Axiom Home Page Forums General Discussion Advice from Axiom Owners Power Amplifier Troubleshooting

I'm not to sure where it's appropriate to post this. But I need some advice and help, regarding my power amplifier woes.

I currently have a Rotel RMB-1095 power amplifier. I've used this amp on and off for many years.

I unfortunately had it lent out to a family member for a year or two. When it returned, I excitedly hooked it up to my system.

I'm running:

-m80's v3
-vp160 v3
-qs10's
-(2) cerwin vega cmx-12
-pioneer elite sc-57

In less then 5 months I hope to place an order for an ep800, but that's a separate topic

Well after hooking it up, it seems both the surround left and front left channels don't work. After triple checking all the hookups, no dice.

I'm in a rural area and there is no Rotel dealer anywhere remotely close. There is also no random electronic/stereo repair service to utilize.

The amount of money to ship that behemoth away, to have it trouble shooted and *maybe* fixed, is a complete unknown.

And here in lies my problem.

I'm looking at the ada-1250x5 amp...but it's going to be around the $3k mark.

Surely, it won't cost me that much to fix the Rotel?

Do you think it's worth it to take a gamble and ship it away?

Is their any technical troubleshooting and self repair possible? Anyone have an idea what is going on with it? Internal fuse possibly?

I would love it if someone could walk me through trying to self troubleshoot this thing. Because it's just sitting in a closet for the last year.

Any help, advice or opinions are most welcomed

I am so sorry to hear this. That Rotel is a real marvel.

Given that two left channels are gone, I'd say it's fuses or problems with a couple of the windings from one of the two massive toroid in that beast. Why it might be fuses or windings would be a good question. There's thermal and overload protection in the unit also which should prevent fuses or windings from opening. Maybe the thermal or overload protection for those two channels is pooched.

You can lift the cover and look for charred bits. See where the windings terminate and measure their output voltages. If windings are gone, that's a new toroid. Voltages in there are hazardous by the way so you better know how to work around them.

I'd definitely try to salvage that beast.

Thank you for the advice. Yeah I definitely would like to salvage it, I agree.

Even when it's been unplugged for a year, I have to worry about voltages?

I took the cover off...this is what it looks like. No noticeable charring

It has been over a year since I've tried hooking it up. Perhaps I should try again and rule out the obvious stuff?


It's such a huge project though to hook it up just to see it not work lol

Had a quick look at the schematic... there are two fuses protecting each channel ... might want to check those. (after waiting for the caps to discharge)

Ok awesome....thank you! It's been unplugged for a year ;), so its probably safe to poke around right?

I dont really know what I'm looking for tho. Not well versed with this stuff

Damn, that looks so sweet. I'd love to caress its innards. Since you have it open, check all fuses.

BTW, that's only half of it. The other half of it is hidden. There's another toroid under the naked one.

If you don't see anything obvious, plug it in and see if it works. Keep your nipples away from it though. You can feel nipple shocks in your 'nads and sphincter.

Sorry but nothing glaring stands out to me...what are the fuses, can you point them out to me?

K so update...plugged it in...

Obvious red lights for the left front and left rear, light up. So the amp is aware and is trying to tell me that something is shot.



So when I press power...there is a click and all lights go off...and then a second click and those two channel red lights come on.

In your picture ... if you look in the upper left there is a blue capacitor with a fuse next to it in a set of clips ... the fuse pops out of those clips. In the glass window you will see a wire going from on end to the other if it’s good. If that wire is broken it’s bad. You need to replace it with the same kind of fuse (look for writing on the metal ends). Note each fuse is probably close to a similar looking capacitor. You’ll find 4 fuses on the side boards and 2 on that front board

If no fuses are bad then it’s beyond your know how to fix ...
any competent repair guy should be able to fix this amp

Ok cool I see it! That's what I was looking for. I've replaced fuses in amps before but just couldnt find one in here. Thank you!

And there is one on the top right too...and both seem fine

Those LEDs are channel protection. I'm keeping my fingers crossed that it's only a fuse.

But you've helped me locate them. I looked for the others now next to the capacitors. I have to take this thing apart to see if they are blown...

But it's a start! Thank you

Btw I’ll bet the blown fuses will be on the left board When facing the front of the unit. Good luck and remember not to stick you fingers in till it’s been unplugged for a while.

