I still have this receiver, recently the remote stopped working. Been using two TiVO remotes with it, and both stopped working with just the receiver at the same time (remotes still work fine with the TV and TiVO).
Testing so far-
I see data on the IR receiver, all the way to pin on 41 on IC901.
I see clock signal on pins 19/20.
VFD works fine, as are all of the mechanical buttons on the board, so I think the micro-controller is "alive".
Seems like there is not a whole lot that go wrong in this circuit, so I am looking for advice on what else I can test.
Link below to the datasheet for what I think is IC901.
TIA.
TMP47C670N
Testing so far-
I see data on the IR receiver, all the way to pin on 41 on IC901.
I see clock signal on pins 19/20.
VFD works fine, as are all of the mechanical buttons on the board, so I think the micro-controller is "alive".
Seems like there is not a whole lot that go wrong in this circuit, so I am looking for advice on what else I can test.
Link below to the datasheet for what I think is IC901.
TIA.
TMP47C670N
Some additional information...
I confirmed the clock is running at about 8Khz (scope shot below).
Also checked the +5V and it has maybe 50mv of ripple.
I confirmed the clock is running at about 8Khz (scope shot below).
Also checked the +5V and it has maybe 50mv of ripple.
Parts list says "CST 4.00MG", which I think would be a resonator. Unfortunately it is buried under the display and I am trying to avoid having to remove it.
"4.00" to me should be 4.0 Mhz but not exactly sure what part this is to find a specification sheet. I found something that could be it (linked below).
One of my theories was that the clock has drifted enough such that the timing for reading the serial data from the remote is no longer within tolerance.
123us converts to 8.130 using an online calculator. Most spec sheets I have seen for resonators in this frequency range are +/- 0.5% that would be a 400hz error, and I am within that.
https://media.elv.com/file/31231_keramikschwinger_2_data.pdf
"4.00" to me should be 4.0 Mhz but not exactly sure what part this is to find a specification sheet. I found something that could be it (linked below).
One of my theories was that the clock has drifted enough such that the timing for reading the serial data from the remote is no longer within tolerance.
123us converts to 8.130 using an online calculator. Most spec sheets I have seen for resonators in this frequency range are +/- 0.5% that would be a 400hz error, and I am within that.
https://media.elv.com/file/31231_keramikschwinger_2_data.pdf
Attachments
4MHz sounds very reasonable and that would translate to a period of 1/4000000 which is 0.25uS or 250nS
If you set your scope to 1uS per division (make sure any 'CAL' variables for the time base are turned to the 'CAL' position then you should see 5 cycles per division. One of the two pins on the chip will be the 'output' of the oscillator and that is the pin to use. The probe capacitance (you should ideally use a divider probe to lower stray capacitance) can be enough to stop the oscillator, particularly if you probe the input. The output pin should drive a standard X1 probe.
If you set your scope to 1uS per division (make sure any 'CAL' variables for the time base are turned to the 'CAL' position then you should see 5 cycles per division. One of the two pins on the chip will be the 'output' of the oscillator and that is the pin to use. The probe capacitance (you should ideally use a divider probe to lower stray capacitance) can be enough to stop the oscillator, particularly if you probe the input. The output pin should drive a standard X1 probe.
Probe is Tek P6109 (150Mhz 10Mohm 11.8pf 10X 1.5M) Scope is Tek 2232
Both pins on the micro look the same on the scope when using chassis as ground.
This is 1uS - looks like 4 cycles per division if I am counting correctly. All of the CAL knobs are locked.
Both pins on the micro look the same on the scope when using chassis as ground.
This is 1uS - looks like 4 cycles per division if I am counting correctly. All of the CAL knobs are locked.
Really odd that I am getting a clear pattern on two very different time scales, no?
This is showing 254ns, which is 3.937 Mhz.
This is showing 254ns, which is 3.937 Mhz.
Seems the processor is likely working ok. Wasn't the suspected problem the IR receiver, IU-1647-4?
It is odd.
Does the remote work when you have the scope displaying this seemingly correct 4MHz signal? Just covering all bases and wondering if the probe is triggering the osc into life at the correct frequency.
That is much more likely.
@Marc03 check the amplitude of the signal going into the uP. Collector of TR903 (on your diagram). What is the other connection to the base of that transistor for? (CNC3) Amplitude on collector I would expect to be 5v peak/peak with clean and sharp edges.
When I stated, my first test was to see if there was data coming through to the micro- there was. Nice 5V square wave.. So the senor, and transistors were all working as expected.
