Hi Eugenio,
What a busy day it has been today!
Okay, so 1738B (what's the "B" for?) looks like it has the tiny TO-5 triac. That one is bound to fail if it hasn't already. It needs some serious attention and is really too old in the design trail to trust. It needs updating before ever considering it for use, never mind a voltage change operation! I'm sorry about the news I had to give you.
Your serial 8196B on the other hand is basically the most recent design requiring no changes to update. This is the power supply that I wish all of them had. To be honest with you, using a step - down transformer to convert it to 230 VAC is the best plan. This also means that the case on your amplifier should be the later charcoal grey colour. It's a nice looking amplifier - as nice as a little cube gets. So the is the one to concentrate on. I think the old one you have is too risky to use, but that is only my opinion.
Hi Tajzmaj,
Serial # 1755 is a little newer than Eugenio's old one and should have two parallel connected TO-220 case triacs. This one is getting close to having a reliable supply. It may still use an LDR (light dependent resistor). This one is more reliable, but still very early in the design process. I wouldn't want to do much to it either. Too bad it wasn't like serial 8196B. Don't leave it running unattended. For sure turn it of if you leave the house for anything. I just simply don't trust the early power supplies that much.
-Chris
What a busy day it has been today!
Okay, so 1738B (what's the "B" for?) looks like it has the tiny TO-5 triac. That one is bound to fail if it hasn't already. It needs some serious attention and is really too old in the design trail to trust. It needs updating before ever considering it for use, never mind a voltage change operation! I'm sorry about the news I had to give you.
Your serial 8196B on the other hand is basically the most recent design requiring no changes to update. This is the power supply that I wish all of them had. To be honest with you, using a step - down transformer to convert it to 230 VAC is the best plan. This also means that the case on your amplifier should be the later charcoal grey colour. It's a nice looking amplifier - as nice as a little cube gets. So the is the one to concentrate on. I think the old one you have is too risky to use, but that is only my opinion.
Hi Tajzmaj,
Serial # 1755 is a little newer than Eugenio's old one and should have two parallel connected TO-220 case triacs. This one is getting close to having a reliable supply. It may still use an LDR (light dependent resistor). This one is more reliable, but still very early in the design process. I wouldn't want to do much to it either. Too bad it wasn't like serial 8196B. Don't leave it running unattended. For sure turn it of if you leave the house for anything. I just simply don't trust the early power supplies that much.
-Chris
Hey Chris!
I agree with you completely. Old ''original'' psu is junk. Mine has just one to220 triac inside which I replaced with bit to247 one. And yes there is some sort of vactrol inside. Can't say from my memory...VTL 5cX...something. It is running quite smooth and reliable enough at all powers for some 5 maybe 7 years now. But man it really takes a lot of nerves, time, equipment etc to do it. And I wouldn't advice anyone to try it. Step down transformer is easiest solution. And maybe even cheapest one! And I also agree that later versions of psu works way better. I have some 40 other PM and PT amps powering my live PA...those work fine till mains holds 🙂
There are many other probably better amps to go. If I'm honest, I don't really love how M400 sounds. But still I'm in love with Carver stuff. Can't explain...
To Eugenio. I would also go with step down transformer...
But if someone really needs it. I have recovered data how mag coil is done. Someone experienced enough.
Cheers
I agree with you completely. Old ''original'' psu is junk. Mine has just one to220 triac inside which I replaced with bit to247 one. And yes there is some sort of vactrol inside. Can't say from my memory...VTL 5cX...something. It is running quite smooth and reliable enough at all powers for some 5 maybe 7 years now. But man it really takes a lot of nerves, time, equipment etc to do it. And I wouldn't advice anyone to try it. Step down transformer is easiest solution. And maybe even cheapest one! And I also agree that later versions of psu works way better. I have some 40 other PM and PT amps powering my live PA...those work fine till mains holds 🙂
There are many other probably better amps to go. If I'm honest, I don't really love how M400 sounds. But still I'm in love with Carver stuff. Can't explain...
To Eugenio. I would also go with step down transformer...
