Electronics Repair Cookbook - Save Time and Money by Fixing Electronics Yourself

[rumreich]

The Electronics Repair Cookbook - Save Time and Money by Fixing Electronics Yourself is now available at Amazon.com.  I hope that some EEVBlog community members find it useful.  It was intended to complement online resources like this forum.

Mark Rumreich

[bob91343]

The title is such that I am amazed that one volume can contain enough information to service anything electronic.  I suspect it is limited to such things as operator error and defective cables but without further investigation I can't really comment.

The reason I say this is that for many years I owned and operated an electronics repair shop and I had several workbenches filled with high end test gear and even with my engineering degree I was challenged often enough.

I commend the author for taking on such a huge subject.

[rumreich]

Hi Bob,

I appreciate your comments. This book is intended to give confidence to beginners who don't have an engineering degree. It's not intended to contain enough information to allow anyone to service anything electronic.

The question that was on my mind for the entire project was how to complement the wealth of online information from YouTube, iFixit, EEVblog, etc.  I had to ask whether a book could provide any value for a beginner deciding whether or not to take the plunge into basic electronics repair. I decided to try.

I didn't want anybody to get hurt, so the book starts with the boring subject of safety. Subjects such as soldering, and how to use a multimeter and scope are introduced with encouragement to watch online videos.  Later chapters delve into the basics of general repair and the repair of common specific items.  Amazon's Look Inside feature shows the table of contents, index, and excerpts of many chapters so people should have a good idea of what they'd be getting beforehand.

Mark

[ChristofferB]

It looks like a really well thought out book, congratulations on its release!

Hopefully it could provide a lot of people with a reason to get excited about electronics - just as DIY'ing a hifi system to save money has for previous generations.

 

[james_s]

There are certainly a lot of repairs that someone without a lot of experience could make. I've fixed countless devices just by reflowing cracked solder joints or replacing bulging/leaking capacitors. Plenty of other stuff wasn't that simple but I'd bet at least 50% of consumer devices that get thrown away have simple problems that someone with the ability to solder and use a multimeter could repair.

[cdev]

I hope you have a section about reforming and replacing capacitors.
I also had an old mint condition (smaller) Variac in my stuff that I didnt realize I had, its exactly what I need for repairing a bunch of stuff thats been waiting for me to fix.

I am now getting it set up -

The use of a variac for reforming capacitors seems very useful, even in solid state equipment, to prevent caps failing when something been sitting unused for even just a few years.

(Edit: This appears to be the very first section of this book. Making it likely to pay for itself pretty quickly, if people just pick up a few of these basic tips.)

This appears to be a quite substantial and fun book which looks like it would have made a really great gift for my younger self.

[james_s]

I've never once re-formed capacitors. If I'm working on anything old enough that re-forming might be needed I replace the power supply capacitors before I even try applying power. I've never seen capacitors in solid state gear that needed to be re-formed, either they were fine or they were dried out and completely defective. A variac is a useful tool but with modern electronics it's enough of an edge case that it doesn't really belong in a beginner book.

[tggzzz]

The use of a variac for reforming capacitors seems very useful, even in solid state equipment, to prevent caps failing when something been sitting unused for even just a few years.

Whether or not it is "solid state equipment" is irrelevant.
What is relevant is whether it is an SMPS or not.

SMPS power supplies deliver a constant output power, whatever the load requires. Give or take the efficiency factor, the input power is the same. Hence if you have a low input voltage from a variac, the input current will be corresponding high (P=VI, of course).

Excessively high current is an excellent way of shortening transistor and capacitor lifetime.

[akimpowerscr]

Even if our repair activities are currently interrupted due to the covid pandemic, it is good to remember that the repair cafes are open access and that you can participate in the work of the repairers.

This will provide you with useful experience that complements the theory developed in the books.

The repair cafes repair all kinds of household appliances and electronics free of charge with reduced technical means (no sophisticated and expensive test equipments).

They are therefore in the same situation as that of amateurs who want to repair their broken devices themselves.

[cdev]

Thank you!

So, are you saying, that if you have an switcher that has been off for several years, you should nver bring it up with a variac, instead, desolder the caps and test them and if necessary, reform the capacitors individually, (or replace them if the ESR isn't low enough) or they may fail with this surge issue?

The use of a variac for reforming capacitors seems very useful, even in solid state equipment, to prevent caps failing when something been sitting unused for even just a few years.

Whether or not it is "solid state equipment" is irrelevant.
What is relevant is whether it is an SMPS or not.

SMPS power supplies deliver a constant output power, whatever the load requires. Give or take the efficiency factor, the input power is the same. Hence if you have a low input voltage from a variac, the input current will be corresponding high (P=VI, of course).

