A funny and interesting add on
FOR THE FUN OF IT
most of the units i repair ( over 100 of this class per year ) come from costumers that love their litle old amps that payed small fortunes at the time to get and if possible to have them working for long time to come to share with chldren or give away to children as a usable working memory.
funny thing is that a 30 year old amp can still play very well if serviced and may be upgraded a bit ... but done properly ... so it is also reasonable that in its 30 yeras of life sometime in the feature it has been srviced before for some reason ...
Notice this in all these amps that have been ""serviced"" before i never seen anything inside done except fuses replaced pots and switches swimming in some oily spray and tops a couple of output tranistors replaced ...
amazing eee
latest one year we have also a new cast of costumers that we call ebayers ...these are people that buy vintage audio from ebay or other similar sites that looks probably ok and may be inside is caniballized but dont really care since they get it very low prize and they are pretty sure that we can make it work no matter what ...
regards sakis
FOR THE FUN OF IT
most of the units i repair ( over 100 of this class per year ) come from costumers that love their litle old amps that payed small fortunes at the time to get and if possible to have them working for long time to come to share with chldren or give away to children as a usable working memory.
funny thing is that a 30 year old amp can still play very well if serviced and may be upgraded a bit ... but done properly ... so it is also reasonable that in its 30 yeras of life sometime in the feature it has been srviced before for some reason ...
Notice this in all these amps that have been ""serviced"" before i never seen anything inside done except fuses replaced pots and switches swimming in some oily spray and tops a couple of output tranistors replaced ...
amazing eee
latest one year we have also a new cast of costumers that we call ebayers ...these are people that buy vintage audio from ebay or other similar sites that looks probably ok and may be inside is caniballized but dont really care since they get it very low prize and they are pretty sure that we can make it work no matter what ...
regards sakis
Service pioneer sa 620
SA 620 is one of the first computerized products of Pioneeror if you prefer computer optimized Pioneer products ....
..yeap eveything is in order inside but it is obvious that the machine is optimized to be able to achive lower cost and still be machine not man made ...
use of more clever pcb rooting,use of flat cables instead of coaxials, but other than that everything inside is placed very orderly
soldering issues here and there dirty pots and switches leacky capacitors a classic story
i was actually thinking that this could be a nice machine (since was computer optimized ) but i was wrong ...measures and plays average ...worst than the luxman above and both of them worst than the P3A no matter how it was configured
amplifier has no nurve, no punch, obviously limited dynamics and bandwidth ...square wave starts to get round corners almost a bit above 4 KHZ ( as is pre and main one thing ) ( which is no miracle to think since 150Pf ceramics are installed in both of drivers and 5Pf miller cap in the VAs stage ...another approach that we have seen before that i dont agree with )
there is one thing to admire though !!! the amplifier user no trimer to adjust ofset and idle ...this come as factory setup ...results is -0.013 ofset for left and -0.016 for right and bias measures 27mv on emmiter resistors of both chanels very sharp and very exact .... means that these people had parts to do miracles at the time ...please notice that inside the amp are classic carbon resistors ...no metal films and no prescision parts ...
here is a picture with the kinky blue VU meter
SA 620 is one of the first computerized products of Pioneeror if you prefer computer optimized Pioneer products ....
..yeap eveything is in order inside but it is obvious that the machine is optimized to be able to achive lower cost and still be machine not man made ...
use of more clever pcb rooting,use of flat cables instead of coaxials, but other than that everything inside is placed very orderly
soldering issues here and there dirty pots and switches leacky capacitors a classic story
i was actually thinking that this could be a nice machine (since was computer optimized ) but i was wrong ...measures and plays average ...worst than the luxman above and both of them worst than the P3A no matter how it was configured
amplifier has no nurve, no punch, obviously limited dynamics and bandwidth ...square wave starts to get round corners almost a bit above 4 KHZ ( as is pre and main one thing ) ( which is no miracle to think since 150Pf ceramics are installed in both of drivers and 5Pf miller cap in the VAs stage ...another approach that we have seen before that i dont agree with )
there is one thing to admire though !!! the amplifier user no trimer to adjust ofset and idle ...this come as factory setup ...results is -0.013 ofset for left and -0.016 for right and bias measures 27mv on emmiter resistors of both chanels very sharp and very exact .... means that these people had parts to do miracles at the time ...please notice that inside the amp are classic carbon resistors ...no metal films and no prescision parts ...
here is a picture with the kinky blue VU meter
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Have enjoyed reading* your insight on many, many different amps, etc.
