Well, I recently purchased a MXR 130 that worked perfectly, nice shape, and it sounds incredible. So I thought I would purchase another to play with it. After reading all this, and other sites, I realize the Carvers are NOT the easy fix as the Sansui's I have been working on.
I replaced the relays, and it still is in protection mode I guess. Doing the first amp alignment procedure I did manage to get the voltage set right, but didn't have the dummy loads in place, so I am not sure if that makes a difference. I also broke the only small plastic screwdriver I had. So I got a new plastic screwdriver, still waiting on the dummy loads.
I did check the idling without the loads, and it's close, but also seems to wander. Waiting on better clips for my Fluke so I don't have any slips and fry me or the unit. I did notice on my working one, that the display does not show, on FM until the relays click in. So I think the second might be okay there because it does show it tuning.
I think I would be better off starting a new thread, and seek your assistance. Not in a hurry, just wanting to learn. I can check voltages okay, I just wish I didn't have to read multiple threads to get all that info, but then again, maybe little by little is the way to go. I have good soldering equipment, just some days my hand resembles that scene in Blazing Saddles.
Previously from anatech said:
QUOTE:
Hi Ciscoguy2,
Sooo ... why did you follow the thread here? Are you having a problem, if so what is it?
I was the Canadian Factory warranty for Carver. END QUOTE:
If I can, I would appreciate working with just one expert.
I replaced the relays, and it still is in protection mode I guess. Doing the first amp alignment procedure I did manage to get the voltage set right, but didn't have the dummy loads in place, so I am not sure if that makes a difference. I also broke the only small plastic screwdriver I had. So I got a new plastic screwdriver, still waiting on the dummy loads.
I did check the idling without the loads, and it's close, but also seems to wander. Waiting on better clips for my Fluke so I don't have any slips and fry me or the unit. I did notice on my working one, that the display does not show, on FM until the relays click in. So I think the second might be okay there because it does show it tuning.
I think I would be better off starting a new thread, and seek your assistance. Not in a hurry, just wanting to learn. I can check voltages okay, I just wish I didn't have to read multiple threads to get all that info, but then again, maybe little by little is the way to go. I have good soldering equipment, just some days my hand resembles that scene in Blazing Saddles.
Previously from anatech said:
QUOTE:
Hi Ciscoguy2,
Sooo ... why did you follow the thread here? Are you having a problem, if so what is it?
I was the Canadian Factory warranty for Carver. END QUOTE:
If I can, I would appreciate working with just one expert.
Okay, an update from what is above.
I have replaced the speaker relays.
I have replaced the main capacitors in this unit.
I have replaced the power resistors, 656, etc
Doing the first test, I can adjust the voltage to 61.+- and that seems fine.
The second test, It's anywhere from 3.9 to 6 and it just seems to wander all over the place, adjusting the Variable resistors doesn't seem to do anything.
Great, I got a message saying moderators have to approve me. What do I need to do for that?
I have replaced the speaker relays.
I have replaced the main capacitors in this unit.
I have replaced the power resistors, 656, etc
Doing the first test, I can adjust the voltage to 61.+- and that seems fine.
The second test, It's anywhere from 3.9 to 6 and it just seems to wander all over the place, adjusting the Variable resistors doesn't seem to do anything.
Great, I got a message saying moderators have to approve me. What do I need to do for that?
Well, I started a new thread, but it seems like I need to get approval from a moderator first. How do I do that?
Okay, thanks, just looking to troubleshoot this beast. Read the other threads, now wishing I had a big overhead projector in my work area so I could read the schematic better. Tough to get old.
Hi Ciscoguy2,
Mooly was kind enough to alert me to your thread. Sorry I didn't see it earlier.
The power supply voltages are regulated. If ther eis a fault condition they will be shut down, and that is what you are seeing. Turning pots will not help. Please set the voltages a little lower than you had them (to be on teh safe side) until we figure out why it is detecting a fault.
I will get notifications now.
-Chris
Mooly was kind enough to alert me to your thread. Sorry I didn't see it earlier.
The power supply voltages are regulated. If ther eis a fault condition they will be shut down, and that is what you are seeing. Turning pots will not help. Please set the voltages a little lower than you had them (to be on teh safe side) until we figure out why it is detecting a fault.
I will get notifications now.
-Chris
Now you got me confused, if the pots don't work, how do I set the voltages down, or are you talking about the 61 volt part? Thanks for replying, looking to try and get this working.