But if someone really needs it. I have recovered data how mag coil is done. Someone experienced enough.
Cheers
Hi Tajzmaj,
I still repair Carver amplifiers and other products. Those amplifiers are excellent performers, so I am not surprised that you like them. Used properly, they were extremely reliable, and they sounded good compared to the standard PA amps of that time period. These days we have other high efficiency amplifiers available. Some even sound good, but it took Carver to create that market.
Yes, the "VTL 5cX...something" is an LDR. It is basically an LED and CDs cell in a tube to block external light. The newer amplifiers changed to an opto-coupler to control the triac. The substitute triac you used sounds like a wise choice. We were instructed to use the funny TO-3 bolt pattern type triacs. All the terminals are mounted on the top, which makes them easier to work with and safer as the terminals are not close to the chassis at all. Your solution was probably less expensive (the triac) and much more reliable than the original parts.
Your PM and PT products are much more refined designs. I especially like the PT-2400. It is very similar to the TFM-75, the nicest looking amplifier Carver ever produced. The best sounding too. It's pretty heavy though. One of these would be great running at home. I would kick the M-400 to the curb and install a PT-2400. Not unless you happen to have a TFM-75 lying about. Then go for that one.
Otherwise Tajzmaj, you have nerves of steel my friend!
-Chris
I still repair Carver amplifiers and other products. Those amplifiers are excellent performers, so I am not surprised that you like them. Used properly, they were extremely reliable, and they sounded good compared to the standard PA amps of that time period. These days we have other high efficiency amplifiers available. Some even sound good, but it took Carver to create that market.
Yes, the "VTL 5cX...something" is an LDR. It is basically an LED and CDs cell in a tube to block external light. The newer amplifiers changed to an opto-coupler to control the triac. The substitute triac you used sounds like a wise choice. We were instructed to use the funny TO-3 bolt pattern type triacs. All the terminals are mounted on the top, which makes them easier to work with and safer as the terminals are not close to the chassis at all. Your solution was probably less expensive (the triac) and much more reliable than the original parts.
Your PM and PT products are much more refined designs. I especially like the PT-2400. It is very similar to the TFM-75, the nicest looking amplifier Carver ever produced. The best sounding too. It's pretty heavy though. One of these would be great running at home. I would kick the M-400 to the curb and install a PT-2400. Not unless you happen to have a TFM-75 lying about. Then go for that one.
Otherwise Tajzmaj, you have nerves of steel my friend!
-Chris
Hey Chris!
I Agree with you again. PT1800/2400 is better sounding but I really don't need that much power at home. I'm using PT2400 for subs and PT1800 for mids at my big p.a. 8 of each 🙂
I decided to use TO 247 triac over the one with fastons on the top because I wanted to keep M400 as original as possible. It is in really nice condition and I would hate to drill another hole to mount that ''to3'' triac.
For home I use mostly my PL700 or some of my diy projects.
Cheers
I Agree with you again. PT1800/2400 is better sounding but I really don't need that much power at home. I'm using PT2400 for subs and PT1800 for mids at my big p.a. 8 of each 🙂
I decided to use TO 247 triac over the one with fastons on the top because I wanted to keep M400 as original as possible. It is in really nice condition and I would hate to drill another hole to mount that ''to3'' triac.
For home I use mostly my PL700 or some of my diy projects.
Cheers
Hi Tajzmaj,
Well, I had a series 1 Lightstar for a while. Didn't need the power, but it was so cool, and pretty good sounding. I had a TFM-75 home for a short while. Love the way it looks, and I think it was the best sounding stock Carver amplifier. The PT-2400 is basically the same animal, so why not use it for the way it sounds? Just curious.
Some DIY amps are great that I have seen around here. Can't fault you for that at all. No offense, but the M-400 is seriously out classed by most of the other stuff you have. I guess the M-400 is just too cool to put away.
I can see why you used the TO-247 case triac. Drilling another hole is done after some though, and sometimes isn't done after some thought too.
