Midas, thanks for the info man. Obviously they were everywhere back in the day, but once in a while I still see them sent out with a package. Not from Clair of course, but a few smaller rental shops around nyc still have some.
Hi Chris (anatech),
Before all, Happy new year to you and all in this forum.
Have you some experience with Carver PT1250 (or PM2.0t, wich appear to be the same)?
I don´t have the service manual for that, (I have only the schematics), and I need some advice about the exactly adjust of the duty-cycle of that PWM power supply.
Thanks in advance if you could help me.
Regards,
Marcos
PS: The fan motors for PM1.5, PM1200, PT1250, etc... is exactly the same "MABUCHI" used in that "tunnel type" Hairdrayer
Before all, Happy new year to you and all in this forum.
Have you some experience with Carver PT1250 (or PM2.0t, wich appear to be the same)?
I don´t have the service manual for that, (I have only the schematics), and I need some advice about the exactly adjust of the duty-cycle of that PWM power supply.
Thanks in advance if you could help me.
Regards,
Marcos
PS: The fan motors for PM1.5, PM1200, PT1250, etc... is exactly the same "MABUCHI" used in that "tunnel type" Hairdrayer
anatech said:
Chris,
What component damage do you typically see when a Carver amp is run for mids and highs only?
My father and I built a a home theater system quite a few years ago using a bi-amp front speaker system powered by a TFM-25 for the mids and highs, and a TFM-45 for the lows. The TFM-25 lost a channel a couple of years ago, and this may have been the problem.
-Win
Concerning the midrange and trebble usage, only oscilloscope can tell the truth about how much time the higher rails are active when they shouldn't. But anyway, if this happens, it should be noticed as abnormally high heating.
Consider that 1 milisecond SOA usually allows for 10 times the rated power dissipation of output devices, and SOA tends to become square above 100us. This holds as long as the duty cycle is kept low like in audio.
Consider that 1 milisecond SOA usually allows for 10 times the rated power dissipation of output devices, and SOA tends to become square above 100us. This holds as long as the duty cycle is kept low like in audio.
carver 2.0 svc manuel
marcos, if you e-mail me i can send you the section of the svc man you need. i can't e-mail any body yet! your talking about the carver that is 11lbs. right they can be a pain in the a55! imix 500 e-mail me i think we know eachother. don't ever underestimate clair! i've still seen some rigs go out with flame linear and sae (sparks and explodes!).....midas by the way, if any body needs carver fans i still have a dozen or so left. con air hair drier is close but draws a lot more current
marcos, if you e-mail me i can send you the section of the svc man you need. i can't e-mail any body yet! your talking about the carver that is 11lbs. right they can be a pain in the a55! imix 500 e-mail me i think we know eachother. don't ever underestimate clair! i've still seen some rigs go out with flame linear and sae (sparks and explodes!).....midas by the way, if any body needs carver fans i still have a dozen or so left. con air hair drier is close but draws a lot more current
Carver commutator lockup
Its easy to see the result of commutator lockup by just monitoring the AC line input current of the amp, while varying the audio input frequency. For example: on a M400 cube driving 13v@8 ohms (~21 watts/ch) the line input current is about 3.8 amps@120vac, current stays steady up to about 5Khz then takes a sharp increase as you increase past that frequency. I measure about 5.6 amps of line current while putting out the same 13v@8 ohms at 15Khz. Almost 50% increase in current while putting out the same power. Yes, these amps do "burn up" more power at hi frequencies.
Its easy to see the result of commutator lockup by just monitoring the AC line input current of the amp, while varying the audio input frequency. For example: on a M400 cube driving 13v@8 ohms (~21 watts/ch) the line input current is about 3.8 amps@120vac, current stays steady up to about 5Khz then takes a sharp increase as you increase past that frequency. I measure about 5.6 amps of line current while putting out the same 13v@8 ohms at 15Khz. Almost 50% increase in current while putting out the same power. Yes, these amps do "burn up" more power at hi frequencies.
Hi Win,
Sorry for the delay. I've been "away" and will not be around that much.
Anyway, when a Carver is used in a manner that locks up the commutators, you will see a lot of overheated parts. Often the mid voltage rail capacitor may explode as well. You may even see a shorted triac, along with unusually high amounts of damage.
The protection circuits used in Carver amps are very good. Normal failures may only show one blown output (change them both) and that's all. If the triac shorts, expect heavy damage due to all the supplies going way up in voltage. It isn't very pretty. I've seen technicians do this (TV guys usually).
-Chris
Sorry for the delay. I've been "away" and will not be around that much.
