RB 1080 Internal Fuse blowing

[Aussie Geoff]

Hi,

I have a new RB 1080 that has blown it's one of internal fuses (the ones between the power supply and the output stage) twice for the left channel. This is my second unit, the other blew the right channel fuses. Once replaced (with 6.3Amp slow blow fuses. the amp is fine again).

I (and the dealer) are at a loss to think why. It happens at lowish volumes (10b or more below reference). I have banana plugs on the speaker cables etc and there is no short. My speakers have a relatively benign impedance curve averaging 6 ohm.

Has anyone else experienced the same thing?

If so what did you do about it?

Thanks

Geoff Costello

[Andrew Pratt]

Have you tried different interconnects? It might be possible the problems on the IC side not the output side but I'm not sure if that could cause a fuse to go.

[aud19]

That is strange :? I mean it is rare but possible you could have got two bad units especially if the they were from the same shipment to the same dealer... You could always ask him to order you a new one direct from Rotel if that's the case...

Other than that you have any electrician friends who might be able to help you trouble-shoot a possible electrical problem...?

You could try the standard "heavy duty extension cord to another part of the house on a seperate circuit" theory to see if it might be that outlet....?

Hopefully some more people will chime in with suggestions... Good luck and keep us updated

Jason




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[Leef DaLucky]

I was wondering if this topic might eventually pop up.
My bud has the exact same problem.
Fuses go all the time in his.
He has just resigned to never turn off the amp, and when he does blow one he has about 20 spares to cover it.
no way to listen to music though, if you ask me.
This is his second as well, and theyre still blowing.
Usually at high volumes too.
if you find out the answer to this please let me know ASAP.

his system:
RB-1080 (might be B stock)
RC-1070
Paradigm Studio 100's V2

I wish you the best of luck and maybe we can get this solved!
Its seriously hindering our Genesis enjoyment.

Cheers,
L.




-----------------------------------
"Some days yer the Dog, others yer the Hydrant."

[Aussie Geoff]

Thanks,

It's good to see someone else with the same problem.

I have spoken to the Australian Rotel Distributors International Dynamics who have suggested two things to try:

• Amplifier Bias Current - can be different between the channels causing a fuse to blow. They have offered to check this and reset if needed.
• Speaker Cables - Can cause problems in very rare cases in combination with specific speakers.

Given that I have had two amplifiers I am trying the speaker cable option first and will let you know how this goes.

My (very helpful) store (Vince Ross Audio World) has also offered me a 3rd amplifier but I don't want to do this just yet until I have eliminated other things.

Geoff Costello

[ROb Aspeling]

Geoff,

I am having exactly the same problem. My dealer swopped out the first amp but the second amp is doing exactly the same. Rotel's agents in South Africa currently have my amp as well as my speaker. They believe that there is a short somewhere in the speaker. ( I never had this problem with my previous Kenwood amp before I upgraded to the 1080). I will keep you posted when I get something from them.

[steveB]

Hi Geoff

I have had no problem with my 1080( latest version) to date , but I have a friend who has a 1080 as well and a few days after he hooked it up one of the channels went dead. Does this mean he has blown a fuse ?
Is there a seperate fuse per channel....He has taken it back to Rotel so I dont know what the problem was.

Cheers
steveB

[Aussie Geoff]

Hi,

Thanks for the feedback and support.

An update. I've had several visits to the (very helpful) store today to work on this:

1) My amp was checked and no has bias current issue (only drawing 24ma etc. and running very cool).

2) I have changed the speaker cables for all my front three speakers and will run for a while to see if that fixes it (no one is particularly hopeful that it will but they believe it is worth trying).