-Chris
Well, I had a series 1 Lightstar for a while. Didn't need the power, but it was so cool, and pretty good sounding. I had a TFM-75 home for a short while. Love the way it looks, and I think it was the best sounding stock Carver amplifier. The PT-2400 is basically the same animal, so why not use it for the way it sounds? Just curious.
Some DIY amps are great that I have seen around here. Can't fault you for that at all. No offense, but the M-400 is seriously out classed by most of the other stuff you have. I guess the M-400 is just too cool to put away.
I can see why you used the TO-247 case triac. Drilling another hole is done after some though, and sometimes isn't done after some thought too.
-Chris
Hi Chris, Hi Tajzmaj
Checked my 1738 and, yes it has the TO-5 triac; the schematics that are on the net are enough to try to update the amp? May be using the 8196 amp I can try to renew the old PS...
You spoke about a triac with faston terminals, is this the one on your photo? So wich one is the best solution on this PS? When I have a little time I'll compare the two PS.
Thanks to all for the hints, I'll buy a step down transformer.
Ciao e grazie
Eugenio
Checked my 1738 and, yes it has the TO-5 triac; the schematics that are on the net are enough to try to update the amp? May be using the 8196 amp I can try to renew the old PS...
You spoke about a triac with faston terminals, is this the one on your photo? So wich one is the best solution on this PS? When I have a little time I'll compare the two PS.
Thanks to all for the hints, I'll buy a step down transformer.
Ciao e grazie
Eugenio
Hi Eugenio,
I can't remember what they look like (TO-5 triacs & PCB). The triac shown in the picture is the current type to be used. I think there are modifications needed to use that one. From memory, I do not think you can use that with the LDR circuit. You certainly can try though. Set your voltages a bit lower than in the manual instructions. The voltage tends to creep up over time. You might want to check it in a month to make sure it isn't rising too far. Check this at night once heavy industry has shut down so your line voltage is in the same ballpark.
-Chris
I can't remember what they look like (TO-5 triacs & PCB). The triac shown in the picture is the current type to be used. I think there are modifications needed to use that one. From memory, I do not think you can use that with the LDR circuit. You certainly can try though. Set your voltages a bit lower than in the manual instructions. The voltage tends to creep up over time. You might want to check it in a month to make sure it isn't rising too far. Check this at night once heavy industry has shut down so your line voltage is in the same ballpark.
-Chris
Hey Chris
Why not use PT2400 at home..haha..I like it's sound for P.A. It delivers some ''true'' power. Clean sounding ''punchy'' amp. I like it.
But for home use I would called little ''muffled'' maybe. Can't explain really. All my amps are re-capped and adjusted...but still. Also I really don't need such power at home and I'm not willing to listen loud fan. I know it could be removed or at least disconnected. But still. I even don't like my M400 very much. It is decent amp but nothing really special. From all Carver stuff I probably prefer nicely refurbished G-class PM1.5, probably...I was even thinking about building ''updated'' clone of it. Something similar to PM1201..just without mag-coil psu. Just simple toroid ad capacitors...
Sadly I'm really busy guy and I have too many unfinished projects already. One day maybe.
For now I'll stick to my Phase Linear 700b. I like it. It is great for some easy listening. I'm using it with AR10pi speakers. Whole setup is nice sounding, but not too accurate not to detailed. Just right for someone who is professionally exposed to all sorts of sound systems every day....
Ah just one more thing about M400. It is revolutionary amp for that time. Today I would call it ''funky'' and ''oldtimer''....I have it just because of such reasons.
Cheers
Why not use PT2400 at home..haha..I like it's sound for P.A. It delivers some ''true'' power. Clean sounding ''punchy'' amp. I like it.
But for home use I would called little ''muffled'' maybe. Can't explain really. All my amps are re-capped and adjusted...but still. Also I really don't need such power at home and I'm not willing to listen loud fan. I know it could be removed or at least disconnected. But still. I even don't like my M400 very much. It is decent amp but nothing really special. From all Carver stuff I probably prefer nicely refurbished G-class PM1.5, probably...I was even thinking about building ''updated'' clone of it. Something similar to PM1201..just without mag-coil psu. Just simple toroid ad capacitors...
