Tytera TYT MD-380 DMR receive issue

[dazzler8985]

I've acquired a pair of TYT MD-380 radios, decommissioned from a school setting. The 'net' in the school consisted of five radios of this exact type.

The 'as supplied' codeplug in each radio is simple, the radio is given a 'contact name', one frequency, list of five contacts and use of basic encryption. My two radios were 'Headteacher' and 'Field'. One radio, 'Field' has issues, 'Headteacher' is the good guy and functions perfectly.

As obtained, 'Field' will not play any audio on DMR at all. It receives a signal from it's counterpart, shown on the screen, but no speech comes through. It will transmit perfectly though, audio is clear and well modulated. The speaker works fine, power on tone and keyboard tones work. Retested with my MD-390, DM-1701, fault persists on DMR rx only.

I've completed the following steps in order to fault find:

Antenna swapped, battery swapped and fully charged. Speaker/mic plugged in and attached, fault persists.

Firmware loaded: Factory MD380-D3.20, original was D2.24. Blank codeplug installed via 'tyt_kd4z_4.0'.
New codeplug, single PMR446 frequency set both on digital and analogue. No encryption set on digital, no CTCSS/DCS set on analogue. Digital contact list set as Local 9, slot 1, colour code 1, admit criteria 'always', in call criteria 'always'.

Analogue tx/rx works perfectly fine, good clear audio both ways. Digital still good tx, no audio on rx but radio shows the presence of an expected transmission.

Known working codeplug from my MD-390 installed in both MD-380s. 'Headteacher' all good, 'fault in 'Field' still persists.

Loaded various version of MD380 Tools and TYT toolz firmware, problem still the same. Loaded Voice Crypt 1.0a & 1.4p alpha. All this firmware functioned perfectly in terms of menu operations, non-encryption setting, etc, but still no audio coming through on DMR even when promiscuous mode was set. I did notice that 'Field' would sometimes display the incorrect time slot on the aforementioned forked firmwares. TX from 'Field' would always work as expected.

Now, sister radio 'Headteacher' was subjected the above procedures and worked perfectly well as part of a mirroring process. No time slot display errors.

So, am I looking at a software/firmware fault or something that it at a hardware level?

Observations and advice greatly appreciated, thank you.

 

[doriboni]

Was the Field radio working properly with the D2.24 firmware? Or did you update directly with a new firmware without trying with D2.24?

Look at the serial numbers of your two radios. Is Field's serial number much earlier than Headteacher's?

Because the very first MD380s used a different vocoder that was completely incompatible with newer firmware.

The new hardware vocoder emitted the sound with the new vocoder and could receive the digital sound of the old vocoder and the new vocoder. But the old hardware vocoder can only transmit with the old vocoder and can only receive with the old vocoder.

If you put the D2.24 firmware back on the radio, does Field radio work properly again?

Otherwise you can always buy a recent MD380 on Aliexpress which has been confirmed to work with all firmwares (md380tools, voice crypt, toolz) and open RTX and M 17 (with hardware modifications for the two last) :

https://www.aliexpress.us/item/32823567440.html

 

[dazzler8985]

Thanks for your reply Doriboni. Both radios have very similar serial numbers, last three digits differ, so they appear to be of the same vintage and of the same vocoder type I guess.

Both radios had D2.24 on them when they came to me, with no DMR rx on Field at all. Field now has got D2.24 back on and still won’t play after test through the various permutations.

I’ve read that most of the MD380 Tools firmware versions should work regardless of the vocoder type in the radio. That said, I still can’t get Field to rx on DMR. Headteacher has always worked fine irrespective of what firmware was loaded on. That said, if I tried to load factory firmware suitable for the new vocoder on either radio, the utility program failed and just shut down.

I’m going to open Filed up and take a look inside to see if there’s any loose connections or signs of corrosion, dry joints etc.

 

[doriboni]

so it looks like a hardware issue...

 

[dazzler8985]

I managed to get hold of the MD-380 schematics and dismantle ‘Field’ today. There is a TC75S51F IC on the VOL_OUT line from the C5000. This IC was not seated properly and was the cause of the issue, no audio getting out from the DAC process. It has been resoldered and now the radio works absolutely fine.

Thanks to Doriboni for the help, problem now solved.