Help with intermittent Alesis RA-150

[kevwright]

Follow up to above - The relays in both amps were faulty. During a test run, the slightest pressure on the top of the relay box would cause the channels to switch on and off. Closer inspection revealed that the contact faces were no longer meeting squarely.
New relays ordered from RS and will fit Monday. Should cure things.
K

[kevwright]

Update - both amps now fitted with new relays and both as good as new. No crackles, drop-outs or dead channels and no more amp or speaker thumping! Great!
Total cost - £8.50 for the two relays from RS.
K

[J M Fahey]

Boy, they do fit *cheap* OEM relays, don't they?
I use the cheapest (1U$) chinese generic which are available everywhere, with no problems at all, they must special order some even cheaper ones.
Oh well.
Congratulations.

[docSanchez]

Dude, that is awesome. Could you point me towards the relays you bought? I don't know how to read relay specs or replace one.

[kevwright]

Hi doc,
I'm in the UK and ordered mine from RS. See HERE for item specs. That should give you an idea of what you need to find at your local stores.
Its just a 12V 10 Amp DPDT power relay.

Regards,
K

[docSanchez]

This is exceedingly late and not at all intended as a bump, but I did finally get around to buying a 24VDC relay and it worked like a charm! My amp now hums merrily along without any ugly cuts or breaks. The stock relay either has really poor construction or the circuit wasn't providing a solid 30VDC for the relay to work with... regardless PROBLEM SOLVED! CASE CLOSED! THANK YOU ALL SO MUCH FOR THE HELP!

[km6xz]

I was not a member when you had the problem but for the last year that Alesis was around(the original company) my shop did all their factory repairs, if a store, shop or customer shipped it to the "factory" it was put on a pallet and sent to me.
So we fixed our fair share of these. 60% of all problems even with new store stock were these relays.

When looking or intermittent problems usually it is either sit and wait for the problem to occur or go induce it by mechanical shock, vibration, flexing, heating etc. Most intermittent are cracked solder joints or oxidized connectors/switches/jacks/relays. In the old days a relay was intended to be opened and the contacts polished or burnished during preventative maintenance. Now, they are so cheap that replacing them is the usual fix. Arcing can make the contacts rough and pitted which corrode or oxidize quickly. Having the relay make or break with high signal and load connected is a sure way to pit relay contacts. Turn on or off the amp with the signal down and it will happen less.

Overall, the RA series was not a terrible amp line, it worked and met spec. The relays were a weakness but even that problem was not in a high number of units until years later when they would all be pitted to some degree. In the daily pallet(s) arriving from SoCal for "factory" repairs, we would get maybe 1 amp, 15-20 ADATs or XTs, several mixers and some monitors with blown drivers and a couple keyboards. Tucked into gaps between boxes were several nano-verbs or other in that line.
So overall, the RA-x00 amps did not have a high defect rate.

[diyjoy]

That 7317 is used in Samson and HArtke products. The chip is rarely at fault, and if both chanels are cutting out, it is EXTREMELY unlikey that two relays have the exact same intermittant problem that occurs at the same time.

As JM suggests, monitor the relay coil voltage. If it is dropping out then the relay is just doing its job. And we then find out what is dropping it.

First, I'd replace the two input related caps, C413,414 on your print. And C416 is suspect.

You can also apply a signal and monitor the amp output bus on the amp side of the relay. If the signal remains there when the relay drops out, then it would seem that the amp was OK. If the signal disappears even there, then teh relay may be being controlled for a legit reason.

My RA-150 has same symptoms but the problem may be somewhere else. So far, I replaced the relay with Radio Shack 12VDC Coil DPDT, C413, C414, C416 and BA4560 mentioned here but to no avail. The relay still trips after about 15 minutes. By the way, C403 and C404 get hot, if that means something...

Any other suggestions? Thanks in advance.

[52 Bill]

My RA-150 has same symptoms but the problem may be somewhere else. So far, I replaced the relay with Radio Shack 12VDC Coil DPDT, C413, C414, C416 and BA4560 mentioned here but to no avail. The relay still trips after about 15 minutes. By the way, C403 and C404 get hot, if that means something...

Any other suggestions? Thanks in advance.

Welcome to the place. Even though your amp is showing similar symptoms, the real cause may be something entirely different.

If the relay is actually turning off, then you need to monitor the amp's voltages to it to see if the relay is suspect or if the protection circuit is kicking in due to a problem with one of the power amps. Seeing as you have replaced the relay, I will assume the problem is somewhere else.