Or just turn the pots down while troubleshooting?
Or just turn the pots down while troubleshooting?
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When the unit is in protect, there is another mechanism in play to drop the supply voltages, it is outside the range of the control trimmer. What I want you to do is set the trimmer to a level just below wher you had it set for the proper voltages. That way when you fix the fault, the voltages do not rise to levels higher than is safe.
The AC input voltage is regulated through the triac. Never, ever short the triac!!!
The unit has a very good protection circuit. It monitors the supply voltages as well as DC offsets and current levels in the amplifier section. If you have an over current indication it will shut down the power supply. It uses sensing to regulate the differnt power supplies as well. So be aware of this when you trouble shoot. You can kill the feedback, then the supplies will rise to maximum and that is very destructive.
The unit has a very good protection circuit. It monitors the supply voltages as well as DC offsets and current levels in the amplifier section. If you have an over current indication it will shut down the power supply. It uses sensing to regulate the differnt power supplies as well. So be aware of this when you trouble shoot. You can kill the feedback, then the supplies will rise to maximum and that is very destructive.
Well, I haven't been looking for the Triac,(TR601) although I know where it is now, haven't been playing with it. I also don't know what the former owner may have done with this unit. Is there a way to test it for connectivity with the unit cold?
If you are getting any power at all, it is working fine. You were able to adjust the supply voltages to the correct level, so that proves the triac and regulation circuit are in fact operating properly. Therefore the fault must be protection kicking in unless we have an intermittent fault in the regulator. I doubt this.
I have special procedures for running these at partial power to troubleshoot more easily. But these do require equipment most do not have, and training. Given we can't do what I would do on my bench, we'll take a different approach. The best guess is that we have is that the protection circuit is operating. So, check the DC voltages on the amplifier outputs. Here I would use an external DC bipolar supply to fire up the amps, and a lower voltage supply to make sure the 15 VDC rails were fully up. If you are getting partial voltage, you may be able to simply measure the output voltages. Make certain your 15 V rails are at least 8 VDC so that the op amps are working.
The other test points are the over-current detection. Make sure the emitter resistors are okay as they sense the voltage across these. Also, I have seen those transistors become leaky but test fine.
Do not mess with the regulator circuit at all, an innocent procedure has the potential to turn that triac on fully. That would run the supply voltages well above the maximum ratings for the capacitors and cook a lot of stuff. I have seen people do this and it is one reason Carver kept a tight lid on service.
Let me know what you find ...
I have special procedures for running these at partial power to troubleshoot more easily. But these do require equipment most do not have, and training. Given we can't do what I would do on my bench, we'll take a different approach. The best guess is that we have is that the protection circuit is operating. So, check the DC voltages on the amplifier outputs. Here I would use an external DC bipolar supply to fire up the amps, and a lower voltage supply to make sure the 15 VDC rails were fully up. If you are getting partial voltage, you may be able to simply measure the output voltages. Make certain your 15 V rails are at least 8 VDC so that the op amps are working.
The other test points are the over-current detection. Make sure the emitter resistors are okay as they sense the voltage across these. Also, I have seen those transistors become leaky but test fine.
Do not mess with the regulator circuit at all, an innocent procedure has the potential to turn that triac on fully. That would run the supply voltages well above the maximum ratings for the capacitors and cook a lot of stuff. I have seen people do this and it is one reason Carver kept a tight lid on service.
Let me know what you find ...
First things first, I spent a bit of time looking at the schematic trying to get an idea of what went where. Problem was is that I had the Schematic on my upstairs computer and going back and forth to where my bench is downstairs wasn't cutting it. So I found a computer and finally got it in place near my work bench.
The second thing is the schematic, what version is the best? There are places where they cross out the numbers and sort of scribble things in. Also, on the bottom of my board, attached to the power resistors are two small resistors that I am not sure they are supposed to be there, or if they are correctly placed. Not exactly sure where they show up on the schematic.
Capacitors 622 and 623 on the schematic show to be 100uf at 25v but my 622 is a 470uf at 50v. I have no idea what other changes the former people did to this unit.
The second thing is the schematic, what version is the best? There are places where they cross out the numbers and sort of scribble things in. Also, on the bottom of my board, attached to the power resistors are two small resistors that I am not sure they are supposed to be there, or if they are correctly placed. Not exactly sure where they show up on the schematic.
