Re: Free TWD 120

Charlie Conger

Thanks Thomas. Excellent work.
Erich downloaded the software files from the internet. They may be newer. There is also some calibration software files running around.

Lastly I see the famous Dallas Semiconductor nonvolatile RAM chip in the photos. Not sure that is one of the models that have an internal battery backup. You might check it out before it looses its mind!

Charlie Conger
713 472 9140

On Sep 23, 2020, at 12:44 AM, Thomas Garson <> wrote:

´╗┐My "new to me" TWD120 arrived today. Thank you Charlie.

As Charlie advised in previous email, it did not pass self test, leaving the front panel LED unmistakably solid red.

However, the repurposed IBM laptop external power supply worked admirably so I dove into it.

After removing a number of screws and a cal sticker, I was presented with a single nice and compact SMD loaded PCB. No out-sourced PWM supplies for Tek. The regulator circuitry occupies a compact "can" in one corner.

As I was working w/o a schematic I had to find supply lines on some chips to check voltages. Voltages were good, but one was a bit noisy. DC to DC portion of supply looked good on (Tek 5000) scope. After sniffing around a bit (figure of speech. It did not smell) I noticed several Motorola T10N05e TO-263 type SMD packages near the supply wall, but outside of it. At first I was puzzled as I could find these parts for sale but no data sheet. Figured out they were N-channel power mosfet. I determined they were used for gates to enable/disable DC power feeding from the supply. Interesting. Squinting trough my trusty Swiss Army Knife magnifier (glass lens!) I noticed serious corrosion on the Source solder connection of one of those FETS (Q104: +8v line), which I theorized may have been the source of the noise I has seen. Reflowed the funky joint. Kicked on the power, waited a minute or so for self test to complete: Bingo! LED now turns Green!

That's as far as I got today. Next thing is I have to pull the software for it off of the floppy discs (fingers crossed) for copying over to the server and then burn a back up disk. After that, get my Win98SE PC set up with SCSI (not too big a deal as I used to do a lot of SCSI stuff) and see if I can actually get the thing to work. At the moment, I'm fairly optimistic this will happen in short order.

A few photos here:

Thomas Garson
Aural Technology, Ashland, OR
By my calculation, the dynamic range of the universe is roughly 679dB,
which is approximately 225 bits, collected at a rate 1.714287514x10^23 sps.

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