AL Silver internal troubleshooting pics

[UncleMeat 1,174]

 

 

If my Silvers are rated at 600 watts, 8 ohms--occasionally dipping to 6 ohms when pushed hard:

 

Will the speaker fuse blow when paired with a bridged mono config 800 watt @ 8 ohm amp?

 

Or

 

Will the speaker fuse blow because the amp has issues keeping up when pushed in that config when the speaker drops to 6 ohms?   

 

 

In that case the speaker fuse will always blow before the amp goes into protection (although it may be soft clipping).  If the fuse did not blow you would risk the speakers failing or at least the XO's burning up depending on how much energy they are drawing.  IIRC Carver reduced the fuse size in later revisions to further protect the speaker components (not sure what the final size was spec'd at but you can find it in the ALS service manual).  If you are pegging the meters on your A-500x amps you are probably sending at least 600WPC to the speakers so that means the fuses will blow if they are at that level for a sustained amount of time.  With the possibility that you are easily exceeding the design spec of your Silvers in delivered power, I'd be wondering why the speaker that does not blow it's fuse isn't, as much as why the speaker that's blowing it's fuse is.

 

I'm not sure that running these vintage speakers at such high levels is a good idea (although many of the members that own them do and have not had failures).  30 years of use and careful abuse is going to take it's toll.  If you have replacement ribbons stashed and extra woofers then it's not a big deal I suppose but for me there are no replacement 60" ribbons available (even for the cost of a pair of AL-III's) so I'll be babying mine.

 

 

[RobertR 847]

Just to cover all the bases, you should be running a mono signal before you conclude absoultely that one speaker blows fuses more easily than the other.  Possibly there is something heavier on the left in your test material.

 

 

Could be that you have internal arcing in a crossover coil.  You could swap them channel to channel, one at a time to test for this.

 

RobertR

[aslan7 955]

"IIRC Carver reduced the fuse size in later revisions to further protect the speaker components (not sure what the final size was spec'd at but you can find it in the ALS service manual)."

 

Yes, the service manual states on 26 January, 1989, the fuse value was changed from a 4 amp MDQ to a 3.2 amp  MDL.  The reason for the change was because the fuse value was too large for proper WOOFER protection.  My AL's have always run 3.2A slo blo 250V fuses.  I'm also allowing my SVS and Velodyne subs to do the heavy bass lifting so the woofers are not "overtaxed" so to speak.

 

Funny the service bulletin statement toward the end of the manual talking about amp Wattage:

 

 

 

 

 

 

 

 

 

"If you are pegging the meters on your A-500x amps you are probably sending at least 600WPC to the speakers so that means the fuses will blow if they are at that level for a sustained amount of time."

 

 The A500x meters are close to the 0db mark (about 3/4 up) when playing hard and the fuse blo's.  They are not pegging to the right lest I melt something.

 

 

 

 

 

 

 

"With the possibility that you are easily exceeding the design spec of your Silvers in delivered power, I'd be wondering why the speaker that does not blow it's fuse isn't, as much as why the speaker that's blowing it's fuse is."

 

 

I'll also try a mono signal test (thanks Robert) as well as check the Audyssey XT32 settings. Maybe the left AL is set a little higher--not sure.

 

Anyways, thank you all for your help!! 

 

 

 

 

 

[RobertR 847]

With a mono signal you can compare your meter calibrations, for one thing, to see if they agree.  I have four A-753x amps (12 channels exactly the same as you have two of), and I can tell you that the meter readings are not 100% reliable.

 

 

RR

[fill35U 1,847]

It should be easy and informative to use a tone (sine) generator for the signal source. If there's a frequency range that blows the fuse consistently, that will give you a clue as to where to look. 

 

Would be nice to have an ammeter to read while you're doing that. Maybe rig a shunt resister and a voltmeter across it? Absolute readings not so important as relative ones across various volume settings and frequencies. Make a chart...

[aslan7 955]

 

 

It should be easy and informative to use a tone (sine) generator for the signal source. If there's a frequency range that blows the fuse consistently, that will give you a clue as to where to look. 

 

Would be nice to have an ammeter to read while you're doing that. Maybe rig a shunt resister and a voltmeter across it? Absolute readings not so important as relative ones across various volume settings and frequencies. Make a chart...

 

You have just exceeded my Financial Planning degree capabilities, Phil  

[fill35U 1,847]

Easiest way for you might be YouTube. Use your computer or phone to play through your system. Lots of vids with test tones as their audio tracks. This YouTuber has a bunch on their vids HERE .

 

Edit: this is simple, too - onlinetonegenerator.com 

 

Edit: and this is highly versatile! - FUNCTION GENERATOR AT wavtones.com 

 

There's lots of free software out there that'll generate test signals, if you don't mind installing on your 'puter. You might already have that feature and not know it! For that matter, there are phone apps, too.  