As I was working on it late yesterday, the micro stopped working all together (nothing on the display, receiver would not power on). Double checked all of the voltages, and the clock again and all were good. So, I started to inspect for bad solder joints, etc. While doing that I also cleaned up a bunch of flux on the board. When I went back to test it after the inspection (and finding nothing wrong), the display came back on AND the remote works.
I am going to keep hunting for something intermittent, but at least now I can be confident that all of the components are good.
As I was working on it late yesterday, the micro stopped working all together (nothing on the display, receiver would not power on). Double checked all of the voltages, and the clock again and all were good. So, I started to inspect for bad solder joints, etc. While doing that I also cleaned up a bunch of flux on the board. When I went back to test it after the inspection (and finding nothing wrong), the display came back on AND the remote works.
I am going to keep hunting for something intermittent, but at least now I can be confident that all of the components are good.
Thanks! And thanks for your help...
Might as well also mention (in case someone else stumbles on this thread) that I am working from a German copy of the DRA-1025R service manual. If someone happens to find an English DRA-1025RA manual, I'd love to get a copy. 😎
Might as well also mention (in case someone else stumbles on this thread) that I am working from a German copy of the DRA-1025R service manual. If someone happens to find an English DRA-1025RA manual, I'd love to get a copy. 😎
Digital scope, aliasing.
Did you check the IR output from the remote? It isn't uncommon for the ceramic resonator to break leads. Glue the new one down if that is the case. You can monitor the drive for the IR LED with your scope to make sure it should be sending. I fixed so many I made a circuit that transmitted and received IR signals and I could connect that to my scope.
Monitor the output from the IR receiver module if the remote checks okay. It will output a signal with other remotes.
Did you check the IR output from the remote? It isn't uncommon for the ceramic resonator to break leads. Glue the new one down if that is the case. You can monitor the drive for the IR LED with your scope to make sure it should be sending. I fixed so many I made a circuit that transmitted and received IR signals and I could connect that to my scope.
Monitor the output from the IR receiver module if the remote checks okay. It will output a signal with other remotes.
Thanks for your reply anatech. Tested with two remotes that both work fine. When I hit the button on the remote, I can see the serial data at the microprocessor. Not sure if you caught up on the rest of the thread, but it started working.. I am unable to get it to NOT work now!! Gotta love those self-healing machines! LOL!
Before I wrapped it up, I figured I would de-ox the speaker relays. That was a mistake.
Before I wrapped it up, I figured I would de-ox the speaker relays. That was a mistake.
There you go! Bad connector maybe just needed to be moved to break oxide.
Don't bother cleaning relays. Just replace them. Once the plating is damaged (arced), cleaning is temporary at best. Make sure the volume is zero when you turn on or off. Besides, a relay is a maintenance item.
Don't bother cleaning relays. Just replace them. Once the plating is damaged (arced), cleaning is temporary at best. Make sure the volume is zero when you turn on or off. Besides, a relay is a maintenance item.
I use a 3 mm red LED, temporarily, or permanently, in parallel with the IR LED.
Easier to check.
3 mm hole in top is made for permanent use, the indication is both of function, and battery strength...some remotes can be damaged by too low battery voltage.
Easier to check.
3 mm hole in top is made for permanent use, the indication is both of function, and battery strength...some remotes can be damaged by too low battery voltage.
Hi NareshBrd,
Putting the LEDs directly across isn't something I would do, the drop on the IR diode is higher. You could put them in series - maybe. Parallel with the drive using a series resistor, but that may reduce the IR diode power depending on the circuit. I try not to modify those things at all.
That is something I haven't seen
Putting the LEDs directly across isn't something I would do, the drop on the IR diode is higher. You could put them in series - maybe. Parallel with the drive using a series resistor, but that may reduce the IR diode power depending on the circuit. I try not to modify those things at all.
Some of the remotes I had to open for cleaning had location on PCB for extra LED, 3 mm red works fine.
No reduction in performance for the ones I modified.
The low battery voltage caused IC failure, but most remotes here are 75 cents to $1.50, the good ones have better material. So not a big deal. The issue happens when you have an odd remote.
Corrosion of contacts is also a headache.
I remove the cells from blood pressure and SPO2 monitors as well, they do take power on standby, and when you need them, you ned to find the spare cells....not good for peace of mind.
No reduction in performance for the ones I modified.
The low battery voltage caused IC failure, but most remotes here are 75 cents to $1.50, the good ones have better material. So not a big deal. The issue happens when you have an odd remote.
Corrosion of contacts is also a headache.
I remove the cells from blood pressure and SPO2 monitors as well, they do take power on standby, and when you need them, you ned to find the spare cells....not good for peace of mind.