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Today I blew out my audio chip. I knew better but just was not thinking.
I was using a random wire antenna with one radial and I had the radio within two feet of the feed point. I was using a Mat10 auto tuner.
All was well on 20 meters but when I went to tune up on 17 meters there was a squeal in the headphones then nothing.
I was using a short adapter ?that I made to plug a set of earbuds into.?
I have had the radio for over a year and have used it with many different antennas with no issues. This is the first time I have used this particular antenna.?
Usually I used tuned antennas either short verticals or efhw antennas.
It probably would have been okay if I had just moved the radio further from the antenna, I just had a senior moment and payed for it.
Luckily, I ordered 3 spare audio chips, now I have two spares.
The radio is repaired and ready for action.
I really wish there was a fix for this issue, maybe some added caps but it is beyond my pay grade to figure it out.
From now on I will be more careful and I will not be using that antenna again with my TX500.
Larry
n0sa
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Thanks for the cautionary tale Larry. Do you think adding a choke may have prevented the issue?
James KK4WXA
On Tue, Feb 27, 2024 at 4:52?PM Larry Naumann < n0sa@...> wrote: Today I blew out my audio chip. I knew better but just was not thinking.
I was using a random wire antenna with one radial and I had the radio within two feet of the feed point. I was using a Mat10 auto tuner.
All was well on 20 meters but when I went to tune up on 17 meters there was a squeal in the headphones then nothing.
I was using a short adapter ?that I made to plug a set of earbuds into.?
I have had the radio for over a year and have used it with many different antennas with no issues. This is the first time I have used this particular antenna.?
Usually I used tuned antennas either short verticals or efhw antennas.
It probably would have been okay if I had just moved the radio further from the antenna, I just had a senior moment and payed for it.
Luckily, I ordered 3 spare audio chips, now I have two spares.
The radio is repaired and ready for action.
I really wish there was a fix for this issue, maybe some added caps but it is beyond my pay grade to figure it out.
From now on I will be more careful and I will not be using that antenna again with my TX500.
Larry
n0sa
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Larry,
What chip did you order and where did you get them? Did you do the repair yourself?
Thank you, Fred/N7PN
On Tue, Feb 27, 2024 at 2:52?PM Larry Naumann < n0sa@...> wrote: Today I blew out my audio chip. I knew better but just was not thinking.
I was using a random wire antenna with one radial and I had the radio within two feet of the feed point. I was using a Mat10 auto tuner.
All was well on 20 meters but when I went to tune up on 17 meters there was a squeal in the headphones then nothing.
I was using a short adapter ?that I made to plug a set of earbuds into.?
I have had the radio for over a year and have used it with many different antennas with no issues. This is the first time I have used this particular antenna.?
Usually I used tuned antennas either short verticals or efhw antennas.
It probably would have been okay if I had just moved the radio further from the antenna, I just had a senior moment and payed for it.
Luckily, I ordered 3 spare audio chips, now I have two spares.
The radio is repaired and ready for action.
I really wish there was a fix for this issue, maybe some added caps but it is beyond my pay grade to figure it out.
From now on I will be more careful and I will not be using that antenna again with my TX500.
Larry
n0sa
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I am not sure a choke would have helped in this case. I was using two- 3 foot long cables, one going to the tuner and the other going to the antenna.
Everything was way too close together, stupid mistake.
A choke surely wouldn¡¯t hurt but I have a strong suspicion that the stray RF was landing on my earbud cord and going directly into the audio chip.
I bought 3- TDA7056AT/N2,518 chips from Utmel , directly from China.
It took a few weeks to get them and shipping was more than the chips, but it was obviously well worth it.
I did the repair myself but I am pretty good at this type of thing. If you aren¡¯t good at this type of repair you could easily do more damage to the radio.
My repair went smoothly and was a success.
I also had a bit of concern that the chips I bought would even work. It seems a lot of Asian parts have a possibility of being duds.
But I got good chips. I am for sure hanging on to the two I have left. They are worth their weight in gold to me.