 

You don't have to physically plug your phone or 'puter into your system, there are inexpensive wireless Bluetooth receivers that can keep things convenient. Some offer darn good sound quality. 

 

You could also buy/borrow/burn a test CD with tones on it.

 

Crudely, perhaps tune to static and use EQ to boost one frequency band and cut everything else? 

[aslan7 955]

Easiest way for you might be YouTube. Use your computer or phone to play through your system. Lots of vids with test tones as their audio tracks. This YouTuber has a bunch on their vids HERE .

 

There's lots of free software out there that'll generate test signals, if you don't mind installing on your 'puter. You might already have that feature and not know it! For that matter, there are phone apps, too.  

 

You don't have to physically plug your phone or 'puter into your system, there are inexpensive wireless Bluetooth receivers that can keep things convenient. Some offer darn good sound quality. 

 

You could also buy/borrow/burn a test CD with tones on it.

 

Crudely, perhaps tune to static and use EQ to boost one frequency band and cut everything else? 

 

Now that I can do Phil!  Easy as pie.

I'll try it. 

 

 

[UncleMeat 1,174]

"IIRC Carver reduced the fuse size in later revisions to further protect the speaker components (not sure what the final size was spec'd at but you can find it in the ALS service manual)."

Yes, the service manual states on 26 January, 1989, the fuse value was changed from a 4 amp MDQ to a 3.2 amp MDL. The reason for the change was because the fuse value was too large for proper WOOFER protection. My AL's have always run 3.2A slo blo 250V fuses. I'm also allowing my SVS and Velodyne subs to do the heavy bass lifting so the woofers are not "overtaxed" so to speak.

Funny the service bulletin statement toward the end of the manual talking about amp Wattage:

"If you are pegging the meters on your A-500x amps you are probably sending at least 600WPC to the speakers so that means the fuses will blow if they are at that level for a sustained amount of time."

The A500x meters are close to the 0db mark (about 3/4 up) when playing hard and the fuse blo's. They are not pegging to the right lest I melt something.

"With the possibility that you are easily exceeding the design spec of your Silvers in delivered power, I'd be wondering why the speaker that does not blow it's fuse isn't, as much as why the speaker that's blowing it's fuse is."

I'll also try a mono signal test (thanks Robert) as well as check the Audyssey XT32 settings. Maybe the left AL is set a little higher--not sure.

Anyways, thank you all for your help!!

0dB on your meters represents 800 WPC @ 8 Ohms if calibrated correctly. But we know that the ALS speakers represent a more difficult load than an 8 Ohm conventional speaker so you might be in the range of 1000-1200WPC at certain frequencies. The fuse doesn't stand a chance since it's designed to fail somewhere above 600WPC. If you are using the amps to drive both the ALS and passive subwoofers then I understand why you'd say less wattage goes into the fuse, but if they aren't passive then all the metered power is going to the ALS.

[RobertR 847]

I'd be extremely leery about running high level, high frequency sine waves.  You could blow output transistors, at an output level well below clipping.  They simply aren't designed for this.

 

 

RR

[fill35U 1,847]

I'd be extremely leery about running high level, high frequency sine waves.  You could blow output transistors, at an output level well below clipping.  They simply aren't designed for this.

 

I'd think keeping it below 5kHz would be fine, and there wouldn't be a need to go higher than that (octave away from the 2k notch). Go much higher, and either the neighbors will howl or their pets will! 

 

Wouldn't running well below clipping be worse than running at clipping? With commutator lockup at high freq she's just a normal Class AB. Worst dissipation would be around 40%, max efficiency at close to full output? 

 

Has anybody blown up an A-500/760x by feeding her high level/high freq tones?

[UncleMeat 1,174]

Any idea what the SPL is with the A-500x amps at max output Jack? I'm running my TFM-35x (rated 250 WPC) today and at 300 WPC peaks and RMS about mid travel my ALS-Hybrids are LOUD! I can't imagine how loud 800 WPC must sound!

[RobertR 847]

fill wrote: Has anybody blown up an A-500/760x by feeding her high level/high freq tones?

 

fill - I have no way of knowing that.  I certainly haven't in any of mine, but then I'm not going to come even close to finding out.  I do know that it happens to amps, and that a lot of guys are surprised when they first encounter it. 

 

We blew up a Lightstar that way a couple of years ago at the Fest. My cautions were dismissed then, too.  I don't remember exactly how much power it was cranked up to, but as best I recall it was around 60%, at 10 KHz, into a pure resistive load..And of course that's a tracking power supply. .It was gone in mere seconds  Bob heard about it afterward and said it was sure to happen - you just can't test SS amps in that way.

 

Anyway, not looking for an argument - just want to be sure the guy with speaker troubles doesn't add amplifier troubles to the mix.