3) They have not had this happen to anyone else in Perth with a 1080 so aren't sure what to make of it. We have some theories from the local (perplexed) Rotel repair agent that may help:

• Mine seems to happen at turn on so It could be driven by the 12v trigger this powers up the RB-1080 power supply capacitors etc before releasing a relay to allow power to the amp circuits. (My previous 1080 worked perfectly until after I got the 1098 with the 12v triggers)
• Loose Power cable (I now have a new one upgraded from the standard Rotel issue which is a little loose in the socket) However no one is very hopeful re this being the cause - however a better quality cable has to be a good thing!
• A hypothetical high or low frequency signal from the pre-pro just at turn on which is is coming through as the 1080 is triggered on. Again this is very theoretical and unproven (especially since before I got the 12V trigger cables I used to leave the 1080 on all the time - in which case the hypothetical signal would have gone straight to a fully working amp and (presumably) the speakers!

If it blows again with the new speaker cable I have agreed to try turning of the 12V trigger and just leaving it on (the new chassis 1080 only draws 36w at idle as tested today so could well be best left on anyway)

So some queries for the others with blown amps or friends with blown amps:

• Do they use the 12v Trigger?
• Did theirs blow at turn on or during normal use?

The answers either way should help with the diagnosis for us all

SteveB - Re your query - yes the RB-1080 amp has two separate fuses inside for each channel positive and negative power supply lead into the amplifier stage. These are T6.3A slow blow fuses that would normally need to draw 300-400W plus to blow! They are not “user replaceable” and are intended as a line of defence against short circuits speakers or cables or (being slow blow) very long term overdriving of the amp!

Regards

Geoff Costello

[Leef DaLucky]

Hi Geoff, i'll ask him this weekend.
I know in the past, its been subtle and he turns on the CD player only to find that the stereo is only broadcasting one channel.
I'll ask about the 12v trigger as well.
as far as i know he's using Monster z1 biwired cable for speakers and some Transparents for IC's (just in case this sounds familiar)

I always wondered if this problem is due to some degree from it being a B stock product. The Stereo guys maintain that they have had no problems with them (either of the 2 amps we've tried) in the store, but i highly doubt they put it through the test like we do when playing some old genesis.

cheers,
L.
P.S. someone at the store suggested it might be his speakers as well, some kinda short. i dunno too much about that scenario though. Doesn't seem too likely.




-----------------------------------
"Some days yer the Dog, others yer the Hydrant."

[ROb Aspeling]

Some feedback.

The local Rotel guys replaced the fuse and did all the tests that could be done. They found the 1080 to be within factory specification and nothing wrong with it. They shifted the blame onto the speaker (Jamo 707). The speaker has been sent to the Jamo guys and they subsequently stripped the speaker right down to the last component, and guess what - there is nothing wrong with my speaker. It is also 100% within factory specification. I will later today have both the Rotel guys and the Jamo guys at my house to try and resolve this problem. (That's what you call service) Will keep you posted!

[Aussie Geoff]

Rob,

Can you tell me:
1) Do you use the 12V trigger?
2) Does this happen at turn-on?

Geoff Costello

[ROb Aspeling]

Geoff

In answer to your questions - Yes, I do use a trigger from the RSP1066 to power up the 1080. I then use a trigger from the 1080 to the 1060DVD. My problem did at first seem to happen at power up but then started happening while I was listening to a CD or watching a movie.

As mentioned, we reinstalled everything yesterday. The Jamo guys installed new electronics into my speaker (ie crossover etc) just in case eventhough they found nothing wrong with the old one. Apparently the design of the 1080 is that of using a balanced concept and therefore the amp is very sensitive to the speakers' electronics. Well, after 6 hours of pounding, music and movies, as well as powering up and then down using the trigger umpteen times, it seems as if my problem has gone away. Rotel only replaced the fuses in my amp so the fault must have been with the speaker. I changed nothing else. I used the same interconnects as well as speaker cables (I bi-wire).
Geoff, try using another speaker on the channel that is blowing. Maybe you have the same problem as I had. Speaker seems fine but has something that the 1080 does not like. BTW, the Rotel guys explained to me that the fuses are only on the output stage and therefore form a circuit with the speakers - they do not believe that the fuses can blow from an input signal nor the trigger. You must also be sure that the fuses used are "slow blow".

[Leef DaLucky]

Hmm i was talking to my bud yesterday about this again.
Here's what he said:

a) the fuse has blown, both on power up and while playing.
b) He's disabled the 12v trigger and started leaving the 1080 on all the time.
c) Hasn't blown since disbled this.

