Problem RA-100 Channel Switching / Power Soak issues

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scoot_001
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Location: Melbourne Australia

Problem RA-100 Channel Switching / Power Soak issues

Post by scoot_001 » Mon Sep 28, 2015 5:26 am

Hi All

A while ago I noticed that the foot switch would stop switching between channels or only go between clean and red modes. When I jiggle the cable the channels will switch back and forth, and then it will work for a while. In trying to work out what the issue was, I started to use the rear FSW jack. This worked fine for a while but at rehearsal last weekend, it started doing the same thing. I removed the foot switch cable from the amp and tried changing the channels manually and things went from bad to worse ...

All of a sudden, stuck on red mode - no sound was coming from the amp.
The Clean and Blue modes were still working fine (manual switching)

I then switched the attenuator off and all of a sudden the red channel works again. I tried this a few times with the same result. So, it is now

Attenuator on = no red channel
Attenuator off = all channels work - but bloody loud ;-)
Still no foot switching

So, I think I now have two problems and am not sure how to attack them.

For the foot switch issue, I wondered if the cable could be part of the issue so I will get another stereo cable and try it out
For the "no red channel" in Attenuator mode, I have no idea where to even start.

Has anyone seen this before
Any ideas of what to look at ?

I think it might be tome for a warrantee repair job ...

Any suggestions appreciated, thanks.

Mesa Boogie RA-100
2 x 1936 Cab
Couple 'a MM Lukes

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elvis
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Re: Problem RA-100 Channel Switching / Power Soak issues

Post by elvis » Mon Sep 28, 2015 11:59 am

Haven't heard of this, but one thing you might look for is that the attenuator makes it a lot hotter in the chassis. When the attenuator is on, the extra heat may make an intermittent connection totally open or shorted due to the metal expanding.
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scoot_001
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Location: Melbourne Australia

Re: Problem RA-100 Channel Switching / Power Soak issues

Post by scoot_001 » Mon Sep 28, 2015 3:37 pm

elvis wrote:Haven't heard of this, but one thing you might look for is that the attenuator makes it a lot hotter in the chassis. When the attenuator is on, the extra heat may make an intermittent connection totally open or shorted due to the metal expanding.

Hi Elvis - thanks for the info. I do run the multi-soak all of the time. I also run the fan on hi just to be sure. In Melbourne Australia - it is early spring so temperatures are pretty mild. Sunday arvo when it happened it was a nice 21 degrees so I suspect this is not the culprit. I will however run it up next weekend when I am back from a business trip.

cheers.

Mesa Boogie RA-100
2 x 1936 Cab
Couple 'a MM Lukes

bandit2013
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Re: Problem RA-100 Channel Switching / Power Soak issues

Post by bandit2013 » Tue Oct 13, 2015 6:35 pm

If there is nothing wrong with the cable, there may be a loose connection somewhere in the amp. I believe this one also has the ribbon cables like all of the other packed amps. You could reseat the ribbon cable that connects to the PCB. Use caution as there may still be high voltages stored in the power supply capacitors. It has been a while since I removed the RA100 Chassis from the shell. Tubes are so easy to access there has not been any need to do this.

scoot_001
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Re: Problem RA-100 Channel Switching / Power Soak issues

Post by scoot_001 » Mon Oct 26, 2015 2:59 am

Thanks for your replies. The amp has been off at the authorised repairer for a few weeks now. Haven't heard anything back yet so I guess it wasn't straight forward. I will let you all know what it turned out being - just in case others on the forum have similar issues.

Mesa Boogie RA-100
2 x 1936 Cab
Couple 'a MM Lukes

WorldDemise
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Re: Problem RA-100 Channel Switching / Power Soak issues

Post by WorldDemise » Thu Jan 04, 2018 12:24 am

I came across your thread as i am having the same issue with the foot switch on my RA 100 . I was wondering if you ever got to the bottom of the problems . mine is doing the exact same thing . I just ordered a new foot switch thinking it might be that because i really haven't been taking care of it properly . i leave it on the floor swilling beer n what not on it allot . I can switch it manually just fine but i would like to have it work properly . Any help is greatly appreciated thank you .

scoot_001
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Re: Problem RA-100 Channel Switching / Power Soak issues

Post by scoot_001 » Thu Jan 04, 2018 6:13 am

WorldDemise wrote:I came across your thread as i am having the same issue with the foot switch on my RA 100 . I was wondering if you ever got to the bottom of the problems . mine is doing the exact same thing . I just ordered a new foot switch thinking it might be that because i really haven't been taking care of it properly . i leave it on the floor swilling beer n what not on it allot . I can switch it manually just fine but i would like to have it work properly . Any help is greatly appreciated thank you .

Well actually, believe it or not, it turned out to be the dang cable. He resoldered all the joints and it has been faultless ever since. I could not believe it. I checked hte cable myself and everything seemed fine not to mention that the cable worked fine in the back socked - just not in hte front socket for about 5 months. Then finally - not at all. Mind you, it took him 5 months to do that (and lots of phone calls ... )

Good luck and regards.

Mesa Boogie RA-100
2 x 1936 Cab
Couple 'a MM Lukes

bandit2013
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Re: Problem RA-100 Channel Switching / Power Soak issues

Post by bandit2013 » Tue Feb 13, 2018 7:11 am

This does not explain why you could not get the Hi gain channel to work with the power attenuator with the manual switch (unless you had the cable plugged into the amp connected to the footswitch). Sometimes poking and prodding around low current circuits such as the channel wires that may be attached to the jacks may compress the solder joint enough if there was a weak joint to start with. That will eventually return to the fail state.

If you try the manual approach pull the footswitch cable from the amp. \


Still puzzled as to why the red channel had no sound with the attenuator on, Almost sounds like the strobe mute was hanging up.

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