come some time ago to my shop for repair ....
in the preamplifier area i neee to replace all elctrolytics ....GIVE OR TAKE 45 OF THEM !!!!!!
it seems that japs were dealing with the wrong capacitor company at the time Normaly when i repair on these devices i select one cap to test ...and if it shows problems i replace all of them any way ....
for the particular unit i thought checking them all for fun ...ALL of them were gone ....but all
now the particular unit has a coaxial volume balance pot ..... i wonder if possible to dissasembly for cleaning and put together again ...
will see
any input regarding the particular devices is very welcome
regards sakis
in the preamplifier area i neee to replace all elctrolytics ....GIVE OR TAKE 45 OF THEM !!!!!!
it seems that japs were dealing with the wrong capacitor company at the time Normaly when i repair on these devices i select one cap to test ...and if it shows problems i replace all of them any way ....
for the particular unit i thought checking them all for fun ...ALL of them were gone ....but all
now the particular unit has a coaxial volume balance pot ..... i wonder if possible to dissasembly for cleaning and put together again ...
will see
any input regarding the particular devices is very welcome
regards sakis
after i had
to replace almost 50 electros that were totaly gone , i lay my hands on the amplifier section .... big syrprize !!!!!! only 4 electros in the amplifier board
2 decoupling , i feedback, 1 input ....and all the rest ceramics ....
i realy thought that this is sypposed to be high quality gear ....i realy expected higher quality parts inside ....am i missing something ????
i t realy feels strange
to replace almost 50 electros that were totaly gone , i lay my hands on the amplifier section .... big syrprize !!!!!! only 4 electros in the amplifier board
2 decoupling , i feedback, 1 input ....and all the rest ceramics ....
i realy thought that this is sypposed to be high quality gear ....i realy expected higher quality parts inside ....am i missing something ????
i t realy feels strange
sakis,
The nakamichi 420 amp is a low power with bi-polar output; that's what I remember...but you probably know better having been in the unit for repairs.
Guys used to use that amp to power their Quad 57's.
I got to hear that set up a while back and did not think much of it.
The 420 amp did not do much to bring out the soundstage the Quad 57's are capable of.
But maybe with your mods, it will be a much better amp once you are done with it.
Good luck.
The nakamichi 420 amp is a low power with bi-polar output; that's what I remember...but you probably know better having been in the unit for repairs.
Guys used to use that amp to power their Quad 57's.
I got to hear that set up a while back and did not think much of it.
The 420 amp did not do much to bring out the soundstage the Quad 57's are capable of.
But maybe with your mods, it will be a much better amp once you are done with it.
Good luck.
thanks for the info
i was actually very dissapointed by the device ...
later on the costumer informed me that at the time and from all the range of products this was the cheapest available ...
figers .... allready whta ive done is much ....i see no pint on going further since even if i do miracles with the amp ..the pre that goes behind it is nothing really special...
so it has life for another 25 yeras and average quality .....
i was actually very dissapointed by the device ...
later on the costumer informed me that at the time and from all the range of products this was the cheapest available ...
figers .... allready whta ive done is much ....i see no pint on going further since even if i do miracles with the amp ..the pre that goes behind it is nothing really special...
so it has life for another 25 yeras and average quality .....
some more info ...since more units keep coming in
as about the pre now beyond capacitor replacements seems that local decoupling and bypass actually helps the unit a lot
as about the main amp eventhough outputs are totally obsolete still some can be found in some authorized Kenwood shops Kenwood had a lot of models that was working with the same type of transistors so may one get lucky there but expect them to be pricy
For the main unit there is a reputation that blows outputs quite often and without obvious reason
Keep in mind that Nak people at the time had a very weird insulation system ( hard to describe also ) that can be effected even by moisture and create leak to ground or form P or N to ground .
Nak people designed a heatsink that actually has absolutely no insulators and the paint on the heatsink was expected to do the insulation job ..Bit risky i think
I had to apply capton stripes both sides to ensure 100% results ..at least in the feature amplifier will not fail from that .
Noticed:
--Increased local decoupling from 4.7 mfd to 100
--Added a better input capacitor
--Found the input filter cap a bit beefy at 680 pf and setled to 390 pf but styroflex better than ceramic
Kind regards
sakis
as about the pre now beyond capacitor replacements seems that local decoupling and bypass actually helps the unit a lot
as about the main amp eventhough outputs are totally obsolete still some can be found in some authorized Kenwood shops Kenwood had a lot of models that was working with the same type of transistors so may one get lucky there but expect them to be pricy
For the main unit there is a reputation that blows outputs quite often and without obvious reason
Keep in mind that Nak people at the time had a very weird insulation system ( hard to describe also ) that can be effected even by moisture and create leak to ground or form P or N to ground .
Nak people designed a heatsink that actually has absolutely no insulators and the paint on the heatsink was expected to do the insulation job ..Bit risky i think
I had to apply capton stripes both sides to ensure 100% results ..at least in the feature amplifier will not fail from that .
Noticed:
--Increased local decoupling from 4.7 mfd to 100
--Added a better input capacitor
--Found the input filter cap a bit beefy at 680 pf and setled to 390 pf but styroflex better than ceramic
Kind regards
sakis
ooops
one thing i ve missed ....
the ground scheme is also weird from today's standards its ground all around rather than a conventional star ground .
Ground is essential for the boards to work .
It is expected that since 0 from power supply is all around the case heatsinks will take ground from there and then give it to boards ...
Well it seems that this is not happening always i added wires from the real o power supply to each board .
Kind regards
sakis
one thing i ve missed ....
the ground scheme is also weird from today's standards its ground all around rather than a conventional star ground .
Ground is essential for the boards to work .
It is expected that since 0 from power supply is all around the case heatsinks will take ground from there and then give it to boards ...
Well it seems that this is not happening always i added wires from the real o power supply to each board .
Kind regards
sakis
Yes, its possible !!
Just partially seperate the segments and use some ‘doxit spray’ and its done !
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