| Topic |
Author |
Posted On |
| SGC SG 2000 repair |
KG2PM |
on 14/10/18 |
| Then by implication, the MC1350 is probably not the mic gain circuit. The schematic does label it as the AGC/ALC chip. So I'll keep scrutinizing the schematic. This radio manual has pages and pages of schematic. Again, thanks for the info. |
| SGC SG 2000 repair |
KG2PM |
on 13/10/18 |
| Well, I am definitely a radio AMATEUR, and do not have a lot of test equipment. I hope to find an elmer in the neighborhood who does, and see if I can get some hands-on help. One final question for now, please. I found the AGC circuit in the schematic and on the circuit board. Does this circuit control the mic gain? It is a Motorolla 8940, MC 1350P. This radio uses a lot of these. Or is the mic gain a different circuit. |
| SGC SG 2000 repair |
KG2PM |
on 13/10/18 |
| Thanks, Zak. This radio was supposedly designed for military/commercial use primarily, amateur use secondarily, so the design should be excellent. I will check the mic amp and gain as a starting point once I figure out where it is and how to do it. |
| SGC SG 2000 repair |
KG2PM |
on 12/10/18 |
I am trying to repair an SG-2000 150 watt transceiver, manufactured by SGC. It dates from around 1995. Unfortunately, it has never worked properly. The problem is this. It seems to be putting out full power in cw. At the 50 watt setting, my MFJ VersaTuner II shows about 50 watts forward power with swr of about 1.4. My MFJ power supply draws about 15 amps. In the 150 watt setting, the tuner shows an swr of about 1.5, and the forward power reading is near 150 watts. The power supply draws about 28 amps at this setting. The radio's digital forward/swr display shows power out when transmitting a cw pulse, as expected. But the radio seems to be barely putting out any power in ssb. In ssb transmit, nothing shows on the forward power position of the radio's forward/swr display, nor on the versa tuner meter. The power supply meter shows only about 2.5 amps drawn in ssb transmit. Shouting into the mic (a replacement) barely makes the tuner meter move. These tests were done on 15 meters.
I inherited this radio almost new from a friend many years ago, but it had never been used. I made a few contacts, but had trouble right from the start. Soon after, the modulator chip failed, and I replaced it. But the radio still didn't work well, so I never used it except as a receiver.
Now I would really like to get it working right. I can hear the ssb voice signal in my other radios in the shack. Presumably the modulator chip is working. But no ssb signal, if any, is going out. Where should I look next for this problem? |