Thank you so much for pointing me on the right direction. I figured they would be the ones on the left too! Good advice

So I can see...

2 on the front board...they are good.

There are 4 fuses on the right board and 4 fuses on the left board.

I will have to dismantle and unscrew things to get to them. Makes me nervous:/ looks complicated


But I can almost guarantee it's the fuses

Oh my God...if I can fix this I will be so happy lol

Thanks so much for your help guys. It's a good place to start

Dunno, but it might be easier to access those fuses by unscrewing the back cover.

Blow the dust out of it.

Totally what I was kinda thinking...I may need to unscrew the sides and heat sinks to gain access.

Ooooh I'm tickled pink..I sure hope I can fix this

Unfortunately I'm off to a 12 hour nightshift and it will have to wait

Thanks again you guys

No, don't do that! Those heat sinks are attached to the output transistors which are in turn soldered to the amp channel boards. Those heat sinks aren't going anywhere.

There is one more thing to check before you start taking this thing apart ... are you sure your speaker terminals are not shorted ... remove the connected speaker wire and look for any small stay wire which might be shorting the terminals. Then turn it on with out the speakers connected and see if you get the same results ...

Lol k fair enough. I'll slowly and methodically look at it closer on days off. I'll keep you updated

Yep, same results with no speakers or inputs hooked up. Just power to amp

Did you not just turn it on without any speakers connected?

Ok. The technical evaluation thus far is that something is pooched inside.

I can almost guarantee it's those fuses. I'm hopeful

Think you can access the fuses by just getting those wires out of the way. Gently disconnect them if you need to (note some connectors lock in place so you might have to squeeze it in the right spot to get it to release. keep track of where they go so you can put them back (note orientation ... don’t force them back in)

Don't be too hopeful. If it is a fuse, ask yourself what caused it to blow. It could be a problem downstream of the fuse. Maybe you'll replace the fuse only to have it blow again. Keep going though. You can add this to your list of adventures.

Hmm I dunno...it would be tough...perhaps I need a pair of longer tweezers or something to try and remove the fuses. They seem pretty buried down the side

I'll give it a go tho

I'll be attacking this tomorrow evening most likely

So hopeful to find a shot fuse or two lol

You need a scope to see down there without taking anything apart.

Or a dental mirror. And flashlight.

Maybe your cellphone camera?

Do you have an ohm meter?

Just unscrew the transformer if you need to

How do the capacitors look? Any signs of bulging on the top? I'm asking because they have the limiting life of the amp. Since it's about 15 years old, there is only so many years left before they will need replacement too.

You can get the ADA1250-5 for about $2600 if you can wait 21 days. Also, there will be a Black Friday sale around Thanksgiving where you will get another 12% off. If you have bought from Axiom before you have a loyal customer discount as well.

The other thing to consider it the ADA1500 is not an AB amp so it is very efficient and does not get that hot.

Although the Rotel RMB-1095 is a piece of work, I love my ADA1500 and I would recommend these amps to anyone.

Those leads on the transformer are likely only short enough to reach their terminations. Not sure therefore Chesser will be able to move it far enough out of the way.

Rich, can you tell on the schematic what all drives those LEDs? Just not sure if those LEDs would be on with a blown fuse.

That thing must have a ton of capacitance which I think may be hiding underneath. If you did send it in for repair, re-capping would be a good thing as Steve suggested.

I could be wrong but I think the way the ADAs are designed, you just change out the power supply instead of having to get into de-soldering and soldering. If it really is like that, it would be very righteous!

That amp is 2850 after loyalty, "I can wait" and black friday discounts and taxes to BC.

The capacitors look ok from what I could tell but I'll look closer when I'm back home tomorrow.

I would love to buy that amp and most likely will one day...but I figure, why spend 3k when I may only have to spend $20 on fuses? Even if it only lasts me a year or two...its worth it I figure

Hell...it would be worth it to spend upwards to 1000 to fix it reckon. Power ain't cheap.

What a beautiful beast!

I have an Anthem PVA 5, 5 channel amp. It worked perfectly for 15-20 years. I retired it for about a year, and when I fired it up, the fault protection red light came on, no output.

I took it to George Meyer repair in Los Angeles. They replaced 24 caps with 105C caps, for about $550. I still haven't hooked it up yet, but they tested it in front of me and I am hopeful it will work for at least another 15-20 years.

Good luck with yours. It is a beauty!

