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Choosing the right replacement cap


Dave Peterson
 

What parameters besides capacitance, voltage, and temperature are appropriate for replacement capacitor selection?

I guess configuration and size, of course. What fits.

This is the typical C1419 for a 465 scope. Just did an online search and am overwhelmed by the number of varieties.

Are there most reliable, quality, trusted brands? Are there some to be sure to stay away from? How to choose!?

Thanks,
Dave


Craig Cramb
 

This is the typical C1419 for a 465 scope

You might run the part number and look on eBay


Mark Vincent
 

Dave,

C1419 is a sealed tantalum that usually does not go bad. If it goes bad, a 47 or 56mfd 25 or 35V Nichicon ULD is what I would recommend. That series is low ESR, high temperature and long life. The UCY and UHE is also very good for life. The low ESR is best. If you change a tantalum with an electrolytic, higher capacitance is recommended to compensate for the lower ESR tantalums have. The ULD is close in ESR to a tantalum so a small raise in capacitance is fine. You may need to increase the rated voltage at times because the manufacturer was too cheap to use the proper voltage, e.g. 16V cap off a rectifier for 12V when the cap should be a 25V type. I use film types for low values such as 4,7mfd 50/63V and smaller values. Higher voltage films with over a mfd I will use on screen decoupling, e.g. signal or video output. Film has very low ESR. I use CDE 318LX/383LX, Nichicon LGR, LGZ (450V snap in), Kemet ALS and others that have the above specs when a snap in or screw type is needed. For restuffing FP style cans, the diameter and length are needed to know if they fit. Doing the power supplies in the 465/475/A will require sizes that will not fit in the cans. Solid wire on the leads for ones that are larger than original and jumpers on the negative lugs on the pc board. The diameter of a few are larger than the original cans. I will use larger capacitance than original for better filtering/decoupling. I usually use the ULD or UCY in the cans unless a snap in is needed in the can. I am picky about the type of electroytics I get. I will usually increase the capacitance from original, if physically possible, for stiffer voltage regulation. I have found that spending more time and money to do a job right the first time has worked for me. I do not like going back to redo work that should have been done right to begin with. A good friend of mine is a broadcast engineer. That is a big reason I make or repair things to run around the clock (for new design) or to run with as few repairs as possible over the years. Buy from places like Mouser, DigiKey or other distributors. They will have new stock and give the specs of their products. Avoid off-brand or old stock. Avoid 85 deg.C types. Those are low hour life and ESR is not low except for a few series in a few brands. Sometimes finding the best quality capacitor can take some time when specs are compared for a number of ones that are suitable in that application. Make sure to see the ones that are in stock from a supplier. The lead times for some parts can be a few weeks to a year and some are subject to a minimum amount if it is a special order. Avoid the exotic types the audiofools like to overpay for. I am telling you about the types I have found that work for myself and customers. What I use is not the only types that will work. I can only give information I know and have had experience with.

Mark


Dave Peterson
 

Thanks Craig and Mark,

Yes, this is C1419 on a 465. Actually C1418/C1419, the two 22uF parallel caps on higher SN scopes. Mine is 29X,XXX (don't have it right in front of me at the moment). One of the two is shorted.

I started with a search on 47uF, 50v as someone in an earlier thread regarding this cap noted the marginality in this supply filter. The supply is "15v unregulated", but many note the actual value can be in the 20s. Making the 25v 22uF's right at their limit. And then adding temperature effects further stresses them/it. I felt 50v was a good "over spec" to handle the application.

So I did follow the link that came up for Mouser, and one of the selection criteria in their results is operating temperature. Considering this caps environment I selected 135+ C, just to see what it turned up. The result is a Nicicon UBW1H470MPD. It is an Aluminum Electrolytic and all of the specs look good for the application. But when I look at, for example Digikey I see other parameters. After some study I see what's meant by ESR, and understand leakage current as it applies to cap usage. I am an EE by trade, so I'm not completely ignorant. But there's a vast difference between some academic understanding and the real world application of discrete components. All my cap experience/understanding is IC parasitic cap.

One spec I don't know what to do with is "Series". I see various references to this alpha-numeric code, as Mark mentioned above. But I haven't found an explanation of it yet. A little tutorial would be helpful and appreciated. A link is fine. I have more studying to do.

I do now know better why the Nicicon is a far better choice than the cheap results on Amazon. So I feel comfortable making an order of, like, 10 of them from Mouser.