Anyway, when a Carver is used in a manner that locks up the commutators, you will see a lot of overheated parts. Often the mid voltage rail capacitor may explode as well. You may even see a shorted triac, along with unusually high amounts of damage.
The protection circuits used in Carver amps are very good. Normal failures may only show one blown output (change them both) and that's all. If the triac shorts, expect heavy damage due to all the supplies going way up in voltage. It isn't very pretty. I've seen technicians do this (TV guys usually).
-Chris
Hi Eva,
I normally monitor the second tiers for this. The third simply turns on full, and off full. The second tier should track the music signal within reason. High level, high frequencies will keep re triggering the commutator so that it never turns off. Locked up.
I can see you understand this concept very well. No surprise there. 😉
-Chris
Yes, for sure!
I normally monitor the second tiers for this. The third simply turns on full, and off full. The second tier should track the music signal within reason. High level, high frequencies will keep re triggering the commutator so that it never turns off. Locked up.
I can see you understand this concept very well. No surprise there. 😉
-Chris
anatech said:
Thanks Chris!
No need to apologize, I'm in no rush and appreciate the reply. 🙂
This amp has been on the shelf for awhile, so It'll be a project for my limited spare time. I want a working amp, but it's more for my education than anything.
A thorough cleaning and visual inspection shows no physically damaged components or brown areas on the PCB. I may have lucked out with only a blown output, we'll see.
This is the first Carver I've worked on, so I may hook up the scope just to watch the rails change. 😉
Carver concerns
I have the Carver TFM-15 CB down here...occasionaly we have voltage sags...I once measured the wall AC & got 63 VAC.
So as I understand it if I happened to be running full power at a "sag" time with lots of HF content my amp would lock into the 'third' PS rail and go poof?
_________________________________________Rick.......
I have the Carver TFM-15 CB down here...occasionaly we have voltage sags...I once measured the wall AC & got 63 VAC.
So as I understand it if I happened to be running full power at a "sag" time with lots of HF content my amp would lock into the 'third' PS rail and go poof?
_________________________________________Rick.......
Hi Rick,
No.
Your TFM-15 uses a conventional power transformer. It does use the commutated supplies, so if you were to run 10 KHz into it and turn it up I think you would see it tend towards thermal runaway. Te zobel will not be happy with you and without that another effect would probably take over and end that amp's life. 😀
-Chris
No.
Your TFM-15 uses a conventional power transformer. It does use the commutated supplies, so if you were to run 10 KHz into it and turn it up I think you would see it tend towards thermal runaway. Te zobel will not be happy with you and without that another effect would probably take over and end that amp's life. 😀
-Chris
crazygreek said:
Hey, I picked up a TFM-15CB, and put it in my system for a listen.
Sadly the high end sounded very "solid state". Yuuch, so it sits
on a shelf. I've been thinking of trying to upgrade it to sound better. But I'm novice tinkerer with solid state stuff.
Interestingly, I didn't realize you could take the bulbs out of
these meters....I guess that is what happened to the one
I got, cause they aren't lit.
Maybe we could start a baby carver improvement thread....
the TFM-15s ; )
Hi SyncTronX,
They can be improved, but I'd rather not have non-technicians running around replacing things without a very good idea what they are doing. Heck, most of the techs I've met hardly know what they are doing!
Honestly, this is still not a conventional amplifier. It does have higher supply voltages, but not as high as the TFM-45/55 types. This is a high power amplifier and things usually go very wrong, very quickly. There is more to "improving" an amplifier than sticking in some "better" components.
-Chris
They can be improved, but I'd rather not have non-technicians running around replacing things without a very good idea what they are doing. Heck, most of the techs I've met hardly know what they are doing!
Honestly, this is still not a conventional amplifier. It does have higher supply voltages, but not as high as the TFM-45/55 types. This is a high power amplifier and things usually go very wrong, very quickly. There is more to "improving" an amplifier than sticking in some "better" components.
-Chris
Jecy.lu took a picture of power supply section of Bob Carver's Magnetic Field Amplifier and sent it to me on JUN 30, 2008. Jecy told me there is nothing special with the audio amplifier section. He wanted me to study and do analysis about it. Please see the attached include schematics for detail:
Jecy.lu worked for a company in Taiwan to design audio amplifier and tuner 20 years before. His boss bought a Bob Carver's amplifier and had him to test it. I don't know how he got the schematics. He had already quit that company and be a sales to sell components.
An externally hosted image should be here but it was not working when we last tested it.
