Re: DAS9100 incorrectly connected resistors on A2 power supply board


Brian
 

Hi Dan


Refering back to my original problem with the DC100A cartridges , I am beginning to wonder if they were just too cold when I put them in the drive ? . The room temperature might have been quite low circa 10 deg C . I have a number of DC1000 cartridges that I know also work in the DAS , I might risk an unused one fresh from the box (I've had the box for quite a few years though) just to see if it works now the temperature is a bit higher - now around the 20 deg C mark . I'll let you know if it works .
Brian

On Monday, 13 April 2020, 21:45:45 BST, Dan G <dgajanovic@...> wrote:

In tracking down the cause of disconcerting hissing noises coming from the T235 transformer
of my DAS9100 A2 main power supply board, I noticed that the two 36 Ohm 2W resistors
(R360 and R362) had been installed incorrectly. They were connected to the anodes of
the two bolt-mount rectifiers CR268 and CR258, but they should have been connected to the
common cathode point. As it was, they were completely inactive since the other end of
each resistor connected via its associated capacitor back to the same starting anode point.

My A2 board is 670-6734-02, and it seems that this was not a one-off error: there is a photo
of such a board on everyone's favorite auction site which shows the same connections.
The -01 version of this board is probably not affected since neither resistor lead reaches
up to connect directly to the diodes (the connections go through the PCB).
I don't know if any -03 revision boards are affected -- I have never seen one up close.

Does anyone know if this was a known issue? My board was made in 1982. Less than a
hundred more were made before Tek rolled to the -03 revision. I've checked
all ServiceTekNotes that are available on TekWiki, but there might have been a mention in
one of the missing issues, or possibly a Wizard's Workshop article (TekWiki only seems to
have a single issue).


dan

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