Hello,
DID copy and paste this message from myself to get more views. I mean an answer
I did open the MC2505 because i need to put the two primary windings in series to make it work at the 230 AC voltage in my country.
I can put two LL2733 on top of the chassis where the original caps are located now and put the new caps on the inside. Because i am in the '' metal construction '' i can make a new bottom plate with maybe some extra holes to allow the mounting of the caps. And the bottom plate will get a kind of hat to create an extra space for the caps and voltage dropping resistors for the input circuit power supply.
BUT first will power it up and connect before making any changes.
The 4 big diodes are still the original? ones from Motorola . It looks like M8207R product code. The transformer is 58,5 volt with a center tap. I wanna replace them with schottky to get some extra voltage to compensate for the use of the chokes ( 0,85 ohm DCR). Will it be enough? i still think that 39 volt witch LCL will be better than just a single cap with 40 volts.
Maybe will add a Belleson regulator later but then need more than 58,5 volts.
Greetings, Eduard
DID copy and paste this message from myself to get more views. I mean an answer
I did open the MC2505 because i need to put the two primary windings in series to make it work at the 230 AC voltage in my country.
I can put two LL2733 on top of the chassis where the original caps are located now and put the new caps on the inside. Because i am in the '' metal construction '' i can make a new bottom plate with maybe some extra holes to allow the mounting of the caps. And the bottom plate will get a kind of hat to create an extra space for the caps and voltage dropping resistors for the input circuit power supply.
BUT first will power it up and connect before making any changes.
The 4 big diodes are still the original? ones from Motorola . It looks like M8207R product code. The transformer is 58,5 volt with a center tap. I wanna replace them with schottky to get some extra voltage to compensate for the use of the chokes ( 0,85 ohm DCR). Will it be enough? i still think that 39 volt witch LCL will be better than just a single cap with 40 volts.
Maybe will add a Belleson regulator later but then need more than 58,5 volts.
Greetings, Eduard
Attachments
If you are changing the input voltage, the output voltage components are not affected. There is no need to prat about with one of the best designs in history!
Don't forget to change the mains fuse to T1.25A from T2.5A
Don't forget to change the mains fuse to T1.25A from T2.5A
Hello,
I did change the primary connection from two windings in parallel to two windings in series to make it work with 230 volts ac in my country.
Did find schottky diodes ( sb12100 12A peak reverse voltage 100 volt). Will wait for more input to decide if i will use them.
greetings, Eduard
I did change the primary connection from two windings in parallel to two windings in series to make it work with 230 volts ac in my country.
Did find schottky diodes ( sb12100 12A peak reverse voltage 100 volt). Will wait for more input to decide if i will use them.
greetings, Eduard
Hi Jon,
Yes and they were not above doing stupid stuff too. Like putting low signal wiring on top of noisy AC wiring, etc.
In the following years McIntosh has always done the flat wire interface to connector incorrectly and they've always done it incorrectly and never changed it. Source of many problems, of course the solution is to new cable and connectors properly interfaced.
Yes, they also did many thing right too. : )
Cheers,
Yes and they were not above doing stupid stuff too. Like putting low signal wiring on top of noisy AC wiring, etc.
In the following years McIntosh has always done the flat wire interface to connector incorrectly and they've always done it incorrectly and never changed it. Source of many problems, of course the solution is to new cable and connectors properly interfaced.
Yes, they also did many thing right too. : )
Cheers,
Hello,
I did start replacing the caps in the power supply.
I am not a technician at all but the way the power supply is wired is not really the best way to do it. Because the resistors in the power supply used to make RC network and/or getting the right voltage for the next stage to be '' fed '' are in the same area mounted between two terminal strips.. The wire feeding the circuit will often depart from the resistor which seems strange to me because the '' energy '' is stored in the cap. So i did replace the old caps containing a few caps inside by seperate ones and mounted the resistors right the different caps and have the circuit getting their supply by using a wire coming from the capacitor.
The grounding of the capacitors in the original design is also a bit strange. There are two terminal strips and in the end the result is that they are all connected to the chassis together with the center taps from the transformer.
Because i did change the power supply into a CLC type and change the two multiple caps by seperate ones i ended up with more wires that need to be connected to ground.
I did connect the center taps and the two caps that are between rectifier and choke to the same cable lug. The caps after the choke to another lug. The caps from the negative power supply used for driver/input to a seperate lug. And then the last lug for the positive supply of the driver./input stages.
These lugs can be bolted to the chassis using the same bolt. Could be possible to only connect the center taps and first caps to the chassis there and the other ones inanother area closer to the input of the circuit???
Will post some photos later.
Greetings, Eduard
I did start replacing the caps in the power supply.
