IC-F521 audio issues

[W7EKB]

Hello, all.

I have agreed to help our local Search and Rescue group with some Icom radios they have been gifted. They have several IC-F521s, some few of which have differing audio "issues". Some exhibit correct transmit audio, but no receive audio. Others have the opposite problem: they exhibit adequate receive audio, but TX audio is missing. At last count there are 5 IC-F521s with these issues. We have at least another 5 or 6 which work very well, and we are very happy with them.

I have bought the necessary programming software and cable and they all program just fine.

I also have copies of the IC-F521 service manual, but at this point I am not sure where to begin looking.

Does anyone here know of a common reason for such audio problems, and would this be relatively easy to fix?

I have a pretty much complete shop with the necessary test instruments, and I have many years experience in electronic repair, although I am 81 years old now and am considerably slower than I once was..

Advice?

Ken Gordon

 

[12dbsinad]

Ken,

Could be several things. First, I'm assuming you're talking about no RX audio out of the radios chassis speaker? I would assume you tried a external speaker as well? The #1 failure of these during a certain production year is the ceramic filter which can cause very poor RX and/or no RX audio. I don't have specific notes on the part as I'm not at the shop and it's been a few years since I've benched one. I can dig it out next week if I can remember. And wow 81 that's great! You're an "old school" guy! Not many of them left, just I.T. geeks now..

 

[W7EKB]

Thank you very much for the informative reply. I will investigate our F521s more closely. And, yes, I tried an external speaker. Still no joy.

Also, I, myself, was an IT Geek (among my other jobs) for over 30 years at the University of Idaho. I operated an HP-UX server, and built the first working small LAN on campus. In the first "micro-computer" I worked on, 1K of RAM cost $1500.00 and the first 5 MB (yes, MB) HD I worked with cost $4995.99. So I go way back with 'pooters.

Ken Gordon

 

[W7EKB]

Well, yesterday, I went through both the IC-F521s, and the IC-F5021s we have been given here. I also have the service manual for the F521s, which I have been studying.

4 of our F521s and, so far, one of our F5021s will not "modulate", i.e., there is no audio coming out of the transmitters. They key all right, and apparently also are emitting the CCT tones to key the local repeater on, but there is no audio reaching the repeater. The fact that all those I have so far tested have the same problem means to me that either I am doing something wrong here, or programming isn't correct, or I am trying to use the wrong mics (supposed to be the HM-100N for the F521s).

I first suspected the microphones I have here were bad, but they ALL can't be bad. Now I am suspicious that the 8V DC to the mics is missing. They are condenser mics and need that DC to output audio. I will test for that shortly.

I have set the mic gain in the programming to 3, which seems correct.

So I am wondering if there is some common problem with these rigs in that regard, or if there is some error in the programming.

I guess I'll keep looking.

I also looked at the ceramic filter(s) in the receiver. Boy, those are tiny. I wonder if there might be a common source for those? We have three F521s with totally dead receiver audio which I would like to fix if possible.

Ken Gordon W7EKB

 

[jeepsandradios]

Where did the radios come from ? Did SAR buy them new and they quit working or were these donated ? I ask as we use ICOM for SAR also and Ive yet to have one mobile quit working. I know on the 521 and think the 5021 there are pads on the board for external accessories. Do they have the external DB9 cables on them ? If so possibly someone was using something and the pads are jumpered or un-jumpered ? I did have a DPW loose audio on a couple F121 back in my dealer days. In the end it was the external speaker jacks full of crap. They started with external speakers in the dump truck but they mounting had it facing down on back wall and speaker plug would work its way out. Over time of jamming it back in the radio crap got in them. I actually removed the plug from the board and ran wire out with the speaker always on. Maybe check that on the no audio ones.

 

[W7EKB]

Where did the radios come from ? Did SAR buy them new and they quit working or were these donated ? I ask as we use ICOM for SAR also and Ive yet to have one mobile quit working. I know on the 521 and think the 5021 there are pads on the board for external accessories. Do they have the external DB9 cables on them ? If so possibly someone was using something and the pads are jumpered or un-jumpered ? I did have a DPW loose audio on a couple F121 back in my dealer days. In the end it was the external speaker jacks full of crap. They started with external speakers in the dump truck but they mounting had it facing down on back wall and speaker plug would work its way out. Over time of jamming it back in the radio crap got in them. I actually removed the plug from the board and ran wire out with the speaker always on. Maybe check that on the no audio ones.

