Recapping vintage Nikko separates

[BrandonS2185]

Hello. I am pretty new with rehabbing vintage gear but recently (and successfully) recapped a Marantz 6300 with no issue. My question is, I just got a free Nikko Alpha 220, Beta 20, and Gamma 20 set. I know they aren't amazing but free is a pretty good price. I'd like to do a recap of the preamp and power amp and have the service manuals and know the values of all the caps. I'd like to tap into this forums deep knowledge base so I'll treat this thread as my personal HELP! page.

My first problem/question is when I get on digi key to order cap replacements I get several options for lead pitch. Is there an efficient way to measure lead pitch or do I actually need to get out a caliper and measure? I'm looking at over 50 caps and that would be annoying. I figure the difference between 2.5 and 5mm really won't be a big deal but I'd like things to fit nicelly.

My second question is regarding the volume attenuator on the preamp. It is really scratchy/crackly when I turn the knob but it is a sealed pot. The manufacturer of the pot is Noble and I have the part number but can't locate it on their site. I emailed them and they aren't responding. Any help for fixing/replacing would be great. I'm uploading a pic of the piece. It is listed as 100kohm x2. It is a 6 terminal design (3x2).

Thanks!

 

[slimecity]

There may be holes where the pins protrude from the pot body on the side soldered to the pcb. I would turn the unit upside down, spray some contact cleaner in between the pcb and pot. Some may get in. This will be an older part and not likely on their website. Try also setting the unit on its back and spraying cleaner on the shaft. Some cleaner could travel down the shaft to inside the body & slider contacts.

Nikko is great gear.

 

[ivandezande]

Cap pitch - don't worry about it with smaller values as long as the board has space. Since new caps are smaller, most time you never have to worry. I never have. Nikko's great stuff. DeOxit that pot if at all possible, otherwise start measuring and get an equivalent Alps pot. Make sure you get the taper and pins right, they make so many you'll either find a match or something that'll work ok.

 

[Goldie99]

Volume Pot - unfortunately, the best route into the pot may involve desoldering and dismantling it.

If it's the same as some of the other Noble pots, it may be assembled with screws from the front of the pot (e.g., as the example in the photo) - https://www.hificollective.co.uk/potentiometers/noble-potentiometers.html - if so, a careful strip, deep clean, and lubrication is likely to cure it. Likely to be fiddly, but probably the best long term solution.

 

[avionic]

There may be holes where the pins protrude from the pot body on the side soldered to the pcb. I would turn the unit upside down, spray some contact cleaner in between the pcb and pot. Some may get in. This will be an older part and not likely on their website. Try also setting the unit on its back and spraying cleaner on the shaft. Some cleaner could travel down the shaft to inside the body & slider contacts.

Kinda piss'n in the wind there.Wasting time and contact cleaner.

 

[BrandonS2185]

Cap pitch - don't worry about it with smaller values as long as the board has space. Since new caps are smaller, most time you never have to worry. I never have. Nikko's great stuff. DeOxit that pot if at all possible, otherwise start measuring and get an equivalent Alps pot. Make sure you get the taper and pins right, they make so many you'll either find a match or something that'll work ok.

Thanks. That's what I figured. The pcb and attached components are all really spaced out nicely so I won't worry about it.

Volume Pot - unfortunately, the best route into the pot may involve desoldering and dismantling it.

If it's the same as some of the other Noble pots, it may be assembled with screws from the front of the pot (e.g., as the example in the photo) - https://www.hificollective.co.uk/potentiometers/noble-potentiometers.html - if so, a careful strip, deep clean, and lubrication is likely to cure it. Likely to be fiddly, but probably the best long term solution.

At first glance it doesn't appear to have screws, but I'll remove it from the unit to take a closer look. I may just have to get a replacement from Alps like ivandezande recommend.

 

[BrandonS2185]

Next question. I know you can generally go up in volts on electrolytic caps but what about film? I want to replace the polyester caps with metalized polypropylene caps but the lowest voltage I can find is like 250. The originals are all 50v. Is this an issue? Parts express is the only place I can find them too. Any help would be great.

