Hi i would like to mod my Nikko NA-500. I am open to every ideas. But i want to start with changing caps. I need your help with choosing which caps and how should i change them?(my hands can change a capacitor, but can't choose the right cap)
Thanks.
Nazim.
This is the link to schematics.
Login - HiFi Engine
Thanks.
Nazim.
This is the link to schematics.
Login - HiFi Engine
The link is incorrect. Try starting with this one:
Nikko NA-500 Manual - Stereo Integrated Amplifier - HiFi Engine
Replacing the old capacitors is probably a good idea but this amplifier is based on Sanyo STK series Hybrid modules and there is little scope for "modding" when the tone controls are wrapped around the input stage module. It would not be wise or simple to modify the circuits here. If you want to mess with an amplifier, use a discrete amplifier design, as you have the opportunity to see and learn how the amplifier works (or not) and what you are actually doing to it. Any damage you do may be repairable then and this is important because you will find you cannot obtain replacement STK series modules (genuine ones, at least). That means binning the remains of your amp. and no one likes that outcome.
I think just recapping the electrolytic caps (the polarized ones) by simply matching the specification on the cap. label is sufficient, using recognized brands like Panasonic, Rubycon, Elna, Nichicon, Nippon Chemicon etc. Where a value cannot be matched, there should be no problem increasing capacitance values up to even 2 x the original. You can also use caps with higher voltage ratings but never use a lower voltage rating.
For most smaller electrolytics, use low ESR caps for their generally better performance. The main smoothing caps (C801 - 6800uF /45V) will not be available as low ESR caps. Use the highest ripple current rated caps instead.
You will find the specifications for these properties in any decent parts catalogue. Google will soon find you definitions if you don't understand what they mean.
Thank you for your kind and helpful reply 🙂
And thanks for correcting the link.
Nazim.
Hi! I have the Nikko NA-500 of my father and have the transformer broken. You can said to me the output voltage? I don't found any info on internet. Thanks!
Hi,
It seems to be 28-0-28 volts AC.
Most likely the protective thermal fuse in the transformer blew. It normally sits just under the outer layer of the transformer. But first you need to determine why the fuse blew in the first place if in fact it did go open.
Measure the resistance of the primary winding. If it's open then the fuse blew.
Cheers
It seems to be 28-0-28 volts AC.
Most likely the protective thermal fuse in the transformer blew. It normally sits just under the outer layer of the transformer. But first you need to determine why the fuse blew in the first place if in fact it did go open.
Measure the resistance of the primary winding. If it's open then the fuse blew.
Cheers
Thanks for you reply!
I try to search the fuse in the transformer, but i don't found. All other fuse are ok. Are you sure that is AC? Is for start to search any replacement for the transformer.
I try to search the fuse in the transformer, but i don't found. All other fuse are ok. Are you sure that is AC? Is for start to search any replacement for the transformer.
Accessibility of the thermal fuse may vary considerably, from almost on the outside to way down inside, unfortunately you can never tell beforehand. Unwrapping a transformer is not exactly for the faint of heart either way.
According to the schematic the thermal fuse is in series with the orange wire and is a 147°C type - this rather high value suggests a location deep inside the transformer, unfortunately. 🙁
However, the way the fuse is drawn may indicate that both ends of it are connected to terminals on the transformer. Please check all the available connections for continuity to the blue wire. Is your unit also a 220 V 50 Hz model as shown on the schematic?
And yes, I am 100% sure that a transformer is a pure AC device by definition, being a bunch of magnetically coupled inductors. AC in, AC out. Any transformer voltage specs you'll find will thus always imply AC as well.
I guess you'd be looking for an EI transformer of about 100 VA - check existing transformer dimensions and available space. 28-0-28 or 2x 28 V secondary sounds about right, that would give about +/-38 Vdc at idle. The smoothing capacitors are rated at 45 WVDC, so it couldn't have been more than +/-40 V stock either way.
According to the schematic the thermal fuse is in series with the orange wire and is a 147°C type - this rather high value suggests a location deep inside the transformer, unfortunately. 🙁
However, the way the fuse is drawn may indicate that both ends of it are connected to terminals on the transformer. Please check all the available connections for continuity to the blue wire. Is your unit also a 220 V 50 Hz model as shown on the schematic?
And yes, I am 100% sure that a transformer is a pure AC device by definition, being a bunch of magnetically coupled inductors. AC in, AC out. Any transformer voltage specs you'll find will thus always imply AC as well.
I guess you'd be looking for an EI transformer of about 100 VA - check existing transformer dimensions and available space. 28-0-28 or 2x 28 V secondary sounds about right, that would give about +/-38 Vdc at idle. The smoothing capacitors are rated at 45 WVDC, so it couldn't have been more than +/-40 V stock either way.