[Scott Dorsey]

wrote:

I thought to ask here if anyone has more experience on the Technics
RS-1506 reel-to-reel tape recorder. I work for a small library
tranferring old recordings to digital domain. We have only one machine
which has quarter-track heads, the Technics, and I recently discovered
that when I use the machine's slowest speed, 3.75 in/s, the tape
transport is not stable. I was transferring a 7" reel and noticed that
when about half of the tape (from a full 7" reel) was on the take-up
reel, the take-up tension roller was vibrating noticeably, with a rate
of perhaps 5-10 Hz. This would get worse towards the end of the tape,
propably because the take-up reel's rotating speed was getting slower.
When I looked closely, I could see that the take-up reel's rotation
was not stable which led to tape tension (and the tension roller)
vibration.

I am assuming the problem is happening with all tapes and not just one.

Replace ALL rubber parts on the machine. Pull the capstan motor,
clean the bearings and lubricate them thoroughly with a light turbine
oil (Castrol OC-11, or Zoom Spout Oil from Ace Hardware, or Royal Purple
Synfilm 32). Disassemble and clean the brakes and if you can replace
the brakes, do so. Put a drop of oil on the reel motor bearings top
and bottom while you are at it. Anything that looks like an idler,
disassemble and clean it. Lubricate idlers with a lighter oil (16 cs
or lighter... watch oil will do nicely).

Once you have done this maintenance (and this is recommended on an annual
basis for the most part), then you can try a tape and see if you have a
problem. That's when the actual diagnosis begins, and it will probably
start with checking the static tape tension.

But that sort of stiction problem usually has to do with brake issues,
dirty guides, or some sort of belt-resonance issue with the tape path.
Idlers exist to break those resonances up, and if they get gunked up
they don't work right.

There's also another thing about this machine. When digitizing tapes,
I always adjust the azimuth for every tape I transfer. To my
knowledge, this is standard practice when digitizing a heterogenic
collection of tapes recorded on various recorders. On this Technics, I
don't do that because it seems there is no single azimuth-adjusting
screw for the heads. Also the guy who has serviced this machine said
that it's not that simple for this machine. Do you agree with this?

It's a pain, but it's not THAT hard. There's no reason not to do it.
You really need to adjust the azimuth for transcription work.

I've already noticed that not adjusting azimuth has a negative effect
on the quality (it's easily detected with tapes that have been
recorded "in stereo" from a mono source). The problem is that we don't
have the means of calibrating the machines (we had it done elsewhere),
so I don't want to touch anything else but the azimuth.

So spend the money and buy an alignment tape. You only need one for
all speeds, if you're willing to use some fudge factors.

ps. I read on this forum messages about trouble with this recorder,
namely head selector switch and left tape-source monitoring selector
switch failing. We just had this in service for head selector switch
failing (the switch was removed and the machine is now permanently in
4-track mode) and I have noticed that the *left* tape-source switch
cracles when it is moved. It's still working, but perhaps not for
long. The other department's RS-1506 had also the same two switches
broken down. I sense a trend here.

Clean them with Cramolin. If that doesn't do it, replace the switch
assembly with a small gold-contact switch. C&K has some locking
gold-contact types that Digi-Key sells. It'll take some mechanical
tinkering to make it look nice, though. The problem is that the switch
contacts get dirty, and with fractions of a microvolt it doesn't take
much to screw the signal up.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."