Capacitors 622 and 623 on the schematic show to be 100uf at 25v but my 622 is a 470uf at 50v. I have no idea what other changes the former people did to this unit.
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In your post above, you mentioned checking the DC voltages on the amplifier outputs. I am not quite sure which part you are referring to, and don't want to just poke around it. I think I might now, but lets keep in mind I can read a schematic but have no idea how it all works. LOL.
So I guess I am wondering if those tiny resistors are correct, and if I should remove and replace the 470uf capacitor with the correct value.
So I guess I am wondering if those tiny resistors are correct, and if I should remove and replace the 470uf capacitor with the correct value.
Hi,
The resistors on the bottom are not factory. They may have installed the wrong values on top and are padding them. Without the unit in front of me it limits my insights' Normally I notice things without actually looking right at them or even intending to see them.
Checking the amplifier DC offsets can normally be done at the midpoints of the emitter resistors. But a gross offset will be just as valid on either end to be honest. Before sparking it up, check that the emitter resistors are close to the correct value. 0R22, looks like these are individual resistors. Sometimes they were dual 0R22 or 0R1 "plate" resistors. Those are non-inductive.
Also measure the voltage across the two resistors (from output emitter to other emitter). If an emitter resistor is open or the voltage is too high it will turn on an overcurrent detect transistor and shut things down.
The resistors on the bottom are not factory. They may have installed the wrong values on top and are padding them. Without the unit in front of me it limits my insights' Normally I notice things without actually looking right at them or even intending to see them.
Checking the amplifier DC offsets can normally be done at the midpoints of the emitter resistors. But a gross offset will be just as valid on either end to be honest. Before sparking it up, check that the emitter resistors are close to the correct value. 0R22, looks like these are individual resistors. Sometimes they were dual 0R22 or 0R1 "plate" resistors. Those are non-inductive.
Also measure the voltage across the two resistors (from output emitter to other emitter). If an emitter resistor is open or the voltage is too high it will turn on an overcurrent detect transistor and shut things down.
Well, I think that's the problem. The schematic has the values for two of the resistors crossed out. Mine has a little scribble that says 39. Or is it 3.9. Is it ohms, or kohms. Looking at the colors, it's 3.9 kohms.
Now on ZD607 and ZD606, I get 11.55 volts on one, and 4.55 volts on the other. I also have two different caps as noted above. I don't know if someone put the 3.9kohm resistors on the bottom because they were the correct number, just not the correct wattage or what.
I got from somewhere I think on this website, the values for the supposed power resistors, and they said it was based on the part number in the service manual. Are they right? I couldn't cross reference them. So I have no clue. I need to find that answer first. Or can I remove those two bottom resistors and see what happens based on the premise that the values in the service manual are correct.
Here is that thread.
"Hello Chris,
That's what I thought he was referring to but had to make sure.
R655 680 Ohm 2W MO
R656 62 Ohm 2W MO
R657 820 Ohm 2W MO
R658 68 Ohm 2W MO
If replacing I would bump them to 3W. The schematic has 100 Ohm for R656 and R658 but are crossed out, the parts list has the current values."
That is the resistors I have in there now.
Now on ZD607 and ZD606, I get 11.55 volts on one, and 4.55 volts on the other. I also have two different caps as noted above. I don't know if someone put the 3.9kohm resistors on the bottom because they were the correct number, just not the correct wattage or what.
I got from somewhere I think on this website, the values for the supposed power resistors, and they said it was based on the part number in the service manual. Are they right? I couldn't cross reference them. So I have no clue. I need to find that answer first. Or can I remove those two bottom resistors and see what happens based on the premise that the values in the service manual are correct.
Here is that thread.
"Hello Chris,
That's what I thought he was referring to but had to make sure.
R655 680 Ohm 2W MO
R656 62 Ohm 2W MO
R657 820 Ohm 2W MO
R658 68 Ohm 2W MO
If replacing I would bump them to 3W. The schematic has 100 Ohm for R656 and R658 but are crossed out, the parts list has the current values."
That is the resistors I have in there now.
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So reading the above info, I found this on the bottom of page 30. Maybe you can decipher it and see if the values are correct.
Hi,
Okay, my earlier response would have been correct and those values seem to make sense to me. I would have to trace the resistors on the bottom to ensure their connections. There are times when the service manual may have a typo, in every brand. Now think of it, 3K9 in parallel with say 680R. That changes the value by how much?