* haven't read them all yet
Any experience w/a Hafler XL280? Any suggested (SIMPLE please!) mods? I have several for home theatre system. Has a slightly sweeter top end than a Belles Series One but lack the bottom end umph(!). Also undecided which has better image/soundstage.
I've look thru the Hafler 200/220 thread elsewhere on this forum several times over the years, gathered the XL280 is the result of "lessons learned" from 200/220 development. For that reason the 280 doesn't respond well to mods.
Thanks in advance for your help.
tony
* haven't read them all yet
Any experience w/a Hafler XL280? Any suggested (SIMPLE please!) mods? I have several for home theatre system. Has a slightly sweeter top end than a Belles Series One but lack the bottom end umph(!). Also undecided which has better image/soundstage.
I've look thru the Hafler 200/220 thread elsewhere on this forum several times over the years, gathered the XL280 is the result of "lessons learned" from 200/220 development. For that reason the 280 doesn't respond well to mods.
Thanks in advance for your help.
tony
Service kenwood ka 70
KA series from kenwood was here before ...somewhere in this thread there is a KA 50 post
importand to remember that in the ka 50 the tone control is "passive" no active parts but to operate will take some output feedback ...topology that is no longer in use since causes instability under strange loads ..... let us also not forget that produces nice sonics with easy and sensitive speakers
KA 70 is by far diferent ... first of all they used the stk 3082 to drive a pair of very nice outputs 3852 series with quiet good results better than luxman and sansui that used the same or similar topology but with the same STK .....very nice of them to operate the STK properly from a bandwidth aspect plus trimmers for ofset and bias BUT they simply skiped the VBE mutliplier .... bias is coming from the STK without any sensor ....bias has a very low margin for adjustment ....but eventually if pushed will result to thermal run away ( unless i missed something under the heat sink )
features a DC protection and the classic bul connecting speakers A and B in series to avoid overload ( working but ???? what about the sound ???)
the fault
amp jumped in for a quick service no upgrades ( budget limmitations ) since it has been serviced before just a few ....years ago .... what was done in the service center previously is to spray the all pcb with i think PHilps red spray ( nice good old clean diesel oil ) that gives to the pcb a nice shiny look but after some times will eventually work as a dust collector that trimers and pots will love ...
then output relay was something wrong with so the tech guy open it to clen the contacts but somewhere on the way he lost the cover ....( ???
) ...so wtf he installed the relay back without the cover ....God i hate things like that
Replaced a few caps , degreased the amplifier , installed a new relay ( omron quiet hard to find ) replace the trimers ,tune everything up and running ....
Trully the amplifier sound quiet nice ....its by far more bright than the KA 50 for sure brighter than the pioneer and the luxman above .... bright krisp clean detailed and real ... generaly quiet .... almost linear ( eventhough high was very good midle was detailed and transparent )
the problem was in the low area ...soundstage was poor ...no serious kick from it and it was obvious the low end bandwidth was limited .... very very emty there
I liked very much that tone control in the midle was realy flat ... often the problem with tone controls is beyond that effect signal on the way 0db is not really never 0db ....
compaired to the P3A is .... very average .... it cannot even achive the 50% of performance in any area ... but still ... think about the use of STK and then that is a really comercial amp and you are half the way there on the way the designer was thinking ...
here is some pictures ... please notice the open relay ....and the dog hair attached to it from all the greasy spray....
kind regards sakis
KA series from kenwood was here before ...somewhere in this thread there is a KA 50 post
importand to remember that in the ka 50 the tone control is "passive" no active parts but to operate will take some output feedback ...topology that is no longer in use since causes instability under strange loads ..... let us also not forget that produces nice sonics with easy and sensitive speakers
KA 70 is by far diferent ... first of all they used the stk 3082 to drive a pair of very nice outputs 3852 series with quiet good results better than luxman and sansui that used the same or similar topology but with the same STK .....very nice of them to operate the STK properly from a bandwidth aspect plus trimmers for ofset and bias BUT they simply skiped the VBE mutliplier .... bias is coming from the STK without any sensor ....bias has a very low margin for adjustment ....but eventually if pushed will result to thermal run away ( unless i missed something under the heat sink )
features a DC protection and the classic bul connecting speakers A and B in series to avoid overload ( working but ???? what about the sound ???)
