I've been using an Alesis Ra-100 in my home studio for about fourteen years now. About two weeks ago it started acting up. When I would first power it up no sound would initially pass or it would be distorted on one side. After 5-10 minutes of being on it would start working normal and continue to work for however long I had the amp on. The power light was always lit even when the sound wasn't passing. So I started leaving it on to avoid the start-up annoyance. This week it quit passing sound all together even though the power light was still lit.
So I did a little digging on google and found a partial schematic and a post where someone was describing the same type of issue that they said was fixed by replacing C4 on the power supply board (10uF 63v). I pulled C4 from my amp and tested it. It was giving me a reading of only 1uF. So I picked up a replacement and dropped it in last night. Now I have no sound and my power light is not lit.
I did more research last night and stumbled upon this site as well as the full schematic. My soldering/testing abilities are good but I don't have a lot of experience with this type of circuit as far as the operation and troubleshooting of it. Where would you guys start checking on this one?
So I did a little digging on google and found a partial schematic and a post where someone was describing the same type of issue that they said was fixed by replacing C4 on the power supply board (10uF 63v). I pulled C4 from my amp and tested it. It was giving me a reading of only 1uF. So I picked up a replacement and dropped it in last night. Now I have no sound and my power light is not lit.
I did more research last night and stumbled upon this site as well as the full schematic. My soldering/testing abilities are good but I don't have a lot of experience with this type of circuit as far as the operation and troubleshooting of it. Where would you guys start checking on this one?
I had issues with one of the Molex connectors causing no sound in mine on one side.
I have had problems with those connector on many devices in the past.
Re-seating them sometimes fixes them and sometimes i have cut them off and hardwire the cable completely to the board.
jer 🙂
I have had problems with those connector on many devices in the past.
Re-seating them sometimes fixes them and sometimes i have cut them off and hardwire the cable completely to the board.
jer 🙂
Jer,
thank you for replying. I have also had issues with those connectors in other devices. I will give re-seating them a shot even though I believe something else is going on in the power circuit since my Power LED is no longer lighting.
Is anyone familiar with the transformer in this unit? Mine has absolutely no markings on it. I have 120v on the primary wires but there are two reds and a white coming off the secondary but I don't know what voltage they should be outputting. I am assuming this is a step down transformer that is feeding the bridge rectifier?
thank you for replying. I have also had issues with those connectors in other devices. I will give re-seating them a shot even though I believe something else is going on in the power circuit since my Power LED is no longer lighting.
Is anyone familiar with the transformer in this unit? Mine has absolutely no markings on it. I have 120v on the primary wires but there are two reds and a white coming off the secondary but I don't know what voltage they should be outputting. I am assuming this is a step down transformer that is feeding the bridge rectifier?
Upon more investigation I am leaning towards the transformer. I have four leads on the primary. Black, Red, Orange and Yellow. They land on the power PCB. Black/Red have continuity and Orange/Yellow have continuity. I have 120 volts on the PCB between black/red and Orange/yellow. So I know I have the correct voltage feeding the primary windings.
The Secondary has 3 wires. Two Reds and one white. They all 3 have continuity. When I check for voltage between these I am getting 0 volts. I am assuming that I should be seeing something between red1-white, red 2-white and red-red but everything is reading 0V.
Granted I still don't know what the output on the secondary is supposed to be but it should be something right lol? and if I do need to replace this thing how the heck do I go about finding the correct replacement without any markings?
The Secondary has 3 wires. Two Reds and one white. They all 3 have continuity. When I check for voltage between these I am getting 0 volts. I am assuming that I should be seeing something between red1-white, red 2-white and red-red but everything is reading 0V.
Granted I still don't know what the output on the secondary is supposed to be but it should be something right lol? and if I do need to replace this thing how the heck do I go about finding the correct replacement without any markings?
The service manual can be found here,
Alesis RA100 Manual - Stereo Power Amplifier - HiFi Engine
There should be approximately 34Vac from the Red and white wire and/or about 68Vac between the two red ones.
Make sure that you have voltage going in to the transformers primary from the line.
Check the switch for continuity.
The symptom's sound like the cheesy connectors or maybe some bad solder joints or cracked traces at the connectors on the board.
The schematic shows the voltages and the wiring color codes of the transformers leads.
jer 🙂
Alesis RA100 Manual - Stereo Power Amplifier - HiFi Engine
There should be approximately 34Vac from the Red and white wire and/or about 68Vac between the two red ones.
Make sure that you have voltage going in to the transformers primary from the line.
Check the switch for continuity.
The symptom's sound like the cheesy connectors or maybe some bad solder joints or cracked traces at the connectors on the board.
The schematic shows the voltages and the wiring color codes of the transformers leads.
jer 🙂
Jer,
I got it sorted out. I don't know if my transformer is an "original" or someone replaced it at some point but I had the red/black and Orange/Yellow primary leads. On the PCB it was labeled (120v) Black, Red, Brown, Yellow for the leads to land. I even took photos before I pulled the leads off the pcb but the red and the orange looked very similar in the photo. Upon not knowing exactly I went with the labeling on the PCB. So after looking at the traces today, I realized that red/black tabs were both line and orange/yellow were neutral. So the Red/black winding was only seeing line and orange/yellow winding was only seeing neutral DOHHHHH!
So upon correctly landing those, I got my output voltage back on the secondary and the replaced capacitor which started all this seems to have fixed my other issues entirely. Talk about a headache lol. Thank you for all of your help. Happy this thing is working again. Maybe it will give me another 14 years before it crashes again.
I got it sorted out. I don't know if my transformer is an "original" or someone replaced it at some point but I had the red/black and Orange/Yellow primary leads. On the PCB it was labeled (120v) Black, Red, Brown, Yellow for the leads to land. I even took photos before I pulled the leads off the pcb but the red and the orange looked very similar in the photo. Upon not knowing exactly I went with the labeling on the PCB. So after looking at the traces today, I realized that red/black tabs were both line and orange/yellow were neutral. So the Red/black winding was only seeing line and orange/yellow winding was only seeing neutral DOHHHHH!
So upon correctly landing those, I got my output voltage back on the secondary and the replaced capacitor which started all this seems to have fixed my other issues entirely. Talk about a headache lol. Thank you for all of your help. Happy this thing is working again. Maybe it will give me another 14 years before it crashes again.
I've got a DM 7X and so far have to resolder (using thicker/better wires ) 4 out of 7 seven pads and have had a replacememt bass drum syustem as well - love the kit, but you shouldn't need to do this to a kit 2 years old (should of stuck to Roland lol)
Good Deal !!!!
I am glad you got it working!!
I remember the issue I had was broken solder around the connection pins on the board, That gave similar symptoms that you were having.
Mine created issues after is was only about 6 years old in 2000 and it had never been removed from the rack it was in for that period of time, That same amp is still working flawlessly to this day. 🙂
:Cheers: !!!!!
jer 🙂
I am glad you got it working!!
I remember the issue I had was broken solder around the connection pins on the board, That gave similar symptoms that you were having.
Mine created issues after is was only about 6 years old in 2000 and it had never been removed from the rack it was in for that period of time, That same amp is still working flawlessly to this day. 🙂
:Cheers: !!!!!
jer 🙂
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