This thread is quite old (2005~2014) but hey, the Carver PT2400 on my bench is twice as old. I worked through this hole thread but did not find the answer to my problem. Both channels behave the same: They do not start on power-on. So I downloaded the service manual and did some measurements. These are my findings
Simple power up from mains
When switched on, there is some power consumption of 5-6W from the mains. Voltage across 2x10.000uF/125 caps builds up very slowly. After >1minute this ends at approx +-30~35volts. Thats all, no LEDs lighting, no sound.
Checking the TRIAC
Monitoring the TRIAC-ouput MT2 with my scope shows triggering at an phase angle of approx 150 degrees. As the voltage drop across the TRIAC is just a short spike once triggered the TRIAC does not hold indicating insufficient load current.
Checking the Power-Amp
With a primary light bulb limiter and the TRIAC shorted the 10.000uF/125 caps charge up to +-70V approx. Amp output is not loaded. The lower LED is active. Feeding audio signal into the input and turning up the volume makes the LED light move up until clipping. The outputs deliver accordingly high voltages. Looks like both amps are still working!
Fokusing on the Supplies
Some investigating on the trigger logic gave me first insights:
-This 4 transistor trigger logic is quite tricky. To understand I simulated it and came to the conclusion that the most early trigger point is a bit after 90 degree phase angle. This is achieved by using the current reversal through the trigger capacitor as a trigger event.
-The opto-couple current delays the trigger point, i.e. reduces the phase angle.
I assume the phase angle I observed is too small to start the engine. And there I am stuck! I do not have a clue howto make this dimmer start. Any ideas?
Simple power up from mains
When switched on, there is some power consumption of 5-6W from the mains. Voltage across 2x10.000uF/125 caps builds up very slowly. After >1minute this ends at approx +-30~35volts. Thats all, no LEDs lighting, no sound.
Checking the TRIAC
Monitoring the TRIAC-ouput MT2 with my scope shows triggering at an phase angle of approx 150 degrees. As the voltage drop across the TRIAC is just a short spike once triggered the TRIAC does not hold indicating insufficient load current.
Checking the Power-Amp
With a primary light bulb limiter and the TRIAC shorted the 10.000uF/125 caps charge up to +-70V approx. Amp output is not loaded. The lower LED is active. Feeding audio signal into the input and turning up the volume makes the LED light move up until clipping. The outputs deliver accordingly high voltages. Looks like both amps are still working!
Fokusing on the Supplies
Some investigating on the trigger logic gave me first insights:
-This 4 transistor trigger logic is quite tricky. To understand I simulated it and came to the conclusion that the most early trigger point is a bit after 90 degree phase angle. This is achieved by using the current reversal through the trigger capacitor as a trigger event.
-The opto-couple current delays the trigger point, i.e. reduces the phase angle.
I assume the phase angle I observed is too small to start the engine. And there I am stuck! I do not have a clue howto make this dimmer start. Any ideas?
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Hi bucks bunny,
I have a feeling that the protection network is preventing full start-up as it should. You probably have a fault elsewhere in the amplifier. Troubleshooting these when they are not right on my bench is pretty futile.
One thing for sure, do not short the triac!!! That controls the amount of power the amplifier receives and it will badly over-voltage internally and you could destroy the amplifier beyond repair. It would trip your breaker or blow that circuit fuse as well.
Carver amplifiers really do require training to understand and service successfully. That one is the same as a TFM-75, a really, really nice amplifier. It is capable of delivering massive amounts of power in normal operation, so respect it. Remember, it does not operate as a normal amplifier, there is a lot going on inside. Any number of things could easily cause protection to operate.
-Chris
I have a feeling that the protection network is preventing full start-up as it should. You probably have a fault elsewhere in the amplifier. Troubleshooting these when they are not right on my bench is pretty futile.
One thing for sure, do not short the triac!!! That controls the amount of power the amplifier receives and it will badly over-voltage internally and you could destroy the amplifier beyond repair. It would trip your breaker or blow that circuit fuse as well.
Carver amplifiers really do require training to understand and service successfully. That one is the same as a TFM-75, a really, really nice amplifier. It is capable of delivering massive amounts of power in normal operation, so respect it. Remember, it does not operate as a normal amplifier, there is a lot going on inside. Any number of things could easily cause protection to operate.