the fault
amp jumped in for a quick service no upgrades ( budget limmitations ) since it has been serviced before just a few ....years ago .... what was done in the service center previously is to spray the all pcb with i think PHilps red spray ( nice good old clean diesel oil ) that gives to the pcb a nice shiny look but after some times will eventually work as a dust collector that trimers and pots will love ...
then output relay was something wrong with so the tech guy open it to clen the contacts but somewhere on the way he lost the cover ....( ???
) ...so wtf he installed the relay back without the cover ....God i hate things like that Replaced a few caps , degreased the amplifier , installed a new relay ( omron quiet hard to find ) replace the trimers ,tune everything up and running ....
Trully the amplifier sound quiet nice ....its by far more bright than the KA 50 for sure brighter than the pioneer and the luxman above .... bright krisp clean detailed and real ... generaly quiet .... almost linear ( eventhough high was very good midle was detailed and transparent )
the problem was in the low area ...soundstage was poor ...no serious kick from it and it was obvious the low end bandwidth was limited .... very very emty there
I liked very much that tone control in the midle was realy flat ... often the problem with tone controls is beyond that effect signal on the way 0db is not really never 0db ....
compaired to the P3A is .... very average .... it cannot even achive the 50% of performance in any area ... but still ... think about the use of STK and then that is a really comercial amp and you are half the way there on the way the designer was thinking ...
here is some pictures ... please notice the open relay ....and the dog hair attached to it from all the greasy spray....
kind regards sakis
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not much to do with hafler ...done a 220 once i had to do total recaping and change a feew things that i didnt like and many of the mechano stuff like wiring cables and so on ...Generally i dont like mosfets ...and also one thing i have to tell you that the repair was done almost 5 yeras ago and there is not much that i like to remember from it ( at the time i wasnt keeping detailed records of my repairs ....) now days my computers are by far more advanced and investments was done to get real time analyzer and distortion meters ...so for the most amplifiers i repiar i keep a digital file/signature in a computer ...
i wasnt much of help ... sorry for that ... but if a hafler jumps in be sure i will make a detailed presentation
i remember that in th particular unit all caps where gone ... had some issue with the mains fuse or switch dont remember ....found decoupling was not enough found twisted wires instead of coaxials .... had some ground issues and also wire rooting ...
that is the only i remember
yamaha C4 service
well been way to busy these days to post results of my latest services but also it has been a time that none of themachines worth to write a few things about ...
here is an interesting machine ... the YAMAHA C 4 preamp ... after building a B1 buffer that aslo playing together with my P3A amps i thought that i will never listen to any other preamp that is so quiet and natural ...
the C4 is a japanese masterpiece i think since its the first preamp that i repair that is so clean and natural while inside is very complicated ( see pictures .... )
all boards are actually faced upside down which is a quiet clever thing since no dust is going in the open switches but also any parts that are under some thermal stress have no room to breath ...( that caused a few things in a long run ... )
soldering was almost terrible inside ...i almost had to resolder everything ...and many capacitors dried out ...all done and replaced ... replaced also 3 lamps with led ...so they will last for ever ......lots of similar problems on the power supply areas too ...
after repaired and fine tuning ( it even features a offset pot ) and from the service manual acceptable tollerance is from 0-200mv after replaciing the trimmer to a mutliturn i managed to bring this to almost zero....
listening impression is that its very dynamic very clean with soft control and as less effect on sound is possible ...if you havent listen to the purity and simplicity of a B1 style preamp you may think that is the best preamp ever ...
frecuence response is somewhere between the moon and mars while compaired to the complexity of the machine the crosstalk figures are one of the best i ve seen in a production preamp
tone control is also very fine ...with parametric also that in flat position ...actually plays flat and tone defeat switch has almost no job to do /
highly recomented !!!!
regards sakis
well been way to busy these days to post results of my latest services but also it has been a time that none of themachines worth to write a few things about ...
here is an interesting machine ... the YAMAHA C 4 preamp ... after building a B1 buffer that aslo playing together with my P3A amps i thought that i will never listen to any other preamp that is so quiet and natural ...