Is that way overkill? Or is it good to get a high temp cap like that? I'll try and re-read Marks answer and understand some more of what he's saying. But I hope I've clarified where I'm at better. Any further help narrowing choices and helping me understand WHY those are better choices is greatly appreciated.

Thanks,
Dave


 

Mark Vincent is spot on regarding electrolytics.
Film caps - Polyester (cheaper and smaller), or Polypropylene (larger and expensive) are usually a no-brainer ultra-long-life substitute for tantalums, not considering their higher price.

One other spec which must be taken into account, is Ripple Current capability, usually specified in AC mA, in datasheets.
An unregulated or switching circuit has significant ripple, and therefore the cap's Ripple capability is more relevant, as opposed to a circuit following a voltage regulator.

Menahem Yachad
www.CondorAudio.com


Dave Peterson
 

This was very helpful to get me started:
https://www.electronics-tutorials.ws/capacitor/cap_3.html

In trying to understand the Nichicon series Mark gave I found this:
https://www.nichicon.co.jp/english/products/alm_mini/index.html

Which linked to this:
https://www.nichicon.co.jp/english/products/pdf/aluminum.pdf

I don't see an explicit ESR spec in the data sheets. I understand from the above that it's frequency dependent, but from Fig 1-8 it looks relatively flat. Is there a proxy for ESR?

I think ripple in this application will be a significant factor. The supply is unregulated and the purpose of the filter is to keep the 50kHz HV oscillator out of the power supply (from the Tektronix service manual). That seems like a potentially strong amount of current noise. There's a reason these keep blowing up.

How are places like Mouser and Digikey with small time onsie-twosie buyers like me? I won't be buying a real of 2000. But I think 10 is a reasonable number when the per cap price is less than $1.00. It looks like Mouser has, for example, the UBW in individual quantities. That means it's in stock and I won't be waiting on the 15 week factory lead time? If I get in the habit of buying "parts" 465s I imagine having a nice stock of these is worth it.

I won't be getting the UBW - too short a life. But now I see what the parameters are and will choose a series with high lifetime and ripple as primary drivers. I think 105C should be plenty inside a scope. Let's see, in F thats: 5/9 * C + ? Oh geez. Let me look that up.

Dave


Dave Peterson
 

I guess I don't quite get what the ripple current spec is actually telling me. That this is the amount of ripple current the cap can take to make the lifetime spec?

A spec with twice the ripple for a given lifetime can take more power supply noise?

A UCY2C470MPD1TD with 375mA ripple and 10000 hr lifetime can take more power supply noise than a ULD1H470MED with 190mA ripple and 10000 hr lifetime?

The UCY is cruising in the 465 HV oscillator supply while the ULD might suffer degradation despite being well within voltage and temperature specs?

How much do I care about ESR in a power supply filter?


Tom Phillips
 

Dave,

Regarding your question "How are places like Mouser and Digikey with small time onsie-twosie buyers..."

I have found that they are amazingly cooperative with small orders. I have been refurbishing many of my personal test equipment units each of which need a variety of replacement electrolytic caps. I end up ordering "kits" of parts after spending a significant amount of time using the search engines on the supplier's web site to find high quality replacements of suitable size and value. I choose only "in stock" parts because the stated manufacturers lead time for non stocked parts is just an estimate and usually requires a substantial minimum order quantity. I also want my "kit" to arrive complete so I can get on with the project. During my last order I found that Mouser didn't quite have all the parts I needed but Newark did and the Newark pricing was better. Digikey is a good supplier too. I just haven't needed to use them recently.

Tom


Dave Peterson
 

Thanks for the feedback Tom. And reminding me of Newark. I bought some small component relays from them years ago, and that transaction was a model of ease.

I've never had a need to order components before, so it's a whole new world. Enjoying the journey.

Dave


John Ferguson
 

I find Mouser an excellent source for my onesie-twosie orders.

I confess to a bit of discomfort with sending them orders for $25 worth of components which cannot possibly be profitable for them. For example, ordering 4 or 5 SMD sensors can require that they take them off a reel, and repackage them with a moisture sensitive card in a sealed packet.  What they charge cannot possibly support the cost of the time spent.

Additionally, they have a section of the site which allows you to accumulate parts in groups under the heading projects.  This can be very useful for re-ordering where I've forgotten  what I needed to complete a reprise of something I scratch built.