And unfortunately it's going to cost me an arm and a leg to ship it somewhere to be trouble shooter and fixed...

And if I rule out fuses...who knows what it needs.

I'm fairly confident the fuses are blown. The family member I lent it to was terrible about hooking wires up backwards...playing with hookups while all powers were on, etc.

I'm confident it's the fuses *crosses fingers*

A fuse is $0.26.

Hey Chesser. Sell that amp to 2x6.

Haha I'll be selling it to someone handy, most likely, if it's not the fuses

I'll also be selling my cerwin vega subs when I'm closer go buying the ep800

Jarring bass from 35 to 60Hz. At least that's how it sounded to me when I heard a CV sub. Maybe yours is different. If you like the CV, it will take you a while to get used to real bass from the 800v4 - saturating, linear, transparent, that permeates your soul.

Yep...they only go down to 32hz I believe

And no...I don't like them. Lol. It's better than nothing tho and I got them for free so I'm not complaining

I had Cerwin Vega subs and mains... In college.

I actually think their cls215(or is it xls?) are a decent tower for the money. My old man picked up a pair brand new for like 1600 bucks.

With proper amplification, those puppies rock and I like the sound of them.

My old man, in a double wide mobile home living room, is rocking out:

2 cerwin vega xls 215, 2 cerwin vega cmx 10 towers for rears, large cerwin vega center channel, (2) svs pc2000, emotiva xpa5 and now has just added transducers bolted to the frame of his couches

...Haha the pressurization of his small room is insane lol


My fondest party speaker days were with the cerwin vega d9's and then my paradigm monitor 90p's. I loved those speakers especially


Surprisingly enough, even though the 90P had their own amplifiers for the 8" drivers...

My m80's can outperform them in the bass and "party" performance.


I've owned so many speakers over the years and the m80 is the best speaker I've ever owned


I really.wish I jumped on the m100 introductory price when they were first unveiled. That's when I bought the m80. Kicking myself for not doing it. I want the m100 so bad one day

Chesser, not sure about your v3 but my v4 is in a different class than my decommissioned v2. You would love the 100s. The HP drivers and new tweeters make a big difference and I think big strides were made in the family of curves and crossovers between v3 and v4.

I hear you about the introductory pricing. I look at the price of the active LFR1100 now and I'm so glad I drank that Kool Aid a few weeks back that Ian's been trying to feed me all those years with the passive LFRs. His generosity also really helps with upgrades.

I had the D8's and the downward firing passive sub SW-12-B. But that was 30 years ago. And they are nothing compared to what you can get now.

Trust me. If you can spare it, save the time and hassle and just upgrade.

Sigh I cant afford it for some time now. But I plan to take advantage of the trade up program one day

Ian was so generous

So here is the story...

I put an order in for brand new m80v3...I got the dual binding posts added(I understand "buy" wiring concepts...but wanted it more for resale value to general public) and die cast baskets. At the time, after taxes and such...I believe they were around $1800.

Less than a month after buying them...they unveiled the m100 and if memory serves me correct, they were going for around 2200 or 2300 a pair.

I voiced my fan boy sadness I missed out lol. Ian private messaged me and offered me a full refund and payed shipping if I wanted to upgrade to m100.

I was going through hard financial times and couldnt think of a way to come up with 500-700 bucks for the difference.

I kick myself in the ass so hard for that.

But I have enjoyed my m80's immensely. They still surprise me and make me smile to this day

I can't wait to upgrade when I can


Ep800 first tho

Those LFR's make me drool

So jelly

I think the m100 is a better match for me overall but I would love to hear a pair of LFR's one day

As I sit on my dark deck, on this cold, Canadian evening, listening to the coyotes howling in yonder field, my heart has been warmed by Chesser's touching story.

Chess, those LFRs I'm getting are active. Do you know what that means?

30 years ago, I could barely afford my own shoes.

I should note, this is one of many reasons why I'm a dedicated and loyal customer for life now.

For awhile, I was really on the fence about getting my subwoofer needs through axiom.

I have spent many years watching the antics and interactions between audioholics, avsforums and axiom. I've been researching subwoofers since 2013. I understand the data, I understand the fan boy clicks...and while i was on the fence at one point, (considering pb16 ultras, psa, rhythmik, monolith, etc) I am no longer on the fence at all.