Excessively high current is an excellent way of shortening transistor and capacitor lifetime.

Does this apply if when you bring the SMPS up with no load, or a very low load, because when I reform capacitors individually I am usually limiting the current with a resistor and a current limited power supply.

[PA0PBZ]

SMPS power supplies deliver a constant output power, whatever the load requires. Give or take the efficiency factor, the input power is the same. Hence if you have a low input voltage from a variac, the input current will be corresponding high (P=VI, of course).

Excessively high current is an excellent way of shortening transistor and capacitor lifetime.

Exactly this! We had a design error in one of our battery powered products where the SMPS would give up when battery voltage got too low. Either fixed with a better battery voltage monitor or a better SMPS, I can't remember.

[tggzzz]

Thank you!

So, are you saying, that if you have an switcher that has been off for several years, you should nver bring it up with a variac, instead, desolder the caps and test them and if necessary, reform the capacitors individually, (or replace them if the ESR isn't low enough) or they may fail with this surge issue?

Yes - except "reforming" is not recommended in old equipment, any more than re-treading a worn car tyre is recommended.

Reforming ought to mean passing a low current to re-grow a dielectric barrier between the plates. Many people use the term in the sense of some touchy-feely woo that means nothing physically.

Old electrolytic capacitors leak fluid and the electrolyte can dry out. Reforming will do nothing useful for that.

The use of a variac for reforming capacitors seems very useful, even in solid state equipment, to prevent caps failing when something been sitting unused for even just a few years.

Whether or not it is "solid state equipment" is irrelevant.
What is relevant is whether it is an SMPS or not.

SMPS power supplies deliver a constant output power, whatever the load requires. Give or take the efficiency factor, the input power is the same. Hence if you have a low input voltage from a variac, the input current will be corresponding high (P=VI, of course).

Excessively high current is an excellent way of shortening transistor and capacitor lifetime.

Does this apply if when you bring the SMPS up with no load, or a very low load, because when I reform capacitors individually I am usually limiting the current with a resistor and a current limited power supply.

I have no comment.

Define in physics/chemistry terms what such reforming is achieving, and how long any beneficial effects last.

Many SMPSs require a minimum load to operate correctly; insufficient load means they might not turn on (by design) or might fail because they are being operated outside their envelope.

[T3sl4co1l]

You could (of course) define a huge flowchart to allow for all sorts of considerations.  Like:
- Does the power supply appear to be this or that type?  (Flyback, forward, bridge or PP; active PFC front end; multistage or PoL outputs; synchronous or passive rectification; etc.)
- For each type, go to the appropriate procedure to inspect it.  Example: passive rectification types, the outputs can most likely be tested/reformed with the primary side deenergized.  Others, you're better off removing the caps and working with them alone, or replacing them to be sure.
- Providing references to other flowcharts to determine the above.

But this is a small part of a far more vast subject, all of which could be written down in flowchart form (or something equivalent to that, lists of prompts, decision trees, etc.), but the sheer volume will overwhelm the reader.  This is one of those domains where, you can write down a "simple" solution -- "apply this set of rules ad nauseum to succeed" -- but the sheer tedium of following that solution, or the number of options that must be selected from, will overwhelm the reader.

(I'm assuming the author has dealt with that issue in a useful way, e.g. providing examples of typical situations.  An approach that provides reasonable coverage of narrow but common situations, so is more likely to produce success than a more methodical approach like I give above.)

(Which I realize, heh, I'm just pulling flowcharts out of thin air -- it hasn't been mentioned specifically, yet.  It is a likely structure to employ, and a technically adequate one -- but still just a straw man as such.)

Tim

[cdev]

When I have old electrolytics, to see if they are still usable I use a current limiting resistor, usually at least 1k, and I put an analog voltmeter across it to measure the voltage drop which each time I raise the voltage from the power supply rises and then falls, as the capacitor charges and the electrolytic layer is re-established.  With my analog meter, which I use because when measuring voltage its visually more insightful to see the needle moving, and no batteries need be used up, I can see that there is some non-linearity to this process - the needle goes down in small jumps. I might raise the voltage across the capacitors as many as ten times over a period of several hours - it varies, the ones that have been used recently may need very little time- they likely didn't even need this reforming- ultimately ending up at the rated DC voltage, or even  higher, since I would rather have it fail then than in a circuit, each time the voltage is raised, it takes some time to fall and stabilize, and ideally at the end there is a very very low leakage current, its almost nothing. Then I remove the current, discharge the capacitor through a resistor and check the measured value and ESR. It often has improved a lot. Some capacitors are not even measurable as capacitors before this is done, (Before this process, some capacitors don't show a value that makes me confident in them, but I dont ever use those specific caps, however its interesting that with some caps both my AVRTT - and my DE-5000 have given bizarre readings that make interesting observations as to what is going on,for example, AVRTT sometimes sees them as diodes!  I keep a digital camera handy when I am doing this I photograph the readings I get on both meters both before and after, to give me a reference..  But most of them do check out as capacitors and likely would not blow up upon reapplication of power, none of them are high voltage caps either, we are talking about DC voltages here, in everyday equipment. If anything seems amiss with a cap I dont use it.  However, maybe I should just toss the bunch of them.

