happy new year every one !!!
This thread is a actually a copy of an existing thread in a Greek forum .Obviously the thread is there to inform and attract costumers and actually working very well .
I presume that there is no point on placing a similar thread in the diyaudio to attract costumers but still articles comments and photos are nice to see and read for every one .
i would like to welcome any forum members if support schematic or any kind of help is needed and i will be more than happy to provide. Don't expect e mail in 2 minutes but i ll do my best to answer as fast is possible .
Most of those amps i keep schematics from, that i will be very happy to share and also i have very good memory resources about common failure and repair tips ...
enjoy
This thread is a actually a copy of an existing thread in a Greek forum .Obviously the thread is there to inform and attract costumers and actually working very well .
I presume that there is no point on placing a similar thread in the diyaudio to attract costumers but still articles comments and photos are nice to see and read for every one .
i would like to welcome any forum members if support schematic or any kind of help is needed and i will be more than happy to provide. Don't expect e mail in 2 minutes but i ll do my best to answer as fast is possible .
Most of those amps i keep schematics from, that i will be very happy to share and also i have very good memory resources about common failure and repair tips ...
enjoy
SERVICE ADCOM GFA 545 ii
THE ADCOM GFA545
ADCOM at that time made simple circuits, simple construction, good design, plenty of streams and power supply , good quality material, extremely large capacity drive, sound upfront , the machines will put the theme literally in the face and no one will find coloring or smoothing the edges ...
In the above totals must be someone to add workmanship which compared to the price I would say that was good.
a think that i found wrong was ... the installation of the board upright resulting in accumulation of dust which is easily turned in maca which if we add a little moisture on prescription the boom is ready .... beyond the repair ( drivers and outputs+ capacitors ) a piece of duct tape between the cooling plate and he board will prevent future problems ...
from the very simple amplifiers which I like very much
fotos and schematic available
THE ADCOM GFA545
ADCOM at that time made simple circuits, simple construction, good design, plenty of streams and power supply , good quality material, extremely large capacity drive, sound upfront , the machines will put the theme literally in the face and no one will find coloring or smoothing the edges ...
In the above totals must be someone to add workmanship which compared to the price I would say that was good.
a think that i found wrong was ... the installation of the board upright resulting in accumulation of dust which is easily turned in maca which if we add a little moisture on prescription the boom is ready .... beyond the repair ( drivers and outputs+ capacitors ) a piece of duct tape between the cooling plate and he board will prevent future problems ...
from the very simple amplifiers which I like very much
fotos and schematic available
Attachments
Last edited:
SERVICE AKAI AM 2400
In the University of Athens we were told that we must declare Engineer and not just ... Electronics this has some basis and for me perhaps a little more because besides my father was mechanically engineer in the rectify surfaces, often skills needed beside electronic conversions to be able to do mechanical also .
The talk is about one AKAI AM 2400 in the hands of me these days, who has excellent mechanical construction but electronics inside was pretty messy and old
One key reason is that i liked very much the selector idea ... and the long piece of metal to keep signals in the back by far better than having them around the amplifier ...
for this unit .... complete recaping outputs and a general shape up ...
nice amp ... well designed .... after finished it i found the preamp to be not really good ...i had high expectations from this machine .... i have one of these on my own and may be in he feature i will make some upgrades
foto and schematic available
In the University of Athens we were told that we must declare Engineer and not just ... Electronics this has some basis and for me perhaps a little more because besides my father was mechanically engineer in the rectify surfaces, often skills needed beside electronic conversions to be able to do mechanical also .
The talk is about one AKAI AM 2400 in the hands of me these days, who has excellent mechanical construction but electronics inside was pretty messy and old
One key reason is that i liked very much the selector idea ... and the long piece of metal to keep signals in the back by far better than having them around the amplifier ...
for this unit .... complete recaping outputs and a general shape up ...
nice amp ... well designed .... after finished it i found the preamp to be not really good ...i had high expectations from this machine .... i have one of these on my own and may be in he feature i will make some upgrades
foto and schematic available
Attachments
SERVICE AKAI AM 6200
What to say anything ... rather ....
Terrible machine which is bad designed and if you look at it its just a cheap mess ...
was a series of AKAI that was nothing to talk about .
Despite these .. was the grandfather's ... so if anything is worth a little love (I am sure the grandfather was ready to give generously!)
A handful electrolytics .... 52 for the accuracy to make it work ... The result is that naturally came in good condition and probably a little better packed with terrible colorful sonics the distant past ... but ultimately this is the value of vintage ... enjoy some photo ...
schematic available
What to say anything ... rather ....
