Hello dear OMs,
Personally, I don't see the point of installing a crowbar circuit.?
This circuit protects against a possible overvoltage that could result from the destruction of the power transistors on the power supply regulator.
The causes of destruction can be thermal or by exceeding the current.
The FT-980's two power supplies heat up far too much (it's a well-known problem!).
The transformer delivers far too much voltage if it's not configured for 2x 117 V for Europe. That's the first thing to look at!
Next, the capacitors after the rectifier are far too high. The filtered voltage is too high and the current flow in pulses to charge the capacitors reduces the transformer's efficiency.
I've modified the two power supplies by halving the capacitor values.
Another problem is a design error in the control circuit which makes the power supply unstable!
It is not conventional to have capacitors (C02) in the regulation loop after the current source T01 !
In attachment you will find all details of my modification.
Test the power supply before re-installing !
73 de F5RCT JMat
(See my rig on QRZ.com !)