That last part is interesting, rob, as i know he has gone out and bought RS "Fast blow" fuses instead of slow blow, as far as replacement parts go.
I think the original fuse in the 1080 was a fast blow.
I wonder if this might be contributing.
Where did you get the info on slow blow fuses?

L.




-----------------------------------
"Some days yer the Dog, others yer the Hydrant."

[ROb Aspeling]

The technician at Rotel told me about the slow blow fuses. Apparently these are fitted at the factory and are imperative in the 1080.

[Marcel54]

Hello,

I'm new on the forum, but I had the same problem. I have a complete Rotel set up (1098, 1095, 1080, 1060) and I connected them through the 12V triggers. The fuses on the 1080 blew and during playing the 1098 was shutting down the 1060, 1080 and 1095. After investigation by the dealer it was concluded that the 12V triggers in combination with a low frequency emission were reponsible for the problem. After I disconnected the 12V triggers (that of course is a pity because I cannot use the system as wanted) my problems were gone for good.

Marcel

[eelco74]

I must say I am pretty amazed. I have a RB-981 for several years now. It has driven some horrible speakers now. Including a rather large transmission line system with a pretty low impedance (up to 1,5 ohms).

1 channel of my RB-985MkII is driving my subwoofer and has to work pretty hard.

However I have never had any fuse blown during operation.

Very strange that it might have to do with the 12V trigger.

[Aussie Geoff]

Leef,

The right fuses are 20mm T6.3A which are time (or slow blow) 6.3A fuses. These support 300-400W continuous for each channel.

Fast blow fuses, or fuses of a lesser rating will blow sooner. The amplifier risks damage if any more powerful fuses are used.

Geoff Coztello

[Aussie Geoff]

Marcel,

I am on a slow diagnosis path with my dealer. Current step is to get a stable (non blowing) set-up. So far (2 weeks) running without the trgger on (wire conected but trigger switch on the 1080 turned off) and we've had no problems. I'll give it a couple more weeks and then try the trigger again - I bet it starts blowing again, so I suspect your dealer is right!!!

Geoff Costello

[steveB]

Well , you can add my 1080 to the list .
My left channel went dead after switching on via
a 12V trigger .....I'm hoping its just the fuse and a one off.


SteveB.

[Aussie Geoff]

Steve,

Interesting... The fuses you need for one side are 2 of 5mm x 20mm T6.3A Fuses (Slow blow, 6.3 amp in metal capped glass tubes). Your dealer can provide them, fit them for you and (if you like and they are comfortable with it) and show you where they are etc.

1) What do you use to drive your RB-1080?
2) What speakers are you driving?
3) Are the speakers bi-wired or single wired?
4) Is the RB-1080 a new model (with the twin speaker binding posts)?

I am interested in trying to eliminate or prove one of three different theories that are being considered:

• That it is the combination of the RPS-1098 and Trigger that does it).
• That it is the combination of speaker cable, impedence and turn on Trigger that does it.
• That it is just the 12V trigger in the new models
  
  Geoff Costello

[steveB]

Hi Geoff ,

I feed the 1080 from my RSX 1065 , it is connected via Van Den Hul D102III interconects . My speakers are B&W 604S3's and the speaker cable is QED silver anniversary biwire.
My friend's blew about 1 month ago , his is connected to an RSX 1055 and B&W604S3's. Mine had a 12V trigger , his didn't. Mine are biwired , his are not . Both are new models , from the same dealer.

I kinda feel it may be a design flaw , I'll see what Int.Dyn. have to say.

Cheers

SteveB.

[Aussie Geoff]

SteveB,

Interesting. I have contacted International Dymanics 3 weeks ago over this and spoke to them and (surprise) at the time they had never heard of it - claimed no other cases etc but were helpful re agreeing a path to diagnose the problem, offered replacement unit etc. - hence my post in this forum (since I'd already had one replacement unit!).

When you contact them I'd be interested (surprised!) if they again try and say "never heard of it"!. Still you never know...