Terrible machine which is bad designed and if you look at it its just a cheap mess ...
was a series of AKAI that was nothing to talk about .
Despite these .. was the grandfather's ... so if anything is worth a little love (I am sure the grandfather was ready to give generously!)
A handful electrolytics .... 52 for the accuracy to make it work ... The result is that naturally came in good condition and probably a little better packed with terrible colorful sonics the distant past ... but ultimately this is the value of vintage ... enjoy some photo ...
schematic available
Attachments
SERVICE BETA 3 UA 600
professional Chinese AMP with history of problems resulting from poor design .....
Upright marginal electrolytics suffering from hypertension and temperature
the machine is honest and correct work in class G sound is is fine and the relation to the price is more than acceptable. Even once a manufacturing fault degrades an otherwise well-designed machine.
At very positive side is the proper construction and thermal cooling fans tri-modal robustness of construction and the power results
for a cheap amplifier beyond the capacitor error is an ok machine
professional Chinese AMP with history of problems resulting from poor design .....
Upright marginal electrolytics suffering from hypertension and temperature
the machine is honest and correct work in class G sound is is fine and the relation to the price is more than acceptable. Even once a manufacturing fault degrades an otherwise well-designed machine.
At very positive side is the proper construction and thermal cooling fans tri-modal robustness of construction and the power results
for a cheap amplifier beyond the capacitor error is an ok machine
Attachments
SERVICE DIY CRESENDO
Here is the crescendo 1982 140W who had been implemented by a colleague during those years full house kit along with protection and is powered by some GREEK company who made pcb but also seek parts for "kit" which was supposed to be some levels of quality .
Problems are well known that the designs of Giesberts had stability issues This machine worked quite well without too much oscillations and offset at the output.
of course this crescendo also features stabilization caps something i would never do in a machine of my own
What was not good was the implementation and the idea was to actually kill everything and start all over again from the beginning ... dismantled everything and did everything from scratch ... costly and difficult job, but at least finished was beautiful.
Apart from the photos I have a set of measuring of course if anyone has an appetite for debate on crescendo it could be very good to make it into a new post.
photo that was the machine before and after ...
Here is the crescendo 1982 140W who had been implemented by a colleague during those years full house kit along with protection and is powered by some GREEK company who made pcb but also seek parts for "kit" which was supposed to be some levels of quality .
Problems are well known that the designs of Giesberts had stability issues This machine worked quite well without too much oscillations and offset at the output.
of course this crescendo also features stabilization caps something i would never do in a machine of my own
What was not good was the implementation and the idea was to actually kill everything and start all over again from the beginning ... dismantled everything and did everything from scratch ... costly and difficult job, but at least finished was beautiful.
Apart from the photos I have a set of measuring of course if anyone has an appetite for debate on crescendo it could be very good to make it into a new post.
photo that was the machine before and after ...
SERVICE DENON PMA 520
The DENON PMA 520 as construction that i dont like very much
I do not like that has no auxiliary power supply ... It has only a stabilization for the amplifier and for the local stabilizers local transitors and locala capacitors that are rather small .....
This of course means that the currents circulating inside the machine is not clean ... and certainly do not make a quiet machine ...
In the minus will also put the electronic input selector who is known for quiet, friendly operation but the acoustic performance is the limited even for use in hifi.
Finally, the topology is the classic Japanese ... high voltage rails which provides much potential headroom but in the end 100% of power is not available cause of the limiters and transformer size that will kneel when 100% of power is requested and distortion figures will hit the sky ....
Generally an average machine ... found burnt resistors in one Chanel fuses soldering and a handful of electrolytics and a final good a good cleaning ...
fotos and schematic available
The DENON PMA 520 as construction that i dont like very much
I do not like that has no auxiliary power supply ... It has only a stabilization for the amplifier and for the local stabilizers local transitors and locala capacitors that are rather small .....
This of course means that the currents circulating inside the machine is not clean ... and certainly do not make a quiet machine ...
In the minus will also put the electronic input selector who is known for quiet, friendly operation but the acoustic performance is the limited even for use in hifi.
Finally, the topology is the classic Japanese ... high voltage rails which provides much potential headroom but in the end 100% of power is not available cause of the limiters and transformer size that will kneel when 100% of power is requested and distortion figures will hit the sky ....
Generally an average machine ... found burnt resistors in one Chanel fuses soldering and a handful of electrolytics and a final good a good cleaning ...
fotos and schematic available
Attachments
SERVICE JBL MPX 300
In our company we do also professional amps ...don't know if there is some interest in presentations in this track, but let's see how it goes.
It was a very wise move by JBL to leave the design of the urei and create some machines that was probably based on topology CROWN-QSC ......