I am not a technician at all but the way the power supply is wired is not really the best way to do it. Because the resistors in the power supply used to make RC network and/or getting the right voltage for the next stage to be '' fed '' are in the same area mounted between two terminal strips.. The wire feeding the circuit will often depart from the resistor which seems strange to me because the '' energy '' is stored in the cap. So i did replace the old caps containing a few caps inside by seperate ones and mounted the resistors right the different caps and have the circuit getting their supply by using a wire coming from the capacitor.
The grounding of the capacitors in the original design is also a bit strange. There are two terminal strips and in the end the result is that they are all connected to the chassis together with the center taps from the transformer.
Because i did change the power supply into a CLC type and change the two multiple caps by seperate ones i ended up with more wires that need to be connected to ground.
I did connect the center taps and the two caps that are between rectifier and choke to the same cable lug. The caps after the choke to another lug. The caps from the negative power supply used for driver/input to a seperate lug. And then the last lug for the positive supply of the driver./input stages.
These lugs can be bolted to the chassis using the same bolt. Could be possible to only connect the center taps and first caps to the chassis there and the other ones inanother area closer to the input of the circuit???
Will post some photos later.
Greetings, Eduard
Hi Eduard,
I really, strongly suggest that you not mess with the grounding on these or any other amplifiers. McIntosh engineers knew precisely what they were doing when they designed these products. I'm not about to start second guessing them. I would also have left the original filter capacitors in place unless they were failing (which I doubt they were).
-Chris
I really, strongly suggest that you not mess with the grounding on these or any other amplifiers. McIntosh engineers knew precisely what they were doing when they designed these products. I'm not about to start second guessing them. I would also have left the original filter capacitors in place unless they were failing (which I doubt they were).
-Chris
Hello Chris,
Always finished it and going back to the original situation would take me at least the same time. lol
The caps being at least forty years old i dont wanna take the risk. Once i had a big cap going bad ( the pressure vent did open up) not with a big bang but still.
The original ones might be ok but i dont wanna take the risk. You can find a lot of postings here about caps going bad in amps much younger than this one ( produced between 1967 and 1977)
Because there need to be done some modifications like adding an input transformer and a 600 hertz/cycles 12 db filter i will ask a professional technician to continue. He will surely optimize the power supply.
Greetings, Eduard
Always finished it and going back to the original situation would take me at least the same time. lol
The caps being at least forty years old i dont wanna take the risk. Once i had a big cap going bad ( the pressure vent did open up) not with a big bang but still.
The original ones might be ok but i dont wanna take the risk. You can find a lot of postings here about caps going bad in amps much younger than this one ( produced between 1967 and 1977)
Because there need to be done some modifications like adding an input transformer and a 600 hertz/cycles 12 db filter i will ask a professional technician to continue. He will surely optimize the power supply.
Greetings, Eduard
Hi Eduard,
I'm an authorized McIntosh technician. Those large capacitors rarely fail or dry out. They aren't the same as the small electrolytic types. The terminal studs allow for very high peak currents to flow, and this amplifier (or any for that matter) rely on this for high transients in the music.
If you must replace those, buy something the same type and value. These will be expensive, but there is a reason why this is so. I think you are focusing on a rare event to justify replacing them, but that is your prerogative. Just put the appropriate type to replace them with.
In the same vein, output transistors are known to fail without reason too. Same as all components. Will you replace them all? The failure rate for these other parts exceeds the failure rate with the filter capacitors. I can make a stronger case to replace them.
-Chris
I'm an authorized McIntosh technician. Those large capacitors rarely fail or dry out. They aren't the same as the small electrolytic types. The terminal studs allow for very high peak currents to flow, and this amplifier (or any for that matter) rely on this for high transients in the music.
If you must replace those, buy something the same type and value. These will be expensive, but there is a reason why this is so. I think you are focusing on a rare event to justify replacing them, but that is your prerogative. Just put the appropriate type to replace them with.
In the same vein, output transistors are known to fail without reason too. Same as all components. Will you replace them all? The failure rate for these other parts exceeds the failure rate with the filter capacitors. I can make a stronger case to replace them.
-Chris
Hello Chris,
I just fired the amp up. No smoke so far. Will check the voltages later.
Maybe the technician will have to adjust the gain a little if possible? Maybe i will try to find some transistors to keep as spare parts.
The main reason for buying this amp was the output transformer because i was afraid to destroy my exopensive altec woofers in case of DC on the output. I thought it was a transformer similar to the Tamura F2032 but it is an autotransformer so just one winding. lol And dont forget the looks of this amp. Reminds me of Marantz gear in the eighties.
The amp will be used up to 600 hertz for my Altec VOT. The Altec can be hard to drive because of high impedance peaks. Most tube amp can do it well. The Hiraga solid state can do it too. Hoping the MC2505 will not disappoint me. Greetings, Eduard
I just fired the amp up. No smoke so far. Will check the voltages later.