Larry
n0sa
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On Tue, Feb 27, 2024 at 03:36 PM, Larry Naumann wrote:
TDA7056AT/N2,518
Thanks so much for sharing all this Larry!! ?It is greatly appreciated!
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Man I have to say this is a little bit concerning. Super light weight field setups tend to have antenna, feed point and the radio quite close to each other. In addition to that the antenna system is often not optimal. I¡¯m dreading the prospect of being in the middle of nowhere and having the radio fail because of this issue. I very much hope there will be a software fix but I cannot actually see this being possible. Short of replacing the chip it¡¯s probably a shielding issue. Maybe Lab599 can come up with an easy DIY fix and instructions.?
On Tue, Feb 27, 2024 at 2:58 PM, ke0vbq < ke0vbq@...> wrote: On Tue, Feb 27, 2024 at 03:36 PM, Larry Naumann wrote:
TDA7056AT/N2,518
Thanks so much for sharing all this Larry!! ?It is greatly appreciated!
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I have used my radio for many activations for both POTA and SOTA with never a problem.
What ?happened today was extreme and totally different from my prior setups.
I have used a 9 foot tall center loaded vertical set up on the same picnic table as my radio with no issues.
I have also use an efhw 40 to 10m antenna ?with only 10 feet of feedline and no choke with no issues.
The antenna I used today had been tested at home with no issues, but I will not use it any more with my TX500.
I am highly confident that my other go to antennas will play just fine but I may make a nice small common mode choke and use it with the TX500.
As I stated earlier, I think the issue was the signal going directly into the amp via the cord on the earbuds. But, that is just my opinion.
Larry
n0sa
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Would it be possible to install a socket to make future repairs easier/faster? ?I haven¡¯t opened mine up so I don¡¯t know if there would be room for a socket to go on the board in addition to the chip.
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Even more concerning is the fact that this chip is now obsolete and the few places that may still have it are running down their stocks. From what I have read there¡¯s no direct replacement for it. Where does that leave the user who¡¯s now forced to send their radio in for repair since the chip will be no longer available. How is service going to repair it? I¡¯m just trying to prepare for the worst case scenario.?
On Tue, Feb 27, 2024 at 3:37 PM, K9NEY < K9NEY@...> wrote:
Man I have to say this is a little bit concerning. Super light weight field setups tend to have antenna, feed point and the radio quite close to each other. In addition to that the antenna system is often not optimal. I¡¯m dreading the prospect of being in the middle of nowhere and having the radio fail because of this issue. I very much hope there will be a software fix but I cannot actually see this being possible. Short of replacing the chip it¡¯s probably a shielding issue. Maybe Lab599 can come up with an easy DIY fix and instructions.?
On Tue, Feb 27, 2024 at 2:58 PM, ke0vbq <ke0vbq@...> wrote: On Tue, Feb 27, 2024 at 03:36 PM, Larry Naumann wrote:
TDA7056AT/N2,518
Thanks so much for sharing all this Larry!! ?It is greatly appreciated!
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The top surface of the chip rests directly on the aluminum case, and there is thermal paste between the two because the case is in essence a heatsink.? So I do not believe a socket is possible - there simply isn't any room.
- Trevor, N6TJL
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Larry did you take any photos of your heroic repair ? Thank you, Greg K7YOM ????? ??Sent from my iPhone.......?
toggle quoted message
Show quoted text
On Feb 27, 2024, at 7:04?PM, Trevor Larson - N6TJL - 3163412 <trevlarson@...> wrote:
?The top surface of the chip rests directly on the aluminum case, and there is thermal paste between the two because the case is in essence a heatsink.? So I do not believe a socket is possible - there simply isn't any room.
- Trevor, N6TJL
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Here's a few pictures of my repair a few weeks ago.? Larry probably did a better soldering job than I did... those pins are so small...    - Trevor, N6TJL
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I took a before picture but not an after picture. It wasn¡¯t an easy job but if one is careful it can be done as seen in photos.