Sadly I'm really busy guy and I have too many unfinished projects already. One day maybe.
For now I'll stick to my Phase Linear 700b. I like it. It is great for some easy listening. I'm using it with AR10pi speakers. Whole setup is nice sounding, but not too accurate not to detailed. Just right for someone who is professionally exposed to all sorts of sound systems every day....
Ah just one more thing about M400. It is revolutionary amp for that time. Today I would call it ''funky'' and ''oldtimer''....I have it just because of such reasons.
Cheers
Hi Tajzmaj,
I fixed a few PT-2400's, but took home the TFM-75. That is almost identical to the PT-2400. The TFM-75 sounds really good, but I guess there are some differences between them. The fan for one, forgot about that.
My favorite amplifier so far is a Marantz 300DC that I reworked. Lovely sounding unit. Your Phase Linear could sound better. It takes some work on your part though. I am discovering that extremely close matching for the diff pairs really makes a big difference in the sound. That would be very worthwhile.
-Chris
That's what I figured. I almost did the same thing - only because it was a ground breaking design. Almost kept an Adcom GFA-1A for similar reasons. The Adcom sounded better.
I fixed a few PT-2400's, but took home the TFM-75. That is almost identical to the PT-2400. The TFM-75 sounds really good, but I guess there are some differences between them. The fan for one, forgot about that.
My favorite amplifier so far is a Marantz 300DC that I reworked. Lovely sounding unit. Your Phase Linear could sound better. It takes some work on your part though. I am discovering that extremely close matching for the diff pairs really makes a big difference in the sound. That would be very worthwhile.
-Chris
Hey Chris
I've rebuilt my PL700...All transistors are matched..actually I've installed matched quad for stereo....converting it to fully comp seemed good idea at the time but than again I wanted to leave it as it is. Of course all other transistors are replaced etc. Not to mention caps...Only thing which is different is I installed decent dc protection. Ah...and I made new chassis. Old one was ripped apart because of weight of power transformer. This amp was completely destroyed when I bought it for something what would be like 50€ today. It's been probably over 20 years ago. I renewed it some 10 years ago...It is nice amp..again ''oldtimer''
Marantz 300DC. I never even see one of those. Here is ex Yugoslavia region it is probably quite rare.
What about Crown DC300. I'm thinking it might be nice addition to ''collection''.
Cheers
I've rebuilt my PL700...All transistors are matched..actually I've installed matched quad for stereo....converting it to fully comp seemed good idea at the time but than again I wanted to leave it as it is. Of course all other transistors are replaced etc. Not to mention caps...Only thing which is different is I installed decent dc protection. Ah...and I made new chassis. Old one was ripped apart because of weight of power transformer. This amp was completely destroyed when I bought it for something what would be like 50€ today. It's been probably over 20 years ago. I renewed it some 10 years ago...It is nice amp..again ''oldtimer''
Marantz 300DC. I never even see one of those. Here is ex Yugoslavia region it is probably quite rare.
What about Crown DC300. I'm thinking it might be nice addition to ''collection''.
Cheers
Hi Tajzmaj,
A Crown DC300. It was a very popular amplifier way back in time. I used to sell them - new. They are known as Amcron in Canada due to a trade name issue. Here, Crown was the name of a cheap boom box thing. So Crown couldn't use their name here, and they chose AMerican CROwN, AMCRON.
Anyway, I do get them to fix, but they are class B in every sense of the word. Not a nice sounding amplifier and really only suited to paging applications instead of sound reinforcement. They are still popular in recording studios.
If you want to create a museum for industry changing models, I guess a case can be made for the DC300. But I'd rather not listen to one.
The Marantz 300DC is an extremely good sounding amplifier, 150 wpc. Good for home use, I think it has 3 dB headroom. (!) Each voltage amplifier section has it's own DC regulator at a higher voltage than the output stage. Each output stage has it's own winding and power supply as well. The voltage amps also get their own windings. The 170DC doesn't have all that wonderful regulation, and is rated for less power, but it is also a really nice sounding amplifier. Of course you have to refresh the amplifier circuits, and do some detail work. Your efforts will be richly rewarded.
