Anybody have an idea what the PA2027 IC is controlling. Does it control Vcc to the 494 and act as a comparator?
If you have the tutorial, section 42 of the power supply troubleshooting page.
If not, let me know.
If not, let me know.
Confirm that R947 and R948 are within tolerance when post the DC voltage measured directly across each one.
Do the same for all other capacitors on the positive 15v.
Are any of the op-amps heating up?
Do you see anything else loading the +15v in the diagram?
Are any of the op-amps heating up?
Do you see anything else loading the +15v in the diagram?
Unless the 2027 is running hot, the heating of the +15v regulator is normal. It's pure insanity how many regulators are poorly designed in an otherwise decent piece of equipment.
If the board isn't starting to break down (physically), you could use a different transistor. Would a TO-220 case transistor fit in the space (it will be installed 'backwards' due to reversed pin configuration)?
If the board isn't starting to break down (physically), you could use a different transistor. Would a TO-220 case transistor fit in the space (it will be installed 'backwards' due to reversed pin configuration)?
The D44 may work OK but it's a high speed transistors and can sometimes cause problems in circuits like regulators. If it's definitely OK, there is no reason to change it. If it does cause any kind of instability (undesireable noise or oscillation), use something slower like a 2N6488.