AFAIK the only difference between the 4040 and the 4140 is the prior`s presence of bass/treble controls. I have the 4040 S2 schematic, if you want it, drop me a pm.
R19 & R20 are 0.22Ohms in 4040 S2 and there are 2 resistors of that type
In my 4140 S2 the value is 0.33ohms and 4 of them as seen in my previous attached photo (2 per channel i guess)
Looks more like the 4040 S3 :
http://audio.cyberkata.org/creek4040s3.jpg
Little confused in here as in the 4040 S2 schematic says voltage drop of 6mV across R19 or R20 which are 0.22Ohms, how much would be for 0.33Ohms?
In my 4140 S2 the value is 0.33ohms and 4 of them as seen in my previous attached photo (2 per channel i guess)
Looks more like the 4040 S3 :
http://audio.cyberkata.org/creek4040s3.jpg
Little confused in here as in the 4040 S2 schematic says voltage drop of 6mV across R19 or R20 which are 0.22Ohms, how much would be for 0.33Ohms?
Creek replied and now I have some schematics.
3mV measuring in 1xemitter resistor or 6mV across both resistors.
The problem is different though, it's in the power supply circuit :
7915 voltage regulator is gone
The original part number is Motorola 7915C MC QQZE8948 but I don't know which new one to get in order to replace it.
Find below the schematic and photos of the +-15V regulators :
Any ideas?
3mV measuring in 1xemitter resistor or 6mV across both resistors.
The problem is different though, it's in the power supply circuit :
7915 voltage regulator is gone
The original part number is Motorola 7915C MC QQZE8948 but I don't know which new one to get in order to replace it.
Find below the schematic and photos of the +-15V regulators :
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Any ideas?
These are bog-standard 78xx/79xx series 1A regulators that been around longer than most people on the forum. You don't need to match them any more than their specified voltage and current ratings. If they are regulating properly (working), that's all you need. http://www.onsemi.com/pub_link/Collateral/MC7900-D.PDF
As you can see, the generic part number is simply 7915. C is commercial grade, T is T0220 package and G means lead-free tinned leads. the rest is batch/date codes.
What is much more important is to find out why the original part failed, which will be due to a short, overload of some sort downstream of the regulator in the preamp or other circuits associated. The load is usually very light on the -ve rail, nowhere near 1A. Has someone been poking around and accidentally shorted the negative 15V supply? If so, you could just put it down to inexperience if there are no further problems caused.
As you can see, the generic part number is simply 7915. C is commercial grade, T is T0220 package and G means lead-free tinned leads. the rest is batch/date codes.
What is much more important is to find out why the original part failed, which will be due to a short, overload of some sort downstream of the regulator in the preamp or other circuits associated. The load is usually very light on the -ve rail, nowhere near 1A. Has someone been poking around and accidentally shorted the negative 15V supply? If so, you could just put it down to inexperience if there are no further problems caused.
Problem started when there was no sound from right channel.
Turning the volume pot all the way up temporary solved the problem and everything was ok.
Switched off the amp at night and the next morning the same problem again.
Did the trick with the pot and all ok again with no issues while the amp was on.
There was no distortion while the amp was running, only the first minutes of start up.
Tried contact cleaner, no luck.
Replaced the volume potentiometer, no luck.
Checked bias all ok.
Today when I switched it on, with sound only from one channel as usual, I used a pencil (the rubber) over the components and when I was touching the regulator, sound came up again.
I noticed that it was way hotter than the other one, also with some discolouration.
No bad joints on the board.
That's why I think the regulator is faulty.
What do you think?
Turning the volume pot all the way up temporary solved the problem and everything was ok.
Switched off the amp at night and the next morning the same problem again.
Did the trick with the pot and all ok again with no issues while the amp was on.
There was no distortion while the amp was running, only the first minutes of start up.
Tried contact cleaner, no luck.
Replaced the volume potentiometer, no luck.
Checked bias all ok.
Today when I switched it on, with sound only from one channel as usual, I used a pencil (the rubber) over the components and when I was touching the regulator, sound came up again.
