Hi! I'm looking for some help with a Niles SI-1230 amplifier I bought recently at Seattle Goodwill. It seemed like a great deal at $25. I'm looking to resell the amplifier but want to test it first to ensure that it functions properly.
Wondering if anyone can suggest what I can do to test it, and/or how to test it. I have a couple of small Klipsch Quintet speakers that have an impedance of 8 ohms that I could use. I also have a digital volt meter. I built a tube amp 15 years ago from scratch, so I'm not completely stupid with regard to electronics...I'd say my knowledge and experience levels are beginner+.
The amp powers on and shows a green light.
Any assistance or words of wisdom would be greatly appreciated. Thank you! -Joe
Wondering if anyone can suggest what I can do to test it, and/or how to test it. I have a couple of small Klipsch Quintet speakers that have an impedance of 8 ohms that I could use. I also have a digital volt meter. I built a tube amp 15 years ago from scratch, so I'm not completely stupid with regard to electronics...I'd say my knowledge and experience levels are beginner+.
The amp powers on and shows a green light.
Any assistance or words of wisdom would be greatly appreciated. Thank you! -Joe
I'm not familiar with that particular unit, but I have used a number of Niles and Sonance 2-channel amps. They are pretty rugged, but realize they might have lived in a closed cabinet.
The most basic test that you can do to determine if it is safe to hook up speakers is to measure the DC offset at the speaker terminals. Turn the unit on with nothing connected, let it warm up for 15-20 minutes. Then for each of the 12 channels, measure the DC voltage across each set of red and black terminals. Expect less than 50mVDC. Less than 20mVDC would be great. More than 100s of mVDC would indicate a problem, and a warning to not connect speakers to that channel. If you saw rail voltage (something like 40-50VDC) at any of the speaker terminals, it would be likely that one or more output transistors are shorted, and any speakers connected to those terminals likely be would be destroyed in short order.
If all the DC offsets look good, you could connect a pair of speakers and a source to each of the 6 amps and try some music.
As for bias, a general check would be, after the unit has been on for 20 mins or so just idling, no music necessary, you would expect to feel a little bit of heat coming off the heat sinks. If a heat sink is cold (or parts of it seem colder than other parts), or if it is running very hot, it might be as simple as the bias needs to be adjusted.
You would have to inspect the PCBs to see if you can figure out where the pots for setting bias are; bias is usually measured across an emitter resistor on one of the output transistors for that channel. On the 2 channel models it was not hard to figure all this out. If this 12-channel model has 6 amp PCBs in it, each board should have a pair of bias pots, emitter resistors, on it, and it should not be too hard to figure it out if you can get access to them. Labeling on the boards may be of help, but the ones I have don't have much other than component numbers. Schematics and not generally available for Niles or Sonance units, unfortunately.
Good luck.
The most basic test that you can do to determine if it is safe to hook up speakers is to measure the DC offset at the speaker terminals. Turn the unit on with nothing connected, let it warm up for 15-20 minutes. Then for each of the 12 channels, measure the DC voltage across each set of red and black terminals. Expect less than 50mVDC. Less than 20mVDC would be great. More than 100s of mVDC would indicate a problem, and a warning to not connect speakers to that channel. If you saw rail voltage (something like 40-50VDC) at any of the speaker terminals, it would be likely that one or more output transistors are shorted, and any speakers connected to those terminals likely be would be destroyed in short order.
If all the DC offsets look good, you could connect a pair of speakers and a source to each of the 6 amps and try some music.
As for bias, a general check would be, after the unit has been on for 20 mins or so just idling, no music necessary, you would expect to feel a little bit of heat coming off the heat sinks. If a heat sink is cold (or parts of it seem colder than other parts), or if it is running very hot, it might be as simple as the bias needs to be adjusted.
You would have to inspect the PCBs to see if you can figure out where the pots for setting bias are; bias is usually measured across an emitter resistor on one of the output transistors for that channel. On the 2 channel models it was not hard to figure all this out. If this 12-channel model has 6 amp PCBs in it, each board should have a pair of bias pots, emitter resistors, on it, and it should not be too hard to figure it out if you can get access to them. Labeling on the boards may be of help, but the ones I have don't have much other than component numbers. Schematics and not generally available for Niles or Sonance units, unfortunately.
Good luck.