Jecy.lu worked for a company in Taiwan to design audio amplifier and tuner 20 years before. His boss bought a Bob Carver's amplifier and had him to test it. I don't know how he got the schematics. He had already quit that company and be a sales to sell components.
anatech, that is not a problem. I know my way around most any high power amp...actually highter power than most silicon amps.anatech said:
Kind of a tube guy here. However, I be willing to learn some from
you npn, pnp guys. I even have me own bench. Nice little workstations or three for what ever should come up.
It is late here and have have a new president. Yeah.
Ok, so let me know what to do and I will do it.
Regards,
Sync
Hi componentbeggar,
Honestly, you are underestimating what is going on and have missed a fair chunk.
Now, this is from your link ...
Your post illustrates exactly why we have trouble when other technicians get into these amps. They are confident that there is nothing tricky going on and assume they know how to deal with them. A hacked amp is the typical result. Even very simple circuits can be well design, elegant solutions to a tricky problem. You need to look more deeply into these if you ever hope to understand them.
No, I am not going to teach a course on these. I've probably posted enough information to explain these amps in enough detail to figure them out.
-Chris
You're kidding - right?
Honestly, you are underestimating what is going on and have missed a fair chunk.
Now, this is from your link ...
Ahhh, that's the output inductor from one channel of the power amplifier. It has zero to do with the power supply.
Your post illustrates exactly why we have trouble when other technicians get into these amps. They are confident that there is nothing tricky going on and assume they know how to deal with them. A hacked amp is the typical result. Even very simple circuits can be well design, elegant solutions to a tricky problem. You need to look more deeply into these if you ever hope to understand them.
No, I am not going to teach a course on these. I've probably posted enough information to explain these amps in enough detail to figure them out.
-Chris
Hi SyncTronX,
When I get to work on redoing an amplifier, it takes a while. There is no recipe that works on all amps. There are often some subtle things that you need to think about before they reveal their secrets.
If you are use to tube amps, that will help. These amps get tube type problems due to high voltages and high heat. The larger amps run at +/- 125 VDC. That's 250 VDC across the circuit, and we are dealing with solid state on consumer type PCBs.
I generally try to determine what operational problems exist first, and repair them. Once the amp is running to spec., I can figure out what deficiencies need to be addressed.
This is a normal amplifier really, so normal upgrade things apply. My definition of upgrading is probably different than most other people's ideas. The first step would be to match the first two differential pairs and tie them together thermally. After that, matching the predrivers forward between complimentary pairs would improve the sound and reduce the measured distortion. You can play with the resistors and caps after this. I normally replace capacitors that don't measure well. I use an HP LCR meter for this job and I'm watching the dissipation factor mostly.
Good luck in your endeavors with this. Let me know where you finish with it.
-Chris
When I get to work on redoing an amplifier, it takes a while. There is no recipe that works on all amps. There are often some subtle things that you need to think about before they reveal their secrets.
If you are use to tube amps, that will help. These amps get tube type problems due to high voltages and high heat. The larger amps run at +/- 125 VDC. That's 250 VDC across the circuit, and we are dealing with solid state on consumer type PCBs.
I generally try to determine what operational problems exist first, and repair them. Once the amp is running to spec., I can figure out what deficiencies need to be addressed.
This is a normal amplifier really, so normal upgrade things apply. My definition of upgrading is probably different than most other people's ideas. The first step would be to match the first two differential pairs and tie them together thermally. After that, matching the predrivers forward between complimentary pairs would improve the sound and reduce the measured distortion. You can play with the resistors and caps after this. I normally replace capacitors that don't measure well. I use an HP LCR meter for this job and I'm watching the dissipation factor mostly.
Good luck in your endeavors with this. Let me know where you finish with it.
-Chris
TFM25 driving ESL's
Unlike me (electronics dummy), you guys on this thread seem pretty knowledgeable on Carver amps. Anyway, I have a couple of Carver TFM 25's bi-amping my home built hybrid ESL's and the treble sounds a bit anemic on the upper end. I read somewhere that Carvers may not be so good at driving ESL's and I'm also wondering if upgrading to 75:1 toroidal transformers ($$$) would correct the weak upper treble. Before I go spending more money on components, I really need to understand whether the treble issue has to do with the step-up transformers or their interaction with the Carver amp. The trannys are 100:1 wound on EI type cores that I bought online from a guy who builds and sells ESL speakers and components (says their good to 20kz but who knows and, again.... could be interaction with the amp). Really, the ESL's sound fantastic with the Carvers except for the anemic upper treble.
