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  #1  
Old 08-16-2015, 10:18 PM
Bill R Bill R is offline
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Icom IC-211 repair

I have on the bench an Icom IC-211 2 meter transceiver. I bought it as a project. Upon power up there was no sound and the display would not change. I found the speaker leads broken off the speaker and after doing a lot of soldering and finding a pair of resistors on the display driver board installed incorrectly it will now tune up, but not down. I did check transmit and the power output is low. Right now I would like to be able to tune down in frequency. Anyone have any experience with this problem? I am missing the PLL and VCO covers and the top control cover as well. It seems to receive and like I said it will transmit, but the power output is low. Any help would be greatly appreciated. The chopper alignment looks good.
Thanks
Bill
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Old 08-17-2015, 01:41 AM
JBL GUY JBL GUY is offline
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When you say the photo chopper is aligned, do you mean the infrared diodes and the photo transistors? Taking that at face value, Turning the knob clockwise should produce a high on pin 4 (IC 10) and turning the knob counter clockwise should produce low on pin 4 (IC 10). This output goes to the LSI and is the up/down control.

If you do not have that change of logic state, then you need to look at the input to IC 11, pins 8 and 6. This is the input to this circuit and comes from the photo transistors in the photo chopper. You will need to look at that signal with a dual channel oscilloscope. You should see to signals shifted by 90 degrees and the lead and lag should reverse when the direction of the knob is changed. If you have good waveforms here then you need to follow the waveforms through the rest of this circuit to IC 9 and then to IC 10.

The output of IC 10 on pin 3 is the CK (clock) pulse train that occurs then the tuning knob is rotated and since you can tune up but not down, this must be okay. You need to look at pin 4 of IC 10, this is the up/down control and it may be stuck in a logic high state. Also note that this is also connected to the ACC socket, make sure there is not an issue there.


You say the RF power output is low, (okay you know what is coming).

How low is it, just a few watts or very low and is it the low in all modes and are you able to adjust the output power in the various modes, even if it is low?

Your issue with low output power can be from a number of sources.

Of course it is never a bad idea to start with the power supply (to the RF PA). Then check the drive to the PA. If the drive is good and the power supply is good, then you may want to look at the output filtering and associated circuitry.

If the drive is low, then things like the APC (automatic power control) circuit and the circuits the feed it. Alignment should be close unless someone has been inside this unit.

Your DMM and your oscilloscope will be your friend.

This is about the best I can do right now. My poor health and medications poke holes in my thought process and make make it fuzzy, so if I have some of the designators incorrect, please bear with me.
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Old 08-17-2015, 01:54 AM
JBL GUY JBL GUY is offline
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Sorry my fuzzy brain forgot to mention that there are individual adjustments for the the power output for each mode and the procedure for each is in the service manual. It might be as simple as an adjustment, that is why I asked if the power is low in all modes.
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Old 08-17-2015, 10:09 AM
Bill R Bill R is offline
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I will check the waveforms on the ics tonight. I really havent done much with the output yet. I want to get it tuning correctly first and receiving. Then i will check out the transmit output. I will have to get a good vhf watt meter first. Working on that. If an alignment is needed i will have to bite the bullet and find an rf signal generator. Thanks for the help guys.
Bill
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Old 08-17-2015, 09:49 PM
Bill R Bill R is offline
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Pin 4 of IC10 appears to switch IF I have the levels from the phototransistors at a very critical point. I was looking at the signal coming from each phototransistor going into IC11. One is a very nice square wave and changes with clockwise and counterclockwise rotation of the tuning knob. The other looks like there is no sharp rise time on the square wave. The leading edge is curved quite a bit. I can make it better, and it will tune up fine, and the brake releases, but it doesn't tune down. There is a very touchy point in adjusting the 3K pot where it will tune up and down. At this position the brake does not release if you spin the dial fast, but it does tune up and down even with the crappy looking input from the phototransistors. I may have a bad phototransistor. Not good since I don't think they are available any longer. I will have to find my antenna to see if it is actually receiving when I tune up and down. I can check FM with my handheld radio. I may have to find another parts set to make one work.
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Old 08-18-2015, 01:37 AM
JBL GUY JBL GUY is offline
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Bill, it sounds like you are making progress.

All of those adjustments seem to interact and can be somewhat fiddly. As you can see, you definitely need to start with good waveforms.

Please keep us informed as you make progress.
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Old 08-18-2015, 12:52 PM
Bill R Bill R is offline
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I need a source for the photo transistors or reasonable substitutes. I know the original ph101 is no longer made.
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Old 08-18-2015, 04:07 PM
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wa2ise wa2ise is offline
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Quote:
Originally Posted by Bill R View Post
I need a source for the photo transistors or reasonable substitutes.
An older mouse, the kind with the ball, may have something you could salvage.

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Old 08-18-2015, 05:46 PM
Bill R Bill R is offline
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If there is room to mount those that might be worth a try. The voltage may be to high though. I will take a couple of mice apart and look.
Thanks,
Bill
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Old 08-18-2015, 10:40 PM
JBL GUY JBL GUY is offline
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If the ones from your mice will not work. there are plenty of photo transistors available from some of the surplus electronic parts suppliers and Mouser, DigKey, Vishay and Jameco carry some also. Of course shipping charges might be an issue with certain suppliers.

You will have to choose what looks like it will work.

You might want to check the little collector bypass capacitor on the photo transistor just in the course of things, if you have not already done so.
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