 

RobertR

[fill35U 1,847]

Thanks, Robert!  

 

Good anecdotal evidence there. Darn shame about the Lightstar, whose was it?

 

Now I'm curious if Bob meant *all* SS amps, or just ones with switching or tracking rails. Certainly everything gets worse at higher frequencies.

 

In any event, thanks for the warning! 

 

 

[RobertR 847]

I'm guessing any SS amp.  My first experience with this was with my homemade.power amp in the early '60s.  Class B, though at the time I didn't know B from sausage..  Couldn't believe how hot it got running 10KHz - I thought just bass tested an amp.  This was as far from Bob's amps as you can get - low power, and Germanium transistors - something that anyone who missed them because they were born too late should be grateful for. My brother, who was studying to become an EE, wised me up, same as Bob - "just don't do it."

 

 

RR

[loner_t 2,571]

Aslan.. curious if the length of speaker wires to the speakers is the same for both of them. 

[aslan7 955]

 

 

Aslan.. curious if the length of speaker wires to the speakers is the same for both of them.

 

 

No

 

One is longer by about 3 feet maybe.

[mbskeam 1,989]

I would use a tone cd to test that the x-over is working right. IE: a inductor is not bad, passing the highs to the woofers or a cap is passing lows to the ribbon.

[loner_t 2,571]

Aslan.. curious if the length of speaker wires to the speakers is the same for both of them. 

No

One is longer by about 3 feet maybe.

 

Is it the speaker with shorter length wire that blows fuses? 

[aslan7 955]

 

 

 

 

Aslan.. curious if the length of speaker wires to the speakers is the same for both of them.

 

 

 

 

One is longer by about 3 feet maybe.

Is it the speaker with shorter length wire that blows fuses?

 

I believe it is. That might be why it blows the fuse first. Did not consider that L_t.

 

I may just switch the wires around to check.

Thank you! (although I'm surprised 2-3 feet would make a difference).

[RodH 4,866]

[UncleMeat 1,174]

Is the speaker that has a buzz the speaker that's not popping fuses?  If it is it's an indication that the resistance in the ribbon assembly is higher (oxidized/loose contact and/or ribbon conductor).

[aslan7 955]

 

 

Is the speaker that has a buzz the speaker that's not popping fuses?  If it is it's an indication that the resistance in the ribbon assembly is higher (oxidized/loose contact and/or ribbon conductor).

 

Speaker blowing fuse also has slight buzz. I'm going to check PDC today Russ per our PM. Also spoke to PMAT last night.

Maybe that's the issue.

[aslan7 955]

FUSE ISSUE:

 

Well I did some troubleshooting today on left AL speaker.  Still don't know why the left speaker fuse occasionally blows when pushed hard toward the 0db A500x meter level.  As Doh-r says, just don't play them so loud. 

 

 

 

  

To address Loner_t, both speaker wires from each A500x are the same length--10 foot on each side.  So much for shorter speaker wire theory blowing a fuse first on left side.

 

I was incorrectly remembering the old speaker wire which was of different length and run to a passive BSR sub in the old days before going to the Amazings (when I was a poor college grad). That old subwoofer and wire are no longer used in my system.

 

I did check the PDC board and connections.  They are nice and tight with good solder welds holding the positive & negative wires securely.  

 

 

 

 

 

 

 

 

 

 BUZZING ISSUE:

 

As far as the buzz goes, I was able to find the vibration 1/3 - 1/2 way up the ribbon in a 2 inch section.  It is fairly easy to find with a flashlight.  I could see the clear "cellophane" in the middle on each side of the silver foil vibrating during playback of the Ballad of Bill Hubbard 60-90 second mark.  There should be no movement at all of course.

 

 

 

 

 

 

 

Pmat mentioned he had some debris (piece of foam?) lodged in his ribbon that was causing the buzz.  I did not see any debris after extensive searching.  I then CAREFULLY used a can of compressed air which I streamed in SMALL gentle bursts to dislodge anything that my be suspect on the left, right and center of the ribbon.

 

 

 

 

 

 

 

 

 

Then, using a heat gun, I CAREFULLY, heated that section moving the gun up and down so the ribbon would not be damaged.  Certainly a nervous feat.

 

 

 

 

 

 

Then I re-torqued the screws on the back side of the ribbon where the offending vibration was emanating.  Maybe 1/3 - 2/3 turn each.

 

 

 

 

 

As the AL Service Manual says, if tightening those screws does not fix the buzz, the driver will need replaced. 

 

For now, the buzz is gone!    

This could last for 6 seconds or 6 years.  Who knows.

 

Now I need to buy a spare ribbon just in case   

Maybe the BobFather has a secret stash!   

 

 

 

 

[weitrhino 1,444]

Nice to hear the issue has at least been temporarily resolved.

 

Hey! That's Bob anointing my amp!