max,
I have watched the video until it stopped at the point where the pinch rollers were pushed out on the 2nd generation mechanism (which I have), why did it stop there?
My issue is that I have replacement rubbers but I cannot seen to be able to get the old rubbers off the bobbin in order to try and get the new ones on the bobbin which is where I gave up previously.
Richard

That is why our pinch rollers come with the metal spine part.
Otherwise it is another project.

Dremel away.

Ralf

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Another idea would be acetone. But using pinch rollers properly attached to the metal is by far the best choice.

Hi Max & Ralf,

I now have zero errors on the DCC output, and I did not touch the pinch rollers.
At the beginning I said that I believed the head was damaged so I have change it and now all is good.
Thanks for your attempts at trying to help me, I did really apprieciate it.

Richard.

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Just for reference where did you get the head from? If it was from another player, don’t throw away the rest away, everything might be useful.

Edit: I just moved the post to the appropriate section to make it easier to find.

Yep, I bought a unit being sold as for spares that also had that gear stripped but also appears to have other issues (cassette present switch not working).
Will put it back together and resell it for spare again - might be useful for someone.
What is the ‘appropriate section’??
Richard.

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Hi Max & Ralf,

For your information, I have listed the old DCC600 unit that I got for spares back on Ebay (http://ebay.us/dc4Ryg?cmpnId=5338273189) if you or the DCC Museum are at all interested.
Cheers, Richard.

eBay message sent!