Smart machine, sturdy construction, proper cooling, carefully designed symmetric limiters, bridging, filter hpf to be able to work and without crossover, very good quality materials and construction, legendary output transistors 2SA1302-2SC3281 (the best bipolar transistor built ever from TOSHIBA)
in quality and power, true and honest machine and generally a very good professional amplifier .
The symmetrical limiters make very nice performance and power will be properly limited without distortions from the limiter it shelf push it hard. and that will mean no danger for the speakers ..
characteristics of a professional .... only disadvantage of the potentiometers were open but in reverse resulting mess and dust inside very easily .... Replaced with Alpha closed ... and go!
fotos and schematic available
In our company we do also professional amps ...don't know if there is some interest in presentations in this track, but let's see how it goes.
It was a very wise move by JBL to leave the design of the urei and create some machines that was probably based on topology CROWN-QSC ......
Smart machine, sturdy construction, proper cooling, carefully designed symmetric limiters, bridging, filter hpf to be able to work and without crossover, very good quality materials and construction, legendary output transistors 2SA1302-2SC3281 (the best bipolar transistor built ever from TOSHIBA)
in quality and power, true and honest machine and generally a very good professional amplifier .
The symmetrical limiters make very nice performance and power will be properly limited without distortions from the limiter it shelf push it hard. and that will mean no danger for the speakers ..
characteristics of a professional .... only disadvantage of the potentiometers were open but in reverse resulting mess and dust inside very easily .... Replaced with Alpha closed ... and go!
fotos and schematic available
Attachments
SERVICE AUDIO INNOVATIONS ALTO
AUDIO INNOVATIONS ALTO .....
The word INNOVATIONS in Greek will mean innovation, modernity or some cutting edge technology ... So the amplifier should be something innovative and new ..
Well actually its not talking on a project with a ziilion design flows , which comes from construction and implementation of how Dynaco did amps before 1970. sad isn't it ;;;
In principle, the amplifier is a blast from the past ... having a capacitor at the output just 2,200 mfd almost equal to a capacitor of a portable cassette player of the yera 1970 ... then the transistor output is the classic old dead slow 2N3055 and to complete the picture, the dc block capacitors at the input is just low enough resulting in a serious roll off from the 60 HZ and below ...
Somewhere here is the time at which the dealer has gotten a lawyer and are looking to fill me up lawsuits ... so maybe i have to rescue this ...
-------------------------------------------------- ------------------------
In practice things are not as sad as the description The amplifier is English substantial school itself is going on the prototypes and concept of the NAD 3020, and in general wants to say :
"" "We are Englishmen and we can prove to the world machines built from simple materials and smart design can create DECENT machines"
The truth is, that they actually DID IT ... although as the transistors are slow with "hard" work to do driving the load through the poor capacitors and at the input may have a roll off but generally for English rock sounds this is not a major problem and if the listener is not party animal things will go more than ok
replaced caps in the power supply with something better and something bigger (6 times up ) and of course the same and the output at 4700 mfd so it can support some more low end ...
bypass .... decoupling, cleaning .... one relay output and the machine is fine ... certainly has cleared a click above and beyond all the comments are a decent English construction ... .... good-looking machine with personality and identity, and because of its simple construction is extremely clean ...
found some resistors with poor soldering ... listen to it and after all i think i liked it .... same on me .... i consider my shelf a 2SA1302 guy
few pics from
AUDIO INNOVATIONS ALTO .....
The word INNOVATIONS in Greek will mean innovation, modernity or some cutting edge technology ... So the amplifier should be something innovative and new ..
Well actually its not talking on a project with a ziilion design flows , which comes from construction and implementation of how Dynaco did amps before 1970. sad isn't it ;;;
In principle, the amplifier is a blast from the past ... having a capacitor at the output just 2,200 mfd almost equal to a capacitor of a portable cassette player of the yera 1970 ... then the transistor output is the classic old dead slow 2N3055 and to complete the picture, the dc block capacitors at the input is just low enough resulting in a serious roll off from the 60 HZ and below ...
Somewhere here is the time at which the dealer has gotten a lawyer and are looking to fill me up lawsuits ... so maybe i have to rescue this ...
