Today, a friend gave me a Mastech HY3003D-3 power supply to attempt to repair for him. It's a 3 channel linear supply, with 2 supplies 0-30V/3A and a 5V/3A supply.
My friend has four of these PSUs and all have the same problem. The issue is that one of the 0-30V supplies (the master) only goes down to approximately 5.5V. Other than that problem, the supply seems to be working properly. I haven't checked it for regulation at full load but all controls seem to be operating properly. A quick check at 1A load indicates that regulation is good.
Just wondering if anyone here has any troubleshooting experience with these supplies, or if this is a common issue with them. I have a schematic for a HY3005D-3, which is very similar, but it's kinda hard to follow and I haven't been able to locate any documentation having a theory of operation. I can figure it out eventually, but it would be much easier to draw from someone who has worked through this problem. Mastech says they only help customers who bought directly from them, and refused to send the correct schematics.
Since all of the units exhibit the same problem, I'm wondering if they have been modified for a specific purpose. Possible, I guess, but no idea of what the modification involved.
Thanks for any help.
Dave M
My friend has four of these PSUs and all have the same problem. The issue is that one of the 0-30V supplies (the master) only goes down to approximately 5.5V. Other than that problem, the supply seems to be working properly. I haven't checked it for regulation at full load but all controls seem to be operating properly. A quick check at 1A load indicates that regulation is good.
Just wondering if anyone here has any troubleshooting experience with these supplies, or if this is a common issue with them. I have a schematic for a HY3005D-3, which is very similar, but it's kinda hard to follow and I haven't been able to locate any documentation having a theory of operation. I can figure it out eventually, but it would be much easier to draw from someone who has worked through this problem. Mastech says they only help customers who bought directly from them, and refused to send the correct schematics.
Since all of the units exhibit the same problem, I'm wondering if they have been modified for a specific purpose. Possible, I guess, but no idea of what the modification involved.
Thanks for any help.
Dave M