From what I have seen myself and also talking to people who repaired these on a regular basis, came to the conclusion this lubricant issue is in all of them, even when they appear to be working. Hence the reason of my statement that they need to be overhauled even if the unit appears to be working. So this is the first issue that absolutely MUST be adressed in all units. Of course apart from these, there may be further issues that need to be fixed. A common problem on these (which most people don't realise is a problem) is unit displays blank when put in FF (despite the tape is recorded). Most will assume the unit has detected a blank piece of tape, say this behavior is completely normal and forget about it. It manifests like this: you press FF, it winds the tape for 1-2 seconds then stops and displays "blank" (despite the tape itself is recorded). This is something that should be checked when buying such a device, because if the seller tests it only in PLAY mode, they will never notice such a problem and sell you device as 100% functional, when in reality it will need to be serviced. Failing to do so can create excess wear on the head drum, so beware as spare parts are not available anymore (even on ebay they're super rare) and if you unit needs new parts a donor will be needed. Even testing in PLAY means you need to let the unit run for 30-40 mins (ideally an entire cassette) as there can be glitches, intermittent problems (like the units resets itself after some time) which won't be noticed if you only play a tape for 5 mins. @RTM In regard to your question about overhauling, I recommend Paul Carrington (don't know anyone from the US): his prices are very good and he has done this kind of repairs for decades, so an expert in the field. Regadless of you being interested or not, I will leave the details here in case someone else reading the thread is interested in his services: https://www.paulcarrington.co.uk/repairs It is to be noted there are not many experts in DAT machines out there and overhauling these TCD-D7/TCD-D8 (or TCD-D3) requires knowing their common issues and how to fix them, so your local electronics repair shop will NOT be able to fix such devices.
I did some more testing, and it seems that the problem is alignment (and that lubrication). It plays quite fine what it records, but there is a lot of noise from tapes recorded on other DAT. I also noticed, after doing the full forward+back rewind, that at some point (in middle of tape!) it slows down. Some people had used oscilloscope for fixing, so I'll have to put it on hold. It also needs calibration tape, oh well.
