This machine is at least 45-50 years old and ideally should have replacement of the electrolytic capacitors in the audio sections--the record and playback amplifiers--and adjustment and calibration. You will need to have an experienced, capable technician perform cleaning, lubrication and adjustment of the tape transport mechanism as well as replacement of the belt in the capstan drive. You'll need to have the heads carefully examined and relapped or replaced if worn.
Once you do all this, you will have a quite fine consumer grade R2R deck. It will record and play back at very low distortion levels at 7.5 ips, the preferred tape speed for this sort of deck which will give you nearly an hour of time per tape "side." At this speed, noise is not a problem with good quality modern high output tapes. If you plan to use if for record and playback, you'll need to have your tech who does the renovation of the deck calibrate the machine to the tape type you plan to use. Typically, this will be to a +3 "standard tape or +6 tape such as SM468.
Teac used a plug-in on the back of the machine. It will not operate without it. If it's lost, there are usually 3rd party sellers offering them on Ebay.
Be prepared for sticker shock if you go on Ebay looking for commercial prerecorded tapes from the ~60's and '70s. They are selling for insane prices. Moreover, the quality is usually mediocre in the later tapes due to high speed duplication techniques. Also, the quality of the physical tape was not even first rate in the day. Although most of these tapes are quite playable today if reasonable storage conditions were maintained over the years, This is not the place to look for the jaw dropping high end audio experience that is typical of well engineered 2 track first or second generation copies of masters at 15 ips on modern tape such as sm900 or current sm468.
There are some recordings that are remarkably high quality 4 track tapes at 7.5 ips to be had from the the early period of 4 track consumer recording in the early 60's. For example, the recordings of classical music on RCA red label, Columbia, EMI, Deutsche Grammophon and several others are often very good. Popular music is much more of a hit or miss, commonly recorded at 3.75 ips which is noisier and carries higher distortion levels. Avoid these tapes at all cost.
The question is whether it is worth the restoration of the machine for your intended purposes.
I have a fairly large collection of commercial 4 track classical recordings that I regularly listen to. I play them back on a Teac 6300 that was restored by an exceptional expert shop in the Washington, DC suburbs, the tech (I believe is a member of this forum "tapetech"), who is just superb. I had all the audio signal path electrolytic capacitors in the repro amplifier changed out for Elna Silmic audio electrolytics. Nichicon Muse non-polarized capacitors are also very good for this purpose. He did the complete mechanical restoration as well. It was fairly expensiv ebut the machine works like a charm and is a keeper. The sound went from dull and muddy to crystal clear.
WIth proper maintenance, these machines very sturdy and last basically forever.--as long as parts are available and quality techs are available to do the needed work.
If you're looking to play the latest generation 2 track high end offerings, there are a wide variety of deck to consider. I have a Tascam BR-20 which is a very robust machine with especially gentle tape handling characteristics and excellent fidelity without any hotrodding modifications. These machines are much later vintage than the Teac 6300 so should not need much restoration work at the point of acquisition.