-------------------------------------------------- ------------------------
In practice things are not as sad as the description The amplifier is English substantial school itself is going on the prototypes and concept of the NAD 3020, and in general wants to say :
"" "We are Englishmen and we can prove to the world machines built from simple materials and smart design can create DECENT machines"
The truth is, that they actually DID IT ... although as the transistors are slow with "hard" work to do driving the load through the poor capacitors and at the input may have a roll off but generally for English rock sounds this is not a major problem and if the listener is not party animal things will go more than ok
replaced caps in the power supply with something better and something bigger (6 times up ) and of course the same and the output at 4700 mfd so it can support some more low end ...
bypass .... decoupling, cleaning .... one relay output and the machine is fine ... certainly has cleared a click above and beyond all the comments are a decent English construction ... .... good-looking machine with personality and identity, and because of its simple construction is extremely clean ...
found some resistors with poor soldering ... listen to it and after all i think i liked it .... same on me .... i consider my shelf a 2SA1302 guy
few pics from
SERVICE KENWOOD KA 5700
it is a bit long ... but believe me it contains things you need to know ...
The idea is for the 5700 KENWOOD talking about a machine that many of us grown up with .sold quite a bit, and obviously in Greece and abroad. Do not imagine loads of power ...just an average clever machine .
What is most interesting is the topology and design which will somehow be linked with several other post which have references to issues such as input impedance and passive preamps .
Initially the amplifier has actually a passive "pramp" (apart from the phono stage that is active ) just an input selector and a potentiometer for volume that works on input impedance of 100K.
This explains all my sayings that the passive "preamp" makes sense, providing the greatest possible clarity of sound in front but only if the machine has at least> 47K of input impedance.
Now as far as the circuit tones is also passive (not active components) and is formed on the feedback chain . The technology has been abandoned years ago because if the load is difficult, the cables are long and the load is capacitive or reactive this topology can easily cause the amplifier to oscillate since load issues might modulate the amp ...
In terms of repairs only electrolytics wanted to be replaced and there was no actual damage . Course were made and related improvements as far as the bias current, the bandwidth, the high pass filters, etc.. Also on important points i removed the ceramic capacitors and got silver mica, together with two wonderful styroflex for input filters .
In my point of view, the amplifier is actually is a small school from KENWOOD and even if the amplifier was not structured as a high end machine in terms of construction and wiring (perhaps with a bit more power) it could be a high end machine.
If someone is interested in more technical details, measurements, and scope readings , I'm at your disposal.
fotos and schematic available
it is a bit long ... but believe me it contains things you need to know ...
The idea is for the 5700 KENWOOD talking about a machine that many of us grown up with .sold quite a bit, and obviously in Greece and abroad. Do not imagine loads of power ...just an average clever machine .
What is most interesting is the topology and design which will somehow be linked with several other post which have references to issues such as input impedance and passive preamps .
Initially the amplifier has actually a passive "pramp" (apart from the phono stage that is active ) just an input selector and a potentiometer for volume that works on input impedance of 100K.
This explains all my sayings that the passive "preamp" makes sense, providing the greatest possible clarity of sound in front but only if the machine has at least> 47K of input impedance.
Now as far as the circuit tones is also passive (not active components) and is formed on the feedback chain . The technology has been abandoned years ago because if the load is difficult, the cables are long and the load is capacitive or reactive this topology can easily cause the amplifier to oscillate since load issues might modulate the amp ...
In terms of repairs only electrolytics wanted to be replaced and there was no actual damage . Course were made and related improvements as far as the bias current, the bandwidth, the high pass filters, etc.. Also on important points i removed the ceramic capacitors and got silver mica, together with two wonderful styroflex for input filters .
In my point of view, the amplifier is actually is a small school from KENWOOD and even if the amplifier was not structured as a high end machine in terms of construction and wiring (perhaps with a bit more power) it could be a high end machine.
If someone is interested in more technical details, measurements, and scope readings , I'm at your disposal.
fotos and schematic available
SERVICE LUXMAN L200
The Luxman l 200 is a machine that has visited us several times over the years .... Not so much because it is machine with problems but mainly because it is a good and sweet machine and appeals to the discriminating listener. Add to that visually is a nice looking machine and the picture is COMPLETE.
electrolytics are to be thrown away as usually ...given the opportunity more capacitance and something better in quality , reasons ... are LINEARITY , endurance longer life and tolerance to higher temperatures.
I would not say that the results are spectacular but definitely finished is a very sweet machine with a little bias current more and a couple of sensitive speakers is a super machine.
classical problem in this is to stabilize next to a resistor to pull 24 volts and turn on the power bulb .... , we convert and put a simple led on it .... not have all this need for that circuit.
fotos and schematic available
The Luxman l 200 is a machine that has visited us several times over the years .... Not so much because it is machine with problems but mainly because it is a good and sweet machine and appeals to the discriminating listener. Add to that visually is a nice looking machine and the picture is COMPLETE.
electrolytics are to be thrown away as usually ...given the opportunity more capacitance and something better in quality , reasons ... are LINEARITY , endurance longer life and tolerance to higher temperatures.