-Chris
Thank you for your fast response. I am aware that it is dangerous to bridge the TRIAC as output voltage could reach crititical levels. But with the 60W bulb dimmer in series of mains supplies this has worked.
You are probably right with your diagnosis.
The circuit diagrams are eye soring!😱
I will get a working carver next days so I hope by comparison I can trace that error.
You are probably right with your diagnosis.
The circuit diagrams are eye soring!😱
I will get a working carver next days so I hope by comparison I can trace that error.
Hi bucks bunny,
Okay, good luck. Look at the commutators and amplifier bias. All the common stuff.
I really don't like what you did to power it up. That's all I will say on the subject.
-Chris
Okay, good luck. Look at the commutators and amplifier bias. All the common stuff.
I really don't like what you did to power it up. That's all I will say on the subject.
-Chris
Dear friend, I have owned a carver C-1 pre-amp and m400t amp since 1982. While in Europe we used it daily and on weekends ram it at full power driving klipsch la scalas for 6 and eight hours at a time. This same so called unreliable amp can be heard today 2022 still playing as good as when new. They are a party on wheels (light). Previously from 79-82 used a sansuii G-22000 to power JBL L-300 and later JBL L-220 speakers. I probably spent total Army paycheck on stereo from 1979-1982. Trust me get the right equipment and a carver C1 or C2 and a M400t and enjoy. To mention marantz and sansuii in the same sentence as carver is a mistake. Won many battle of the stereo’s while stationed in Germany from 1978-1984 and carver led the way. Check it out.
I used one of these cube M400t amps for 20 years. At one point I had two of these. One each bridged to drive a pair of DQ10s. I moved to smaller more efficient speakers and diy chip amps. Yet, I had nothing but great hi-fi sound from that combo. Some are confusing the T for tubes. This T series had nothing to do with the later Carver Tube amp he would use for that later series transfer function. This T series transfer function, was nulled against a pair of Mark Levinson ML-2 mono amps.
Well, heck. I know these cubes better than most from a service perspective, and listening to them. Also by comparing them against other products from all manufacturers.
These cubes were the first kick at the can for Bob Carver. They sounded okay and did succeed as a proof of concept. But the Carver line of amplifiers improved with each model year. To be honest, the cube sounded pretty bad against the newer Carver amplifiers. As for sounding as good as new, I know they don't. They still function, which is pretty cool. But performance has degraded over time and they can sound better. All products degrade slowly over time. I wil say that Bob Carver is an impressive designer, and he also had a great team of engineers he worked with. I talked with some of them during the course of our association.
Anyway, I'm glad you still like your cubes. There are worse sounding amps out there for sure. But they are murder to work on when they have a problem as they will not run apart so that you can test and troubleshoot. So service costs are higher, and for that reason I usually am very careful about agreeing to service them.
I have had several customers blow the woofers using LaScalas over the course of time. Did warranty for Klipsch as well. They were stupid loud. DQ-10's wouldn't survive a lot of power, serviced those for years too. Enjoy your stuff, but keep it real folks.
These cubes were the first kick at the can for Bob Carver. They sounded okay and did succeed as a proof of concept. But the Carver line of amplifiers improved with each model year. To be honest, the cube sounded pretty bad against the newer Carver amplifiers. As for sounding as good as new, I know they don't. They still function, which is pretty cool. But performance has degraded over time and they can sound better. All products degrade slowly over time. I wil say that Bob Carver is an impressive designer, and he also had a great team of engineers he worked with. I talked with some of them during the course of our association.
Anyway, I'm glad you still like your cubes. There are worse sounding amps out there for sure. But they are murder to work on when they have a problem as they will not run apart so that you can test and troubleshoot. So service costs are higher, and for that reason I usually am very careful about agreeing to service them.
I have had several customers blow the woofers using LaScalas over the course of time. Did warranty for Klipsch as well. They were stupid loud. DQ-10's wouldn't survive a lot of power, serviced those for years too. Enjoy your stuff, but keep it real folks.
I remember the original Cube, my buddy had that that one. The M400a. It sounded 'ok' it had enough power to drive his dq-10s. Yeah I got my Hi-Fi ideas from him. ha ha. The M400t, however was the first 'real' 'Carver' amp with any hi-fi cred. I have heard his earlier Phase Linear gear was pretty good though. I've always wanted to listen to later Carver 'T' series, named after his tube amps transfer function? And his Sunfire amps and subs. I have never had an opportunity.