When you find an answer - let us all know. So far (for me) no Trigger and new speaker cables has done the trick - but I'll need another weeks runing to be sure.

Geoff Costello

[Al K]

Using 12v trigger to power RB1080 with RSX1055 and so far no problem With new RB1080. I'll let you know how things go after I get some additional mileage on the RB1080!

[Al K]

Aussie,

Well, things are still going well with my 1080! I have switched it on using 12V trigger dozens of times with no problems. Using RSX 1055/W 12V trigger connection to RB1080. I use Apature interconnects and the speakers are B&W 603 S3 up front/W Tara cables.

AL

[steveB]

Got my baby back and it works fine.
No one knows what is going on , Rotel told me that they dont
know of any problem with the 1080 . and my dealer thinks it
was a power spike ( which is BS ) .
I just hope I dont have to disconnect it all again.

Cheers

SteveB

[ROb Aspeling]

Oh well, I thought it was too good to be true. I powered up my system last night to watch a movie with some friends and yes, you guessed it, the left channel was blown again. Luckily I stocked up on the fuses just in case and was able to replace the blown one. I have now disconnected the trigger and will leave the amp permanently on. I've done this before with other amps without any ill effects. It seems to me that it's got something to do with the trigger eventhough the Rotel guys told me this was impossible. :cry:

[ROb Aspeling]

Oh well, I thought it was too good to be true. I powered up my system last night to watch a movie with some friends and yes, you guessed it, the left channel was blown again. Luckily I stocked up on the fuses just in case and was able to replace the blown one. I have now disconnected the trigger and will leave the amp permanently on. I've done this before with other amps without any ill effects. It seems to me that it's got something to do with the trigger eventhough the Rotel guys told me this was impossible. :cry:

[Aussie Geoff]

Rob,

I think you are right re the triggers. I have run mine for 1 month turned on 24 x 7 and with no trigger connection = No blown fuses. To test a theory that it was some kind of turn on pulse comming from the RSP-1098 I have now run for several weeks with the RSP-1098 trigger connected but the RB-1080 not set to be trigger activated = Still no blown fuses.

The next step (which I am hesitant to take) is to reactivate the trigger setting on the RB-1080....

Geoff

[aud19]

The next step (which I am hesitant to take) is to reactivate the trigger setting on the RB-1080....

Unfortunately it looks like that's the only way to narrow down the cause.. :?

Good luck Geoff...

Jason




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[ropotamo]

Hi gentlemens,

two days ago I updated flash and upgrade my 1098 to 2.1.1 From that time there is no sound from my 1080 to my fronts B&W 803. I did the same upgrade procedur several times with the same result all the time. I was blaming new soft but this evening I hooked fronts to 1095 and everything is ok. That means there is something wrong with 1080. I have checked fuse on the back and this is ok. Unit is still switching on (through trigger!) and it seems to be working like before, but the sound has gone. It is a new 1080 unit, it was single wired. Interconnects and speaker cables are both Audioquest. Till update everything was alright. How should I check internal fuses?

[ropotamo]

Hi gentlemens,

two days ago I updated flash and upgrade my 1098 to 2.1.1 From that time there is no sound from my 1080 to my fronts B&W 803. I did the same upgrade procedur several times with the same result all the time. I was blaming new soft but this evening I hooked fronts to 1095 and everything is ok. That means there is something wrong with 1080. I have checked fuse on the back and this is ok. Unit is still switching on (through trigger!) and it seems to be working like before, but the sound has gone. It is a new 1080 unit, it was single wired. Interconnects and speaker cables are both Audioquest. Till update everything was alright. How should I check internal fuses?

[Azeke]

I have also just blown the left channel on my RB-1080, I am utilizing the 12v trigger on my RSP-1098. I have replaced the internal fuse on the left channel of the RB-1080. Needless to say, I will not connect the 12v trigger this weekend, perhaps I will during the week to test the 12v trigger theory. I will keep you all posted.

Regards,

Azeke

[Adz]

I just sent this entire thread to Mike Sheehan at Rotel. Andrew - Is he the VP of Rotel for North America you mentioned in another post going on right now?