I would not say that the results are spectacular but definitely finished is a very sweet machine with a little bias current more and a couple of sensitive speakers is a super machine.
classical problem in this is to stabilize next to a resistor to pull 24 volts and turn on the power bulb .... , we convert and put a simple led on it .... not have all this need for that circuit.
fotos and schematic available
SERVICE MARANTZ 1060
It has been many discussions on the vintage and a some machines really deserve attention , Though there is a lot of people who sell at unrealistic prices of visually looking nice machines in very good outer condition but by no means we know what is done inside for service and the conditions of the electronics inside ...
I have often said that many do not deserve to be fixed for actual listening reasons .... does not deserve because initially not working properly and there is not much you can to do to change that .... You may only fix it o keep in a secondary system and have more as an antique.
Fortunately this is not the rule .... some of the amps really worth working with upgrade and fix them
That marantz 1060 is unfortunately one of the evil machines ... is not that the average technician likes ... many capacitors output also NPN transistor everywhere and this makes it non-symmetric and general technology of 1970...
Finished after various changes and very good cleaning ... sonics were really unic a true vintage sound loudness as much as you like wrong ..but can give an almost tube sweet sound ... unique things that definitely will not be ever heard of today's amps ....
fotos and schematic available
It has been many discussions on the vintage and a some machines really deserve attention , Though there is a lot of people who sell at unrealistic prices of visually looking nice machines in very good outer condition but by no means we know what is done inside for service and the conditions of the electronics inside ...
I have often said that many do not deserve to be fixed for actual listening reasons .... does not deserve because initially not working properly and there is not much you can to do to change that .... You may only fix it o keep in a secondary system and have more as an antique.
Fortunately this is not the rule .... some of the amps really worth working with upgrade and fix them
That marantz 1060 is unfortunately one of the evil machines ... is not that the average technician likes ... many capacitors output also NPN transistor everywhere and this makes it non-symmetric and general technology of 1970...
Finished after various changes and very good cleaning ... sonics were really unic a true vintage sound loudness as much as you like wrong ..but can give an almost tube sweet sound ... unique things that definitely will not be ever heard of today's amps ....
fotos and schematic available
SERVICE LUXMAN LV 92
I think it is good to do a break to focus only on a machine that, while has not much to say as an amplifier I think it would be nice to see the upgrade step by step and to explain some "how" and some ""why".
The machine is the Luxman LV 92 has nothing extreme is a simple honest machine production 2ch35 watts which was bought used just 70 euro. So lets see what happened.
POWER SUPPLY
In power capacitors were 2 nichicon 6800/50V REPLACED 2 nippon 10.000/63/105 ... there the benefit is more power and cleaner better body and generally cleaner sound.Down under the caps added two bypass ERO 1.0 mfd / 63volt which improve the response speed of the electrolytic and a significant improvement in the fast transitions.
AUXILIARY POWER SUPPLY
In separate power supply is only one regulator 15 V to support secondary functions of the machine (preamp and protection circuits) replaced the electrolytics in the area of protection (nothing to do with sound issues) and added a 1000 mfd 2200/63/105, which of course is not to do with sound but we want regulator to work more "peaceful" and added 100nf decoupling.
In the second part of the auxiliary power supply for the preamplifier and phono circuit tones stabilization is done by Zener and resistors ... definitely not the best but since the filtering is done locally in each unit ensure that it works on quietly.
tone control
The circuit is made around a 4558 ... now this is very outdated and a philips 5532 replaced (I say again that since 5532 is an upgrade, but unfortunately not all of the 5532 on the market work the same good ... their quality from manufacturer to manufacturer changes and unfortunately much ... there one should be careful.)
In tones of were just two simple electrolytics 22mfd / 25 volt which I thought I was not enough i replaced with 100mfd / 63v plus decoupling. Vima mks 100nf/63 ... benefit there is that the we want to be as clean as possible (remember that from stabilization by Zener and resistors which is not the best) The decoupling close to the IC makes cleaner power and helps greatly to improve speed and rejection of any "dirt" that can be "carried" from the power supply .
Changed and the surrounding electrolytics here and there replaced the cheap electrolytic at the input of the amp from simple 2,2 mfd polarized electrolytic capacitors to 2,2 mfd / 63v MKP CSF thomson who offer extremely high linearity less delay ... by far greater range and generally a much better behavior.
AMPLIFIER
Initially all the electrolytics was changed ... the input of the amp also was replaced from a simple electrolytic with the 2,2 mfd / 63v MKP CSF thomson for the same reasons that happened in the preamp circuit ... I thought that the decoupling of power with just 22 / 63 was inadequate ... I went up to 100/63 and I added Vima mks 100nf/63 in order to ensure that the current will be as clean, quiet and rich as possible.
