[ARSCLIST] Nakamichi Tape Deck Problem

[Sirnailhead JR Superfly <sirnailheadjr@xxxxxxxx>]

Hey All...

I'm sort of an amateur archivist, mostly working on underground bands of
the last 20 years that may have only recorded demos on cassette.  I
haven't had the money for a new deck in many years and about 6 months ago
I found a used Nakamichi 480 model from the mid 80's.  It pulled tape and
seemed to play and record fine when I turned it up and seemed worth the
$30.  I hadn't used it in a while, but when I tried the other day I found
something rather strange.  The tape will play clearly for 20-30 seconds,
then will start to lower in volume and have sort of a muddy sound, not
unlike a tape left in the sun.  If I hit stop and play again it sounds
perfect again for a similar amount of time, and it seems I can do this
over and over with the same results.  Any idea what the problem is?  I
cleaned the heads when I got it and there was nothing obviously wrong to
my very amateur eyes.  My question would be is it worth the expense.
There is a local shop that does work in Nakamichi and I'd bet it would
cost $100 or more.  Do older consumer grade Nakamichis hold up over time
and would it be possible to get it "tuned up" to make sure the speed it
correct, heads OK, etc?  If I were to put $120-150 into it would it
likely be as good or better as anything I could buy new in the same price
range?  I have piles of cassettes that I can't really do much with until
I have a deck that works properly, but I'm not in the market for a new
high end deck.  Any ideas on what other decks I might consider if this
one is beyond hope would be much obliged.  Thanks.  Randy