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1. #ICOM IC 7800 POWER PROBLEMS UPDATE#
2. #ICOM IC 7800 POWER PROBLEMS MANUAL#
3. #ICOM IC 7800 POWER PROBLEMS FULL#
4. #ICOM IC 7800 POWER PROBLEMS SOFTWARE#
5. #ICOM IC 7800 POWER PROBLEMS FREE#

#ICOM IC 7800 POWER PROBLEMS UPDATE#

If you update from an earlier version, review all previous update information as well for additional feature details.

#ICOM IC 7800 POWER PROBLEMS MANUAL#

Thoroughly read Section 16 (UPDATING THE FIRMWARE) of the instruction manual (here) for details of what the update requires.Refer to IC-7800 Information for Firmware version 3.10 for details.

#ICOM IC 7800 POWER PROBLEMS SOFTWARE#

#ICOM IC 7800 POWER PROBLEMS FULL#

I expect it is either not achieving full output (or over-driving the PA) due to the wrong-value resistor I installed. The radio also happily drives the tuner, and seems to measure the proper SWR when fed with 25 and 100 ohm loads. RTTY and FM showed full-scale at 100% and otherwise mirrored the RF Power setting as I backed it down, as expectedĪfter this change, I measure differing voltages at CP1601 depending on drive and power output, which is what I would expect. To my delight, the radio started behaving normally! SSB with no modulation showed no power deflection, and modulation made it bounce as expected. So, I pulled it out and replaced it with as close of a temporary resistor as I had locally: 200 ohm.

#ICOM IC 7800 POWER PROBLEMS FREE#

To further test it, I disconnected the ribbon cables going to the main board, which should free up one side of it and measured again. I tested this in-circuit and it seemed like a dead short. However, I couldn’t get anything like reasonable values for these without taking them out.īut, there’s a 300 ohm resistor in the HFOR line, R960. There are a number of capacitors and resistors around IC960 before the HFOR line leaves for the main board, which I tried to test in-circuit. This, to me, seemed to be the problem: basically a static invalid feedback signal to the CPU, which it interpreted as power output when there was none in SSB mode, and potentially less than full output in FM or RTTY mode, when there was plenty. I measured 1.7VDC here during transmit regardless of modulation input or the RF Power setting. There is a check point in the ALC signal on the main board – CP1601. Since the radio was showing zero SWR deflection, and since the ALC and Power meters were based on the HFOR line, I focused there. The forward and reflected power is sampled on the PA board at the antenna connector and fed to IC960 where it is amplified and fed to the CPU on the main unit via the HFOR and HREF lines. My guess was that the confusing power output indications to the CPU yielded a “not a good match” determination by the radio itself.Īll of this led me to think that something in the power metering or ALC circuits was not right. Even when connected to a dummy load, the radio would kick off a tune cycle, the tuner would achieve a satisfactory result, but the radio would kick the TUNE indicator off after it was done. In FM or RTTY mode, the power supply would show about 22A draw even though the radio claimed it was putting out less than 80% power.Īnother very interesting manifestation was that the radio wouldn’t drive an external tuner.

The power draw would fluctuate as expected with voice peaks, even though the power meter did not show any activity. This specification means that even on the 50MHz band, frequency error is less than 2.5Hz In addition, a 10MHz reference frequency can be input and output for accurate tuning. In SSB mode with no modulation, the radio would only pull an additional two amps or so, despite the meter showing about 50W output. The IC-7800 uses the OCXO (Oven Control Crystal Oscillator) unit which is stable to within ☐.05ppm at 0☌ to 50☌. However, I ruled this out by looking at the current draw on the power supply. ALC should mirror the modulation input, regardless of power.Īt first, this seemed reminiscent of the self-oscillation problem that could occur in the 756 and 746 radios, where the RX line wasn’t fully pulled to ground during transmit, causing similar behavior with power deflection during transmit with no modulation. Lastly, in SSB mode the ALC meter would show full deflection with no modulation if the RF Power was set over about 40%, and zero if it was set under that level. Further, in FM or RTTY mode, the power meter would show about 80% deflection when RF Power was set to 100%. With modulation, some meter activity over the static level could be seen, but never full deflection. In SSB mode, pressing the mic key shows about half-scale deflection of the power meter with no modulation and regardless of the RF Power setting. The radio now exhibits a strange symptom related to the Po (power output) and ALC meters.

After repairing it with new parts, the radio powers on, but all is not well. The result was a totally-dead appearance, which I resolved as detailed in this recent post. Recently my Icom IC-7000 died during transmit.