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tx-500 lost audio output

Scott N4AAJ
 

Several weeks backs I was preparing to activate a local park and the audio output stopped working on my tx-500. I was sending a low power carrier (tone with power=30) into my Elecraft t1 tuner at 28mhz to obtain an impedance match and the radios audio output stopped working. I was using the headphone adapter and have verified (with the speaker mic mic) that the issue exists inside the radio.

The radio seems to.work as it should in all other respects, just no audio out.

From reading previous posts on this group it looks like the audio IC may have failed. From what I understand the chip is an NXP TDA7056AT and many have failed before.

I've reached out (email and called) to Lab599's US repair service and did not initially get a response. Several days later I sent another email and got an answer. The answer said they were traveling for the holidays and would get back to me. Nothing... So I sent two more emails. Nothing yet... I sent another email to Lab599's support email today asking what to do to initiate a repair. On the site they say contact the service folks before sending the radio. I cannot.get a response.

Is this typical customer service for Lab599?

Can anyone please suggest an alternate service that would be willing to troubleshoot the radio's audio output issue or just simply reach the chip?

I love the radio and would.like to put it back I to service.

Thank you,
Scott Fusilier
N4AAJ
 

Scott -

I encountered the same audio failure last week under the same conditions you describe.? Here is a good thread that describes the failure and the chip that needs to be replaced:?/g/Lab599/topic/98158235#3348??I've also seen references to newer TX-500's having a different audio chip that isn't as susceptible to this particular failure scenario.

Based on all of the poor feedback I've seen here, I didn't try to contact Lab599 US support.? I think it's just a single person, not a service/repair company......

While the TDA7056AT chip is EOL, you can still source them from China (sources are mentioned in that other thread).? They're pretty inexpensive, so I purchased a dozen of them -- and the repair/replacement doesn't seem terribly involved.??


Unfortunately, it doesn't seem like the Lab599 US service situation is going to change in the foreseeable future.

Regards,
- Trevor, N6TJL
 

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Scott,

Email Roman at Lab599 in Russia and he will reply to you. Roman will get the Lab599 USA service center to reach out to you. I do believe parts are going to be hard to get unless Lab599 USA center has the parts already.?
Best of luck, 73!

Ammed Ismail?
KN6STX

On Jan 5, 2024, at 7:03?PM, Scott N4AAJ <scottfusilier@...> wrote:

?Several weeks backs I was preparing to activate a local park and the audio output stopped working on my tx-500. I was sending a low power carrier (tone with power=30) into my Elecraft t1 tuner at 28mhz to obtain an impedance match and the radios audio output stopped working. I was using the headphone adapter and have verified (with the speaker mic mic) that the issue exists inside the radio.

The radio seems to.work as it should in all other respects, just no audio out.

From reading previous posts on this group it looks like the audio IC may have failed. From what I understand the chip is an NXP TDA7056AT and many have failed before.

I've reached out (email and called) to Lab599's US repair service and did not initially get a response. Several days later I sent another email and got an answer. The answer said they were traveling for the holidays and would get back to me. Nothing... So I sent two more emails. Nothing yet... I sent another email to Lab599's support email today asking what to do to initiate a repair. On the site they say contact the service folks before sending the radio. I cannot.get a response.

Is this typical customer service for Lab599?

Can anyone please suggest an alternate service that would be willing to troubleshoot the radio's audio output issue or just simply reach the chip?

I love the radio and would.like to put it back I to service.

Thank you,
Scott Fusilier
N4AAJ

 

Can anyone verify that newer TX-500s have a different audio chip?
Larry
n0sa
Scott N4AAJ
 

Thank you for all the information. Late last night I received a reply to one of the new messages I sent to the US service email address. The reply message gave me an RMA reference and address to send the unit to for repair. This is what I needed to get the ball rolling.

I will follow up here on post repair.

73 @all and thanks for your help
Scott N4AAJ
Scott N4AAJ
 

I am curious if this failure could be avoided by using a torroid to isolate the audio line before it goes into the rig?

In my experience with the radio so far I've noticed feedback noise in the audio out any time I tune up on 15m, 12m, 10m, or 6m.? I've had the radio shutdown completely due to rf 'feedback' on the coax. This is with sending a carrier at reduced power. Adding an isolation torroid (rf choke) seems to cure the issue. In the future I plan to alway run an rf choke on the coax. Don't want to risk this failure again. I was not running a choke between the tx-500 and atu when the audionoutput failed.

?Wondering an audio line choke is necessary or could prevent the issue?

It should also be noted that I have other portable rigs thatbI run with the same configuration and they don't seem to be bothered by any feedback on any of the amateur hf bands.


Thank you for any feedback,
Scott N4AAJ
 

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Scott,

I have been wondering the same thing. ??

I noticed that 5B4AIY mentioned in his eham review of the rig that the audio chip operates in bridge mode and is dangerous. ?