SAR was gifted or bought new radios. These old ones were then donated by them to, or were bought by, one of the SAR members, who then asked me to fix any that needed fixing and to reprogram them. We got around 10 of the F521s, and 3 of the F5021s. I went through them all. He intends to donate the radios to selected military veterans who are hams. We split the cost of the programming software and cables.

Three of the F521s show completely dead receive audio. I understand from someone else on this forum that there were certain serial numbers of these radios which had ceramic filters which could fail in them. Since there are two such filters in each radio, I don't know which of the filters failed yet. In any case, I have not yet found a source for the filters. Furthermore, from what I can see so far, they are very tiny and will be difficult for me (age 81) to see, let alone replace. I have checked all other possible reasons for dead audio and this is all that is left.

Now, last night I discovered why some of these radios also showed no audio on transmit: it was simply a case of using the wrong microphone. Someone had apparently figured that almost any Icom mic in that series of radios would work. Wrong. The F-521s require the HM-100N, while the F-5021s require the HM-152. Obviously, the mics are wired differently enough so that the radios require the correct mic.

I also learned from somewhere that the heat-sink compound in the F521s for the output amplifier can have either an incorrect amount or be improperly placed, so I have been checking that. I have so far found two that were not correct, and fixed those. The finals in both were still OK.

These are neat radios. Very rugged and capable, although somewhat difficult to program. They have many features which are interesting, although not particularly of use to hams. The F521s have a 256 channel capability. The F5021s 128. Both are enough for anyone.

The programming manual for the F521s is 88 pages long. There does not appear to be such a manual for the F5021s, but the help files in the programming software is quite extensive.

Later, and thanks for the help.

Ken Gordon W7EKB

 

[12dbsinad]

Check all the traces on the board. When running some options boards like a UT-109/110 it requires the AF trace to be cut to send audio to the board. If the board is removed and trace isn't soldered back, you will not get any RX audio.

 

[W7EKB]

Check all the traces on the board. When running some options boards like a UT-109/110 it requires the AF trace to be cut to send audio to the board. If the board is removed and trace isn't soldered back, you will not get any RX audio.

Thank you for the suggestion: I went through all of our defective F521s and checked that. ALL were OK but one. That one had a UT-110 chip in it. I removed that chip and re-connected the two cut traces. Still no receive audio. Dead silence, in fact, like the others, other than the first beep when turning the rig on.

And THAT says to me that the audio amp and speaker are OK.

I am still thinking that one of the IF filters has failed. I'll get one of my o'scopes out and check to see if I can see signals before and after the filter.

Might anyone know where one might be able to buy replacement filters? Icom, maybe? But I wouldn't think that Icom would still have parts for such an old rig. But I will check.

We also have one F521 which won't transmit. I suspect that the output device is dead.

One other interesting matter is that all of these output 25 watts at maximum despite programming power output to "high". But 25 watts is enough for most of what we are trying to do.

Ken Gordon W7EKB

 

[W7EKB]

OK, gang, I went through all six of our defective F521s over the past two days and have discovered some "interesting" things about them.

I first programmed all of them to turn the squelch to zero in case the squelch settings were interfering with my attempts to troubleshoot these.

To repeat, we have 6 units with various issues.

Three units have obviously failed transmitter output modules. Two of those have no receiver issues, however. By setting another receiver near the suspect transmitters while keying them on using 146.52 MHz, I can easily copy a clear and noise-free signal. This says to me that the output module has failed, but that all other bits of the transmitter circuitry are OK.

Three other units have various receiver issues from "signals weak and noisy" to receiver completely dead (1 unit)

The audio output and speakers in all units appear to be just fine.

There are two IF filters in each receiver, a 1st IF at 46.35 MHz, and a 2nd IF at 450 kHz. I understand from some previous investigation on the web that there is a likelihood that one or the other of the IF filters may be bad in some of these units. But I am still in the dark about which (1st or 2nd) filter is the suspect one. Might anyone here know?

