Here is an alternative method of repairing a
radio that has a bad mb3756. Besides the 8
volt regulator function the mb3756 also controls
T/R switching. Pin 6 supplies 8 volts but only
during RX. Pin 8 supplies 8 volts but only dur-
ing TX. To be able to use a LM7808 voltage
regulator as a substitute for the mb3756, the
T/R switching voltage between pins 6 and 8 will
have to be done with a relay. You can used a relay
that is found in many fuel injected GM cars.
The car that I got this one from was junk, so my
relay was free. You wouldn't want to buy a new
one though, they cost about $40. But you can use
any relay from a 23 channel rig, or any relay
with a 12 volt coil and is at least SPDT like
the radio shack 275-240 (it's about $5)


Parts list: A spdt relay with a 12 volt coil.

2 of electrolytic capacitors, the value is not
critical but they should be at least 16 volt and
roughly 100uf to 470uf. I used 25 volt 330uf
that I pulled out of a junk radio.

Some wire and solder.
2 of the LM7808 regulators. Radio Shack does not
sell the 7808, but they do sell the 5 volt 7805.
You can convert the 7805 to 8 volts with resistors.

Instructions using 7808 regulator and stock clarifier

Instructions using 7808 regulator and modified clarifier

Instructions using 7805 regulator and stock clarifier

Instructions using 7805 regulator and modified clarifier