I noticed that it was way hotter than the other one, also with some discolouration.
No bad joints on the board.
That's why I think the regulator is faulty.
What do you think?
Monitor the voltage at the -15V ouput. That's the arbiter of the regulator's operation.
If you have -15V and the regulator is heating up, then an intermittent fault further down is overloading it. It has no heatsink so only a small load, say 200mA, is permissable and though it has overload protection, it's not perfect so it can still fail on overload, particularly with no heatsink.
Let's see what measurements reveal and go from there. Meantime, check any connectors to the preamp section, controls etc as it seems that jumping things about there restore operation so the fault is less likely electronic and possibly mechanical. It could even be from flexing a broken PCB track. Take it gently.
If you have -15V and the regulator is heating up, then an intermittent fault further down is overloading it. It has no heatsink so only a small load, say 200mA, is permissable and though it has overload protection, it's not perfect so it can still fail on overload, particularly with no heatsink.
Let's see what measurements reveal and go from there. Meantime, check any connectors to the preamp section, controls etc as it seems that jumping things about there restore operation so the fault is less likely electronic and possibly mechanical. It could even be from flexing a broken PCB track. Take it gently.
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If the draw was small, possibly the mains high also, then the 330R dropping resistor could have left much voltage across the reg slowly cooking it to failure even for few mA in the course of time. You could lightly sink those regs with clip-on sinks after the fix, for security against possibly high ambient temp inside a small case amp like this.
If the failure is due to a short downstream after the reg, then the cause of its failure is obvious, and you may evaluate the heat on the regs after all is repaired, as a secondary housekeeping task only
If the failure is due to a short downstream after the reg, then the cause of its failure is obvious, and you may evaluate the heat on the regs after all is repaired, as a secondary housekeeping task only
This is the second schematic I got from Creek:
Can you point me where further down to check?
What do you mean it's probably a mechanical error?Jumping things?
An externally hosted image should be here but it was not working when we last tested it.
Can you point me where further down to check?
What do you mean it's probably a mechanical error?Jumping things?
OK, nice to have the schematic. Unfortunately, it is clearly copyright.
To explain your query; when we poke broken components, circuits etc. that suddenly start or stop working, voltages are likely changing grossly - perhaps several times in rapid succession where connections are weak and so "jumping about". This may re-establish connections temporarily or change the electronic state of a device, clear a short, discharge a capacitance or any number of changes which could bring an amplifier back to life. They could just as easily kill it completely but let's remain positive.
A mechanical fault means what it says; there is a physical break in the circuits such as broken or poor soldering, PCB track cracked, component lead detached, relay or switch contact poor and so on. An electronic fault is considered to be located inside the devices, even though in strict terms, they may be similar faults.
"Further downstream" is where the 15V supplies are going here which is to the 3 opamps and Moving Coil LP cartridge preamplifier (called MC gain stage here). Checking the latter should be unnecessary since it is a positive rail only circuit. All that is required is to monitor the negative supply pins of the opamps which are universally pin 4 for common DIP8 opamps. Google the details of how to find the pin no. sequence if you can't deduce it from the existing markings like the notch on the opamp case. Possibly there are other circuits using these supplies that aren't shown here. You could check this if the PCB underside tracks are visible or if you have the complete schematic.
If any of these voltages is incorrect at the opamp pins themselves or fluctuates more at that location when you perform your poking about with a rubber point, that may help to locate the problem if you take care not to cause damage by flexing the PCB too much. That can cause some of the mechanical faults. Using instruments, we would simply observe the output or supply voltages with an oscilloscope at each point, to check for normal, stable operation. Without such, you have to use logic with simpler tools to gradually narrow the area of faults by a "divide and conquer" process. Obviously, if you are only measuring the amplifier in one state (e.g. working) you won't find much unless you can cause it to stop. There is a clue with heat here though, since the fault returns the next day, suggesting warming up is involved in making or breaking a circuit. Resolder both regulators first, before wasting time and money on other chances and take Sala's experience on board.