The biggest reason for that is how much I love all their other products AND the customer service and how generous they have been with me. I'd be willing to pay more than the competition just to support my fellow canadians. But with loyalty discounts, "I can wait" discounts, and free shipping...their prices are better too

And when I heard a user talk about preferring ep800 over the pb16ultra in actual blind listening tests...especially when I'm 70% music....that was even more reason.

Sticking with axiom is a no brainer for me

Proud to own their products

I look forward to getting the m100s one day

Yes indeed sir. It means you needed to spend a lot of money on amplification *smirk*

I've never heard speakers like that before. Very curious to experience the difference one day

Ian has been more than generous to his customers MC, so that does not surprise me at all. My wife and I are actually considering calling off USA Thanksgiving and instead going up to visit them to say thanks (and return the speakers that were part of the trade in that we have not gotten return labels for yet... I feel bad about that).

It's a 10 hour drive from my house though. I'd have to buy something...

Naturally Haha

Yeah, I hear their amazing customer service stories everywhere.

I can't wait to see the difference an ep800 makes to my system!

After that I'll be working on upgrading my mains

He hee hee. Yes sir!

Steve, can you pick me up? I want to also express my gratitude. I'm only a 32 hour drive away from you and another 29 hours to Axiom.

To active LFRs

Haha no. I dont have money to buy them let alone run them properly. The m100 is more of a party speaker/work horse and suits my needs and tastes a little better. Lol

The active lfr is a little too refined for this redneck

Dude, I have a wayyyyyy redder neck than you. Do you have a primitive weapons wall in your living room with edged tools accenting every table surface? I've got a tiger fork, Spetznaz shovel and a samburu spear within reach. How's that for redneck?

So if they're good for me, they're good for you.

It is impossible to not respect Axiom for what it has introduced to the market. The dedication has been nothing short of tremendous.

Haha..well u sold me. If I ever win the lottery a pair of active lfr in piano gloss rosewood are happening

I have a dagger on display, does that count? Lol

Or how about my whiskey dragon bottle holder on my coffee table? :p

I'm sure they are amazing.

But when I enjoy and push my axioms...I'm usually drunk and stoned, teetering the line where I first sense distortion, dialing it back a smidge...and letting it rage through eclectic playlists for hours...on extended stereo. Of course, every song is different so I have to play with the volume accordingly.

I dont see me getting lost in a 3d soundscape in the prime listening position. I want soul crushing output and muscle flex. And I'm sure the lfr can provide that in spades...but for my budget, the m100 seems a better fit


I've had people dancing in my living room to the m80s thumping and people cant believe when I tell them my subwoofers are off. Lol

They pound. And sound fantastic. And that's without external amplification to boot

It will probably move enough ... Plus I'll bet it's connected with spade connectors to the board ... think that thing was designed to be repaired.


PM me with your email and I'll send you the schematic ...

but to answer your question the protection IC is a MPC1237HA ...
Looks like the left front and left surround channels share one side board and the right Front and right surround the other. If either channel on the board has a problem that whole side will cut out and both lights will light. Don't really know much about this chip other then it disconnects the speakers if it detects dc offsets (It also disconnects them to prevent pops on power down) ... so ... if it's not the fuses it could be that the DC bias pots need to be cleaned ... of course you'd have to redo the bias adjustment if you cleaned them. Otherwise ... I'd let a tech look at it.

On the power supply there are 8 80V15000uF caps in there ... since you asked ...

According to Ian and Craig Chase, there really is no prime listening position with LFRs. There is stereo everywhere.

If you like pounding, the active 1100s will play more than 10 dB louder than the M100s; according to specs, they're good to 129 dB at 3 feet away. That basically means if you provided them with the 4400 Watts peak they're good for, at 3 feet away they'd blow off both of your 'nads while they liquified your brain. And they'd do it in 3D.

Haha well I'm definitely sold now

I wonder how much I could sell my son for on the chinese black market? *evil grin,)*

Oh .. if only one fuse is blown on a channel ... the lights will light
if both are blown ... not sure ...

My brain nearly melted as I was using my cellphone to look at the schematic Rich sent me.

There are four fuses in the left channels: 401 and 402 on the front and 501 and 502 on the surround. If any of those blow in any combination, then *both* left channel LEDs (D004 and D005) will come on. Don't ask me why Rotel didn't just use a single LED and call it "left channel protection" or protection chips for each channel (which admittedly would have complicated the design).

