Dick Pierce wrote:
On 1/5/2011 6:54 PM, Trevor Wilson wrote:
wrote in message
...
I have an approximately 10 year old Pro-Ject 1.2 turntable. Over the
last year, the big heavy platter has begun scraping as it spins, and
has finally ground to a halt. If I elevate the platter, by putting a
shim (two old CDs) between it and the sub-platter, that elevates it
enough that it spins again, but with lots of wobble. Obviously not
an ideal fix.
I don't know what's happening, but I'm guessing the sub-platter
(which is what actually spins, driven by the motor/belts) has
descended/sunk a bit.
Has anyone experienced anything similar with this turntable? Is
there any way to fix this problem?
Thanks in advance!
**Common problem with some of the Pro-Ject TTs. The platter sags!
Remove the mat and look at the platter from the side. You will
probably note that the outer rim has saged, relative to the spindle.
Cheap, crappy die casting I guess.
Are you SERIOUS? The platter has sagged? Please!
**I've seen the problem several times with cheap Pro-Ject turntables. When I
saw the first one, I reacted the same way you just did - I refused to
believe it. Explaining to a client was even more difficult. When I saw the
second one, I was slightly less surprised. By the time the third one rolled
along, I realised that there was a major problem. I also noted that more
expensive Pro-Ject turntables did not exhibit the problem.
If the platter was made of butter, yeah, I could believe
is. But even the crappiest imaginable diecast part if
not going to sag except under some pretty extreme loads,
like a stack of a couple of thousand LPs all at once,
maybe. And cheap diecast Al isn't going to sag, it's
going to crack. Aluminum is simply not going to cold-
flow at those loadings. And the loading required to
cause more than micron-type deflections is many orders
of magnitude beyond what you would encounter.
**Regardless of what you, me and everyone else thinks, I've seen the effect
several times. I don't know enough about metallurgy to understand what is
occuring, but occuring it is. Or was. I've not seen the problem for several
years. And to reiterate: The platter is some kind of cast alloy. It is not
(pure) aluminium. I have never seen the problem with any other brand.
A more likely explanation is something like the platter
bearing mount has slipped, the suspension has sagged or
similar.
**More likely? Certainly. The reality is something else. Examining the
platter form the side will reveal that the outside edge has sagged relative
to the centre. Weird? Certainly.
But the claim that even the crappiest of diecast platters
has sagged, essentially under it's own weight is, well,
extraordinary.
**I agree. It is, however, the fact.
--
Trevor Wilson
www.rageaudio.com.au