Everyone please share your thoughts on:
a) Suitability of Carver TFM 25's for driving ESL's
b) what might be causing the anemic upper treble
thanks y'all,
Charlie
Unlike me (electronics dummy), you guys on this thread seem pretty knowledgeable on Carver amps. Anyway, I have a couple of Carver TFM 25's bi-amping my home built hybrid ESL's and the treble sounds a bit anemic on the upper end. I read somewhere that Carvers may not be so good at driving ESL's and I'm also wondering if upgrading to 75:1 toroidal transformers ($$$) would correct the weak upper treble. Before I go spending more money on components, I really need to understand whether the treble issue has to do with the step-up transformers or their interaction with the Carver amp. The trannys are 100:1 wound on EI type cores that I bought online from a guy who builds and sells ESL speakers and components (says their good to 20kz but who knows and, again.... could be interaction with the amp). Really, the ESL's sound fantastic with the Carvers except for the anemic upper treble.
Everyone please share your thoughts on:
a) Suitability of Carver TFM 25's for driving ESL's
b) what might be causing the anemic upper treble
thanks y'all,
Charlie
Hi Charlie,
One question for you. Do the clip lights (headroom exhausted) ever flicker on when listening at lower levels? Does the amplifier ever run hot or shut down?
-Chris
See now, there is a potential problem right there. Normally a Carver amplifier will drive any reasonable speaker load. I guess your first job would be to have your mystery transformers tested. Failing that, try to find a cheap ribbon tweeter and try that transformer out. Keep in mind that this will probably be a lower power part.
One question for you. Do the clip lights (headroom exhausted) ever flicker on when listening at lower levels? Does the amplifier ever run hot or shut down?
-Chris
PM 1200 - saving the butchered beast
Hi all,
I am new to this forum and to Carver in general.... sort of.
In a previous life (1986) I was working for "The Communicator Shop" a now defunct establishment in Melbourne, Australia which sold, among other top end stuff at the time, Carver amplifiers.
I was somewhat smitten at the time (perhaps due to all the marketing hype) but I never owned one of the things... until now.
I picked up a PM 1200 on e-bay which was going 'for parts' but now that I have it and have found that it is internally complete, I have set myself the task of resurrecting it from the grave (armed with the service manual, of course)
Someone has tried some fault-finding and has:
1/ Cut the lines to Q3 and Q8 on one of the amp boards (I guess to isolate these)
2/ Removed the first 3 pins which connect the same amp board to the power board (again, guessing to try and isolate)
3/ R86, R85 and Q23 on the same board are fried and C24 is missing
4/ Removed D28-D26 as well as R67 (first bank of 6A diodes on the power board)
Other than that, the TRIAC appears ok and there is no sign that the transformer is faulty (from a quick check) The unit has NOT been powered up since I got it.
NOW.... (apologies for the long winded post) I would love to receive some feedback as to the degree of my foolishness to attempt this..... it's the challenge that's got me, I would love to fix this thing.
I see from reading these posts there are some real experts among you! May I pick your brain?? Perhaps some of you would like to see some pics of the management before I start to pull things apart?
Thanks everyone...... terrific forum by the way!
Hi all,
I am new to this forum and to Carver in general.... sort of.
In a previous life (1986) I was working for "The Communicator Shop" a now defunct establishment in Melbourne, Australia which sold, among other top end stuff at the time, Carver amplifiers.
I was somewhat smitten at the time (perhaps due to all the marketing hype) but I never owned one of the things... until now.
I picked up a PM 1200 on e-bay which was going 'for parts' but now that I have it and have found that it is internally complete, I have set myself the task of resurrecting it from the grave (armed with the service manual, of course)
Someone has tried some fault-finding and has:
1/ Cut the lines to Q3 and Q8 on one of the amp boards (I guess to isolate these)
2/ Removed the first 3 pins which connect the same amp board to the power board (again, guessing to try and isolate)
3/ R86, R85 and Q23 on the same board are fried and C24 is missing
4/ Removed D28-D26 as well as R67 (first bank of 6A diodes on the power board)
Other than that, the TRIAC appears ok and there is no sign that the transformer is faulty (from a quick check) The unit has NOT been powered up since I got it.
NOW.... (apologies for the long winded post) I would love to receive some feedback as to the degree of my foolishness to attempt this..... it's the challenge that's got me, I would love to fix this thing.
I see from reading these posts there are some real experts among you! May I pick your brain?? Perhaps some of you would like to see some pics of the management before I start to pull things apart?
Thanks everyone...... terrific forum by the way!