I also have had nothing but trouble with my 8 month old RB-1080 since investing in the Rotel brand as my first step into high-end separates -- I've blown out both the left and right channel amps. Rotel refuses to exchange it for a new one unless they are satisfied that's it a flaw in my 1080 as opposed to something else which is probably impossible to assess (my dealer is pretty much useless and extremely unhelpful but that's for another thread currently going on). In fact, the last time it was repaired and sent back to me, I hooked it up to my old pioneer elite system which has of course different speakers and cables than my current Rotel system and guess what -- within a couple of days, the amp's channel blew out again. Oh and did I fail to mention that while it was hooked up to my old Pioneer system, my less than one year old speakers in the Rotel system were out having new crossovers put in to address the potential that it was the speakers causing the 1080 problems (which now we know it isn't). Not much else to say.




Adz

[Stevebez]

Well I am feeling a bit of buyers remorse here after reading this thread and just having bought a RB1080 (used) to complement my 1075 and 1066.

Two things :-

It seems there is an older version of the 1080 and a "newer" version. How do you distinguish between the two and what has been changed?

Has the fuse blowing issue been resolved? Perhaps its got something to do with the amps very high damping factor. The internal resistance of the amp is soo low that a feedback current from the speaker pops the fuse. This may occur at startup,but not not exclusively so. The rebond current from the speakers may spike sufficiently to blow the fuse on the 1080, but in the 1075 for example the internal resistance is large enough to avoid this.

This leads me to believe its possibly a design flaw - the internal damping of the amp has been designed too low for the internal circuit capacity.

Is there anyone out there who has a 1080 and NOT had any problems...?!!!! 8O

Rgds Steve.

[Olaf]

Dear All,

Hesitant to answer, but yes I have an RB-1080 (old model) and have had no problems so far.

I am not using a trigger connection between my RSP-1098 and RB-1080 but instead use the RSP-1098 trigger to power on the RLC-1050 which in turn provides power to my components.

I am using AudioQuest Slate bi-wire cables, my speakers are Phonar P400 4 Ohm, and I am using AudioQuest King Cobra interconnects.

Having read the entire thread it sounds like a trigger problem to me,

Regards,
Olaf

[Aussie Geoff]

Stevebez,

From the long history of RB-1080 threads etc in this and other forums most people have had no problems with the RB-1080 - fuses, hum or otherwise. Remember the "older model" RB-1080 you have has won several awards etc and had great reviews like this one here.

Now the newer series 3 RB-1080 has some difference components (heat sinks extrusions, speaker binding posts etc. You can pick it by the dual WBT (clear covered) speaker binding posts on the rear panel. However if yours works fine you are not loosing anything.

Some RB-1080s (being grounded 3 pin amplifiers) have exposed ground loops in the system (usually from cable TV) - as would any 3 pin amplifier. This is usually fixed with a ground loop isolator or better earthing on the cable box. A very few people (I was one) got problems with noise on the mains coming through to the amplifier - this was fixed by a cheater plug and is also fixed with the newer series 3 models changed ground scheme (no more cheater plug for me!

The fuse blowing issue seems to affect a very few users. For me it is related to the turning off and on with the triggers and my main speakers - so I just don't use them. It happenned with both my old model RB-1080 and the new one - so that won't help. Your explanation re damping factors etc sounds right - since most people who use triggers have no problems - it may well be just certain speaker / speaker cable combinations that trigger the fuses at turn on (my speaker has virtually no crossover in it - just mainly a capacitor for the tweeter and it's impedance, while a nominate 6 ohms drops to 4 in the bass region.

The RB-1080 sounds great. Enjoy the sound. If you are unlucky enough to blow fuses - loose the triggers.....

Hope this helps

Geoff

[Stevebez]

Thx Geoff!

Well looking forward to get delivery - hopefully before easter. How can I determine from S/N or otherwise which series the amp is ? Its apparently 18mnths -2yrs old.