Also consider that pushing the reg may be affecting something else nearby. It's worth checking these for voltage changes too when you are testing - note from the schematic that common connections make it difficult to know what the actual fault is so sometimes lifting leads is the only way to test them. That compounds any damage so you don't do this unless necessary.
To explain your query; when we poke broken components, circuits etc. that suddenly start or stop working, voltages are likely changing grossly - perhaps several times in rapid succession where connections are weak and so "jumping about". This may re-establish connections temporarily or change the electronic state of a device, clear a short, discharge a capacitance or any number of changes which could bring an amplifier back to life. They could just as easily kill it completely but let's remain positive.
A mechanical fault means what it says; there is a physical break in the circuits such as broken or poor soldering, PCB track cracked, component lead detached, relay or switch contact poor and so on. An electronic fault is considered to be located inside the devices, even though in strict terms, they may be similar faults.
"Further downstream" is where the 15V supplies are going here which is to the 3 opamps and Moving Coil LP cartridge preamplifier (called MC gain stage here). Checking the latter should be unnecessary since it is a positive rail only circuit. All that is required is to monitor the negative supply pins of the opamps which are universally pin 4 for common DIP8 opamps. Google the details of how to find the pin no. sequence if you can't deduce it from the existing markings like the notch on the opamp case. Possibly there are other circuits using these supplies that aren't shown here. You could check this if the PCB underside tracks are visible or if you have the complete schematic.
If any of these voltages is incorrect at the opamp pins themselves or fluctuates more at that location when you perform your poking about with a rubber point, that may help to locate the problem if you take care not to cause damage by flexing the PCB too much. That can cause some of the mechanical faults. Using instruments, we would simply observe the output or supply voltages with an oscilloscope at each point, to check for normal, stable operation. Without such, you have to use logic with simpler tools to gradually narrow the area of faults by a "divide and conquer" process. Obviously, if you are only measuring the amplifier in one state (e.g. working) you won't find much unless you can cause it to stop. There is a clue with heat here though, since the fault returns the next day, suggesting warming up is involved in making or breaking a circuit. Resolder both regulators first, before wasting time and money on other chances and take Sala's experience on board.
Also consider that pushing the reg may be affecting something else nearby. It's worth checking these for voltage changes too when you are testing - note from the schematic that common connections make it difficult to know what the actual fault is so sometimes lifting leads is the only way to test them. That compounds any damage so you don't do this unless necessary.
Nothing,
I did what you suggested but the problem exists.
When the amp is cold I have to turn the volume all the way up in order to "wake up" one channel.
The hottest part is in the joint between the 100nF cap, the 330R and the regulator (12 degrees difference with the other leg).
Unless all the above are acceptable and the problem is on the volume pot side, but I've already replaced it.
I did what you suggested but the problem exists.
When the amp is cold I have to turn the volume all the way up in order to "wake up" one channel.
The hottest part is in the joint between the 100nF cap, the 330R and the regulator (12 degrees difference with the other leg).
Unless all the above are acceptable and the problem is on the volume pot side, but I've already replaced it.
Hi .. If poking around inside with a pencil makes a difference I would take a closer look at the underneath of the pcb You say the solder joints to the regulator are good why not just resolder them just in case.. It really sounds to me like a bad connection Do double check where the pcb track forms into component pads! they can crack at that point and are very hard to see.
A small distraction - The relays fitted to S series Creek amplifiers are like a lot of relays - bad with low level signals because of contamination from industrial air and the symptom is as you describe - a need to turn volume up high to get the audio to "start".
Power off, remove mains plug and pop the cover on the relay. (There is bead at the bottom edge of the cover that clips over another on the base moulding and needs a little coaxing with a small blade as a lever under the long sides). Pass a couple of small folded strips of stiff paper several times between the relay contacts, with slight pressure from a finger whilst pushing the contacts together. Note that only one side of each set of contacts will be used so don't waste effort scrubbing the others too.
It is better to use a spot of contact cleaner or even WD spray on the first strip of paper, as long as residues are removed. No, no need for shock horror stories about WD - it does work reliably when used sparingly and with common sense.