-Chris
A Crown DC300. It was a very popular amplifier way back in time. I used to sell them - new. They are known as Amcron in Canada due to a trade name issue. Here, Crown was the name of a cheap boom box thing. So Crown couldn't use their name here, and they chose AMerican CROwN, AMCRON.
Anyway, I do get them to fix, but they are class B in every sense of the word. Not a nice sounding amplifier and really only suited to paging applications instead of sound reinforcement. They are still popular in recording studios.
If you want to create a museum for industry changing models, I guess a case can be made for the DC300. But I'd rather not listen to one.
The Marantz 300DC is an extremely good sounding amplifier, 150 wpc. Good for home use, I think it has 3 dB headroom. (!) Each voltage amplifier section has it's own DC regulator at a higher voltage than the output stage. Each output stage has it's own winding and power supply as well. The voltage amps also get their own windings. The 170DC doesn't have all that wonderful regulation, and is rated for less power, but it is also a really nice sounding amplifier. Of course you have to refresh the amplifier circuits, and do some detail work. Your efforts will be richly rewarded.
-Chris
CROWN DC300
Anatech,
A Crown DC300 is an AB+B design simply owing to the fact that the predriver drives the load through 5.6 ohm resistors allowing the predrivers to be biased harder than normal, hence the "A" in the AB+B
Marantz 300DC runs of +/-70v rails so it is impossible to have 3dB of headroom. You would meed at least +/-85v rails to do this.
Anyway, I do get them to fix, but they are class B in every sense of the word. Not a nice sounding amplifier and really only suited to paging applications instead of sound reinforcement. They are still popular in recording studios.
If you want to create a museum for industry changing models, I guess a case can be made for the DC300. But I'd rather not listen to one.
The Marantz 300DC is an extremely good sounding amplifier, 150 wpc. Good for home use, I think it has 3 dB headroom. (!) Each voltage amplifier section has it's own DC regulator at a higher voltage than the output stage. Each output stage has it's own winding and power supply as well. The voltage amps also get their own windings. The 170DC doesn't have all that wonderful regulation, and is rated for less power, but it is also a really nice sounding amplifier. Of course you have to refresh the amplifier circuits, and do some detail work. Your efforts will be richly rewarded.
Anatech,
A Crown DC300 is an AB+B design simply owing to the fact that the predriver drives the load through 5.6 ohm resistors allowing the predrivers to be biased harder than normal, hence the "A" in the AB+B
Marantz 300DC runs of +/-70v rails so it is impossible to have 3dB of headroom. You would meed at least +/-85v rails to do this.
Anyway, I do get them to fix, but they are class B in every sense of the word. Not a nice sounding amplifier and really only suited to paging applications instead of sound reinforcement. They are still popular in recording studios.
If you want to create a museum for industry changing models, I guess a case can be made for the DC300. But I'd rather not listen to one.
The Marantz 300DC is an extremely good sounding amplifier, 150 wpc. Good for home use, I think it has 3 dB headroom. (!) Each voltage amplifier section has it's own DC regulator at a higher voltage than the output stage. Each output stage has it's own winding and power supply as well. The voltage amps also get their own windings. The 170DC doesn't have all that wonderful regulation, and is rated for less power, but it is also a really nice sounding amplifier. Of course you have to refresh the amplifier circuits, and do some detail work. Your efforts will be richly rewarded.
Chris...
I know Amcron story. I have actually few of Amcron MA1201. Good sounding amp though.
I think I might grab DC300 if I find one in good cosmetical condition and not unreasonably expensive. I agree with your wife. It is good to know when to stop sometimes...fact is I really don't need another amp. It is just fun restoring it..
Cheers
I know Amcron story. I have actually few of Amcron MA1201. Good sounding amp though.
I think I might grab DC300 if I find one in good cosmetical condition and not unreasonably expensive. I agree with your wife. It is good to know when to stop sometimes...fact is I really don't need another amp. It is just fun restoring it..