Maybe the technician will have to adjust the gain a little if possible? Maybe i will try to find some transistors to keep as spare parts.
The main reason for buying this amp was the output transformer because i was afraid to destroy my exopensive altec woofers in case of DC on the output. I thought it was a transformer similar to the Tamura F2032 but it is an autotransformer so just one winding. lol And dont forget the looks of this amp. Reminds me of Marantz gear in the eighties.
The amp will be used up to 600 hertz for my Altec VOT. The Altec can be hard to drive because of high impedance peaks. Most tube amp can do it well. The Hiraga solid state can do it too. Hoping the MC2505 will not disappoint me. Greetings, Eduard
Hi Eduard,
Most good amplifiers have DC output protection, most commonly by relays. Lately I've seen mosfet type protection "relays". I need to check these out as they may be the perfect answer to the relay replacement game.
A different amplifier protection is used very successfully in Carver equipment like the big amps. What they do is have a supply that stores minimal energy, and the protection shuts the power supply down very, very quickly. It isn't uncommon for a 375 watt Carver amplifier to have only suffered one shorted output. In other cases the bias components fail and perhaps a driver transistor. The point I'm making is that total failures with a Carver is typically not an extensive repair job and very seldomly damages the speakers in failure mode. However, most speakers damaged while running on a Carver die because very few speakers can handle the very real 375 wpc that an M 1.5t delivers. Same goes for an M 4.0, Lightstar, or TFM-45 or TFM-75 amplifiers. It's usually the complete failure of the speaker that causes a failure in a Carver amplifier. Actually, the M 2.0 is another animal that Carver made.
The McIntosh should make you happy. If it doesn't you can try a higher powered model, or go with a Carver amplifier. Keep in mind that you should have a Carver serviced by a competent technician who has been trained on Carver amplifiers. Do not attempt to service one of these yourself. They work differently than most other amplifiers. The power supplies on the bigger ones are +/- 125 VDC. I kid you not! That and the charge doesn't drain off for quite some time.
-Chris
Most good amplifiers have DC output protection, most commonly by relays. Lately I've seen mosfet type protection "relays". I need to check these out as they may be the perfect answer to the relay replacement game.
A different amplifier protection is used very successfully in Carver equipment like the big amps. What they do is have a supply that stores minimal energy, and the protection shuts the power supply down very, very quickly. It isn't uncommon for a 375 watt Carver amplifier to have only suffered one shorted output. In other cases the bias components fail and perhaps a driver transistor. The point I'm making is that total failures with a Carver is typically not an extensive repair job and very seldomly damages the speakers in failure mode. However, most speakers damaged while running on a Carver die because very few speakers can handle the very real 375 wpc that an M 1.5t delivers. Same goes for an M 4.0, Lightstar, or TFM-45 or TFM-75 amplifiers. It's usually the complete failure of the speaker that causes a failure in a Carver amplifier. Actually, the M 2.0 is another animal that Carver made.
The McIntosh should make you happy. If it doesn't you can try a higher powered model, or go with a Carver amplifier. Keep in mind that you should have a Carver serviced by a competent technician who has been trained on Carver amplifiers. Do not attempt to service one of these yourself. They work differently than most other amplifiers. The power supplies on the bigger ones are +/- 125 VDC. I kid you not! That and the charge doesn't drain off for quite some time.
-Chris
Off topic a little, but since Chris is here, it is probably easier to ask him one quick question instead of start a new thread. It is probably just a short answer 🙂
<off topic>
I have a Carver M500T sitting in garage for yearsssss. Is there any recommendation on the best way to bring back to life?
For other amps such as my MC2120, I could use a variac to ramp up the voltage over time. Since Carver's power supply is different, I am not sure this method is still valid.
</off topic>
FWIW, the mc2120 is a close cousin of mc2105 without the signature glass panel. Mine has developed a (suspect) relay problem which one channel doesn't always engage upon power on. Once it is engaged, the channel will stay on until the next power cycle. Hence, it is time to bring back the Carver (love those classic analog meters).
Thanks!!
<off topic>
I have a Carver M500T sitting in garage for yearsssss. Is there any recommendation on the best way to bring back to life?
For other amps such as my MC2120, I could use a variac to ramp up the voltage over time. Since Carver's power supply is different, I am not sure this method is still valid.
</off topic>
FWIW, the mc2120 is a close cousin of mc2105 without the signature glass panel. Mine has developed a (suspect) relay problem which one channel doesn't always engage upon power on. Once it is engaged, the channel will stay on until the next power cycle. Hence, it is time to bring back the Carver (love those classic analog meters).
Thanks!!
