Doesyour TRS-80 Model III no longer turn on or only partially work? I.e. completely dead or no power floppy drive or serial board?

The common culprit is ablown R25 Fusible Resistor on your power supply.

Alot of TRS-80model III computers with a floppy drive will have two Astec power supplies.One for the main computer board and CRT monitor and the second for the floppydrive(s).

I am selling two ofthese OEM Fusible Resistors so you can repair your Astec Power supply. If your Powersupply looks like the one in my photo, then these fusible resistors will workon it.

I am including somescreen shots of the Sams TRS-80 model III service manual which indicates powerissues are usually attributed to the R25 fusible resistor burning out (goingopen). Your R25 Fusible resistor may look different than the ones I am sellingas show in a photo where I display two different failed ones from astec power supplies.

You can easily test yourR25 Fusible resistor with a multimeter set to Continuity check. If you getcontinuity across the two pins it still works, If you get nothing it has failedand needs to be replaced. I found this is a very common failure on model IIIpower supplies.

Listing is for twoFusible Resistors, no PSU is included: only shown for installation andcompatibility.

Please contact me withany questions I am happy to help.

NOTE: Your PSU may haveother problems such as a failing or failed supression capacitor (incorrectlycalled a RIFA capacitor). Or failing electrolytic capacitors. These Fusibleresistors are a first obvious item to check prior to further troubleshooting.

DONT BUY ANOTHER 43year old Power supply when all you need is a new Fusible Resistor!