This input filter was ceramic capacitors have been replaced with silver mika which changes significantly the behavior of the machine on high frequency .
PHONO STAGE
In the phono stage changes were made in all electrolytics and in some places boost capacity to filter for the best ... and at some points like the input caps were replaced from 4.7 electrolyte to 10 mfd offering better linearity little better and more responsive to low (generally I like the phono stage if you have electrolytic at the input because it adds a nostalgic tone to sound, although it is generally not the best practice) in contrast to the integrated output came again 2,2 mfd / 63v MKP CSF thomson for the same reasons.
SETTING
The tuning was not much to change with .... Just increased the quiescent current around 35% to gain all the known benefits since the client has small speakers effective and the intention to use he amp on quite casual listening levels ....
It is understood that in general this will raise some temperature above the machine and maybe if the listener finally decides to have a party with this machine it will never make it .... But this scenario will not happen and the listener is quite one ...
One may ask: will changes like that effect the sonic signature of the amp ? i will say YES ... big time ... hopefully though for the best
One may ask: Does it worth the idea? The answer is yes ... the machine produced by far better bass.... was far more clean and clear with a better body with sound sweet and meaningful content. If you think that all these were made with a relatively low cost ... then the value for money is too good and therefore we have achieved our purpose
fotos and schematic available
I think it is good to do a break to focus only on a machine that, while has not much to say as an amplifier I think it would be nice to see the upgrade step by step and to explain some "how" and some ""why".
The machine is the Luxman LV 92 has nothing extreme is a simple honest machine production 2ch35 watts which was bought used just 70 euro. So lets see what happened.
POWER SUPPLY
In power capacitors were 2 nichicon 6800/50V REPLACED 2 nippon 10.000/63/105 ... there the benefit is more power and cleaner better body and generally cleaner sound.Down under the caps added two bypass ERO 1.0 mfd / 63volt which improve the response speed of the electrolytic and a significant improvement in the fast transitions.
AUXILIARY POWER SUPPLY
In separate power supply is only one regulator 15 V to support secondary functions of the machine (preamp and protection circuits) replaced the electrolytics in the area of protection (nothing to do with sound issues) and added a 1000 mfd 2200/63/105, which of course is not to do with sound but we want regulator to work more "peaceful" and added 100nf decoupling.
In the second part of the auxiliary power supply for the preamplifier and phono circuit tones stabilization is done by Zener and resistors ... definitely not the best but since the filtering is done locally in each unit ensure that it works on quietly.
tone control
The circuit is made around a 4558 ... now this is very outdated and a philips 5532 replaced (I say again that since 5532 is an upgrade, but unfortunately not all of the 5532 on the market work the same good ... their quality from manufacturer to manufacturer changes and unfortunately much ... there one should be careful.)
In tones of were just two simple electrolytics 22mfd / 25 volt which I thought I was not enough i replaced with 100mfd / 63v plus decoupling. Vima mks 100nf/63 ... benefit there is that the we want to be as clean as possible (remember that from stabilization by Zener and resistors which is not the best) The decoupling close to the IC makes cleaner power and helps greatly to improve speed and rejection of any "dirt" that can be "carried" from the power supply .
Changed and the surrounding electrolytics here and there replaced the cheap electrolytic at the input of the amp from simple 2,2 mfd polarized electrolytic capacitors to 2,2 mfd / 63v MKP CSF thomson who offer extremely high linearity less delay ... by far greater range and generally a much better behavior.
AMPLIFIER
Initially all the electrolytics was changed ... the input of the amp also was replaced from a simple electrolytic with the 2,2 mfd / 63v MKP CSF thomson for the same reasons that happened in the preamp circuit ... I thought that the decoupling of power with just 22 / 63 was inadequate ... I went up to 100/63 and I added Vima mks 100nf/63 in order to ensure that the current will be as clean, quiet and rich as possible.
This input filter was ceramic capacitors have been replaced with silver mika which changes significantly the behavior of the machine on high frequency .
PHONO STAGE
In the phono stage changes were made in all electrolytics and in some places boost capacity to filter for the best ... and at some points like the input caps were replaced from 4.7 electrolyte to 10 mfd offering better linearity little better and more responsive to low (generally I like the phono stage if you have electrolytic at the input because it adds a nostalgic tone to sound, although it is generally not the best practice) in contrast to the integrated output came again 2,2 mfd / 63v MKP CSF thomson for the same reasons.