So far its been my experience that high quality brands after reforming almost always test out not just as good, and have what I consider to likely be acceptable ESR although high by today's standards, still usually a very low DF and for whatever voltage a low enough ESR that I dont see any heat being generated, its usually in the fractional ohms, like 0.07 ohms was a value seen on a reformed 1000 uf  capacitor that I did use. (It was a Rubycon marked 1000 uf but it tested as over 1500 uf being used to replace a generic 1000 uf that was bulging.) And its been working for a couple of weeks now in a converted ATX supply that gets used occasionally as a non-bench supply, running (fused) things that I need that aren't in need of constant current.  Its not being used as a PC supply. And it has a fan.


So far the ones Ive used have worked okay. But none have been there very long.

[tggzzz]

The first Tek 485 that I resurrected had a PSU cap that needed "reforming". Once reformed it stayed good(ish) for 12 hours, and then needed reforming again. I replaced all the "similar" caps. For that and other reasons, I'm not a fan of reforming caps.

The symptom was that it would take 60s to spring into life. If switched off and on it would spring to life as expected - unless it had been switched off for >12 hours. Only being able to attempt two transient debugging sessions per day was slow.

Now, when next "reforming" your capacitor, what makes you confident something equivalent won't happen?

[cdev]

The first Tek 485 that I resurrected had a PSU cap that needed "reforming". Once reformed it stayed good(ish) for 12 hours, and then needed reforming again. I replaced all the "similar" caps. For that and other reasons, I'm not a fan of reforming caps.

The symptom was that it would take 60s to spring into life. If switched off and on it would spring to life as expected - unless it had been switched off for >12 hours. Only being able to attempt two transient debugging sessions per day was slow.

Now, when next "reforming" your capacitor, what makes you confident something equivalent won't happen?

Good question!

 I am not wedded to doing this. I suppose being happy that I could be more confident things wouldnt blow up when switched on for the first time in a few years - i.e. saving the equipment and convenience is the main reason I have.

But for equipment I care about I shouldn't be reforming it if there really is a risk of reformed capacitors that test out okay at the beginning not being reliable enough to last long enough to not blow up the next time they are off for more than a few years.

I'd like to know more about what signs to look for. I now have lots of ways to test capacitors.

To be honest, replacing all the capacitors in some beloved old pieces of equipment completely makes a lot of sense, maybe more sense, and I plan to do that, actually with several of the older pieces of equipment I have fairly soon. But they get used enough to be likely to be okay, but then again, you never know, I suppose.

Other people here recommend it as the thing to do every decade or two.
Honestly, I don't consider hardware like my 30 year old scope and stereo receiver "antique" so I couldn't care less what they look like, in terms of "authenticity". 

I just want the equipment to work well and not require my going in there again soon.

I also have to balance spending with not spending. Safety being my top priority.

When I was a kid I used to order parts from the big companies, come to think of it.

So might as well. I'd be interested in any resources anybody has on aspects of this issue.

In another thread a few folks here posted some great links on this issue which I consumed in detail and based my current practice on what I read there. But I dont think I had considered the liklihood that the reforming might not stick long, and thats important.

I have been lucky in that all the old caps I have used have had higher capacitance values than they were marked and a low enough ESR to not be of concern to me, and I tested them all multiple times with both my AVRTT and DE-5000 - with the caveat that I wasn't able to find the ESR specs of older discontinued caps.

[Conrad Hoffman]

Manufacturers actually recommend reforming caps that have been on the shelf for a while, but it's just a "tune-up" before testing. Probably so the leakage numbers aren't crazy high. My experience with reforming caps in older equipment is they quickly degrade when you shut the power off. IMO, the people the book is aimed at probably shouldn't be messing about reforming caps anyway. They probably don't have the equipment or the need. My attempts at writing introductory troubleshooting pages have shown me just how difficult it is to do well, so congrats on the book!

[cdev]

Yes, and lets face it, some older equipment really is worth saving. And doing it right so it lives on for an extended time is likely worth doing if you open them up at all.

Thank all of you for this invaluable info.

Any advice as where to get electrolytic caps for recapping things, especially which brands are the most reliable while not being expensive?

