Troubleshooting IR Sensor After Extending from Circuit Board ~740mm

Thread Starter

brianWreaves

Joined Sep 16, 2021
27
Hi All, I'm moving my little Douk Audio M3 amp behind my TV. So now I have to move the IR sensor outside the amp so I can control it. Using a 4-core shielded cable from an old USB cable I did just that, but it's not working.

Here are a few photos:

Photo of the circuit board top where the sensor was remvoed and 3 of 4 wires are soldered in place.Photo of the circuit board bottom of 3 wires soldered in place.Photo of the back of the IR sensor soldered to the free end of the cable with heat-shrink.Photo of the front of the IR sensor soldered and shrinked.
(wow soldering looks so bad up close)

Is there a method I can use to test if I ruined the sensor, likely when removing it... maybe too much heat? There is no visible damage, I've confirmed the wiring is correct, no shorts between the 3 pins, and continuity from the board to the sensor. The cable length is ~740mm so perhaps the length is an issue??? I didn't damage the amp...
 

ericgibbs

Joined Jan 29, 2010
18,650
Hi Brian,
A quick recheck of the sensor would be to replace it back onto the PCB.

Can you post a photo of the other side of the PCB near those terminals, it may be a multilayer PCB.?
E
 
Last edited:

ericgibbs

Joined Jan 29, 2010
18,650
Hi Brian,
Did you refit the sensor directly back onto the PCB in order to test the sensor.?
The copper tracking to the right side of the top view appears to be damaged?

Also, there appears to be fine wires shorting on both sets of pads, the 6 pad and 3 pad.

E
 

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Thread Starter

brianWreaves

Joined Sep 16, 2021
27
I have not tried yet but I hope to put the sensor back on tomorrow to test.

The 'fine wires' are actually fibres from cotton swap I used to clean the board.

I'll report back once I have a go.
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
27
I'm in Australia so I'll have to find one here. However, I have another board with one on it, I think. If they look the same, should they work the same?

Another issue I have is the IR frequency the AMP remote uses is the same as my Samsung TV. Obviously that is very annoying! My guess is this can be changed but can it be changed by a beginner like me?
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
27
@ericgibbs The video & Bitsbox TSOP2438 IR are using a different IR as the pinout is different. So obviously the IR didn't work on my breadboard. Testing my amp's IR pinout still works:
  1. PIN01 - Rout
  2. PIN02 - GND
  3. PIN03 - 3.3V

Once I corrected the pinout the IR still didn't work so I must have fried it.

I found ZD1952 (datasheet)locally that may work but I'm unsure how to determine if it is a correct replacement. Any further assistance you can share?
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
27
I did purchase the ZD1952 (datasheet) and was able to confirm I had everything correctly connected on my breadboard and thus further confirmed my IR receiver is faulty.

I removed the existing 3 wires from my amp's board and confirmed the pins. Previously, I didn't find voltage on PIN01 but this time I do:
  • PIN01 - Rout 3.2V
  • PIN02 - GND
  • PIN03 - 3.3V

Without the board's drawings, how can I determine if PIN01 or PIN03 is the Vcc and which is Rout? Or is there a method I can use to try one without causing damage to the board using diodes or similar on a breadboard?
 

ericgibbs

Joined Jan 29, 2010
18,650
Hi Brian,
I have just spent about 20 minutes searching the web for any circuit diagrams with no success.:(

I will keep digging around, if I find any info I will post.

E
 
Last edited:

ericgibbs

Joined Jan 29, 2010
18,650
Hi Brian,
Try this method.

With the IR detector disconnected.

Using a 470 Ohm resistor, connect one end to pin #2 GND on the PCB

Connect the other end to say pin #1 PCB pad, measure the voltage on pin #1 PCB pad.
If that is the actual 3.3V supply, it should remain at 3.3v

Then try moving the resistor from pin #1 to pin #3 pad of the PCB, measure voltage on pin #3.
If that is the IR detector output pin I would expect to fall below 3.3v

  • PIN01 - Rout 3.2V
  • PIN02 - GND
  • PIN03 - 3.3V
Post what you measure

Ask if you don't follow my description
E
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
27
Thanks for that, @ericgibbs ... Yes, that is how it was originally oriented and I too suspect the same for the pins power & signal alignment.

After checking with 470 Ohm:
  • PIN01 & PIN02 - dropped from 3.25v to 3.19v
  • PIN02 & PIN03 - maintained 3.3.v
So, it is as we suspected.

Next I used the breadboard to test but added an LED so I can see when the remote is being detected.

A close-up image of an electronic breadboard setup showing a wired IR receiver and a lit blue LED. The receiver has three legs connected with jumper wires to the extended cable to the amp.

As soon as I switched on the power at the wall the LED turns on, as it is in the photo. It didn't do that with the workbench power supply. When I press the [Power] button on the remote, the LED flickers as I would expect but the amp does not turn on. When I switched the power off at the wall, the LED turns off. If I quickly press the [Power] button on the remote, the amp turns on for a moment.

I switched the power on at the wall again and the voltage readings between PIN 01 & 02, and then 02 & 03, were the same as if the resistor was in place. I also tried the workbench power supply again and it worked as expected but it doesn't have anything other than an LED on PIN01 of the IR receiver.

Either I've damaged something or I'm missing something???
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
27
Unfortunately, with the LED removed the amp did not respond to the remote until the power was switched off at the wall. I tried the remote with the amp manually turned on as well but with the same results.
 

ericgibbs

Joined Jan 29, 2010
18,650
As soon as I switched on the power at the wall the LED turns on, as it is in the photo. It didn't do that with the workbench power supply.
Hi,
This suggests that the TSOP is conducting when it should not be, when there is no IR being received.

Have you tried with the TSOP connected as it was in the original position on the PCB?
E

Update:
Is your TSOP a 1738 or 1838 type, their connections are different.
 

Thread Starter

brianWreaves

Joined Sep 16, 2021
27
Is your TSOP a 1738 or 1838 type, their connections are different.
I have no way to know which for the original IR receiver and I see no mention of it for the new one. However, my meter readings on the PCB seem to match up with the new IR receiver datasheet and troubleshooting above thus far.

As you suggested, I continued troubleshooting by removing the wires from the PCB, added the new IR receiver and everything works as expected. My firs thought was poor wiring/soldering so I added the wires again, checked my work, and tested. Unfortunately, the same issues continued.

I then moved the LED from the breadboard to the PCB to see if the remotes buttons were being sent to it. The LED lit-up with power On at the wall switch and blinked with the remote. So the IR receiver on the breadboard is doing something to affect the LED but the amp is not responding.

Then I decided to just use 3 separate strands of wire, instead of the 4-core shielded USB cable I was using. Maybe there was an issue with the shielding. Well, I guess the PCB had reached its limits of my poor (de)soldering skills as half of PIN01 pad is now gone, PIN02 lifted & shifted, and PIN03 completely came off, top & bottom.:mad:
I was able to salvage it enough to attach the wires and test with the breadboard again but the same issues persist. There is little likelihood I can reattach the IR receiver on the PCB again given how fragile it is now, it doesn't work as it is, and the amp can be replaced for less than it would cost to have it repaired by a real technician. This is a very disappointing outcome!
 
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