Hello everyone,
I'm turning to the Badcaps community to help me troubleshoot the radio Rx card from my (old) garage door opener. While I could just ditch that card and replace the whole system, I first would like to understand "why" it suddenly stopped working, because that's just how I am wired...!
Some basics: the receiver works on a 30.875 Mhz frequency. Yes, I'm aware this is not in use anymore in a looot of places. It does not use any rolling code, it's just a regular dip-switch code that you have to set up on both the receiver and transmitter. The receiver handles up to 4 channels, each of them having a dedicated slot on the PCB where a relay modules attaches. This relay module is wired to the main IC through 1 "signal pin" (+0V in normal condition, +5V when the correct coded signal is emitted by the transmitter). That main IC seems proprietary, I can't find anything on it (marked CARDIN ZELIG.2 XE15AB) but it looks fairly basic, hooked up to all dip switches and outputs +5V on dedicated signaling pins to trigger the control relays. Here there is only one relay module on channel A (CH.A). The Rx unit is connected to an output that goes to a master unit that is then wired to the opener (and various other appliance, you could even factor in an induction loop). That output is a NO contact (+24V) which, once shorted, is interpreted as the "opening signal" by the master unit. Below, an annotated picture of that main Rx PCB.
The "antenna / signal" section works perfectly fine: if you stick your ear next to the PCB, you can hear a very subtle high-pitch noise when you press the remote button, in sync with the transmitter led blinking. When the code is the same on Tx and Rx, the CH.A signal pin turns from +0V to +5V. This circuit goes to the last pin of the relay connector.
The relay itself is a SY-9-K that clicks when its coil is energized with +9V. I have tested it on my bench and it works (clicks when hooking up my bench PSU and feeding +9V to one pin of the coil and GND to the other). However, in normal operation, both these pins receive +9V from the main PCB. There is what I suspect to be a NPN transistor for which I think the collector (bottom left?) is hooked up to one of the coil pin (the NA one; pin 10 of the connector). The base (bottom right?) receives +5V constantly through pin 8 of the relay connector. I am not sure if that's a transistot or anything else. It is marked 6B, with a "5" engraved vertically. Datasheets pointed me toward a transistor but... who knows. Picture below:
Here's where I'm stuck: I don't understand why the relay does not activate. Obviously something is wrong by my transistor knowledge is not that good and I don't understand what should happen. Basically :
- normal operation: the transistor gets +9V / +0V / +5V (upper, left, right)
- correct signal: the transistor gets +9V / +5V / +5V, but shouldn't that +9V go to GND (or anything lower) instead ?
Measurements taken with my multimeter in diode mode on that transistor:
- left (V) -> up (COM) : 0.653V
- left (COM) -> up (V) : 1
- right (V) -> up (COM) : 1
- right (COM) -> up (V) : 1
- left (V) -> right (COM) : 0.653V
- left (COM) -> right (V) : 1
Anyway, here where I'm stuck. Any support would be greatly appreciated: I suspect it's that transistor not doing its job, but it looks OK by my not-so-good standards on diagnosing them.
Cheers!
I'm turning to the Badcaps community to help me troubleshoot the radio Rx card from my (old) garage door opener. While I could just ditch that card and replace the whole system, I first would like to understand "why" it suddenly stopped working, because that's just how I am wired...!
Some basics: the receiver works on a 30.875 Mhz frequency. Yes, I'm aware this is not in use anymore in a looot of places. It does not use any rolling code, it's just a regular dip-switch code that you have to set up on both the receiver and transmitter. The receiver handles up to 4 channels, each of them having a dedicated slot on the PCB where a relay modules attaches. This relay module is wired to the main IC through 1 "signal pin" (+0V in normal condition, +5V when the correct coded signal is emitted by the transmitter). That main IC seems proprietary, I can't find anything on it (marked CARDIN ZELIG.2 XE15AB) but it looks fairly basic, hooked up to all dip switches and outputs +5V on dedicated signaling pins to trigger the control relays. Here there is only one relay module on channel A (CH.A). The Rx unit is connected to an output that goes to a master unit that is then wired to the opener (and various other appliance, you could even factor in an induction loop). That output is a NO contact (+24V) which, once shorted, is interpreted as the "opening signal" by the master unit. Below, an annotated picture of that main Rx PCB.
The "antenna / signal" section works perfectly fine: if you stick your ear next to the PCB, you can hear a very subtle high-pitch noise when you press the remote button, in sync with the transmitter led blinking. When the code is the same on Tx and Rx, the CH.A signal pin turns from +0V to +5V. This circuit goes to the last pin of the relay connector.
The relay itself is a SY-9-K that clicks when its coil is energized with +9V. I have tested it on my bench and it works (clicks when hooking up my bench PSU and feeding +9V to one pin of the coil and GND to the other). However, in normal operation, both these pins receive +9V from the main PCB. There is what I suspect to be a NPN transistor for which I think the collector (bottom left?) is hooked up to one of the coil pin (the NA one; pin 10 of the connector). The base (bottom right?) receives +5V constantly through pin 8 of the relay connector. I am not sure if that's a transistot or anything else. It is marked 6B, with a "5" engraved vertically. Datasheets pointed me toward a transistor but... who knows. Picture below:
Here's where I'm stuck: I don't understand why the relay does not activate. Obviously something is wrong by my transistor knowledge is not that good and I don't understand what should happen. Basically :
- normal operation: the transistor gets +9V / +0V / +5V (upper, left, right)
- correct signal: the transistor gets +9V / +5V / +5V, but shouldn't that +9V go to GND (or anything lower) instead ?
Measurements taken with my multimeter in diode mode on that transistor:
- left (V) -> up (COM) : 0.653V
- left (COM) -> up (V) : 1
- right (V) -> up (COM) : 1
- right (COM) -> up (V) : 1
- left (V) -> right (COM) : 0.653V
- left (COM) -> right (V) : 1
Anyway, here where I'm stuck. Any support would be greatly appreciated: I suspect it's that transistor not doing its job, but it looks OK by my not-so-good standards on diagnosing them.
Cheers!
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