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Stewart World 2.1 - Dead Channel!

Lonnybass

Lonnybass

Jul 19, 2000
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San Diego
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Endorsing Artist: Pedulla Basses
#1
Last night I ran my Stewart 2.1 in the bridged mono configuration for the first set, worked great, sounded great.

At some point during the second set, Channel 2 went dead and never came back. I tried recycling the switch, checked the fuse, nothing. No power light, no signal clipping light, completely dead.

I switched over to stereo and ran my cabinet on Channel 1 during the third set and it sounded fine again, but Channel 2 is now dead as a doornail.

Does anyone have any suggestions, thoughts on a problem or suggested fix? I opened up the box to see if anything was smoked and nothing seems visibly damaged. Wondering what makes sense to do for a fix. This amp has served me reliably for 16 years and I'd hate to ditch it!

Lonnybass
 
#6
BassmanPaul said:
Time to upgrade to a Class D power amp. Truthfully I fear that the amp may cost more to fix than to replace.
Click to expand...

Class H to Class D is anything but an upgrade, truth be told. :cool: the switching frequency of the H is several times quicker resulting in a more musical experience, imo.
the Stewart amps are supposed to be equipped with protection circuitry to avoid damage to amp and load. perhaps this failsafe function has latched up.
gl
 
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#7
Lonnybass said:
Does anyone have any suggestions, thoughts on a problem or suggested fix? I opened up the box to see if anything was smoked and nothing seems visibly damaged. Wondering what makes sense to do for a fix. This amp has served me reliably for 16 years and I'd hate to ditch it!Lonnybass
Click to expand...
You said you checked a fuse. My 2.1 has two circuit breakers. Try to reset the Channel-2 circuit breaker (do it with power off!!).

If you have the wherewithal to do some troubleshooting, you can consider checking power supply voltages by comparing one channel to the other. Realize the amplifier is a dual-mono configuration, so even the power supplies are duplicated. If a power supply seems dead, the protection circuitry could be detecting an output short or circuit failure.
 
#8
IIRC, there is a protection fuse inside for each channel. Replacing this alone is not a fix, probably, if it is in the fault chain, as something else has caused it to blow. I would fix mine if it broke, using the spare in the meantime.
 
#10
pacojas said:
Class H to Class D is anything but an upgrade, truth be told. :cool: the switching frequency of the H is several times quicker resulting in a more musical experience, imo.......
Click to expand...

Yah, I wish I still had my horse. Quick and maneuverable. Aside from permanent installations, every sound support company has or is moving to Class D. And when those sites with permanent installs have a failure of an amp, it gets a Class D replacement. The only market for Class A, A/B, G, or H is hi-fi enthusiasts or those wanting the SVT/Marshall/HiWatt/Orange experience and have the money to do such.

Are traditional class A/B solid state amps doomed?
 
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#11
pacojas said:
Class H to Class D is anything but an upgrade, truth be told. :cool: the switching frequency of the H is several times quicker resulting in a more musical experience, imo
Click to expand...

Really? Would you explain how this is possible, and how it is even comparable?
 
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#12
I checked both of the breakers on the rear panel and tried to reset each, neither seems to have tripped. Gonna poke around a little more and see if I can find the fuse and check the voltages with a meter.
 
#14
The manual states "Bridged Mono Mode: Make the appropriate input connection to channel 1 input only (when the Mono/Stereo Switch us in the Mono position, the Channel 2 Input is disengaged)." It also says you need to wire the sp outs in a diffrerent way for Bridg mode:
"Important: follow these speaker hookup instructions carefully. Failure to do so could damage your amplifier.
Channel #1 Positive (+) Terminal = Speaker Positive (+)
Channel #2 Positive (+) Terminal = Speaker Negative (-)
Channel #1 Negative (-) Terminal = no connection
Channel #2 Negative (-) Terminal = no connection"
I hope this helps.
 
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#16
Class H doesn't have a switching frequency, the high rail(s) enable and disable with the audio amplitude. Completely unrelated "switching" mechanisms to each other.

Maybe you simply prefer one amp over the other for an entirely different reason than "switching frequency"?
 
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#17
Lonnybass said:
That's my concern as well. Ughhhhhh. This is a sad day.
Click to expand...

Fix or replace?
That's a tough one. It may be a simple fix, but if you can't figure it out for free it will probably cost at least $100 bench time from a decent tech. That's about 2/3rds the price of buying a new power amp with at least a three year warranty. It's about 1/4th the price of buying one with a 5 year transferable warranty. Both light weight, and more powerful.

If you sold the amp as broken, or gave it to charity, I'll bet some electronic tinkerer with fix it, and sell it for may $100, buy they are going to be competing with modern amps that are much higher value today. I don't really know what it's worth, but I don't think they are well sought out amps.

It doesn't sound like you need a bridge amp. You might have fallen into the mindset that more power all the time is needed. Bridging itself probably didn't break the amp, but if you don't need to bridge the the amp may last you years a years if you do nothing.


I'd say, Mark the channel as bad, and sell it or give it away. Consider if you need to bridge, and get a new amp.
 
#18
Kickass said:
The manual states "Bridged Mono Mode: Make the appropriate input connection to channel 1 input only (when the Mono/Stereo Switch us in the Mono position, the Channel 2 Input is disengaged)." It also says you need to wire the sp outs in a diffrerent way for Bridg mode:
"Important: follow these speaker hookup instructions carefully. Failure to do so could damage your amplifier.
Channel #1 Positive (+) Terminal = Speaker Positive (+)
Channel #2 Positive (+) Terminal = Speaker Negative (-)
Channel #1 Negative (-) Terminal = no connection
Channel #2 Negative (-) Terminal = no connection"
I hope this helps.
Click to expand...

All was hooked up correctly per the manual (as I have done before), and worked fabulously the first set. The second channel failed during the second set.
 
#19
I have the same amp and years ago, one of the channel trim pots on the front got scratchy and then would cut out in certain positions. I contacted Stewart and they sent me a replacement pot for free. It included a wiring harness from the pot body with a clip in connection. No soldering needed. It seems that a lot of the internals are modular inside these. Try contacting them. They don't make the World amps anymore but they might support them. > Invalid Link Removed
 
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#20
agedhorse said:
Class H doesn't have a switching frequency, the high rail(s) enable and disable with the audio amplitude. Completely unrelated "switching" mechanisms to each other.

Maybe you simply prefer one amp over the other for an entirely different reason than "switching frequency"?
Click to expand...

yup!
i'm not sure where i got the idea that my Stewart 1.2 was Class H with SMPS. their website states the amp is A/B w/high frequency SMPS. perhaps this explains my preferences.
[Invalid or Expired Link Removed]
 

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