Cheers
Ah one more thing...
If I would buy DC300 it wouldn't be for class in which it's operating. I like the design..haha...
Cheers
If I would buy DC300 it wouldn't be for class in which it's operating. I like the design..haha...
Cheers
Hi MOER,
You're right. I can't remember where I got that figure from, I did read it somewhere. I wonder if that was for the actual stated output power and the rated power, or something stupid like that. Mine is due to visit my bench soon, so I can take actual measurements.
Interestingly, there is a couple of 85 VDC rails in there. They are for the voltage amp regulators I spoke about. I see they specify the Vamp supplies and raw power supplies at 70 VDC, but I recall getting different values when I measured it last. Something to do next time.
Well, back to fixing stuff. That 300DC may make it up sooner than planned since my curiosity has been peaked.
-Chris
You're right. I can't remember where I got that figure from, I did read it somewhere. I wonder if that was for the actual stated output power and the rated power, or something stupid like that. Mine is due to visit my bench soon, so I can take actual measurements.
Interestingly, there is a couple of 85 VDC rails in there. They are for the voltage amp regulators I spoke about. I see they specify the Vamp supplies and raw power supplies at 70 VDC, but I recall getting different values when I measured it last. Something to do next time.
Well, back to fixing stuff. That 300DC may make it up sooner than planned since my curiosity has been peaked.
-Chris
Hi Tajzmaj,
You know about the #1 failure point in those amps I guess. The voltage doubler capacitors for the CCS circuits. The details are difficult to make out on the schematic I'm looking at. I think anyone familiar with these amplifiers are more than used to this repair.
-Chris
You know about the #1 failure point in those amps I guess. The voltage doubler capacitors for the CCS circuits. The details are difficult to make out on the schematic I'm looking at. I think anyone familiar with these amplifiers are more than used to this repair.
-Chris
M400 Repair
Studied all the internet intelligence on "Blows Fuse." I did ohmmeter tests on all the TO-3 semis. All looked good.
I put 30v AC in with the triac shorted out. 25 and 50 supplies scaled but 75v one didn't. Looking at it with a scope, there was termendous 120 ,hz ripple on both positive and negative 75v. More than 20 volts.
I traced this to the large 4000 u 80v capacitors both being open. Seemed that would not cause fuse to blow until one realizes that the triac servos the power supplies referencing the 75v bus. With its level really low the thing cranked it so far trying to get the 75v -- the duty factor got too high and fuse pops.
Another symptom was that you could see the level LEDs light just before the fuse pops.
Locally I found 1000 u 100v and tacked them in. Solved the problem, all works. On EBAY I found 3000u 80v in the same form factor; putting
both in should give me the 4000 I had to start.
Oh, another symptom that is now gone was the ticking in the speakers
even with no input.
FWIW. It sure is a sob to work on!! Note that beryllium oxide is very toxic if breathed in powder form; I suppose the white paste is safe but I'm careful with it. Bill Hale Loveland CO
Studied all the internet intelligence on "Blows Fuse." I did ohmmeter tests on all the TO-3 semis. All looked good.
I put 30v AC in with the triac shorted out. 25 and 50 supplies scaled but 75v one didn't. Looking at it with a scope, there was termendous 120 ,hz ripple on both positive and negative 75v. More than 20 volts.
I traced this to the large 4000 u 80v capacitors both being open. Seemed that would not cause fuse to blow until one realizes that the triac servos the power supplies referencing the 75v bus. With its level really low the thing cranked it so far trying to get the 75v -- the duty factor got too high and fuse pops.
Another symptom was that you could see the level LEDs light just before the fuse pops.
Locally I found 1000 u 100v and tacked them in. Solved the problem, all works. On EBAY I found 3000u 80v in the same form factor; putting
both in should give me the 4000 I had to start.
Oh, another symptom that is now gone was the ticking in the speakers
even with no input.
FWIW. It sure is a sob to work on!! Note that beryllium oxide is very toxic if breathed in powder form; I suppose the white paste is safe but I'm careful with it. Bill Hale Loveland CO