UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Retired Texas TI99/4A engineer needs help please.

SiriusHardware · 21st Oct 2018, 9:06 pm

I think there is a clue in the fact that the PSU is not yet able to run a known good TI99. Something is still wrong with the PSU.

For the time being forget about the computer as a load and try running the PSU up with combinations of high wattage resistors or lamp loads on the 5V and 12V outputs and see if it can deliver ripple free output with the maximum expected load on it.

Testing / faultfinding the PSU with the computer as a load poses a certain amount of risk to the computer if the 5V rail decides not to limit itself to 5V for any reason.

21st Oct 2018, 9:06 pm	#7
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,556	Re: Retired Texas TI99/4A engineer needs help please. I think there is a clue in the fact that the PSU is not yet able to run a known good TI99. Something is still wrong with the PSU. For the time being forget about the computer as a load and try running the PSU up with combinations of high wattage resistors or lamp loads on the 5V and 12V outputs and see if it can deliver ripple free output with the maximum expected load on it. Testing / faultfinding the PSU with the computer as a load poses a certain amount of risk to the computer if the 5V rail decides not to limit itself to 5V for any reason.