My hifi stuff today is way better, but for the time, basically the 80s decade, it was as good as I could find. Any amp, nulled against a pair of $15000 Mark Levinson amps, doesn't just sound 'ok'. And it didn't it was as clean and 3D as stereo could sound, out of those DQ-10s. I'd like to see if those old DQ-10s could be improved today, with a rebuilt XO... maybe I can talk the guy I sold them to re-build them. I was able to sell both my Cube amps in the early 2000s. They were still going strong then. The one thing bad about the combo is maybe the sound stage wasn't as large as it should have been. And the DQ-10s were soo in-efficient, that they did lack some dynamics, fast transients, etc..
My hifi stuff today is way better, but for the time, basically the 80s decade, it was as good as I could find. Any amp, nulled against a pair of $15000 Mark Levinson amps, doesn't just sound 'ok'. And it didn't it was as clean and 3D as stereo could sound, out of those DQ-10s. I'd like to see if those old DQ-10s could be improved today, with a rebuilt XO... maybe I can talk the guy I sold them to re-build them. I was able to sell both my Cube amps in the early 2000s. They were still going strong then. The one thing bad about the combo is maybe the sound stage wasn't as large as it should have been. And the DQ-10s were soo in-efficient, that they did lack some dynamics, fast transients, etc..
Well, there are more transparent amps today, but many from the late 70's and 80's can be really improved to the point where they are better than most. They basically had better designs back then, and they were built better on average. Certainly more reliable at times.
Many current and recent (like two decades back - maybe further) amplifiers had designs polluted by ideas that were not technically correct. It is all about market share and perception and not actual performance. The promise of performance is there, surrounded by a good story. There was no shortage of this way back then, but these days the internet allows "designers" to gain more traction. Finding the truth is somewhat more difficult these days.
Many current and recent (like two decades back - maybe further) amplifiers had designs polluted by ideas that were not technically correct. It is all about market share and perception and not actual performance. The promise of performance is there, surrounded by a good story. There was no shortage of this way back then, but these days the internet allows "designers" to gain more traction. Finding the truth is somewhat more difficult these days.
I was lucky. Back then I didn't really do any diy audio. I was lucky that a buddy was blazin' trail, lol. I had a Hegeman pre-amp that sounded really good for what it was. It was a good system that had synergy. So many folks got it wrong when piecing a system together. Impedance mis-matches etc. When I did get around to diy audio and upgrading. I sort of understood the way to go... I bought some Lowthers, threw them on open baffles. Built a big-fast-efficient modern sub, ran it with the Cube for a bit. Built a couple small chip amps, biased those to class-A. Modded a universal player. Used an amorphous core TVC as a 'preamp'. That was hi-fi...
I’m posting this here due the thread’s “Carver-ish” nature - providing a Sunfire True Subwoofer Signature enough power.
Having read its specs etc from several sources, I wonder: does this thing need its own 20A circuit? Following an old, slightly flawed hot rod mantra, “if a little is good, lots is gooder!”
Years ago I ran 3 dedicated 20A to power a plethora of equipment. One for the low power stuff (TV, pre/pro, blu-ray player, etc). The other two to feed six* 2 ch power amps* and five** subs that all under full power might pull a total ~1.8Kw though the manufacturer has on the amps’ rear panels “440 watts & sub 150 watts.
*its complicated
**the Sunfire will replace the existing LFE/Center ch sub
https://skyfiaudio.com/products/sunfire-true-subwoofer-signature-12-dual-drivers-bob-carver
Thnx in advance for reading this far. Very grateful for your time and expertise
Tony
Having read its specs etc from several sources, I wonder: does this thing need its own 20A circuit? Following an old, slightly flawed hot rod mantra, “if a little is good, lots is gooder!”
Years ago I ran 3 dedicated 20A to power a plethora of equipment. One for the low power stuff (TV, pre/pro, blu-ray player, etc). The other two to feed six* 2 ch power amps* and five** subs that all under full power might pull a total ~1.8Kw though the manufacturer has on the amps’ rear panels “440 watts & sub 150 watts.
*its complicated
**the Sunfire will replace the existing LFE/Center ch sub
https://skyfiaudio.com/products/sunfire-true-subwoofer-signature-12-dual-drivers-bob-carver
Thnx in advance for reading this far. Very grateful for your time and expertise
Tony
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If the circuit breaker doesn't trip, then one circuit is all you need.
