Alesis RA500 Amplifier

[Thermaltake]

Hi, I have some strange problem with my Alesis amplifier. One day I want to power the amplifier like every other day but it was completely dead, I opened it and checked the capacitors on PSU and found out that two big ones 63V 10000uF were strange but when I measure them they were fine. I decided to replaced them anyway with nippons because that Suscon is junk, I also replaced two 25V 220uF and one 35V 1000uF in that PSU because their capacitance was low under that 10% drop tolerance. After replacement amplifier turned On but signal from my sound card was not getting in amplifier, there was no sound and no bars were jumping on display on amplifier. Anyone have idea why and what to do ?

[Thermaltake]

Re: Alesis RA500 Amplifier

I forgot to say yellow lights on the side on display appears when I power it On but they are gone in a seconds so I think there is no shorts or cracked solder.

[charis]

Re: Alesis RA500 Amplifier

Hi.
Does the relay kick in?
If no check the voltages.
Maybe the lights go off because goes to protection mode.
Also check the 2 preamp pcb voltages (and the potentiometer) after that go for the output mosfets check.

[Thermaltake]

Re: Alesis RA500 Amplifier

Hi.
Does the relay kick in?
If no check the voltages.
Maybe the lights go off because goes to protection mode.
Also check the 2 preamp pcb voltages (and the potentiometer) after that go for the output mosfets check.

Nothing is kicking inside of the amplifier it's quiet. Could it be that relay is dead or something ?

Yellow lights appear when I turn it on but that's normal, amplifier did that when it was working normally it's like his initialization or something when you power it up.

I will check that mosfets and other voltages and let you know more when I do that.

[Thermaltake]

Re: Alesis RA500 Amplifier

I forgot to ask why check output mosfets if input is not coming through.

[charis]

Re: Alesis RA500 Amplifier

If you have blow mosfet the relay wont open to protect your speakers and psu.
If the relay dont close put it 12 v on the input pins and see if work.
If works and the mosfets are right check the 12v rail.
I dont have a schematic.

[rhomanski]

Re: Alesis RA500 Amplifier

Here's the schematic.

[charis]

Re: Alesis RA500 Amplifier

Ok very simple.
After the transformer and brige rectifier the power goes to TA7317 who works as over curent ,voltage,speaker terminal short detector.The use about 50v.Pin 6 is the relay drive output pin 8 the muting pin1 current detection Pin2 voltage detection.The vcc for the chip should be about 50v on Pin9 -50v on pin5.
To open the relay Pin 6 they send 5v square pulse with 3ms time period.
When the relay close feed j7 and j8 terminals(where are also +15 -15v) and the signal from C1815 who is NPN transistor for muting and conect to pin 7 who is the part to the discharge circuit and have a diode protection D403.
Also the relay have on the second side 2 caps c116 c216 after 2 same 4.7 resistors r161 r162 2watt.
So check Vcc check pulse on pin 6 check Vee -50v.If all ok go to relay check voltages and also the c116 c216 and r161 r162 .
Also the chip monitor the voltage and curent who goes to j4 and j6 terminals(you find there also +15 -15v)

[Thermaltake]

Re: Alesis RA500 Amplifier

Can you show me on pictures I can't find any of those numbers beside mosfet or anything that you are saying I'm kind of new at this so...

[keeney123]

Re: Alesis RA500 Amplifier

So go to the schematic that rhomanski provided and go to page 14 find the TA3717p you will notice the marking U1, that is the chip number on the board. Pin1 usually has a indented circle on it. You can also google the pin out of TA3717P or google that number for the data sheet. That should start you off.

[budm]

Re: Alesis RA500 Amplifier

https://www.badcaps.net/forum/attach...0&d=1459801803
Where is J1 Female connector for the +/- 15V power supply for Op Amp? Unless you removed it to take the pictures, otherwise check and see if you do have +/- supplies.

[Thermaltake]

Re: Alesis RA500 Amplifier

https://www.badcaps.net/forum/attach...0&d=1459801803
Where is J1 Female connector for the +/- 15V power supply for Op Amp? Unless you removed it to take the pictures, otherwise check and see if you do have +/- supplies.

I removed it because my phone could not fit in case

[keeney123]

Re: Alesis RA500 Amplifier

If you go to your picture "1" of 9 at the bottom left in the middle of that section of the board is J1. The male connector is with the pins sticking out. The female connector would be the connector that would slide over the male pins.

[Thermaltake]

Re: Alesis RA500 Amplifier

Looks like relay is dead, need to replace it and it won't be that dong woo junk again for sure and see if anything else is dead.

[budm]

Re: Alesis RA500 Amplifier

Looks like relay is dead, need to replace it and it won't be that dong woo junk again for sure and see if anything else is dead.

Can you please explain as to the Relay is Dead? The rely coil gets the DCV but it does not click on? or the relay is turned on but the contacts are bad?

[Thermaltake]

Re: Alesis RA500 Amplifier

It looks like one leg is broken and plastic is kind of melted on it.

[Thermaltake]

Re: Alesis RA500 Amplifier

Amplifier is working again, relay is doing click now and working properly.

[keeney123]

Re: Alesis RA500 Amplifier

Alright success!

[Thermaltake]

Re: Alesis RA500 Amplifier

Thanks everyone for helping

[budm]

Re: Alesis RA500 Amplifier

Thanks for the follow-up.