General Question- Electronics from 70's and 80's

[proton32064]

I have a question since I am new here and I don't know if this is the right forum to ask these questions or if I am wasting your time.
I am 67 and have a lot of Radios and Electronics I grew up with which puts a lot of them at 50 years or older.
A lot of the capacitors are obviously bad but this is my problem.
An example would be the Panasonic RC-7469 Clock Radio and the Panasonic RF-888 Radio.
I have others like a Canon L-162 Nixie Desktop Calculator 110AC, etc.

I have the Service Manuals to some of these and other electronics I have and grew up with and a lot of the capacitors listed are oddball which are no longer made.
I could give examples but it would be a waste of your time at this point.
Let's just say I have talked to Mouser and Digikey and most of the Capacitors in these units are no longer available anywhere.
Is this the place I can get help dealing with these types of problems of finding work arounds or sources to get these and other older devices restored?
If not, I appreciate your time.

[Per Hansson]

Sure, it's never a problem to find a replacement unless it is super niche stuff but in stuff that is only 50 years old that really should never be a problem, just might not look original any longer if they for example used multipart capacitors (they are no longer made so you'd use individual capacitors instead as an example).

[CapLeaker]

What oddball capacitors are you talking about? The 70's and 80's electronics have not oddball caps in values. Some may have 3 legs or something, but that's a non issue. Now that gear that's older than this, well that may be a different story. I looked at that clock and that thing is no problem at all to find replacement caps.

[proton32064]

Thanks for the response.
I will be happy to give you some examples from a Panasonic RF-888 Radio I want to restore.
Unfortunately. we have company flying in 1 1/2 hrs.
Let me have them come and go so I can get back into it.

I will appreciate any help you guys can give.
But I will give you a quick example from a Proton Clock Radio I am about to recap.
a 0.68uf at 16v.
Yes, I know I can go higher voltage but I am going to have to really high.
I learned Formulas in College Physics for multiple Capacitors in Series and Parallel but that was almost 50 years ago.
I am probably going to have to brush up on that and hope you guys can help me if I get stuck.
But let my company come and go and I will get back to it.
I just appreciate you guys are willing to help.

[CapLeaker]

Just jam a 1uF cap in there, if you can't find a 0.68uF. I did find 0.68uF 25V. Doesn't matter if there is a 16V or a 50V capacitor in there. Same with 0.68uF vs 1uF. There is a +-20% tolerance on capacitors anyhow.

[proton32064]

I know this is a stupid question but I did try to find the answer myself before asking here.
I am recapping an old Proton Clock Radio and I am including a portion of the parts list from the Service Manual.
If you look at the Description for the Electrolytics they all have this format:

Example:
Electrolytic 1uf 50v +50-10%

My question is about the +50-10% part.


Every replacement capacitor I bought on Digikey, even audio grade, had a tolerance of + or - 20%.
To be honest I didn't put much weight on the tolerance when ordering as I am new at this.
I am not asking you guys to give me a course in electronics.
I know what the various components do and how they work.

But I don't understand the tolerance variable and how critical it is.
It appears that the tolerance of the capacitors I am buying is out of spec since the Service Manual wants less than -10%. and all the capacitors I bought are + or - 20%.

If the short answer is " Don't worry about it", I can accept that.
But I am curious what this means in real world.
If I bought the wrong Capacitors for a clock radio while I am learning I will go back and buy the right ones.
I just need to know how critical the tolerance ratings are under these circumstances..
Many Google searches said it was acceptable under most circumstances but it is acceptable in re-capping an old clock radio?
All I am going to be doing is working with different radios.
If this is critical with audio I will reorder the right ones and pay strict attention to tolerances in the future.
Thanks.








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[Per Hansson]

Older caps just had crappier tolerances due to manufacturing tolerances, there will never ever be any problems to replace a cap that was originally rated +50 / -10% with one rated + / - 20%

[stj]

anything under 4.7uf can be replaced with a polypropylene film cap these days

[proton32064]

Thanks guys,
I really appreciate it.
I have been trying to learn this kind of stuff for years and read a lot of books on it.
I just want to understand enough to diagnose my own issues.
But at 67 I guess I am a slow learner,
Little pieces like this really help.
Every little but I understand a little bit more.

[petehall347]

dont trust parts lists as they are often wrong because of production changes . always go off what was actually fitted originally .. if anything has been changed in the past check out the schematics .

[redwire]

I outright replace "shotgun" all the electrolytic capacitors in 1970's 1980's gear. They just dry out after 40-50 years.
Service manual bill-of-materials lists for caps usually are missing production changes. They are only good to point out spots where a high accuracy or special part is needed.

The Panasonic RF-888 radio has 25 electrolytics. Nothing too exotic. As stj mentioned, caps under about 4.7uF are better changed over to film caps. RF-888JB Service Manual
A weird radio sorta. It uses +ve ground for example. Caps across the dial light switch? Karaoke mic input? I find that funny. Mains rectifier diodes RVDC08P1R might be selenium?, something to check.
C74 is 10V 200uF on the PCB layout pic, but 2,200uF 10V on the schematic and Bill of Materials.

Just make a list of the caps, take PCB pictures and change them out one at a time and double-check polarity is right, in case you get distracted by as phone or bathroom call. Don't nail the dial cord with a soldering iron, cover it with tinfoil maybe.