Those fuses I referred to above are likely buried as Rich mentioned before.

There could be other circumstances that lead to the LEDs being on besides blown fuses. For example, an internal fault in the protection chip.

Chess, when you plugged it back in, did you cycle the power switch?

BTW, in case it wasn't clear above, the entire left channel (and right channel), use a single protection circuit. So if one channel has been abused, both channels will be pooched.

I was just sharing this Rotel stuff vs. ADA with my eng homies. How times have changed. The ADA is so much simpler, more elegant in its design and execution. BTW, I've tried to kill my 1000 by abusing its outputs and have not been able to do so.

Boom!

Off to the store for fuses

Saaaweeet! Did you check all the fuses on that side? Which one was blown?

Make sure you get the exact same fuse. That one is a slow blow which is the way most engineers like it.

Nice Job ...

Buy a few off those fuses in case something else is wrong which re-blows the fuse ...
Or if you accidentally short your speaker leads again in the future ... (that protection IC protects the speaker ... the fuses are suppose to protect the amp ...)

When you get it working tape the extras to the inside cover so you have them when needed.

Actually I thought the opposite ... this is the simpler amp in that all the components are discrete (except for the op-amp and the speaker protection IC). You can really see how the thing works. Its very testable making it an easy piece to fix.

I have not looked at the ADA but I'm sure all the complexities are in the chips. Simpler in number of components more complex in understanding how it works. Most engineers just following the reference design and read up on each chip to attempt to understand what pin does what. Often the chip internals are a complete mystery, maybe you get a block diagram, although sometimes they give you the internal (simplified?) circuit (which usually is not that simple). Just MHO ...

It was just the one fuse.

I can't thank you all enough!


I now will be doing the tedious task of hooking it all up! Stay tuned!

You worked up the courage and did all the work, dude. Congrats. I'm glad you managed to salvage that hunk. Let's hope she doesn't blow!

thanks. *fingers crossed*

Rich, "simpler" was an over-simplification on my part. Andrew worked on that thing for 2 years. I'm sure others were helping him with it. And how many years before that were others working on it like Tom Cumberland? At least 8 or 10. So there's lots of history with it and one of the reasons I really dig Ian is because he had the intestinal fortitude and vision to know what is the right thing to do.

I'm not sure the ADAs use a chip other than for protection; I have not looked closely at the amp channel boards. I don't know where technology is today with regard to class D ICs. I know when I was involved with it in 2002, we had to build high current and high voltage channels with class D amps from scratch and it was a total nightmare because we couldn't achieve the required stability and EMC.

When I look at the guts of the ADA, it's simple in that you can readily see where everything is and it's easy to access. It should be straight-forward to replace the rectifier/filter board for example when it comes time to re-cap because it's readily accessible and has what looks like four screws. Ditto with the amp channel boards.

The insides of the ADA1500 look like this:

Look at that! It's so freakin' clean. Glorious, 105C caps...none of that 85C stuff that sissy engineers use. LOL!

I’d be very surprised if there was not a IC in there doing the heavy lifting. That said there is a lot more to coming up with a great design then just putting a chip on the board and following the reference. A great deal of work goes into getting all you can out of that chip. There is a lot of trail and error and trade offs which need to made ... and that’s just the amp board. Now you have support circuits like balance inputs along with the single ended ones and their interaction. Power supplies are a big deal. Problems like ripple on your supply caused by one amp may cause havoc in another. Keeping noise down Yada,yada,yada And then ya get into cases and case layout, testing to meet and pass government regulations ... documents on design, test, QA, build steps, user manuals ....

Wait did you say only a couple of years??

Well yeah a couple of years but remember that Ian and Andrew are the Chuck Norris and Chuck Norris Jr. of audio.

It's a hybrid amp so of course the real amplification is coming from chips. I can tell you this; I have owned dozens of amps in my life, this one takes the cake. It's so good I had the wife's approval to buy another one. Can it compare to a McIntosh? I don't know since I have never heard one. But to get this amount of amplification with a Mc would be 4x the price. I cannot believe it would be that much better.

I think the name "hybrid" is given to an amp that is a combination of tube and solid state. There are chips in there for sure but is there a single class D amp chip that each channel is built around or was the amp designed from "scratch"?

They are good value and it was the right product to bring to market particularly given the multi-driver active speakers.