I may be an audio lover but I cringe at "audiophile" priced goods.

-----

This now deceased engineers estate sale capacitors that I got a bunch of are old but - every single one of the caps he painstakingly saved in his basement (which was crammed full of electronic stuff but it was all at least a decade old. most older) were in the first tier of Japanese and US manufacturers!

[helius]

Any advice as where to get electrolytic caps for recapping things, especially which brands are the most reliable while not being expensive?

The most reliable brands of electrolytics would be the so-called "first tier" as listed in this guide. When the same specification parts as the originals are used, the price is certainly not much of an issue. Most lines from the above companies are around 10 cents each in small quantities, with larger caps being maybe a dollar each. Using "bad" manufacturers really is a penny-pinching exercise.

I may be an audio lover but I cringe at "audiophile" priced goods.

I don't think there is any connection between "audio" type capacitors and quality. The usual criteria for "audio" capacitors (SILMIC, Black Gate, etc) is that they use exotic materials and have some properties that are usually not important for electronics. For example, here is ELNA's description of SILMIC. You can see that it's 90% woo-woo marketing and maybe has 10% content about what might be useful in some circuit (properties of elongation in response to charge, also called "microphonic" effects).

I'll also note that shotgun "recapping" is unlikely to fix equipment in most cases. There are certain situations where capacitors are obviously under great stress and therefore a common failure point (secondary-side switching PSU reservoir caps, for example). Or if there are physical signs of damage: bulging, electrolyte leakage, heat dissipation.

[GerritMax]

I'd defenately say this book is aimed at people like me.
I did play around with simple electronics in the early 90's but haven't done much since.
Usually I scavenged parts from old broken equipment and build my own stuff with it, like a power supply etc.
I'd buy this book unless I get it for christmas 

[bdunham7]

Yes, and lets face it, some older equipment really is worth saving. And doing it right so it lives on for an extended time is likely worth doing if you open them up at all.

Thank all of you for this invaluable info.

Any advice as where to get electrolytic caps for recapping things, especially which brands are the most reliable while not being expensive?

I may be an audio lover but I cringe at "audiophile" priced goods.

I don't reform or recap, although I do replace quite a few capacitors for various reasons.  However, concentrating on the electrolytics in older equipment is a mistake.  In an old radio you may have RF/IF caps with 'silver mica disease', paper/wax caps with leakage and perfectly good electrolytics (that I would restuff anyway).  In some test equipment you may have blown RIFA caps, some audio equipment has microphonic 'orange drop' capacitors, and we haven't even mentioned tantalum.  El-caps are at least down in 5th place, maybe lower, in the list of components likely to fail.  I have an old Zenith radio that is going to need 20-30 components replaced--but the electro-caps and the tubes are all good.  So much for 'wear' items.

As for where to buy, that depends on where you are.  As to what, someone posted a list of 'good' brands, as long as you include the second list of brands (Kemet, Cornell, EPCOS, etc), you have a pretty comprehensive guide as to what is good--everything they have listed there in the second tier and lower I would avoid.  There's no point in paying any extra for the 'audio' grades of anything, but if the cost isn't higher, they are often just fine technically.

[tggzzz]

Any advice as where to get electrolytic caps for recapping things, especially which brands are the most reliable while not being expensive?

The most reliable brands of electrolytics would be the so-called "first tier" as listed in this guide. When the same specification parts as the originals are used, the price is certainly not much of an issue. Most lines from the above companies are around 10 cents each in small quantities, with larger caps being maybe a dollar each. Using "bad" manufacturers really is a penny-pinching exercise.

That's a reasonable list, but each manufacturer will have several 100uF 10V electrolytic, and some won't be a good match for your requirements.

[helius]

That's a reasonable list, but each manufacturer will have several 100uF 10V electrolytic, and some won't be a good match for your requirements.

Yes. So what I'd recommend is to pick a few (or several) of the manufacturers that is stocked through your favorite distributor(s), and then download their whole catalog. From the catalogs you can find replacement parts with the correct ratings (including dimensions!) and other characteristics that might be important for each application, such as temperature rating, life rating, ESR, and leakage.

[tggzzz]

That's a reasonable list, but each manufacturer will have several 100uF 10V electrolytic, and some won't be a good match for your requirements.

Yes. So what I'd recommend is to pick a few (or several) of the manufacturers that is stocked through your favorite distributor(s), and then download their whole catalog. From the catalogs you can find replacement parts with the correct ratings (including dimensions!) and other characteristics that might be important for each application, such as temperature rating, life rating, ESR, and leakage.

Plus frequency and RMS current

[bdunham7]

C'mon guys, no need to get all technical.  The #1 criteria for replacing electrolytic capacitors is....lead spacing.