Sony TCD D7 DAT rewind and recording problems

[zsoleee]

Hi
I am new to Sony TCD D7 DAT.
I got a machine it can play well but fast forward / backward turning don't work. I see dashes on LCD and hear sound but after 2sec it loads again and I do not see any movement on tape.
I have already watched long video on youtube regarding that. Think something is wrong with gearbox but accordig to the video it won't be peace of cake disassembling the gearbox.. or?

Anther issue with recording. I put analog sound in but if I want to replay I do not see anything on VU meter and very rarely I could hear fragments of music. Could be something with capacitors in the RF block or the RF part is "misaligned" from the head. As I mentioned before playback from other machine is ok. Maybe somebody replaced the head already but it is only assumption. There are two potentio meters on the RF board. As I heard it never should be touched? Does it somebody know what the really do? Is there possibility to match with head again or?

[TIMTAPE]

Welcome, I have this same model and as a technician have somehow managed to keep it going well for many years, but when I bought mine second from the original owner it had barely been used and had been stored very well. I've also stored it very well since buying it. But it is a complex and miniaturised little device. It's fragile inside and difficult to work on. The display screen in the cassette lid connected by the flat ribbon cable to the body of the machine makes servicing and testing even more difficult. Cleanliness and generally high standards of work are paramount. Probably very few technicians if they are still alive and well will work on them. DAT is very much an obsolete audio format. Parts are very hard to find. Unfortunately that seems to be how it is these days with these little engineering marvels from Sony. But if you have the skills and patience, and the relevent parts can be obtained perhaps you will have success in restoring it. All the best with it.

[Simondm]

Do you have a cleaning tape? If not, get one intended for computer ("DDS") applications.

A computer drive is significantly different from an audio drive, and will automatically recognise a cleaning tape (using the hole pattern on a bottom corner of the cartridge). It will then do a cleaning cycle automatically.

As far as I know early DAT drives (i.e. audio ones) don't detect cleaning tapes (later ones might). To use a cleaning tape in a DAT drive, just let it run for about 20 secs, then eject it without rewinding it (don't ever rewind it!).

Cleaning tapes are mildly abrasive, and will both clean the heads and the tape path, reducing friction and improving s/n ratio. IPA and a cotton bud is NOT recommended, not least because it's not very effective, and (officially) you can damage the head drum if not cautious (supposedly). Access in the small drives is next-to impossible anyway, without teardown.

The issue you may be having is that one of the guides in the tape path is wrongly adjusted. This will prevent the drive locking correctly to the two datastreams. The adjustment involves looking at the head output with a 'scope (it's analogue at that point!), and cautiously adjusting for maximum output, but it's not an easy thing to do.

The other thing is that the TCD-D3, -D7 & -D8 all have small head drums and a corresponding Omega wrap (270 degrees, I think), making the adjustment harder. The larger drives use a 90 degree wrap, and the tape path is simpler.

I used to own a TCD-D7, but it was stolen in a burglary. I revived my TCD-D8 a few years ago by using a DDS cleaning tape, exactly as above. I had similar symptoms to yours above.

Historically Sony were not very good at designing tape paths for reliability. The DAT DTC 1000 had mechanics very much like a scaled-down version of U-matic video recorders, and the loading ring system is a common failure point with them (the pinion gear is nylon and splits - I have one that's done that which I need to fix!). Note that the symptoms would be different if that was the issue (it would generate a load error), BUT the effects you describe are consistent with a loose guide somewhere in the tape path (fix described above).

The omega wrap of the miniature DAT recorders is probably even more like U-Matics. And because it's omega, it's even more sensitive to guide issues (and/or lacing problems generally).

I'd recommend John Watkinson's book on R-DAT for detail (Focal Press but probably out of print now).

[edit] I thought this would be unavailable: https://www.amazon.co.uk/Rotary-Head-Digital-Audio-Tape/dp/0240513061 [/edit]

By the way, The audio tapes are measured in running time, so the one shown on the book cover is a two-hour tape. Computer tapes are measured in metres: a 60m computer tape is 120 mins approx and a 90m one is three hours (at normal audio data rates). They had much more stringent quality control than the audio ones (if they have a proper DDS symbol on them).

You can usually use both 60m and 90m computer (DDS) tapes in audio drives, but they will profile the heads differently, so it's not wise to keep doing swapping. DDS-2 and later computer tapes are the wrong formulation for audio recorders so won't work. That said, there's probably some manufacturer somewhere...