Hi DCC lovers .
, I have a fault on my DCC 91 thats been driving me insane for weeks trying to locate and find it.
It plays pre recorded tapes just fine. It also plays recorded tapes from another machine (my DCC600 I no longer have).
It will “erase and silence” a Tape (record over and mute the music) but …It will not play its own Recordings back.
It appears to make the recording on the Display as normal, but does not play that recording back.
Errors are 999999993. So 99% rate.
Checked the TDA1316T with multimeter no shorts on head drive outputs.
Replaced elctrolytics on R/W board Write area of the board. No Corrosion no visual leaking all good.
R/W is getting a clock at 3.072mHz and some apparent oscilloscope waveforms of incoming DATA on WDATA.
Write current has been tried a few times in different settings with no effect still 99% error loss.
The RDMUX stream is quite interesting. It shows a normal variable music defined waveform during playback of a prerecorded tape (working state audio working fine etc).But when playing a Self Recorded tape shows a very different waveform missing the audio as such, almost like it has a wave of short pulses alternating around a zero point. It’s almost as though the machine isn’t laying down the stream correctly?
So im so confused and tried so many things, and wondered if you knew of anything else I could try to see if we can get this unit working again so I can make some recordings with 14yr son as he’s very keen to restore the machine with his father. - So the pressures on for dad to fix it. Would really appreciate any help you can advise.
Here’s a few pics of the RDMUX stream (the pic that’s got less in the waveform is the faulty playback stream, after attempting a recording ).
Based on the data presented and our experience with repairing 2nd gen DCC players, like yours, the head is, most likely, the culprit. We can’t be absolutely sure, but if the TDA is ok, usually the head is gone. Never seen a TDA fail in a 2nd gen for that matter, but it could happen.
We would switch out the head, just to test and make sure, but I understand that this might not be possible for you.
Thanks Ralf for that info, and sharing that with me. I value your info and experience very much.
it certainly could be …I have no idea what a good head W coils would read in ohms etc.
The head coils are reading about 25-30ohm per coil (thats with head connected to TDA) with respect to GND. Head disconnected TDA O/P are in Meg Ohms so no TDA shorts. TDA has temperature rise to stabilise at 54C during recording state, and appears to enter into the record state and erase (with something maybe noise or ?) the tape as existing music gets wiped over with “something”. Thats why I opted to swap out the boards bigger caps thinking it might be a supply noise issue under loading of record current - nope.
So (appears on the surface that TDA is “ok”) but indeed it could be a bit tricky without any spare bits to start swapping out parts. I might be a bit stuck at the current stage of repair …mmm ok I prob need to have think about how to go forward.
I guess heads are …quite rare ?
Hi,
Yes heads are really rare, we have a few new ones in stock, but it might be cheaper to find a donor with cosmetic damage f.i. That would help you with the head situation, but if it is not the head, it would help pinpoint the problem to something specific. All the components in the second gen machines can be switched, so I would start with the head and RW board.