I'm not saying this is the problem and solution but it will help maintain best possible sound quality and is something overlooked by a lot owners of old gear.
Power off, remove mains plug and pop the cover on the relay. (There is bead at the bottom edge of the cover that clips over another on the base moulding and needs a little coaxing with a small blade as a lever under the long sides). Pass a couple of small folded strips of stiff paper several times between the relay contacts, with slight pressure from a finger whilst pushing the contacts together. Note that only one side of each set of contacts will be used so don't waste effort scrubbing the others too.
It is better to use a spot of contact cleaner or even WD spray on the first strip of paper, as long as residues are removed. No, no need for shock horror stories about WD - it does work reliably when used sparingly and with common sense.
I'm not saying this is the problem and solution but it will help maintain best possible sound quality and is something overlooked by a lot owners of old gear.
Bloody thing I fixed it,
de-soldered and re-soldered all the points in the volume and balance path along with some who seemed dry.
Cheers guys for your help.
Btw since the amp is still open I was thinking of replacing caps, heard about the signal path and the power supply ones , any recommendations?
de-soldered and re-soldered all the points in the volume and balance path along with some who seemed dry.
Cheers guys for your help.
Btw since the amp is still open I was thinking of replacing caps, heard about the signal path and the power supply ones , any recommendations?
Great that you got down to doing it. It's amazing how many auto-processed PCBs failed this way, years after manufacture. Ask any TV tech.
For caps, use decent commercial grade electrolytics with low ESR from a reputable supplier - There are many quality brands that people gossip endlessly over in the various audio chat forums but good, economical standards are Panasonic FR,FC,FM for smaller values and TSHA for the main electros. Everyone has favourite brands with a nice ring to them and other manufacturers like Nichicon, Rubycon, Nippon Chemicon, Elna, Samwha etc. have near equivalents to these types - some with marks like "for audio" with gold stripes on them which is only suggestive - there are no special audio caps any more than there are audio resistors or wire. Other than for the MC preamp, there aren't any input caps but there are a couple of 10uF coupling caps between opamps and there are decoupling caps to ground on the power rails. FC or FR would be good generally for the smaller values used as you'll find that very low ESR ranges like these only go so far up in value.
Voltage ratings are not critical above that specified, so you can substitute higher voltage types and even capacitance values if need be - just watch out for size and lead spacings so that parts fit.
Where there are film caps in the signal path, its nice to replace polyester (MKT) with polypropylene types (MKP) but beware the size increase is enormous and that carries its own penalties of proneness to noise and interference. The input cap. to the power amplifier, is often important. It will be shown in the schematic which I presume you also received. Make that a good one if fitted, though it's possibly an NP (non-polarized) electrolytic type.
For caps, use decent commercial grade electrolytics with low ESR from a reputable supplier - There are many quality brands that people gossip endlessly over in the various audio chat forums but good, economical standards are Panasonic FR,FC,FM for smaller values and TSHA for the main electros. Everyone has favourite brands with a nice ring to them and other manufacturers like Nichicon, Rubycon, Nippon Chemicon, Elna, Samwha etc. have near equivalents to these types - some with marks like "for audio" with gold stripes on them which is only suggestive - there are no special audio caps any more than there are audio resistors or wire. Other than for the MC preamp, there aren't any input caps but there are a couple of 10uF coupling caps between opamps and there are decoupling caps to ground on the power rails. FC or FR would be good generally for the smaller values used as you'll find that very low ESR ranges like these only go so far up in value.
Voltage ratings are not critical above that specified, so you can substitute higher voltage types and even capacitance values if need be - just watch out for size and lead spacings so that parts fit.
Where there are film caps in the signal path, its nice to replace polyester (MKT) with polypropylene types (MKP) but beware the size increase is enormous and that carries its own penalties of proneness to noise and interference. The input cap. to the power amplifier, is often important. It will be shown in the schematic which I presume you also received. Make that a good one if fitted, though it's possibly an NP (non-polarized) electrolytic type.
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