Even in multi amped systems, when the amps need to be turned on one at a time. One circuit is often adequate.
Even in multi amped systems, when the amps need to be turned on one at a time. One circuit is often adequate.
Circuit breakers come in several curves, some permit high starting current to motors that need it.
Be careful, choose the right one.
Your fuse type will provide clues.
Be careful, choose the right one.
Your fuse type will provide clues.
Didn't know there is more than one type*. Please name them*.
No fuses in my power panel
I forgot to mention the Sunfire purportedly, however unlikely under the right conditions, could exceed 2700 watts.
Current I have “automation” managing system “turn-“ on using four Furman Miniport-20a. They “fire”one at a time, about 2 seconds apart:
1. Left channel w/sub
2. Right channel w/sub
3. Center channel w/LFE
4. Rear channels w/subs
Thanks for everyone’s advice.
Tony
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'A' or 'L' is lighting, fastest blow.
'B' is for things like heaters, some overload being allowed, trips slower.
'C' is for motors, starting torque allowed, trips slowest.
Look up the relevant details for your country.
A/B/C has substitutes or equivalents elsewhere too....same function, different name or letter.
'B' is for things like heaters, some overload being allowed, trips slower.
'C' is for motors, starting torque allowed, trips slowest.
Look up the relevant details for your country.
A/B/C has substitutes or equivalents elsewhere too....same function, different name or letter.
I’ll copy and save
for my next trip to Lowe’s or City Electric.
I’m in the US. Where are you?
SIde note: the equipment in my previous reply currently share two dedicated 20A circuits. A 3rd dedicated 20A feeds the TV, pre/pro, EXOs, BDP, DVR & CD player through an APC power conditioner. I believe I’ll “spread the load” by tapping that 3rd feed for something small until I get around to adding a fourth 20A.
Many thanks. Tony
In the font, letters, phonetics, and spirit of harmony:
“Shu-kria” for you willingness to share your expertise!
“Shu-kria” for you willingness to share your expertise!
Different uses get different designations. From city-wide power breakers down to street transformers. Specified by licensed engineeres.
But in normal domestic power breakers there is often no choice. I remember when there was a "T" for air conditioner compressors but that seems to be vanished. The average homeowner or residential electrician "can't be trusted" to pick the right part.
"Standard" domestic breakers to at least 50 Amps have lots of room for short-term overload without risk to insulation.
Staggered-start should be ample (even over-kill) for anything smaller than a stadium. Your "4,000 Watts!" box won't pull thousands of Watts steady, or for more than about 1/4th second. (My well-pump pulls 5,500 Watts for about 1/20th of a second before settling to 1,600W.)
A more delicate case is refrigerators on small engine-generators. I try to switch-off my iceboxes before I start the genertor, and let it come to speed before I cut-in the two boxes one by one. However my well-pump starts on a 3,500Watt generator.
https://www.allumiax.com/blog/time-current-characteristic-curves-for-selective-coordination
https://library.e.abb.com/public/9147d214ed83662e852575cf005ac7b5/1SXU210170B0201.pdf
'The average homeowner or residential electrician "can't be trusted" to pick the right part'
Very true...
I have seen burnt 16A L series breakers used for 1.5 ton a/c, 30A start (locked rotor) current...32 A C series is appropriate.
Here 6-32A same price, or similar, no sense in putting a smaller breaker, which always fails at a bad time...
And don't even talk of the 25 cent Chinese breakers, they will put any mark as long as the order is big enough.
In Bombay, they used good Indian breakers at the main distribution boards, and all the branches had these.
Indian at that time were $1.20 or so, duty paid Chinese were 35 cents each.
In an apartment complex with 1500 flats, each using say 12, that is a big price difference.
Very true...
I have seen burnt 16A L series breakers used for 1.5 ton a/c, 30A start (locked rotor) current...32 A C series is appropriate.
Here 6-32A same price, or similar, no sense in putting a smaller breaker, which always fails at a bad time...
And don't even talk of the 25 cent Chinese breakers, they will put any mark as long as the order is big enough.
In Bombay, they used good Indian breakers at the main distribution boards, and all the branches had these.
Indian at that time were $1.20 or so, duty paid Chinese were 35 cents each.
In an apartment complex with 1500 flats, each using say 12, that is a big price difference.