What I intend to do is to buy (if they are not TOO expensive) three of the output modules, if they are still available, and to install those in the three transmitters which have no output. If that works, I will have at least two working units. The 3rd unit also has receiver issues.

Two of those with receiver issues MAY be fixable with the replacement of an IF filter, but I hesitate to do this since I am still not sure which filter might be suspect.

In one receiver, it also appears that the RF input stages might be defective. I am not sure what, if anything, I should do about that one.

Lastly, there are two different output ICs available: one is a 25 watt output unit, and the other is a 50 watt output unit. From what I have been able to tell, all our present unit exhibit a maximum of 25 watts output on "high". Since this is the case, I intend to replace the failed ones with the 25 watt units, as I am not sure that something else may have to be tweaked to enable the full 50 watts output.

Any advice or other information will be greatly appreciated.

Ken Gordon W7EKB

 

[ramal121]

For the IF filters a quick check I use is to have a signal generator, and a test lead with a loop at the end. If it can generate around 0dBm or better I start with the 1st IF freq and swish the loop around the rf board to see if I hears anything. Then I try the 2nd IF. If there is a bad xtal it will fail with one of these two. You can compare your testing with a known working radio. Speaking of xtals, don't forget to sniff the 2nd IF oscillator xtal with a freq counter or receiver to see it that is alive.

 

[W7EKB]

Thanks for the suggestions: I do have a couple of good signal generators: an HP-8640B and an HP-606. I also have at least two decent 'o'scopes and know how to use them.

I'll take a closer look at the receivers after I have repaired the two transmitters.

Now to see if Icom has the parts I need.

Ken Gordon W7EKB

 

[ramal121]

Sounds good. I'll give a few more thoughts

First off, to really get down to to some heavy trouble shooting requires getting the main board out and "spatchcocked" out on the bench to get to all the areas to check. When I was a bench tech at a Motorola MSS we had all the fun jigs and stuff to do this. How to do this with any old radio may be a challenge.

Another thing to try on the IF filters is to bridge them with a disk cap with the leads cut short. 10 to 100 pf seems to work OK. If the receive does not change or degrades some then the filter is good. If you notice an improvement in receive then that device is certainly suspect.

As far as transmit I will add this. Put a amp meter on the power lead. If on transmit you get several amps but no tx power out the radio is trying but nothing is coming out the chute. This would point to the pin diodes in the T/R switching circuit or a burned open, cracked solder somewhere toward the antenna out. If amps are low on transmit well yea the PA is probably toast. I have replaced many of the hybrid PA's in the past and that usually takes care of things. That is pretty straight forward.

Sometimes you will just have to go from stage to stage with a RF millivolt meter or an oscilloscope to determine where the fault lies and then decide what components will fix things up. This is true in both the RX and TX chain. Good luck to you!

 

[W7EKB]

Thank you for the suggestions. I am working on these issues for the next few days. So far, it looks as though the problems cannot be too difficult to fix, at least for 3 of the 4 F521s with receiver problems. One of the 4 is completely dead except for the audio output which is working just fine. That one may end up as parts.

Parts are available from Icom America and are, mostly, inexpensive, so there is hope.

Later,

Ken Gordon W7EKB

 

[W7EKB]

OK. I have, first, taken a closer look at the two which don't transmit. Laying the antenna of a hand-held on the case of the dead transmitters, and firing them up on 146.52, I receive a clear and noise-free signal.

I then opened both up, and removed the final amp IC. In both cases, they were the 60 watt versions of the Mitsubishi RA60H1317M IC. Replacing one of those with a Mitsubishi RA30H1317M caused the radio to output 25 watts and it is now working fine.

Neither of the two with dead 60 watt ICs had properly implemented heat-sink compound. Only about 1/2 the heat-sink was covered with it.

In addition, although the 30 watt IC is still available from Icom America, the 60 watter is not. This says to me that the 60 watt IC was prone to failure.

I am finding the 30 watt IC, the Misubishi RA30H1317M, available on eBay, all for prices around 1/2 that asked by Icom America ($84). One problem I have is that many sellers of this IC are based in China, and from some past experience, I am highly suspicious of those. It was somewhat common for Chinese sellers to be selling "faked" and counterfeit transistors in the past. For instance, power transistors, mounted in what looked like the proper case, but with 2N2222s inside.

