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DX2950DX ept695015BR schematic

R

RidgeRunner260

Active Member
Jun 28, 2021
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I have the radio mentioned in the subject. It currently has.

-No receive audio, does receive an RF signal but no audio heard from the main speaker or external.

- PA function does not work either.

-if you turn the radio on/off you can hear a brief burst of static.

Here is the interesting part while turning on/off the speaker audio started working but with a loud buzzing sound. Also the PA function started to work.

The schematic I have is for a ept695015z and it seems slightly different. Does anyone have a schematic? Or any suggestions to offer on my problem.
 

This may be what you're looking for? It doesn't list the board num so I'm just posting it in case it is.
 

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  • sch295070dx.pdf
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Well, it looks like supply voltage comes in on pin 5 TDA2003 and I'm reading 24 volts. Pin 4 is the output and I'm reading 8 volts.

sp5it said:
Measure voltage on output pin of audio amplifier chip. If 1/2 power supply - OK
If not, bad chip.
Click to expand...
Going by sp5it's reply I'd say I'm operating at 1/3 of supply voltage. I suppose the next thing to do is remove it.
 
It appears to be powered by Q51. I see the 13.8 going into Q51 and 24 volts coming out. Have you read the datasheet on a TDA2003? It appears to be powered from a higher voltage. It it possible this is normal?
 
Ya I'm not sure I'm lacking all of the documentation I need. I have a 6m version of the radio I could pop the cover off to see if they are similar.
 
I popped the cover on my 5054, and checked Q51 and that is outputting 24 volts. I then removed IC7 from my 2950, and used my meter on diode check and every pin open, even for case to ground pin.
 
Put your measuring meter (DVM) back to DC check the TDA2003 output - if it's 24V then switch the DVM to AC and recheck - still get an output - you have a ringing squeal - sucking all the power - chip could be getting hot too. Might want to think about replacing some of those larger value (bigger case size) electrolytic caps - they might have reached the end of the life cycle (old or compromised)
 
Just to put a resolution to this for people searching in the future. I ended up replacing IC7 (TDA2003). I now have audio. I left the rig on the bench for 24 hours with open squelch on the volume down to a bearable limit so I didn't go nuts. I checked the insulator and re-greased it too.
 
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No pictures, so I can't see if it has the original suicidal power supply with the big, heavy transformer and too-small regulator circuit with two metal TO-3 transistors on the heat sink.

When that regulator fails, it will send unregulated 24 Volts DC into the radio and amplifier. Hence the "suicidal" nickname.

Later production uses a packaged chinese-made "brick" switchmode power supply. They don't have that bad habit.

Could it be you're using the chassis for the negative side of the meter probes? Better to use the circuit ground than the chassis on the original versions.

73
 
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