galaxy squealing

lemans66 · Post by **lemans66** » Sunday 26th Aug 2007, 16:34

I had a lighting strike and it burned L903 and L904 0n the small board eptdssb902 where the wires come in from the fuse.The radio is a galaxy saturn .I replaced the two disc and the radio seamed to work fine,but when I got a radio check everybody said it was squealing so bad that they could hardly here my voice.It keys the same watts and swings the same as aways.Nobody works on radios in my area so I need help.

nomadradio · Post by **nomadradio** » Sunday 26th Aug 2007, 19:14

The Saturn has two ground circuits in it. The chassis is NOT connected to the negative side of the DC power supply. Each of these is a separate, er, "ground". An array of small disc capacitors is bridged across these two separate grounds to put the cabinet metal at the same RF potential as the pc board's power-supply ground circuit.

When lightning enters from the line cord, it will try to reach the best ground it can, probably the one on your antenna system. It can put a surge through one or more of the disc caps that bridge the two ground circuits together for RF currents.

Check behind the mike socket, and see if any small disc capacitors look scorched.

Also, check each of the mount screws that hold the main pc board to the chassis. There will be one or more disc caps at each of these connecting the pc board's "circuit ground" (power supply negative) to the chassis ground on that mount screw. These will be found at four of the five mount screws on the main pc board, as a rule.

And if you find no burned disc caps shorting the two ground circuits to each other, have a look at the connections on the rear of the mike-gain control. There is a small RF choke between the control's counterclockwise lug and the shield side of the wire that leads to the mike socket. If that choke blows open, the mike audio will squeal no matter where the mike gain control is set. Only the pitch of the squeal will change as the mike gain is turned up or down when this choke becomes an open circuit.

73

lemans66 · Post by **lemans66** » Monday 27th Aug 2007, 4:56

I checked the things that you told me to check and found a bad solder joint on one of the disk at the mic.Resoldered it and no more squeal.I thank you so much for your help.There realy are nice people left in this old wortd. Thanks Lemans66

nomadradio · Post by **nomadradio** » Wednesday 29th Aug 2007, 16:16

Glad to hear it was that simple.

Congratulations.

73