Rgds Steve

[JonLeach]

Hi All

i'm rather concerned i have bought a dud, sounds great all the same.

i have a RSP1066/2x981'sRB1080 (Used) old model i think?? and leave them all switched on. i have had no problems what so ever. i always have all my hifi switched on all the time.

Jon

[JonLeach]

Hi All

i'm rather concerned i have bought a dud, sounds great all the same.

i have a RSP1066/2x981'sRB1080 (Used) old model i think?? and leave them all switched on. i have had no problems what so ever. i always have all my hifi switched on all the time.

Jon

[Stevebez]

My 1080 has not arived yet ... seems like only after easter now

Sorry to pester but anyone know how to differentiate between the different versions of the amp ? And exactly what has been changed in the design?

Thx
Steve

[Azeke]

Steve,

The newer RB 1080's have four clear binding post in the rear (for biamping purposes). Some have said that the ground plane issue has been rectified with the newer version (this is of course is unsubstatiated). I have owned my 1080 for approximately 4 months now and have had the fuse blowing issue (once), of course this can also be related to the fact I was repositioning my speakers with the amps on (lesson learned), the amps to seem to be very sensitive. I have since hooked my 12V trigger and not a peep (ground noise) from the amp or speakers.

Hope this helps,

Azeke

[Azeke]

Well, I purchased a new DVD player (Pioneer DV-59AVi) to replace my old Panasonic C-320, connected all cables, including the analog multi-channel. Turn on my pre-amp and wouldn't you know it, the 1080 have blown it's fuses once again :E . Took the RB-1080 to my vendor this morning, he said it must go to the company's service center and should return in a few days, bummer. When it returns, I don't think I am going to utilize the 12v trigger.

I have contacted Rotel in reference to this issue and I am awaiting a call back to discuss the specifics.

Edited update: Spoke with Shane at Rotel, and informed him of this issue, I also asked him if this issue could possibly be related to the 12V trigger (1098 firmware upgrade 2.12), he said he would investigate this matter.

Any comments/suggestions are welcome.

Regards,

Azeke

[Aussie Geoff]

Azeke,

As an update. So far I believe the fuse issue relates to a combination of:

• Speaker type (mine have a minimal crossover - none on the bass driver and a high pass capacitor on the tweeter)
• Speaker cable (I was using a very high gauge (thumb thick) copper cable)
• The very high damping factor of the RB-1080 and its design which puts the speaker effectively in circuit with the amplifiers output transistors
• Power up cycle - especially by the trigger.
• A design issue with the RB-1080 which causes excess current draw on turn on for a fraction of a second as it powers up the amplifier and (with the high damping) brings the speaker coils into circuit

I didn't want to change my speakers but I have gone for quite different speaker cable (IXOS GAMA) which has a thinner cable and a higher cable resistance. This had a great side effect of noticeably cleaning up the sound as well as reducing the number of fuses blown to once a month (was weekly).

I have moved to having the trigger connected to the RB-1080 and active on my RSP-1098 but not used to turn the RB-1080 (i.e. the RB-1080 Trigger switch set off). Basically no problems since then. I have tried both leaving it on and using the switch. Given I am getting a low power draw from the RB-1080 when left on (12-20w) I mostly leave it on, with my RMB-1075 still on normal trigger. Three months so far and NO Fuses blown

Geoff

[Azeke]

Thanks Geoff for the update.

It seems since I have upgraded my software on the RSP-1098 (2.12) and utilized the 12V trigger, I have had the blown fuses issue. I informed Rotel of this situation and they stated they would investigate this issue. In the interim, once I receive my 1080 from the shop I will not utilize the 12V trigger, until which time this issue is addressed by Rotel.

Regards,

Azeke

[pbuxton]

Hi everyone.

I am new to the club rotel forum.
I just bought an rb 1080 and rc 1090,
which sounded great until the left channel went out
today. After having read this entire thread I fear that
I am up for endless fuse changing in the most
expensive amp/preamp system I've ever bought.
I was wondering Azeke if I should ask for the newer
model with the four binding posts as a way to ensure
that this short issue is solved immediately.
Have you heard anything to confirm this?
Thanks for any replies.
Preot