DIYbanter - View Single Post - Why should someone replace ALL the capacitors on old Tube equipment?

Ralph Mowery

In article ,
says...

By the way, why are all the caps now rated at some oddball figure.
For example, instead of .05, it's ,047? or instead of .003 it's .0033.

Same for the 'lytics instead of 30mf, they are 33mf and so on.....

A for electrolytic caps, it seems that the newer ones have a much
shorter life than the old ones did.

Nope. The old ones filtered at 120 Hz. The new caps filter at 100 to
300 KHz. Internal dissipation follows frequency.

Can you explain that. I dont understand...
(I would think that a 'lytic in a power supply would only need to filter
at 120hz, or would some filter at 60hz also, depending on the
configuration?

That's
why those old radios still work after 60 or 80 years, while most stuff
made today is in a landfill in less than 10 years.

Todays products are intentionally designed to be difficult to repair
and to only last as long as the warranty period. With the proper
design tools and models, it is possible to predict the life of an
electronic (or mechanical) product. Anything that lasts longer than
the warranty period is deemed to be "over-designed". It is then
redesigned using lower rating or cost components so that everything
blows up at the same time. I've seen it happen.

I totally agree. You cant identify parts anymore and if you can, you
cant get them. Especially ICs.

In the 60s and 70s, I loved to work on electronics. Mostly tube stuff.
The early transistor stuff was not too bad, but as soon as they began
using ICs, I lost interest in working on it.

Now, 40+ years later, I am gtting back into it, but only working on
antique tube stuff, which is what i enjoy. Modern stuff is far too
complicated, far too small (hard to see with my aging eyes too), and
does nothing but frustrate me.

Sure, I have built every computer I have owned (or rebuilt from parts of
thrown away ones). But with computers you just change boards, not
individual components.

I guess going back to the tube stuff makes me feel young again!

Capacitors such as .047 have been around a long time. I don't know why
it is such an odd value as I doubt the extra .003 would be noticable in
the circuits most of them are used in. As the tollorance on most of the
electrolytics are very broad I don't understand the odd values either.

The capacitors operating at 100 KHz and over are in the switching
supplies that are most often used now. That puts a lot of strain on
them that the old 60 Hz didn't.

I have started working on some of the surface mounted devices. It does
take different equipment, but not hard to replace the bad components in
most cases. You just have to invest in a stereo mcroscope
for about $ 200 and a hot air rework station. For just the hobbiest
there are some that have the hot air bun and soldering iron for less
than $ 100. Tweezers instead of needle nose and very small solder and
liquid flux. Lots of good info and how to on youtube.

I only started doing the SMD after I retired at 62.

I did put together my computers up to about 10 years ago. Then found I
could get a used one off ebay for almost nothing that will do what I
want. That is almost less than MS wants for some of the operating
systems and the used ones have the operating system on them.