Hi Fred,
There is a way to soft start a Carver power supply, but that means working on the AC side of the power supply and it's dangerous as heck. I can't recommend anyone do this so I can't really tell anyone how with this method.
There doesn't seem to be any other way to power it up than to just plug it in and turn it on. Make sure there is nothing else connected to it, no speakers. If a fault occurs, the protection will shut it down.
I don't think the light bulb test will work because the Carver draws a lot of current initially to bring the supplies up. Because it has an active regulator, the lamp might cause all kinds of strange behavior.
The final way you can do this is to get a bipolar DC power supply and slowly ramp up the rails. Short the supplies together (all positive together, and all negative together) and power it up to about +/- 25 VDC. Stop there while you watch for current draw. A lot is bad, very bad. You could then disconnect tier 1 voltage leads (the lowest voltage) and turn the supply up some more and stop at +/- 40 VDC. I you disconnect the tier 2 supplies you can take the highest tier up to +/- 70 VDC. You should already know if you are going to have issues or not before now. If this passes, plug it in and spark it up. Make sure you have removed all your wires and clip leads before doing this.
Keep in mind that bad things can happen at any point. This can be a risky venture and I'm not that happy with the thought of you trying this. Doing anything I have suggested is purely at your own risk. These are not normal testing methods and can put you in contact with lethal voltages if you aren't very, very careful. If you have the least doubt about these procedures, take your amplifier to a technician that knows these amplifiers well.
Nice amplifier though. Pretty too.
-Chris
There is a way to soft start a Carver power supply, but that means working on the AC side of the power supply and it's dangerous as heck. I can't recommend anyone do this so I can't really tell anyone how with this method.
There doesn't seem to be any other way to power it up than to just plug it in and turn it on. Make sure there is nothing else connected to it, no speakers. If a fault occurs, the protection will shut it down.
I don't think the light bulb test will work because the Carver draws a lot of current initially to bring the supplies up. Because it has an active regulator, the lamp might cause all kinds of strange behavior.
The final way you can do this is to get a bipolar DC power supply and slowly ramp up the rails. Short the supplies together (all positive together, and all negative together) and power it up to about +/- 25 VDC. Stop there while you watch for current draw. A lot is bad, very bad. You could then disconnect tier 1 voltage leads (the lowest voltage) and turn the supply up some more and stop at +/- 40 VDC. I you disconnect the tier 2 supplies you can take the highest tier up to +/- 70 VDC. You should already know if you are going to have issues or not before now. If this passes, plug it in and spark it up. Make sure you have removed all your wires and clip leads before doing this.
Keep in mind that bad things can happen at any point. This can be a risky venture and I'm not that happy with the thought of you trying this. Doing anything I have suggested is purely at your own risk. These are not normal testing methods and can put you in contact with lethal voltages if you aren't very, very careful. If you have the least doubt about these procedures, take your amplifier to a technician that knows these amplifiers well.
Nice amplifier though. Pretty too.
-Chris
Thanks, Chris!!
I am quite cautious with high voltage as I take care of all my the gears. However, it doesn't mean I fool around in the area that I don't quite understand 🙂
I have to admit that the techs in my area (San Francisco Bay Area!!!) are ridiculously incompetent and expensive. I spent more money with these techs (McIntosh certified, wherever that means ...) to fix my mc2120 than the amount I paid for it, sigh. Perhaps, most have jump to fix smart phones 🙂
I think I will have to trust my "leap of faith" and power up the M500T. I just can't stop thinking these scams will charge me 2 hours of work and give me a dead amp back!!
Sorry for the vent, folks!!
I am quite cautious with high voltage as I take care of all my the gears. However, it doesn't mean I fool around in the area that I don't quite understand 🙂
I have to admit that the techs in my area (San Francisco Bay Area!!!) are ridiculously incompetent and expensive. I spent more money with these techs (McIntosh certified, wherever that means ...) to fix my mc2120 than the amount I paid for it, sigh. Perhaps, most have jump to fix smart phones 🙂
I think I will have to trust my "leap of faith" and power up the M500T. I just can't stop thinking these scams will charge me 2 hours of work and give me a dead amp back!!
Sorry for the vent, folks!!
Hi Fred,
It's that way here too. I know some pretty useless McIntosh certified techs. It used to mean you knew your stuff and had morals. I don't know about now.
I hear more horror stories like yours everyday. You certainly aren't alone. The good techs have to clean up after these folks. I'm getting pretty sick of doing it too.
-Chris
It's that way here too. I know some pretty useless McIntosh certified techs. It used to mean you knew your stuff and had morals. I don't know about now.
I hear more horror stories like yours everyday. You certainly aren't alone. The good techs have to clean up after these folks. I'm getting pretty sick of doing it too.
-Chris
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