The plastic sleeving of modern electrolytic caps continues to shrink over time and that pulls the rim of the top cover disc down. So eventually, with a little heat to soften the plastic, the centre of the disc rises slightly until you get that domed appearance. In my limited experience, original caps or a full set of replacements, will all bulge the same limited way as your pic shows, without it being a problem. Caps that fail in a bad way and burst or leak from pinholes in the can, do so in different ways - usually all messy ones.
When ever I come across the dought about a 10,000uf power supply cap
I would solder a new 10,000 cap through long thick leeds from
the underside of the pcb or suitable point. Then observe whether the
symptom goes away.
In the picture shown above you could peel off the plastic cover with a
knife from the top and look to see whether the aluminum can has
also bloted up.
As a generel rule all electrolytics more than 10 years old should be replaced to
look after(safe guard) the nice piece of equipment you enjoy.
John.
I would solder a new 10,000 cap through long thick leeds from
the underside of the pcb or suitable point. Then observe whether the
symptom goes away.
In the picture shown above you could peel off the plastic cover with a
knife from the top and look to see whether the aluminum can has
also bloted up.
As a generel rule all electrolytics more than 10 years old should be replaced to
look after(safe guard) the nice piece of equipment you enjoy.
John.
The original caps in many Japanese, Euro and US models for example, will and should last a lot longer than 10 years. 20-30 years and occasionally even more is not unusual for quality audio products from the 1970s-1990s at least. Perhaps there are also environmental temperature and usage factors but routinely replacing large caps after 10 years is either wasteful or their quality is really poor. Some repairers do routinely replace the PS caps without even testing for ESR which tells you that their reasoning is likely based on suspicion, internet stories or making no-bounce repairs with little concern for the high cost of quality replacements.
There is no need to peel off the sleeving and top cover to check for a burst can, as simply depressing the bulge with your finger will show if it is false, as phase in #6 wrote and is common with most large electrolytic caps featuring the incised bursting seal in the case, since around 1990. I've seen many of these but seldom found the seal actually burst or leaking unless the device regularly gets quite hot - as in cheap SMPS and occasional cheap class D amplifiers.
There is no need to peel off the sleeving and top cover to check for a burst can, as simply depressing the bulge with your finger will show if it is false, as phase in #6 wrote and is common with most large electrolytic caps featuring the incised bursting seal in the case, since around 1990. I've seen many of these but seldom found the seal actually burst or leaking unless the device regularly gets quite hot - as in cheap SMPS and occasional cheap class D amplifiers.
True, Chinese caps are variable and high risk but even the top global brands are now manufactured there. Some of their local brands are awful for sure. e.g. I bought allegedly new "Nover" brand 10mF caps some years ago - all covered with tiny pimples projecting through the sleeving. That would likely be caused by impurities or undispersed components of the aluminium alloy and shows how slack even the control of raw materials is. It also showed how disengaged the selling agencies are when they have no clue about the products.
It's a NAD those main reservoirs will be fubared - they are known for it.
From experience, you will undoubtedly find they will physically rattle if shaken hard once removed, they will have shrunk and dried up so much internally.
PS: Spec some 63V (same diameter) 105degree from Nichicon as replacements, the original 50V ones are too close to the rails.
From experience, you will undoubtedly find they will physically rattle if shaken hard once removed, they will have shrunk and dried up so much internally.
PS: Spec some 63V (same diameter) 105degree from Nichicon as replacements, the original 50V ones are too close to the rails.
Last edited:
This also is typical of NAD caps in this series of smaller integrated amps.
I bet one at least rattles when shook side to side
I take (hope) you’ve replaced them rather than trying to repair