the C4 is a japanese masterpiece i think since its the first preamp that i repair that is so clean and natural while inside is very complicated ( see pictures .... )
all boards are actually faced upside down which is a quiet clever thing since no dust is going in the open switches but also any parts that are under some thermal stress have no room to breath ...( that caused a few things in a long run ... )
soldering was almost terrible inside ...i almost had to resolder everything ...and many capacitors dried out ...all done and replaced ... replaced also 3 lamps with led ...so they will last for ever ......lots of similar problems on the power supply areas too ...
after repaired and fine tuning ( it even features a offset pot ) and from the service manual acceptable tollerance is from 0-200mv after replaciing the trimmer to a mutliturn i managed to bring this to almost zero....
listening impression is that its very dynamic very clean with soft control and as less effect on sound is possible ...if you havent listen to the purity and simplicity of a B1 style preamp you may think that is the best preamp ever ...
frecuence response is somewhere between the moon and mars while compaired to the complexity of the machine the crosstalk figures are one of the best i ve seen in a production preamp
tone control is also very fine ...with parametric also that in flat position ...actually plays flat and tone defeat switch has almost no job to do /
highly recomented !!!!
regards sakis
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my approach was to use a potentiometer and a cd player ... well compaired to this almost no comercial preamp managed to produce even close to sound and natural very very few i would say .
of course gain and full drive was never the question here ....
the truth is that with this configuration eventhough the beneffit of very clear is unbeatable there is an obvious absense of dynamics ...using a B1 improved the dynamics but WITHOUT messing up with the sound ....
after that the all sytem become more tollerant regarding what pot you use in the input ...now days i ma listening from 2x50k from alpha that actually performs superior compaired to the prize i pay for ...
regards sakis
of course gain and full drive was never the question here ....
the truth is that with this configuration eventhough the beneffit of very clear is unbeatable there is an obvious absense of dynamics ...using a B1 improved the dynamics but WITHOUT messing up with the sound ....
after that the all sytem become more tollerant regarding what pot you use in the input ...now days i ma listening from 2x50k from alpha that actually performs superior compaired to the prize i pay for ...
regards sakis
hmmm done the thing ....
Sansui AU 999 is made like a tank !!!
key things ....
3 way tone controls are made by rotary switches (no pots) and aslo feature some parametric also with rotary switches ... given the complexity /number of resistors and caps it works ok i d say but nothing really extreme
tone has bypass function that doesnt help much cause the amplifier is not linear any way frequency response is not what we used to think now days and has problems both on the low and high ends ( that could be fixed i presume but i dint want to mess up with the circuit ....idea is to bring it in original condition and thats it !! )
construction is more than perfect for the time .... input buss is sealed with metal covers .... all pots and switches also covered in metal covers resulting a clean amp even after 40 years
excelent control of bias and ofset but the sound didnt thrill me
i will not say more since i am trying to see a 40 year old machine with todays standards and instruments ... that is not fair
i would say a machine that is made to last for ever only remember every 40 years to change all electrolytics inside and tou are fine ...
sweet nice sonics and memories from the past
kind regards sakis
Sansui AU 999 is made like a tank !!!
key things ....
3 way tone controls are made by rotary switches (no pots) and aslo feature some parametric also with rotary switches ... given the complexity /number of resistors and caps it works ok i d say but nothing really extreme
tone has bypass function that doesnt help much cause the amplifier is not linear any way frequency response is not what we used to think now days and has problems both on the low and high ends ( that could be fixed i presume but i dint want to mess up with the circuit ....idea is to bring it in original condition and thats it !! )
construction is more than perfect for the time .... input buss is sealed with metal covers .... all pots and switches also covered in metal covers resulting a clean amp even after 40 years
excelent control of bias and ofset but the sound didnt thrill me
i will not say more since i am trying to see a 40 year old machine with todays standards and instruments ... that is not fair
i would say a machine that is made to last for ever only remember every 40 years to change all electrolytics inside and tou are fine ...
sweet nice sonics and memories from the past
kind regards sakis
SERVICE Sansui AU 117
AU series was mostly nice amps ... AU 117 is a simple made low till very low power but yet remains a very simply made clean and sweet machine ....
outputs blown, elctros half dead , quiet dirty ,and been repaired a couple of times before for the same reason untill totally blown ...
caps replaced , few resistors , a good clean , and since outputs was not easy to locate i thought replacing with MJE 15032-33 more power,faster ,and easy ... worked really fine ...