SETTING
The tuning was not much to change with .... Just increased the quiescent current around 35% to gain all the known benefits since the client has small speakers effective and the intention to use he amp on quite casual listening levels ....
It is understood that in general this will raise some temperature above the machine and maybe if the listener finally decides to have a party with this machine it will never make it .... But this scenario will not happen and the listener is quite one ...
One may ask: will changes like that effect the sonic signature of the amp ? i will say YES ... big time ... hopefully though for the best
One may ask: Does it worth the idea? The answer is yes ... the machine produced by far better bass.... was far more clean and clear with a better body with sound sweet and meaningful content. If you think that all these were made with a relatively low cost ... then the value for money is too good and therefore we have achieved our purpose
fotos and schematic available
SERVICE LUXMAN LV 105 U
This machine of LUXMAN is a hybrid effort from the manufacturer that the first stage and the second stage is transistor tubes is next while the output is mosfet ...
a very decent machine which has its own clean and unic sound dont expect t to be tube sound but together with the mosfet output stage they managed to put much of the warmth of the tube to the final result .
Let us not forget that it is a consumer machine though specs are way better than hifi..
The quality of construction and the quality of materials is the same as the big brother of the previous series LUXMAN M03 - M05, where apart from the quality also share the same problems ...
The basic problems are the temperatures formed on the vertical pcb's No1 reason where a perfect machine as the M03 is literally destroyed at the moment soldering issues start to appear on the vertical pcb's ... When the time comes NO protection or fuse will prevent the amp from blowing .
The specific amp suffered from the same soldering issues and the entire board of the driver was re soldered from the beginning and will live for many years to come. Put a little cleaning ... and a handful electrolytics and we are just fine
enjoy some foto and schematic is available
This machine of LUXMAN is a hybrid effort from the manufacturer that the first stage and the second stage is transistor tubes is next while the output is mosfet ...
a very decent machine which has its own clean and unic sound dont expect t to be tube sound but together with the mosfet output stage they managed to put much of the warmth of the tube to the final result .
Let us not forget that it is a consumer machine though specs are way better than hifi..
The quality of construction and the quality of materials is the same as the big brother of the previous series LUXMAN M03 - M05, where apart from the quality also share the same problems ...
The basic problems are the temperatures formed on the vertical pcb's No1 reason where a perfect machine as the M03 is literally destroyed at the moment soldering issues start to appear on the vertical pcb's ... When the time comes NO protection or fuse will prevent the amp from blowing .
The specific amp suffered from the same soldering issues and the entire board of the driver was re soldered from the beginning and will live for many years to come. Put a little cleaning ... and a handful electrolytics and we are just fine
enjoy some foto and schematic is available
SERVICE LUXMAN M 03
Leading machine I would say ... a machine that s a real performer ...loads of power ...huge power supply Mt 200 outputs plenty of current ... a vey nice classic amp
Unfortunately till today I have plenty visits of them and they all have the same problem .. The pcb's are upright and vertical oriented while the temperature increase on transistors heat is transferred the first stages above them The heat dissipation is rather poor and in conjunction with the poor solder mask on the pcb soldering issues appear.
If the protection manages to prevent or stop the amp before anything happens from the imbalance produced by the loose parts then all is ok if not the amp will eventually blow with no even one fuse to manage to protect it properly .
This machine blown outputs and drivers due to soldering issues ...alla ha d to be replaced togethere with a few electrolytics ...
Look at the photo "wattmeter" where the amplifier peak power at 8 Ohms shows around 300 watts on one channel only driven while both of them are talking about 260 + 260 watts marvelous ... dont you think ? ...
On of the excellent machines from Luxman ....
Leading machine I would say ... a machine that s a real performer ...loads of power ...huge power supply Mt 200 outputs plenty of current ... a vey nice classic amp
Unfortunately till today I have plenty visits of them and they all have the same problem .. The pcb's are upright and vertical oriented while the temperature increase on transistors heat is transferred the first stages above them The heat dissipation is rather poor and in conjunction with the poor solder mask on the pcb soldering issues appear.
If the protection manages to prevent or stop the amp before anything happens from the imbalance produced by the loose parts then all is ok if not the amp will eventually blow with no even one fuse to manage to protect it properly .
This machine blown outputs and drivers due to soldering issues ...alla ha d to be replaced togethere with a few electrolytics ...
Look at the photo "wattmeter" where the amplifier peak power at 8 Ohms shows around 300 watts on one channel only driven while both of them are talking about 260 + 260 watts marvelous ... dont you think ? ...
On of the excellent machines from Luxman ....
