Hello,
I have just discovered that my "trusty" DIY PSU no longer outputs 12V.
I see in fact about 0.5V
The unit has been very reliable over the 6 year in intermittent operation; until now.
I removed the cover & quickly found (under no load) the LM1085 IT-12 regulator (3A, fiixed 12V LDO output) was getting very hot.
I had fitted an aluminium heat dissipation sink (75mm x 50mm) & this quickly became too hot to touch & I could smell trouble & switched off before magic smoke appeared.
According to the data sheet this regulator has thermal protection & current limiting, so I was surprised at what seems a failure of this component.
Then I saw that it is temperature rated to 125 C; much higher than I would ever have expected.
Of course there may be upstream problems, the rectifier bridge maybe ................
I have not checked yet the two capacitors, but they look OK.
Anyway I ask for guidance, maybe I should rebuild from the transformer & include a bigger heat sink?
I have just discovered that my "trusty" DIY PSU no longer outputs 12V.
I see in fact about 0.5V
The unit has been very reliable over the 6 year in intermittent operation; until now.
I removed the cover & quickly found (under no load) the LM1085 IT-12 regulator (3A, fiixed 12V LDO output) was getting very hot.
I had fitted an aluminium heat dissipation sink (75mm x 50mm) & this quickly became too hot to touch & I could smell trouble & switched off before magic smoke appeared.
According to the data sheet this regulator has thermal protection & current limiting, so I was surprised at what seems a failure of this component.
Then I saw that it is temperature rated to 125 C; much higher than I would ever have expected.
Of course there may be upstream problems, the rectifier bridge maybe ................
I have not checked yet the two capacitors, but they look OK.
Anyway I ask for guidance, maybe I should rebuild from the transformer & include a bigger heat sink?