Results are very sweet ...a very clean machine as said before with low power but the sound is very clean ..very balanced rich from every aspect ... obvious lack of banks ... but yet very detailed sound ...
tone controls is effective but yet quiet clean .... flat position is not really flat but better than others i ve seen ...
for this type of amp i would say one of the best i ve ever listen to ...
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FUNNY PART
Amp has been to service center before ...had 3 resistors blown so the tech guy replaced them together with a fuse and let go ... didnt check nothing else
then amp fails again another resistor and another fuse blown both replaced but since this resistor made the amp to have excesive offset the tech guy checked the outputs one by one ...
then the amp was blown after the"repair" simply all electrolytics was half dead but moslty output tranistors was loose from the heatsink and most importand the white grease has been converted to powder over somany years ...
eventhough amplifier is small efficient cooling is required...
Mje 15032-33 worked happily with 40ma bias to a useable bandwidth of almost 30KHz ...fairly good for this amplifier
AU series was mostly nice amps ... AU 117 is a simple made low till very low power but yet remains a very simply made clean and sweet machine ....
outputs blown, elctros half dead , quiet dirty ,and been repaired a couple of times before for the same reason untill totally blown ...
caps replaced , few resistors , a good clean , and since outputs was not easy to locate i thought replacing with MJE 15032-33 more power,faster ,and easy ... worked really fine ...
Results are very sweet ...a very clean machine as said before with low power but the sound is very clean ..very balanced rich from every aspect ... obvious lack of banks ... but yet very detailed sound ...
tone controls is effective but yet quiet clean .... flat position is not really flat but better than others i ve seen ...
for this type of amp i would say one of the best i ve ever listen to ...
--------------------------------------------------------------------
FUNNY PART
Amp has been to service center before ...had 3 resistors blown so the tech guy replaced them together with a fuse and let go ... didnt check nothing else
then amp fails again another resistor and another fuse blown both replaced but since this resistor made the amp to have excesive offset the tech guy checked the outputs one by one ...
then the amp was blown after the"repair" simply all electrolytics was half dead but moslty output tranistors was loose from the heatsink and most importand the white grease has been converted to powder over somany years ...
eventhough amplifier is small efficient cooling is required...
Mje 15032-33 worked happily with 40ma bias to a useable bandwidth of almost 30KHz ...fairly good for this amplifier
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Service sansui aud 22-33
two of them come in to the shop the same day ....odd i dsay
typical story one of them come from a friend in northen Greece fellow tech that made a mistake and blow the all amplifier ( device under repair on his work bench ) probe of his scope fallout and short circuited a few things inside the amp ...other belongs to an everyday costumer ...
the blown one had a few resistors one driver two outputs and a fuse ( caps where allready been replaced in my friends shop ) so i had to replace the all set of outputs for symmetry reasons and i was lucky enough to find original sets from the AUD 33
the other one needed a serious cleaning ...two handsfull of caps a relay and a hell of a lot of soldering for both ...
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the specific amp has a quiet strange topology for a good japanese amplifier...meaning that from topology aspect there was an input and vas board frontwise next to tone control area ( as can be seen in the photos ) and then an other, back board that features PSU ,driver, protection and output parts .
then the two boards are wired with cables that actually are leaning above the main transformer terrible design i d say
selector topology is bad crosstalk figures are terrible and sure audible ( no instruments for that )
generally i would say that the schematic is more than perfect but seems that the designer wasnt arround when somobody f@@ked around with the execution ... Add to this that the solder mask was terrible leaving very litle room for soldering resulting that in both critical boards ther was plenty of soldering to be done to ensure that the amp will contact in the feature also ... another execution mistake
thumbs down for this machine and one of a few Japanese that i ve seen made so bad ( i will not post comments about sound performance cause i didnt bother to listen to it ...repair it scope it and let go ...)
enjoy some pictures
two of them come in to the shop the same day ....odd i dsay
typical story one of them come from a friend in northen Greece fellow tech that made a mistake and blow the all amplifier ( device under repair on his work bench ) probe of his scope fallout and short circuited a few things inside the amp ...other belongs to an everyday costumer ...
the blown one had a few resistors one driver two outputs and a fuse ( caps where allready been replaced in my friends shop ) so i had to replace the all set of outputs for symmetry reasons and i was lucky enough to find original sets from the AUD 33
the other one needed a serious cleaning ...two handsfull of caps a relay and a hell of a lot of soldering for both ...