SERVICE SANYO PLUS 55
Wonderful machine.... one of the best ever made i think ... if you seethe schematic and choice of parts it can be on of the best machines ever designed .... from schematic to final product i think was a long way to go and some things were actually missed ...
famous outputs J50 K135 /dual mono construction
Initially the machine was tweaked ... someone tried to change one of the 4 electrolytics which apparently was wrong since we never change one !!always changing all and especially if those originally placed vertically .
If this was the only problem .... This particular amp has the trimmers oposite arranged basically means trimmers do the same job for the bias but for one max is lefte while in the other max is right . It means that if you do not notice one can make a mistake and tune on ch. with much bias current and the other a bit.
Result is one of the two pcb with full of boiling components serious soldering issues .
REPLACED all electrolytics and the machine began some balance tune it a bit and then found that all 5k6 AND ALL 4K7 resistors had drifted value and also need to be replaced ...
Welcome to the main drawbacks of the upright and vertically oriented boards and compromise played between designer and manufacturer
If the machine was mine would reconstruct it to a larger box and horizontal orientation ...
Otherwise, the amplifier is known for its quality and is a machine that deserves to be both repaired and upgraded ... now as construction suffers primarily from temperature issues but still sounds by far better its European cousins the musical fidelities ...
fotos and schematics available
Wonderful machine.... one of the best ever made i think ... if you seethe schematic and choice of parts it can be on of the best machines ever designed .... from schematic to final product i think was a long way to go and some things were actually missed ...
famous outputs J50 K135 /dual mono construction
Initially the machine was tweaked ... someone tried to change one of the 4 electrolytics which apparently was wrong since we never change one !!always changing all and especially if those originally placed vertically .
If this was the only problem .... This particular amp has the trimmers oposite arranged basically means trimmers do the same job for the bias but for one max is lefte while in the other max is right . It means that if you do not notice one can make a mistake and tune on ch. with much bias current and the other a bit.
Result is one of the two pcb with full of boiling components serious soldering issues .
REPLACED all electrolytics and the machine began some balance tune it a bit and then found that all 5k6 AND ALL 4K7 resistors had drifted value and also need to be replaced ...
Welcome to the main drawbacks of the upright and vertically oriented boards and compromise played between designer and manufacturer
If the machine was mine would reconstruct it to a larger box and horizontal orientation ...
Otherwise, the amplifier is known for its quality and is a machine that deserves to be both repaired and upgraded ... now as construction suffers primarily from temperature issues but still sounds by far better its European cousins the musical fidelities ...
fotos and schematics available
Nice thread Sakis... very impressive work
I would like to know what is maca.... this word was published in the first posts.... it looks to me that is oil from automobile and kitchen mixed with dust that goes attached into components.... that thing needs WD40 or Kerosene to dilute..... is this maca?
Stain from Marantz champagne colour panels can be removed with WD40
regards,
Carlos
I would like to know what is maca.... this word was published in the first posts.... it looks to me that is oil from automobile and kitchen mixed with dust that goes attached into components.... that thing needs WD40 or Kerosene to dilute..... is this maca?
Stain from Marantz champagne colour panels can be removed with WD40
regards,
Carlos
SERVICE MARANTZ 2238
flagship category ... big machine,fast sweet accurate with extremely sensitive radio extremely honest in terms of power and response generally a serious machine that had legendary performance at the time.
If it wasn't so loaded with a thousand things and so many functions it could touch the first limits OF HIGH END ..... In real life if the parts were just a bit better and design was just a bit more simple then performance could be superb ..
In positive is sweet sound of the preamp that beyond all provide also tones for bass middle treble ... the loudness also adds plenty of sonics and sweet info which is also the main character of these machines.
The main capacitors were already changed ... All small ones were also replaced which is a condition that will maintain the safe operation of the machine for many years finally a very good cleaning except chemicals and ultrasound we have had to remove the oil from previous SPRAY cleaning ...
( may be Wd 40 ha ha ha )
flagship category ... big machine,fast sweet accurate with extremely sensitive radio extremely honest in terms of power and response generally a serious machine that had legendary performance at the time.
If it wasn't so loaded with a thousand things and so many functions it could touch the first limits OF HIGH END ..... In real life if the parts were just a bit better and design was just a bit more simple then performance could be superb ..
In positive is sweet sound of the preamp that beyond all provide also tones for bass middle treble ... the loudness also adds plenty of sonics and sweet info which is also the main character of these machines.
The main capacitors were already changed ... All small ones were also replaced which is a condition that will maintain the safe operation of the machine for many years finally a very good cleaning except chemicals and ultrasound we have had to remove the oil from previous SPRAY cleaning ...
( may be Wd 40 ha ha ha )