I reviewed the datasheet for the audio chip and saw he was right. ?

The audio leads on the chip are floating, neither one is grounded as far as I can tell.?

Consider that the audio leads are connected to a coil in the speaker, and I could see high RF voltages being induced on the audio line—high enough perhaps to burn out the audio chip. ??

It would seem all the failures are from transmitting, not sudden failures during rx. ?To me that means RF is feeding back into the audio chip and burning it out. ?

I think the solution will be either a low pass filter on the audio lines or some diode setup to limit voltages on the audio lines vs ground. ?

In addition, have a look at a teardown of the rig online. ?Notice how the case internally is anodized and there is no ground strap between the boards internally. ? I wonder if there is also insufficient grounding within the rig. ?I believe a proper fix includes one or two ground straps between the boards.?

As a separate note on poor grounding on these sets, I opened my bp500 after receiving it back from repair for the overvoltage defect, and I saw that someone had scrapped off the tiniest bit of anodizing from the red cover and put some foil under it and under a circuit board screw in an attempt at grounding. ?I replaced that w a proper ground strap as the foil was mostly cut. ?This just shows me grounding wasn’t properly addressed throughout..esp on a rig that will most likely operate very close to an improvised antenna in the field. ?

Can someone who has a schematic of the rig give us an idea of a simple RF filter/voltage protective circuit for the floating bridge audio leads??

73,
Tom, N2YTF

Sent by phone, please forgive my brevity and poor typing.

On Jan 6, 2024, at 9:55?AM, Scott N4AAJ <scottfusilier@...> wrote:

?I am curious if this failure could be avoided by using a torroid to isolate the audio line before it goes into the rig?

In my experience with the radio so far I've noticed feedback noise in the audio out any time I tune up on 15m, 12m, 10m, or 6m.? I've had the radio shutdown completely due to rf 'feedback' on the coax. This is with sending a carrier at reduced power. Adding an isolation torroid (rf choke) seems to cure the issue. In the future I plan to alway run an rf choke on the coax. Don't want to risk this failure again. I was not running a choke between the tx-500 and atu when the audionoutput failed.

?Wondering an audio line choke is necessary or could prevent the issue?

It should also be noted that I have other portable rigs thatbI run with the same configuration and they don't seem to be bothered by any feedback on any of the amateur hf bands.


Thank you for any feedback,
Scott N4AAJ

 

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Virtually the same happened to my radio. However, the email was immediately answered. They requested I verify no audio on the pin. Once that was verified, I was given an address outside the country to ship to. Only a couple weeks later, the radio was returned, repaired, no cost.?

Meanwhile I bought a spare just in case.?
73,


Bill Watkins
K0WHW
kf7yxs@...


On Jan 5, 2024, at 22:52, Ammed Ismail <amiwood@...> wrote:

?Scott,

Email Roman at Lab599 in Russia and he will reply to you. Roman will get the Lab599 USA service center to reach out to you. I do believe parts are going to be hard to get unless Lab599 USA center has the parts already.?
Best of luck, 73!

Ammed Ismail?
KN6STX

On Jan 5, 2024, at 7:03?PM, Scott N4AAJ <scottfusilier@...> wrote:

?Several weeks backs I was preparing to activate a local park and the audio output stopped working on my tx-500. I was sending a low power carrier (tone with power=30) into my Elecraft t1 tuner at 28mhz to obtain an impedance match and the radios audio output stopped working. I was using the headphone adapter and have verified (with the speaker mic mic) that the issue exists inside the radio.

The radio seems to.work as it should in all other respects, just no audio out.

From reading previous posts on this group it looks like the audio IC may have failed. From what I understand the chip is an NXP TDA7056AT and many have failed before.

I've reached out (email and called) to Lab599's US repair service and did not initially get a response. Several days later I sent another email and got an answer. The answer said they were traveling for the holidays and would get back to me. Nothing... So I sent two more emails. Nothing yet... I sent another email to Lab599's support email today asking what to do to initiate a repair. On the site they say contact the service folks before sending the radio. I cannot.get a response.

Is this typical customer service for Lab599?

Can anyone please suggest an alternate service that would be willing to troubleshoot the radio's audio output issue or just simply reach the chip?

I love the radio and would.like to put it back I to service.

Thank you,
Scott Fusilier
N4AAJ

 

So……..is there any way to prevent blowing out the audio chip that us users can do that won’t void the warranty or anything? ?Is it only occurring when using a headphone adapter or even with the stock speaker-mic?

How difficult is it to replace the chip? ?Is it advisable to just install a socket in place for easier replacement of the chip if it keeps failing?
 

On Sat, Jan 6, 2024 at 04:28 PM, JM99 wrote:
"...is there any way to prevent blowing out the audio chip that us users can do...?
That would be helpful to know.
?
--
73, Norm/KC1BMD

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