You can only check for dead shorts in-circuit (Tantalum do fail this way, and some modern SMD caps - both very unlikely to be present in a vintage amp), the electrolytics need otherwise be pulled from PCB.
30 years of age does actually not mean a lot. Most of the caps are still "good" or "good enough". However there are certain models that are known to fail (like blue Philips), A bit of Google will help. Visible leaks are mostly easy to spot - immediatly replace all of the same model and do a really good cleanup.
Replacing everything is not what I would do. I would exchange RIFA caps on sight, maybe for an extra good feeling X- and Y-caps on mains in in general.
If the amp does otherwise run, don't touch any of the caps, it costs money, time and won't improve anything (likely). It might introduce problems, that were not there in the first place...
Hi thank you for the very kind and valuable advice
I will begin asap
The small caps are quite cheap
The big ones are very expensive
Resistors also are not a big issue for cost
One question about cleaning the boards
It's not clear to me which could be the best liquid to use with a soft brush like the one for teeths
I like shining things a lot
I will begin asap
The small caps are quite cheap
The big ones are very expensive
Resistors also are not a big issue for cost
One question about cleaning the boards
It's not clear to me which could be the best liquid to use with a soft brush like the one for teeths
I like shining things a lot
Thank you very much again I have seen video using acetone
other stain removers like trichlorethylene It smells bad but i used it to degrease rcas and was excellent indeed
I swear the sound after using it was much better
other stain removers like trichlorethylene It smells bad but i used it to degrease rcas and was excellent indeed
I swear the sound after using it was much better
Those are very aggressive solvents and I would caution against their indiscriminate use.
Acetone is way too agressive and will likely damage plastic parts and printings. Isopropanol is great.
Howevery be careful to not carelessly soak mechanical parts (trimmer, pots, relais). And always a good dry is required.
Another option is destilled water with some detergent, rinse with destilled water only afterwards. This too needs to dry (way longer than with Isopropanol, so the impatient DIYer hardly ever does this - and the destilled water is not that cheap, unless you have tumble dryer). If you have more robust electronics, I might even consider tap water plus detergent, then rinse with destilled water.
Howevery be careful to not carelessly soak mechanical parts (trimmer, pots, relais). And always a good dry is required.
Another option is destilled water with some detergent, rinse with destilled water only afterwards. This too needs to dry (way longer than with Isopropanol, so the impatient DIYer hardly ever does this - and the destilled water is not that cheap, unless you have tumble dryer). If you have more robust electronics, I might even consider tap water plus detergent, then rinse with destilled water.
That is nippon chemicon kmh series, if you look in the datasheet they don’t even have such a KMH 22000uf/63v/105c.
Hi thanks a lot
I like this approach very much
In some equipment I have seen even soil and grease
I could use a soft brush soaked with water and detergent
Hi thank you very much indeed
I have a bad feeling
Next time I will buy from a respectable vendor
I have to try tme.eu
The prices are very good indeed
I deal with quite a few 70's to 90's era amps and receivers, and I've found that most 'bad' caps that are causing an issue will be either swollen, split open, or leaking. The exception are main power supply caps which are producing an AC hum due to either a short or change internally brought on by sitting, and often being suddenly powered back up after 20 years on a shelf somewhere.
I get a lot of guys who bring me their receiver who have already sourced most of the parts, often they're bought whole 'kits' to refurb their receiver or amp.
I have a pair of those very same Nippon 22,000uF caps sitting on my bench next to my power supply that I took out arbitrarily from a 1990's Paradigm receiver. The owner had brought me three of the same model receivers to fix, he bought full kits for each one.
One receiver had most of its caps swollen and leaking, one had only the two 22,000 caps swollen, and the third had no obvious bad caps or issues. All three worked when I got them here.
After going through each one, and replacing all the caps, plus several other components that were suspect, I ended up saving the parts in a jar just to show people. The two 'good' caps tested at 2,147, and 21,991uf the swollen caps both read high, one at 24,411uf and the other at over 33,000 uF. One leaking cap read 900uf, and another read perfectly fine at 20,540uf but had leaked all over the board.