------------------------------------------------------------------
the specific amp has a quiet strange topology for a good japanese amplifier...meaning that from topology aspect there was an input and vas board frontwise next to tone control area ( as can be seen in the photos ) and then an other, back board that features PSU ,driver, protection and output parts .
then the two boards are wired with cables that actually are leaning above the main transformer terrible design i d say
selector topology is bad crosstalk figures are terrible and sure audible ( no instruments for that )
generally i would say that the schematic is more than perfect but seems that the designer wasnt arround when somobody f@@ked around with the execution ... Add to this that the solder mask was terrible leaving very litle room for soldering resulting that in both critical boards ther was plenty of soldering to be done to ensure that the amp will contact in the feature also ... another execution mistake
thumbs down for this machine and one of a few Japanese that i ve seen made so bad ( i will not post comments about sound performance cause i didnt bother to listen to it ...repair it scope it and let go ...)
enjoy some pictures
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service UK POWER MATRIX
i do pro amps also .... but since this thread is made for P3A and comparsions to other comercial amps ( where ever it works ) i will write very few here for this ( pro amps )
litle brit come in to the shop with all shorts of problems few caps few resitors two mos outputs a small relay ... No schematic on this one still the people from the matrix company seemed to be very helpfull and willing but yet no schematic ...
Obviously the amp was canibalized from someone in the past while trying to repair but the effort was terrible ...soldering was very bad choise of parts was obviously wrong from quality and value aspects.
since i had no schematic i had to mixmatch a few things from one chanel to the other guess a few other things since trying to get a hand drawn schematic will consume more time than the repair it shelf ...
So i got the lilte brit fixed and working propely ofset is absolutelly zero ...all relays click properly and amp happilyputs almost 50 volts on a resistive load of 8R and the same in about 4R
strange is that all this is coming from a 600 w trafo ... sound is good amp is working very nicelly and seems to run kind cool also ...
interesting spot will be a small relay that exists in the drive circuit and this i didnt understand what the exact perpus might be but here i will ask forum members for their contribution in the topic
some pictures
i do pro amps also .... but since this thread is made for P3A and comparsions to other comercial amps ( where ever it works ) i will write very few here for this ( pro amps )
litle brit come in to the shop with all shorts of problems few caps few resitors two mos outputs a small relay ... No schematic on this one still the people from the matrix company seemed to be very helpfull and willing but yet no schematic ...
Obviously the amp was canibalized from someone in the past while trying to repair but the effort was terrible ...soldering was very bad choise of parts was obviously wrong from quality and value aspects.
since i had no schematic i had to mixmatch a few things from one chanel to the other guess a few other things since trying to get a hand drawn schematic will consume more time than the repair it shelf ...
So i got the lilte brit fixed and working propely ofset is absolutelly zero ...all relays click properly and amp happilyputs almost 50 volts on a resistive load of 8R and the same in about 4R
strange is that all this is coming from a 600 w trafo ... sound is good amp is working very nicelly and seems to run kind cool also ...
interesting spot will be a small relay that exists in the drive circuit and this i didnt understand what the exact perpus might be but here i will ask forum members for their contribution in the topic
some pictures
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company is still active ... i think also they have a new line of amps just coming out ... fine amp well designed and very effective for only two sets of outputs per chanel
had a chance to test it and push it quiet hard on a gig last night well it just managed perfectly with 4 ohm load and clip condition for about 6 hours ...
still the small relay on the drive circuit ( probably part of protection circuit ) remains a mystery but simply since there is no time to hand draw a schematic
kind regards sakis
had a chance to test it and push it quiet hard on a gig last night well it just managed perfectly with 4 ohm load and clip condition for about 6 hours ...
still the small relay on the drive circuit ( probably part of protection circuit ) remains a mystery but simply since there is no time to hand draw a schematic
kind regards sakis