You may have a high load on the supply with only 4.5 VDC across it. Check to make sure the voltages on the feed side are both equal before jumping to any conclusions. From memory, the zener diodes do run very warm and I'm of the opinion they don't have to run that hot. Sometimes the factory would increase resistor values to drop current in the zener diodes, again various models and brands. So these values are not super critical, you just need to make sure the zener is always conducting and doesn't drop out. One thing with zener diodes is that the more current they conduct, the lower their dynamic impedance is. Better for noise performance, but they get hot and fail sooner run hot. The bypass caps take care of noise, and the load doesn't change much, so I feel you could drop the current (increase resistor values) a bit to run things cooler.
I do increase these to 3 watt resistors. If it were my set, I would redesign it to use a regulator circuit with the voltage reference fed with a constant current source. That would give you a very quiet supply for your op amps.
Anyway, you have a drop from about 12 volts to 4.5 volts (should be 16 volt rails). Could be a capacitor since only one polarity is down but keep an open mind. An op amp driving heavy current to one side can also drag down the supply. Let it run like this for a bit, then check the temperature of each op amp and bypass capacitor to see if any are running warmer than the others. In my case, I would run that supply from a separate power supply without the rest of the receiver powered up from the feed side (35 to 40 VDC bipolar would do it). That's across the 8200uF 42 V capacitors. If you are careful, you could feed the 16 VDC rails with a tracking power supply watching the current. Looks like a bipolar 16 VDC supply is intended, but someone may have installed 12 V zeners. Just increase the supply and watch the current, if one begins to increase sharply, it is probably a zener conducting - or your fault. Simply allow something to get warm (not hot!) so you can find out where the current is going easily. Low tech, but it works and saves time. I used to do this with CPU boards that used a lot of logic chips. The bad one would generally get pretty warm and was easy to find in a sea of chips. That was a 5V rail, and I had to disconnect the 5V feed before trying that trick. Sometimes I had a lot of current at 1 VDC, so you have to watch the current draw.
Let me know ...
-Chris
Okay, my earlier response would have been correct and those values seem to make sense to me. I would have to trace the resistors on the bottom to ensure their connections. There are times when the service manual may have a typo, in every brand. Now think of it, 3K9 in parallel with say 680R. That changes the value by how much?
You may have a high load on the supply with only 4.5 VDC across it. Check to make sure the voltages on the feed side are both equal before jumping to any conclusions. From memory, the zener diodes do run very warm and I'm of the opinion they don't have to run that hot. Sometimes the factory would increase resistor values to drop current in the zener diodes, again various models and brands. So these values are not super critical, you just need to make sure the zener is always conducting and doesn't drop out. One thing with zener diodes is that the more current they conduct, the lower their dynamic impedance is. Better for noise performance, but they get hot and fail sooner run hot. The bypass caps take care of noise, and the load doesn't change much, so I feel you could drop the current (increase resistor values) a bit to run things cooler.
I do increase these to 3 watt resistors. If it were my set, I would redesign it to use a regulator circuit with the voltage reference fed with a constant current source. That would give you a very quiet supply for your op amps.
Anyway, you have a drop from about 12 volts to 4.5 volts (should be 16 volt rails). Could be a capacitor since only one polarity is down but keep an open mind. An op amp driving heavy current to one side can also drag down the supply. Let it run like this for a bit, then check the temperature of each op amp and bypass capacitor to see if any are running warmer than the others. In my case, I would run that supply from a separate power supply without the rest of the receiver powered up from the feed side (35 to 40 VDC bipolar would do it). That's across the 8200uF 42 V capacitors. If you are careful, you could feed the 16 VDC rails with a tracking power supply watching the current. Looks like a bipolar 16 VDC supply is intended, but someone may have installed 12 V zeners. Just increase the supply and watch the current, if one begins to increase sharply, it is probably a zener conducting - or your fault. Simply allow something to get warm (not hot!) so you can find out where the current is going easily. Low tech, but it works and saves time. I used to do this with CPU boards that used a lot of logic chips. The bad one would generally get pretty warm and was easy to find in a sea of chips. That was a 5V rail, and I had to disconnect the 5V feed before trying that trick. Sometimes I had a lot of current at 1 VDC, so you have to watch the current draw.
Let me know ...
-Chris