no fm audio

[minime]

hey im after abit of help iv got a magnum deltaforce it work's fine on am and ssb but has no audio on the fm when transmitting the talk back work's as well.. iv changed the audio chip kia4558p thinking it mite have been that but it's not

the radio come to me and the mic wire was hanging out of the socket and iv check the center pin to see if the 5volt's is there and well it isn't the im just wondering if the wire's in the mic plug have shorted and blowen some think around that area

has anyone seen or had this probblem befor ???

[163TM847]

Check the FM deviation VR hasnt broken, The little tiny VR's they were very fragile.

The voltage to the centre pin comes from the main 12v feed from the on/off control through a coil [the coil looks like a resistor] This can often blow but the radio would still work fine with a standard mic as a standard mic the centre pin wouldnt be used, If you have TX audio on AM/SSB then i doubt it will be a voltage problem or the 4558 IC

[koberk]

After checking the VR, sadly it probably means feeding the rig with a test tone, and following its progress thru the modulation chain using a scope.
Not easy, but it will result in an answer, be it a duff component, a logic error, or a dodgy connection.
Good luck.
Nice rig.

[zephyr]

As Nick said, see below.

[minime]

thank you for getting back to me on that lad's
iv checked the L123 and it has gone open circuit, iv put a pice of wire accross the two point's to see if the audio will come back on fm but nothink

iv got a feeling it's one of the semiconductors around that area, or could be the fm discriminator chip

but as soon as i find some think ill let you all know lad's