Anyway, so far, I have two F521s which had dead transmitters, now working just fine at 25 watts output. I am using silver-based heat-sink compound that I normally use for computer CPUs. That seems to work fine.

Ken Gordon W7EKB

 

[W7EKB]

So, on to the 5 bad receivers: from testing, it appears that at least two of these have bad 450 kHz filters. Those filters are, fortunately, large enough that I can replace them fairly easily, and they cost less than $6.00 each from Icom America.

Assuming there is much interest in what is happening here, I will report progress (or lack of it) in the order as it occurs.

One of my o'scopes and signal generators are getting a work-out.

Ken W7EKB

 

[EWC_BDN]

Changed a lot of those filter across a few brands. ICOM is the hardest to disassemble, but the easiest for the actual replacement. it's not even close. The ground pins on the filters take a lot of heat to melt the solder because the ground runs everywhere on the radio and it sucks the heal from the joint everywhere. But on ICOM it's not a problem for some reason.

 

[W7EKB]

Changed a lot of those filter across a few brands. ICOM is the hardest to disassemble, but the easiest for the actual replacement. it's not even close. The ground pins on the filters take a lot of heat to melt the solder because the ground runs everywhere on the radio and it sucks the heal from the joint everywhere. But on ICOM it's not a problem for some reason.

Thanks for that info. I have 5 F521s here with dead, or mostly dead, receivers. I have some 450 kHz filters coming from Icom. Although these rigs are pretty old, they still seem to be very usable radios.

As I am telling the folks I am doing this for, transmitters are easy, receivers can be a real *****.

Later,

Ken Gordon W7EKB

 

[12dbsinad]

Thanks for that info. I have 5 F521s here with dead, or mostly dead, receivers. I have some 450 kHz filters coming from Icom. Although these rigs are pretty old, they still seem to be very usable radios.

As I am telling the folks I am doing this for, transmitters are easy, receivers can be a real *****.

Later,

Ken Gordon W7EKB

Glad you got them figured out. Every time I hear of a dead receiver or poor RX of that vintage radio 9 times out of 10 it's a bad filter. They had bad batches of them back then that caused lots of issues across multiple brands. I'd love to know how many radio's got thrown in the trash for a 6 dollar part. 10 years ago our shop replaced them by the boat loads.

 

[W7EKB]

That part is all of $8.69 from Icom America now. Still very inexpensive.

I managed to get another F521 operational today. I replaced the power output IC which had gone open. No power output. I am finding, so far, that the Mitsubishi RA60H1317M IC is prone to failure. I'm not sure why, although in at least one case I have dealt with over the past two or three weeks, the heat-sink compound was not applied correctly. It was covering less than 1/2 of the heat-sink. Also, it was that white crap which I have never liked.

I used some of that silver-based grey stuff which is normally used for computer CPUs, and made certain it was properly applied.

I have been replacing the bad Mitsubishi RA60H1317M power output ICs with the Mitsubishi RA30H1317M. All of these F521s I am working with output 25 watts in HIGH, and none output 50 watts.

One can find the Mitsubishi RA30H1317M by many sellers, most of them in China, all over eBay, but not the RA60H1317M. The Chinese want less than $30.00 for the 30. The trouble is, of course, can you trust that the Chinese ones are not counter-feit? Anyway, since they are so cheap, I bought ONE from a Chinese seller who had (apparently) sold 96 of them and there were no complaints from buyers. It LOOKS excellent, but...

Anyway, I installed it in a bad F521. It seems to work adequately, although power output is a bit lower than the others: about 20 watts output instead of 25, that MIGHT be alignment. We'll see. Anyway, if it is fake, I haven't lost much time or money on it.

So far, out of the batch of 6 non-working F521s, I have fixed 2 so far, and expect to get at least another 2 or 3 operational yet.

I hope the SAR folks appreciate the effort. On the other paw, this is kinda fun, resurrecting radios that others would throw away.

One user, the retired sheriff here (and retired Army-officer veteran) is absolutely delighted with the one I gave him. He is like a kid with a new toy.

Ken Gordon W7EKB