If I didn¡¯t like the radio so much, this issue would be a deal breaker but I really like the radio.
Plus, I still have two spare chips. And if I do not pull any stupid stunts I should be just fine.
And yes, the chip rests against the back of the case with applied heat sink grease.
You must make sure to get the replacement flat on the board by making sure to remove all the solder from the pads before installing the new chip.
Larry
n0sa
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On Wed, Feb 28, 2024 at 12:31 PM, Trevor Larson - N6TJL - 3163412 wrote:
those pins are so small...
SO20 case, 1.27mm leads spacing. It's huge, actually )))
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This does make me wonder if the issue is frequency dependent?
Right before this happened I ran the radio on 40 and 20 meters with no problem.
It was when I went 17 meters that the issue occurred.?
I know there are many variables such as the actual match/mismatch of the antenna but I seem to recall reading an earlier
post that someone else¡¯s radio had the issue when on 17 meters.
Just Curious
Larry
n0sa
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Larry, Are these the chips you used?
On Wed, Feb 28, 2024 at 11:29?AM Larry Naumann < n0sa@...> wrote: This does make me wonder if the issue is frequency dependent?
Right before this happened I ran the radio on 40 and 20 meters with no problem.
It was when I went 17 meters that the issue occurred.?
I know there are many variables such as the actual match/mismatch of the antenna but I seem to recall reading an earlier
post that someone else¡¯s radio had the issue when on 17 meters.
Just Curious
Larry
n0sa
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Hey Larry,
When my audio ic failed it was on 10m. However, I use an end fed random wire and tuner all the rime. My experience has been that the tx-500 would act strangely during the tune-up procedure on bands 15m and higher (I don't often use 17m). During tune-up is when the audio chip failed for me. When I say act strangely, I mean ii would hear weird varying audio tones during tune-up and I've even had the unit shit down completely. This only happens on the higher bands and seems to be eliminated with a feedline choke before the tuner.
I am currently waiting on shipping from an audio chip replacement repair (Lab599 US Service). I had the rig well over a year before it failed. I will not tune-up the rig again on 15m and above without an inline choke. I will likely unplug the audio line as well. I was using headphones plugged into a pigtail straight to the rig. I'm a cw op an do t use the speaker mic.
Again, 17m may be included but I've only experienced the weirdness on tune-up 15m and above. I've put the rig through the same tune-up procedure on 20/40/80 countless times and never seen the behavior i described above. I believe it is frequency related. This is just my opinion due to experience with the radio.
73, Scott N4AAJ
On Wed, Feb 28, 2024, 11:29 AM Larry Naumann < n0sa@...> wrote: This does make me wonder if the issue is frequency dependent?
Right before this happened I ran the radio on 40 and 20 meters with no problem.
It was when I went 17 meters that the issue occurred.?
I know there are many variables such as the actual match/mismatch of the antenna but I seem to recall reading an earlier
post that someone else¡¯s radio had the issue when on 17 meters.
Just Curious
Larry
n0sa
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Yes James, those are the chips but they may be sold out
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Thanks for the info Scott. Sounds like a similar setup to what I was using.
And yes, the radio made a weird sound when it failed during tuning, it was almost like the radio was complaining ?
Good to know the choke helps, looks like I will be making myself a nice compact one to use.
Good idea to unplug the headphones too.
Larry
n0sa
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I would think lowering the tuning power in settings could be helpful, too. In fact that¡¯s what I¡¯m going to do.?
On Wed, Feb 28, 2024 at 9:38 AM, Larry Naumann < n0sa@...> wrote: Thanks for the info Scott. Sounds like a similar setup to what I was using.
And yes, the radio made a weird sound when it failed during tuning, it was almost like the radio was complaining ?
Good to know the choke helps, looks like I will be making myself a nice compact one to use.
Good idea to unplug the headphones too.
Larry
n0sa
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Larry Naumann
Fred-N7PN
N8XMD
Trevor Larson - N6TJL - 3163412