The power supply circuit: http://www.eserviceinfo.com/download..._TDR-3100.html
It was flashing on and off, making a whistling noise which went on and off.
A few bulging Luxon GR Series capacitors on the logic board were removed, and this temporally fixed this problem.
But the tuner voltage (typically 30V) was excessive (and rising! - but did not damage the tuner!
)
C15 in the power supply was too hot to touch, and it was found that the capacitors on the +5V rail (the only one being monitored) were faulty (but not bulging).
So all of the capacitors (except the 400V unit) were replaced in the power supply, along with a couple on the logic board. They included the ones near the power supply connector and under the tuner (a bit difficult to get at! - with 105C units - an apparently hot area).
The problem was fixed completely.
The reason why the capacitors on the logic board failed is when C15 went bad, the 30V rail increased beyond the 35V rating of the capacitors on the logic board connected to the 30V rail, causing them to fail.
One other thing: Why would such a supply have 30V connected to the optocoupler - where 3.3V or 5V is typically connected to the optocoupler.
It was flashing on and off, making a whistling noise which went on and off.
A few bulging Luxon GR Series capacitors on the logic board were removed, and this temporally fixed this problem.
But the tuner voltage (typically 30V) was excessive (and rising! - but did not damage the tuner!
)C15 in the power supply was too hot to touch, and it was found that the capacitors on the +5V rail (the only one being monitored) were faulty (but not bulging).
So all of the capacitors (except the 400V unit) were replaced in the power supply, along with a couple on the logic board. They included the ones near the power supply connector and under the tuner (a bit difficult to get at! - with 105C units - an apparently hot area).
The problem was fixed completely.
The reason why the capacitors on the logic board failed is when C15 went bad, the 30V rail increased beyond the 35V rating of the capacitors on the logic board connected to the 30V rail, causing them to fail.
One other thing: Why would such a supply have 30V connected to the optocoupler - where 3.3V or 5V is typically connected to the optocoupler.
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