View Single Post
Old 28th July 2020
  #4
Here for the gear
 

So I see it's been awhile since this post was active but I recently acquired a DW8000 for free. When I powered it up the readouts displayed 88 across the board and then went out within 3-5 sec. I am well experienced in electronics troubleshooting and repair but... not so much in the digital arena, certainly not as complex as this unit. However
TS, repair and mods of power supplies, power regulation, vacuum tube and solid state audio amps
I have that covered.
Now back to the DW8000. I verified proper operation of the power supply by verifying proper voltages and stability of all output values. Even so I pulled the 3 primary filter caps and tested their value accuracy and ESR. Amazingly the tested as good as the new Nichicon replacements I had ordered. I changed the internal battery, tested/cleaned all connections, ground points, controls, etc. No improvement over the initial as found response. Note I chose not to reset the processor because No programing tape came with the unit. I decided to check current values at each and all output pins of the PS. I could not find these values online so not sure what they should be.
All registered values under an amp accept pin 3 of connector 2a which was 3.5 - 4.0 amps while maintaining the spec voltage of +5vdc. This seemed to me to possibly be a problem. I used an infrared probe to scan KLM661 and located elevated temperatures in ICs 49-55. These ICs ma be associated with the RAM. No info in the service manual but what little I could find for free indicates they are RAM chips. Note all the chips heating up are identical. Texas Instruments SN74S189.
IC3 (regulator) on the PS board was also registering high temps along with the rectifier.
For this reason, I chose to not probe the 661 board for voltages at individual points for as I say "Releasing the Smoke Monster"
With all this, Did you determine a resolve for your DW?
Thanks Mark