Are you saying that:
- The reel table is eccentric, or
- The reel hub adapter/hold-down is eccentrically mounted, or
- The tape reel itself is eccentric?
Bear in mind that I don't own now nor have I ever owned/worked on an Otari deck, but for the first issue in the list on my Tascam decks I've been able to get the reel tables to spin concentrically by repositioning them on the motor shaft or by taking the reel table apart (the face of the table mounts to the reel table hub by three screws...I just took out the three screws and rotated it by 120° and then tried it again to see if it helped.
If it is #2 I just loosen the center-screw that holds the reel-adapter to the reel-table, slightly shift it in the appropriate direction and retighten repeating as necessary until it spins concentrically.
If it is #3, keep in mind that many reel
flanges, especially the thin three-screw flanges, are eccentric relative to the reel
hub. If the
hub is spinning eccentrically relative to the reel table/hub adapter, stop the transport, loosen the hold-down and shift the hub slightly in the direction it needs to go, but
don't judge whether or not the reel is spinning concentrically by how the flanges look unless you know for certain that the flanges and the hub are concentric to each other. Every time I load a reel I put the deck in EDIT mode, position myself at the side of the deck and look across the top of the reel I'm working on; I look between the flanges so I can see if the tape wrapped on the reel hub is moving up and down (eccentric), or if it is nice and steady (concentric).
I just know in my experience it takes some time and tweaking to get it right. 6-screw precision reels fit on the reel adapter more snugly and are a bit less of a headache with all of this as long as the reel adapter is spinning concentrically.
Couple questions:
- Have you considered that your back-tension might be off? Try this...if you have a cal tape, reproduce a 10kHz tone and then, while watching the VU meters, apply light back-tension to the supply reel (like just letting a finger drag on the reel flange)...does the output level increase? If so you may need to increase the back-tension.
- Does the 0.5dB deviation happen across all tracks? If not, maybe it is a tape path alignment issue. 0.5dB deviation especially at higher frequencies is not that much an issue and may be expected particularly on edge tracks.