Any cap that gets hot is not a good sign. Are the caps really getting hot or are they warm because they are close to the zener diodes and dropping resistors? These caps are part of the low voltage supply and if there is a problem with them it could be the cause the drop out, but you won't know until you start monitoring the amp.

[diyjoy]

Thank you for the welcome.

This is how it went.
1. I noticed crackle from left channel when it's on and then about 15 minutes later the relay trips.
2. I replaced the relay and the crackle is gone but it still trips after about 15 minutes.
3. I replaced caps mentioned above and IC (BA4560) on driver board of both channels but it still trips after about 15 minutes.
4. I disconnected left channel power supply plugs (J3-B & J4-B) and it trips after about 15 minutes.
5. I disconnected right channel power supply plugs (J5-A & J6-A) and reconnected left channel and it trips after about 15 minutes.
6. I disconnected both channel power supply plugs and it trips immediately, then flickers on and off.
7. During all these steps, C403 & 404 which are part of +-15 VDC supply, get too hot to touch on their own.

[MarkusBass]

Instead of such tests I suggest checking what voltage you have on the capacitors. They are in parallel to two Zener diodes: Z1 and Z2 (both 15V). Maybe they failed and the voltage in much higher than expected. Also make sure that the voltage selector 115/230V is in correct position.

Mark

[diyjoy]

Instead of such tests I suggest checking what voltage you have on the capacitors. They are in parallel to two Zener diodes: Z1 and Z2 (both 15V). Maybe they failed and the voltage in much higher than expected. Also make sure that the voltage selector 115/230V is in correct position.

Mark

It's set at 115V.
I checked voltages at Z1, Z2 and they start out with +- 15VDC, then slowly rise until +-17VDC when the relay trips. Possibly a stability problem somewhere?

[jacesyntax]

resistors

Hello everyone

I have an Alesis RA-150 that has been getting cranky over the last couple of months. At first the signal would just drop out for a split second and then come back, but now the signal drops out randomly and doesn't come back on unless I give the unit a light smack or if I crank the volume knob or input signal way up. Sometimes it is just one of the channels; sometimes they both go out. Sometimes they drop way down in volume and are distorted. I've also noticed the problems tend to occur more frequently the longer the unit has been powered on.

From what I have read, the problem is with the relay on the power supply board. Unfortunately, all my electronics experience is with tube amps and guitar pedals, so I don't know how to replace the relay.

I have the service manual for the RA-500, which has the same PCB:
[ATTACH]11250[/ATTACH]

The schematic is on page 16 for the power supply board (where the relay is) and page 17 shows the PCB layout (the relay being in the upper right corner)

Another things I had noticed when this problem was just beginning was that the resistors R401 and R402 had begun to burn slightly, so I replaced both of them with a 5W version instead of the stock 1W.

Finally, I have a picture of the relay itself:
[ATTACH=CONFIG]11251[/ATTACH]

If anyone could point me to a replacement relay that won't blow (I think from what I've read on the internet that a higher amp rating does the trick) that would be just the greatest.

If the relay isn't the problem, then... well, I'm going to need quite a bit more help then

Thank you all very much in advance for your assistance and advice: it is greatly appreciated.

I need to replace R401 and R402 resistors but I dont know where you order them or what power they need to be. I just know they need replaced. any help would be appreciated. Thanks.

[52 Bill]

I need to replace R401 and R402 resistors but I dont know where you order them or what power they need to be. I just know they need replaced. any help would be appreciated. Thanks.

Welcome to the place.

It might be better for you to start a new thread for your amp, this one has been here for a while and it might get confusing.

Why do you need to replace R401 and R402?

[pebell]

I have an RA 150 and a RA 300 and both amps are giving a similar problem.
The 300 is the older of the two and this sometimes cuts out either channel. If a hit the amp, it sometimes comes back on. Sometimes its just distorted in one channel. Or if I crank the volume up for a split second, this brings the channel back.
The 150 only has this problem in the left side. Will just cut off randomly and even a light tap on the bass speaker cone (I know, shouldn't really do it) will bring the channel back. Or a firm slap on the amp itself.
Must be a common problem with these Alesis amps. Will look at the relays and report back.
K

Thank you so much for mentioning that tapping the speaker cone will also bring the channel back. I too suffer from dropping channel(s), and this one symptom was why so far I hestitated blaming the amp (RA300) for it - figured it might be my beloved Dynaudio BM 6's that were at fault. But literally everything you mention, from slapping it, cranking the volume up, to tapping the speaker cone, mine does as well. I'll order a new relay and attempt to replace it. I'm not really savy when it comes to electronic circuitry, but thank god I know how to solder (thanks dad ;-D).