 

[roger2]

Next question. I know you can generally go up in volts on electrolytic caps but what about film? I want to replace the polyester caps with metalized polypropylene caps but the lowest voltage I can find is like 250. The originals are all 50v. Is this an issue? Parts express is the only place I can find them too. Any help would be great.

The voltage rating for caps is the nominal maximum working voltage it can handle. So yeah you can go up in voltage with film caps.

But one thing you shouldn't do is use caps with longer leads than necessary. The fact that you are looking at film caps at Parts Express makes me wonder if the ones under consideration might be axial where the original polyesters are radial? If so then I would not do that replacement. Polyester caps seldom go bad. There is not much to be gained unless perhaps these caps are directly in the signal path. Even then, I wouldn't use replacement caps that had longer leads than the originals (i.e. axials to replace radials).

As to your earlier question about lead spacing on electrolytics, yes it is common for newer caps to have closer lead spacing (LS). If you search, sometimes you can find new caps with LS (and sometimes body diameter) to match the originals. But if the new LS is less, don't just jam the new cap down into the old PCB holes. That would cause stress at the point where the leads enter the cap. Better to put a couple of bends into one lead so that it remains perpendicular to the bottom of the cap body and also such that the lead end entering the PCB is perpendicular to that surface. When bends like this are used, sometimes (because the body of the cap is smaller than the original), positioning can be done to move the cap slightly further away from local heat sources. That won't always matter, but sometimes it can. While on that subject, a survey should be done before ordering parts to see where the hot running components are inside the amp. Any electrolyctics physically close to a hot component would be ideal candidates for 105°C replacements.

 

[BrandonS2185]

The voltage rating for caps is the nominal maximum working voltage it can handle. So yeah you can go up in voltage with film caps.

But one thing you shouldn't do is use caps with longer leads than necessary. The fact that you are looking at film caps at Parts Express makes me wonder if the ones under consideration might be axial where the original polyesters are radial? If so then I would not do that replacement. Polyester caps seldom go bad. There is not much to be gained unless perhaps these caps are directly in the signal path. Even then, I wouldn't use replacement caps that had longer leads than the originals (i.e. axials to replace radials).

As to your earlier question about lead spacing on electrolytics, yes it is common for newer caps to have closer lead spacing (LS). If you search, sometimes you can find new caps with LS (and sometimes body diameter) to match the originals. But if the new LS is less, don't just jam the new cap into the old PCB holes. That would cause stress at the point where the leads enter the cap. Better to put a couple of bends into one (or both) leads so that the lead remains perpendicular to the bottom of the cap body and also such that the lead end entering the PCB is perpendicular to that surface. When bends like this are used, sometimes (because the body of the cap is smaller than the original), positioning can be done to move the cap slightly further away from local heat sources. That won't always matter, but sometimes it can. While on that subject, a survey should be done before ordering parts to see where the hot running components are inside the amp. Any electrolyctics physically close to a hot component would be ideal candidates for 105°C replacements.

Thanks for the detailed response! The vast majority of the caps I selected are Panasonic FM series caps with a 105*C rating. The rest (ones that I could not find Pana FMs for) are audio grade Nichicons.

I may hold off on the film caps then if the benefits aren't that noticeable.

 

[roger2]

A good thing to do for any new project is search past threads on that particular model. Many pieces of gear have known issues that may have been discussed by others who have already been down the path that you are starting out on. People who may have posted 5 or 10 years ago are not likely to see your thread today. But they might have solved problems in your amp that you are not yet aware of. While (before, actually) you have the amp on your bench it is good to know as much as you can about it.

https://www.google.com/advanced_search?hl=en

In google advanced search:
in the box labeled "this exact word or phrase:" enter "Nikko Alpha 220" (for example)
in the box labeled "site or domain:" enter "audiokarma.org" and then do another search using "diyaudio.com"

You'll get lots of hits for most pieces of gear. Some (or much) of what pops up may not be helpful. But often you can find valuable information.

 

[BinaryMike]

You will sometimes find that uprating the temp and/or voltage rating for new electrolytic caps will help you find something with wider lead spacing to match PCB hole spacing in older gear. And in most circuits, you can go up as much as 2X in capacitance for the same reason. Understand that aluminum electrolytics never had close tolerances, so design engineers don't normally expect the parts used in production to be near their nominal values. That said, I also think it's best to avoid extremes.

