I sure would like to find specs or replacement for this protection relay; just hope that it's really the whole problem.
Type DH2SU, 24 V DC, 2A 120VAC, DEC (Korea), K2735
I wanted to fix this chip amp for my daughter to use, but it won't turn on. Used to take several attempts, so I'm hoping it's just the relay.
Type DH2SU, 24 V DC, 2A 120VAC, DEC (Korea), K2735
I wanted to fix this chip amp for my daughter to use, but it won't turn on. Used to take several attempts, so I'm hoping it's just the relay.
When I turn most amps on I hear a relay click, then a few seconds later it clicks again and the speakers come on.
With this amp, the relay never makes the first click. There's some power supply voltage, as the indicator lights for the input momentary butons work, but then they fade out and turn off.
I can see a transistor, resistor, very small electrolytic cap, and relay. The relay never clicks. I guess I should remove the relay and test it, possibly jumper the outs just to force the amp on.
The fact the relay never makes any first click indicates to me the possibility the relay is stuck or coil burned out. If the coil were burned out, I'd expect the relay to be stuck in the normally closed mode with speakers connected? That impression comes from the norm of hearing a relay click (activate coil) to disconnect the speakers, then a few seconds later click again to reconnect the speakers (de-activate coil). Usually when the protection circuit goes, it's the capacitor in the timing circuit which time show long the relay disconnects the speaker.
Of course, it could be something more complicated with the protection circuit, like some valid fault. It seems reasonable that some control voltage comes on, but weird that it turns back off without any relay snap.
With this amp, the relay never makes the first click. There's some power supply voltage, as the indicator lights for the input momentary butons work, but then they fade out and turn off.
I can see a transistor, resistor, very small electrolytic cap, and relay. The relay never clicks. I guess I should remove the relay and test it, possibly jumper the outs just to force the amp on.
The fact the relay never makes any first click indicates to me the possibility the relay is stuck or coil burned out. If the coil were burned out, I'd expect the relay to be stuck in the normally closed mode with speakers connected? That impression comes from the norm of hearing a relay click (activate coil) to disconnect the speakers, then a few seconds later click again to reconnect the speakers (de-activate coil). Usually when the protection circuit goes, it's the capacitor in the timing circuit which time show long the relay disconnects the speaker.
Of course, it could be something more complicated with the protection circuit, like some valid fault. It seems reasonable that some control voltage comes on, but weird that it turns back off without any relay snap.
Actually a burnt out relay coil is about the last thing on the list. ANything is possible of course, but far more likely that whatever is responsible for turning the relay on is what is at fault.
A lot of amps have a speaker relay. This relay usually delays its turn-on a few seconds to give the amp a chance to fully turn on. This avoids speakers going THUMP when you power up. Many of those relays also will remain off if the circuit detects a problem in the amp, for example DC voltage on the output. This prevents your speakers catching on fire.
If you have a two stage click, chances are it is two different relays. SOme systems have power supply relays as well as speaker relays.
A lot of amps have a speaker relay. This relay usually delays its turn-on a few seconds to give the amp a chance to fully turn on. This avoids speakers going THUMP when you power up. Many of those relays also will remain off if the circuit detects a problem in the amp, for example DC voltage on the output. This prevents your speakers catching on fire.
If you have a two stage click, chances are it is two different relays. SOme systems have power supply relays as well as speaker relays.
Enzo,
Makes sense, I problabhy never had an amp with just one relay before..always none or 2. I was basing some of my conjecture on a claim by the previous owner that if you tried many times it would sometimes turn on, and work fine. Some of my interest in the relay was to see whether it was stuck, and then I wanted to force its "on" mode (with a dummy load or no load on the speaker output terminals). This amp is not worth much, so if I blow it it's only a small loss, and I don't want to waste much of my or your time on it. The previous owner's stories made me think it was just some fault in that relay which prevents the "thump" and the relay is one of the few mechanical things likely to be intermittent...but of course other things can be intermittent and his stories are just hearsay. I don't think there is any power relay. I'm seeing other symptoms that indicate that the power supply itself may be at fault, and the stories from the previous owner unlikely. There's a LED display that should illuminate too (I suspect it should come on immediately), and neither the background nor foreground of that display illuminates, just the correct LED above a button (if I press and hold) (LED blinks on then drains down; then curiously will blink again and then drain down slowly after shutoff) (I supsect I'm using those LEDs to viisually monitor some power supply, so I need to get out the meter). Unfortunately I sold most of my test equipment last year. So first I'm trying to get a schematic. Then find out what I can with my meter and no scope. I'm shocked there appear to be no power supply output fuses unless they are really well hidden, just one internal line-cord power fuse. I'll start with checking the 4 main diodes...and take it from there, looking for 3-pin regulators (or zeners??). I'm guessing the diodes might be acting as the power supply output fuses.
winter0316...I don't think I'd have any trouble finding a replacement for the relay, what I wanted was specs or a replacement that would tell me the pinout. But I suspect if I take the board out I can figure out the pin-out of the relay, which is really what I need. I probably have similar relays with a good clue to the pinout anyway.
Makes sense, I problabhy never had an amp with just one relay before..always none or 2. I was basing some of my conjecture on a claim by the previous owner that if you tried many times it would sometimes turn on, and work fine. Some of my interest in the relay was to see whether it was stuck, and then I wanted to force its "on" mode (with a dummy load or no load on the speaker output terminals). This amp is not worth much, so if I blow it it's only a small loss, and I don't want to waste much of my or your time on it. The previous owner's stories made me think it was just some fault in that relay which prevents the "thump" and the relay is one of the few mechanical things likely to be intermittent...but of course other things can be intermittent and his stories are just hearsay. I don't think there is any power relay. I'm seeing other symptoms that indicate that the power supply itself may be at fault, and the stories from the previous owner unlikely. There's a LED display that should illuminate too (I suspect it should come on immediately), and neither the background nor foreground of that display illuminates, just the correct LED above a button (if I press and hold) (LED blinks on then drains down; then curiously will blink again and then drain down slowly after shutoff) (I supsect I'm using those LEDs to viisually monitor some power supply, so I need to get out the meter). Unfortunately I sold most of my test equipment last year. So first I'm trying to get a schematic. Then find out what I can with my meter and no scope. I'm shocked there appear to be no power supply output fuses unless they are really well hidden, just one internal line-cord power fuse. I'll start with checking the 4 main diodes...and take it from there, looking for 3-pin regulators (or zeners??). I'm guessing the diodes might be acting as the power supply output fuses.
winter0316...I don't think I'd have any trouble finding a replacement for the relay, what I wanted was specs or a replacement that would tell me the pinout. But I suspect if I take the board out I can figure out the pin-out of the relay, which is really what I need. I probably have similar relays with a good clue to the pinout anyway.
Fixed. Feel dumb as I am. It's the power switch. It's a push-push latching button like a ballpoint pen, except it doesn't work right, it only connects momentarily and there's no latching relay or anything...just the switch is subtly broken. Hold the "on" button and all works well, protection relay and all. It was just momentarily charging the PS caps momentarily when I pushed the 'on' button momentarily. I was wondering what shut it off, as there's nothing to kill all the power, just the relay to disconnect the speakers. Enzo was right, only one ckick when speakers come on, an a click at shutoff; so relay is normally open, closes to connect speakers.
Now for some listening tests...got the amp for $15.00, 100 watts a channel claimed. FIne for he kids.
Now for some listening tests...got the amp for $15.00, 100 watts a channel claimed. FIne for he kids.
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