Sep 16 2007

IC-7000 Heat Issue Revisited

Published by at 2:41 PM under A-All posts,Amateur Radio

Many people may not realize that there is a TCXO (Temperature Compensated Crystal Oven) toward the rear of the IC-7000. This is the source of much of the heat the radio produces while not transmitting.

Performing the fan modification actually may not provide any benefit. A friend has operated two 7000’s 24/7 for several months for various reasons and neither has as much as hiccuped from heat, even when airflow challenged a couple times by accident.

Next time I get mine close to my bench, I’m undoing my fan mod simply to save wear and tear on the fan. The control panel does get warm to the touch and the fan mod did not cool that down at all due to the construction of the radio.

I still think mine is a super all (almost) band transceiver and enjoy using it every day.

4 responses so far

4 Responses to “IC-7000 Heat Issue Revisited”

  1. WA9FVPon 12 May 2010 at 11:37 PM

    I think the mai
    n issue with the IC-7000 is the power management and component placement. Out of the 5 or 6 7000’s I repaired, I found that the highest heat concentration was near IC-1901 and R1902 (both mounted on the bottom side of the main board). R1902 is a 1.8 ohm in series with the 14v power. It feeds the 14 volts to R1902, a 7808 3 terminal regulator. The 8 volts from IC1901 feeds voltage to just about every board including the CPU, PA, Main, DDS and DSP. After 8 hours in receive mode I measured temperatures, using a Fluke 189 and a thermal probe, that exceed 92.4 degrees “c” or 198 degrees “f” on the top side of the main board. It’s hotter on the bottom side and I can guarantee it’s hotter than hell! With a few screws removed on the main board, there’s enough room to reach under the board with my “pinky” and feel the regulator. It burnt my finger!

    There’s a second 7808 (IC2001) and a 1.8 ohm resistor (R2011). It feeds 8 volts to an RF amplifier IC on the main board and the control head. Here’s where it gets strange. In previous models and that included Yaseu and Kenwood. They would feed 12 volts to the control head and regulate down to 8 or 5 volts to power logic or analog circuits. The IC-7000 regulates down to 8 volts on the main board feeds the control head. To power LED’s and the LCD backlight, there’s a switching supply that kicks the voltage up to 12 volts. A 7805, 5v regulator (IC101) also feeds off the 8 volt line and powers the logic circuits. In my opinion, the current needed to run the control head adds to the heat problem on the second 8 volt regulator and creates additional heat on the main board.

    While making the heat measurement I discovered that if the top cover is removed temperatures drop about 10 degrees “c”

  2. Walton 13 May 2010 at 6:12 PM

    I tried my calibrated finger as well to check that IC…with the same results! More heat sinking would have made the radio larger I guess so they decided to take the compact route. I don’t know why but I have seen several radios myself with 8 volt supplies that didn’t seem very well thought out. Alinco turned out the 610 (if I remember correctly) to replace the 605 and it had plenty of issues. A Motorola tech friend of mine had a 610 I helped him with – until he pinched a wire fed by the 8 volt regulator putting the cover back on.

    I think a lot of people get spooked feeling the display panel area get so warm as well.

    The up/down/up voltages remind me of an “Angry 5” military radio I used to have.

  3. WA9FVPon 17 May 2010 at 10:14 AM

    The temperatures I measured were on the top side of the main circuit board just above the 7808 regulators. The regulators were mounted on the bottom of the board. After 8 hours, receive only, I measured 98.4 degrees “C”. If you calculate the thermal loss through the PC board and the package it’s self, I’m sure the die temperature is a lot hotter.

    Using My IC-7000 as a ginni pig I fabricated a heatsink that solders to the 7808 regulator tabs and mates with the chassis. After 8 hours of run time, receive only, the temperature at the same spot on the main PC board measures 59 degrees “C”. As soon as I document the mod, I’ll up load it.

  4. Walton 18 May 2010 at 7:11 PM

    Sounds good! A lot of folks would be interested to see it. My log file shows a lot of interest in the heat issues.

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