 

[BrandonS2185]

A good thing to do for any new project is search past threads on that particular model. Many pieces of gear have known issues that may have been discussed by others who have already been down the path that you are starting out on. People who may have posted 5 or 10 years ago are not likely to see your thread today. But they might have solved problems in your amp that you are not yet aware of. While (before, actually) you have the amp on your bench it is good to know as much as you can about it.

https://www.google.com/advanced_search?hl=en

In google advanced search:
in the box labeled "this exact word or phrase:" enter "Nikko Alpha 220" (for example)
in the box labeled "site or domain:" enter "audiokarma.org" and then do another search using "diyaudio.com"

You'll get lots of hits for most pieces of gear. Some (or much) of what pops up may not be helpful. But often you can find valuable information.

Thanks. I did a regular search on google and didn't really turn up much. I'll try the advanced function and see what I get.

You will sometimes find that uprating the temp and/or voltage rating for new electrolytic caps will help you find something with wider lead spacing to match PCB hole spacing in older gear. And in most circuits, you can go up as much as 2X in capacitance for the same reason. Understand that aluminum electrolytics never had close tolerances, so design engineers don't normally expect the parts used in production to be near their nominal values. That said, I also think it's best to avoid extremes.

The most "extreme" I got on upping the capacitance was going from a 16v cap to 35v.

 

[roger2]

Thanks. I did a regular search on google and didn't really turn up much. I'll try the advanced function and see what I get.

........

Searching as described above...

106 hits at audiokarma.org
https://www.google.com/search?hl=en..._occt=any&safe=images&as_filetype=&as_rights=

51 hits at diyaudio.com
https://www.google.com/search?hl=en..._occt=any&safe=images&as_filetype=&as_rights=


Advanced search allows you to limit the sites searched, which eliminates most of the junk. Of course any information found should be taken with a grain of salt, as with anything posted on internet forums.

good luck with your project

 

[BrandonS2185]

Volume Pot - unfortunately, the best route into the pot may involve desoldering and dismantling it.

If it's the same as some of the other Noble pots, it may be assembled with screws from the front of the pot (e.g., as the example in the photo) - https://www.hificollective.co.uk/potentiometers/noble-potentiometers.html - if so, a careful strip, deep clean, and lubrication is likely to cure it. Likely to be fiddly, but probably the best long term solution.

Thanks for the advice. I pulled the pot from the unit and you were right! There are tiny screws. I loosened them and sprayed some DeoxIT and worked the knob about 50 times. Hopefully that does the trick.

 

[BrandonS2185]

I have finished recapping my preamp. It's was a pretty easy task. I am now working through recapping the Nikko Alpha 220 power amp. There are two caps left but they are located on the power transistor PCB under the heat sink. It would take me a lot of effort and a couple hours to desolder all the wires, unscrew all the transistors and pull the entire section out of the amp just to get to these two caps. I know I can desolder them and remove them from the underside pretty easily but getting new ones in would be next to impossible with everything still intact.

My question is can I simply solder in the new caps on the underside of the PCB? There are other small filter caps on the underside so I can't see putting these electrolytic caps on the underside as being a problem. I've uploaded a pic of the bottom of the PCB. Our transistor board is the middle one. You can see the heatsink through the gaps in the board.

Thanks.

 

[BinaryMike]

If you have sufficient clearance for the new caps between the cabinet bottom cover and PCB, without extending capacitor leads, then I see no problem with bottom side installation. If you're replacing little ceramic disc types, then just don't. They almost never go bad.

 

[gpounce32768]

I overhauled an Onkyo a while back which had 4 or so electrolytics mounted on the underside of the board, set in plastic tubing and glued down. I did a full recap on that unit, lots of bad caps on it 5 or 6 had leads rotted to the point where they literally fell out of the cap during desoldering. An old JVC quad I worked on had a number of resistors mounted on the solder side of one board. One of the resistors had been pressed on so its lead bridged to another pad, disabling one of the channels- so be careful with lead isolation if mounting parts on the solder side.