Tascam DA-20 Slant Block Alignment? (Ping Scott Dorsey!!)

[Stephen]

Archived from groups: rec.audio.pro (More info?)

Well I've pretty much figured out that this low mileage beast is way out
of alignment.
Of course I don't have a service manual, but I do have a scope and other
tools.

Bottom line, is their a quick and dirty way to align the slant blocks to
get them mechanically in the ballpark?

I have many DAT's that were recorded on known good machines that I can use
to play while I tweak.

I've played with the two alignment posts on the slant blocks till my
fingers are sore with no luck. I either get tons of digital noise, no
sound at all or a cyclic drop out, almost like a head is bad. No matter
what I tweak I can't get rid of the mistracking although I can get pretty
dammed close. Of course I am more than likely doing this all wrong but if
I had a test tape and a FSM I wouldn't be tinkering

Is their some rule of thumb that Tascam/Pioneer uses to get these things
in the ballpark? IOW start with them fully CCW, turn 5 times etc....

The one on the left (looking straight on through the door) is hidden by
the transport so I have to unload the tape to turn it, the one on right
can be adjusted on the fly.

Any ideas?

I just need to make this beast work for a couple of weeks and then it's
history. It has very low useage on the heads and with the exception of the
alignment is virtually brand new.

I appreciate any help!

Stephen

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

Stephen <keys_n_things@yahoo.com> wrote:
>
>Well I've pretty much figured out that this low mileage beast is way out
>of alignment.
>Of course I don't have a service manual, but I do have a scope and other
>tools.
>
>Bottom line, is their a quick and dirty way to align the slant blocks to
>get them mechanically in the ballpark?
>
>I have many DAT's that were recorded on known good machines that I can use
>to play while I tweak.

No, don't do it. You need a real alignment tape, not one recorded on a
"known good" machine.

>I've played with the two alignment posts on the slant blocks till my
>fingers are sore with no luck. I either get tons of digital noise, no
>sound at all or a cyclic drop out, almost like a head is bad. No matter
>what I tweak I can't get rid of the mistracking although I can get pretty
>dammed close. Of course I am more than likely doing this all wrong but if
>I had a test tape and a FSM I wouldn't be tinkering

You've screwed it up now. Send it to Eddie Ciletti at Tangible Technology
with a letter saying exactly what you did. He may be able to undo it,
but my suspicion is that the alignment posts aren't the problem. There are
a _lot_ of possible alignments there, and if your tape tension is off or
the tracking head is off or any one of a number of other things aren't right,
it won't lock. You need a scope and the real alignment disk and the full
alignment procedure in the manual, and you need to start at the beginning of
the alignment procedure and work your way through it so that you aren't
misaligning one thing to partially compensate for another. But now that you
have the posts misaligned it's going to be a little harder....

>Is their some rule of thumb that Tascam/Pioneer uses to get these things
>in the ballpark? IOW start with them fully CCW, turn 5 times etc....
>
>The one on the left (looking straight on through the door) is hidden by
>the transport so I have to unload the tape to turn it, the one on right
>can be adjusted on the fly.
>
>Any ideas?

Get the service manual. The alignment procedure is maybe twenty or thirty
pages long but it's not that bad once you get the hang of what is going on.

>I just need to make this beast work for a couple of weeks and then it's
>history. It has very low useage on the heads and with the exception of the
>alignment is virtually brand new.

The most popular problems with these machines involve tape tension, and bad
decoupling caps on the servo and discriminator circuits.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

"Stephen" <keys_n_things@yahoo.com> wrote in message
news:34u4gsF4fscthU1@individual.net...
>
> Well I've pretty much figured out that this low mileage beast is way out
> of alignment.
> Of course I don't have a service manual, but I do have a scope and other
> tools.
>
> Bottom line, is their a quick and dirty way to align the slant blocks to
> get them mechanically in the ballpark?
>
> I have many DAT's that were recorded on known good machines that I can use
> to play while I tweak.
>

You can sort of get it in the right ballpark without an alignment tape, but
you will need to remove the transport form the chassis and remove the
loading mechanism to access both guides properly with the machine running,
and you holding the tape in the mechanism with your fingers while you
twiddle and watch the scope. You will need a good dual beam scope as well.
And you will need to find both the RF signal and the Head Swap signals and
trigger properly off them. Assuming you can manage all that, you will then
have to know what the RF signal should look like and how to adjust the
guides to get it. This is the kind of thing that takes a while to master.
The first few times you will get it wrong.

Even if you get it in this ballpark, it will probably not be close enough to
the centre spot to eliminate the odd glitch as you have found out already.
Plus you have all sorts of other things to contend with like tape tension.
Which means you will have to take it to a tech anyway who can get it to the
first ballpark in a few minutes, so you won't really have saved very much by
doing so.

No, there are no shortcuts for this.




Gareth.