I had charged both of the two good caps when I last tested them, at maybe 3/4 of their rated voltage, then just left them sit there pins up on the shelf. A year later I checked both and both were still holding onto nearly the same voltage as I had left them with. Now several years later both still held voltage after being left on the shelf charged for over 2 years. They lost a few volts but still were charged well over 40v after two years. They were from a receiver built around 1988.
I don't really buy into all old caps are junk, and find that many are still functional but I likely would never install a 'vintage' component unless it was for cosmetic more than sound or performance reasons. All too often sound is hindered more by using a 'similarly rated', but physically much smaller modern capacitor. In my opinion, an amp being repaired should be brought back to how it was when it was new, not 'improved' to what I feel it could be or might be using modern components.
Sometimes you don't have a choice but sometimes it creates more issues than it solves.
I get a lot of guys who bring me their receiver who have already sourced most of the parts, often they're bought whole 'kits' to refurb their receiver or amp.
I have a pair of those very same Nippon 22,000uF caps sitting on my bench next to my power supply that I took out arbitrarily from a 1990's Paradigm receiver. The owner had brought me three of the same model receivers to fix, he bought full kits for each one.
One receiver had most of its caps swollen and leaking, one had only the two 22,000 caps swollen, and the third had no obvious bad caps or issues. All three worked when I got them here.
After going through each one, and replacing all the caps, plus several other components that were suspect, I ended up saving the parts in a jar just to show people. The two 'good' caps tested at 2,147, and 21,991uf the swollen caps both read high, one at 24,411uf and the other at over 33,000 uF. One leaking cap read 900uf, and another read perfectly fine at 20,540uf but had leaked all over the board.
I had charged both of the two good caps when I last tested them, at maybe 3/4 of their rated voltage, then just left them sit there pins up on the shelf. A year later I checked both and both were still holding onto nearly the same voltage as I had left them with. Now several years later both still held voltage after being left on the shelf charged for over 2 years. They lost a few volts but still were charged well over 40v after two years. They were from a receiver built around 1988.
I don't really buy into all old caps are junk, and find that many are still functional but I likely would never install a 'vintage' component unless it was for cosmetic more than sound or performance reasons. All too often sound is hindered more by using a 'similarly rated', but physically much smaller modern capacitor. In my opinion, an amp being repaired should be brought back to how it was when it was new, not 'improved' to what I feel it could be or might be using modern components.
Sometimes you don't have a choice but sometimes it creates more issues than it solves.
Hi ! thank you very much for your kind and very valuable advice
I have some about 50 years old amps in the garage Nothing special at all I got them for little money
Speaking of restoration i would replace all smaller caps with new ones, check transistors for short circuits and remove and check the big ones caps in the power supply But 50 years are half a century I am not a collectionist so for me performance is more important than original parts for sure
To save some money i am very interested in understanding of to check industrail caps The big ones of course
I remember at least a very nice amp called Unison Research Unico using industrial caps with great results At least on the basis of the review
I believe in industrial parts also for mains transformers for instance I love things like this one here depicted immensely
I have some about 50 years old amps in the garage Nothing special at all I got them for little money
Speaking of restoration i would replace all smaller caps with new ones, check transistors for short circuits and remove and check the big ones caps in the power supply But 50 years are half a century I am not a collectionist so for me performance is more important than original parts for sure
To save some money i am very interested in understanding of to check industrail caps The big ones of course
I remember at least a very nice amp called Unison Research Unico using industrial caps with great results At least on the basis of the review
I believe in industrial parts also for mains transformers for instance I love things like this one here depicted immensely
Hi ! in the meantime i have ordered a DATS V3 impedance meter
https://www.daytonaudio.com/product/1650/dats-v3-computer-based-audio-component-test-system
from a video i see that there is a zero function that should avoid the leads resistance issue
I have big expectations about this device It seems very smart and allows for easy impedance measurements
I will use it to check mains transformers windings I have the feeling that impedance plays an important role in transformers
But i am shockingly ignorant I studied some electricity at school and grabbed very little
i have a bad feeling about having got fakes The price was too tempting 😢
Next time i will buy only from reputable vendors
I have found tme.eu