I try very hard to drive the total price of an order up to $50 assuming that will help share their costs.

I did have a telephone conversation with one of their reps years ago on this subject and asked why they didn't have a minimum order like Digikey had at that time.  She said something like they hoped one of my projects would turn into a big deal and I would remember them when it came time to order reels instead of onesie-twosies.

Alas, I'm not smart enough to come up with anything like that.


n4buq
 

I might be wrong, but I have to think that, for the most part, their systems are automated and little is done by hand. If they weren't making money, they wouldn't do it. I'm a very pleased customer of many, many very small orders.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "John Ferguson via groups.io" <jferg977=aol.com@groups.io>
To: TekScopes@groups.io
Sent: Wednesday, November 25, 2020 10:24:48 AM
Subject: Re: [TekScopes] Choosing the right replacement cap


I find Mouser an excellent source for my onesie-twosie orders.

I confess to a bit of discomfort with sending them orders for $25 worth
of components which cannot possibly be profitable for them. For example,
ordering 4 or 5 SMD sensors can require that they take them off a reel,
and repackage them with a moisture sensitive card in a sealed packet.
What they charge cannot possibly support the cost of the time spent.

Additionally, they have a section of the site which allows you to
accumulate parts in groups under the heading projects.  This can be very
useful for re-ordering where I've forgotten  what I needed to complete a
reprise of something I scratch built.

I try very hard to drive the total price of an order up to $50 assuming
that will help share their costs.

I did have a telephone conversation with one of their reps years ago on
this subject and asked why they didn't have a minimum order like Digikey
had at that time.  She said something like they hoped one of my projects
would turn into a big deal and I would remember them when it came time
to order reels instead of onesie-twosies.

Alas, I'm not smart enough to come up with anything like that.








toby@...
 

On 2020-11-25 11:11 a.m., Tom Phillips wrote:
Dave,

Regarding your question "How are places like Mouser and Digikey with small time onsie-twosie buyers..."

I have found that they are amazingly cooperative with small orders. I have been refurbishing many of my personal test equipment units each of which need a variety of replacement electrolytic caps. I end up ordering "kits" of parts after spending a significant amount of time using the search engines on the supplier's web site to find high quality replacements of suitable size and value. I choose only "in stock" parts because the stated manufacturers lead time for non stocked parts is just an estimate and usually requires a substantial minimum order quantity. I also want my "kit" to arrive complete so I can get on with the project. During my last order I found that Mouser didn't quite have all the parts I needed but Newark did and the Newark pricing was better. Digikey is a good supplier too. I just haven't needed to use them recently.

+1. I use Digikey constantly, they will ship a single part just as
efficiently as 10,000. I've had (free) deliveries of tiny orders within
11 hours of ordering.

Just a happy customer.
--T



Tom





Ke-Fong Lin
 

Hi John,

I'm a regular "user" of Mouser and Farnell (UK).
Mouser offers free fedex express (basically 2 days) from Texas to France for order above 50 or 70 euros (but I think it's 50).
Farnell does free UPS for 30 euros (ok UK is next to France with a small arm of sea to cross).

I believe they have a business model to do just that, small orders. Along with probably big ones, of course.
Small orders are not only hobbyiest, but I believe for prototyping purpose, "professionals" may place that kind of order.
And plus, a few very good Nichicon capacitors can look cheap enough, but they're even cheaper when you buys in the 10000s.
I'm wondering at why price, let's say Samsung, gets its capacitors for their consumer TV.

All in all, they probably make some kind of profit, or at least break even.

Best regards,


Dave Peterson
 

Thanks everyone for the endorsements on these component suppliers. Makes me feel good about joining in, and you have given me some good ideas on how to order - like accumulating a shopping list and ordering when it's over a certain value.

Ke-Fong, you bring up a point that was on the edge of my mind last night: this 465 scope C1419 cap is clearly a marginal element of these scopes. Why would they do that? Because, as I well know being in the R&D branch of tech development: cost, cost, cost. Sometimes you don't know where the marginality in a design is until you get it in the field. And mass manufactures have to get each and every component down to the lowest possible cost. Given the serial numbers on these things it's clear Tektronix made well over 300,000 of them. That's a lot of C1419s. And that's just one component in the whole scope.

I guess I'm not a restoration purist in taking on 465 repair. I'm very willing to use modern components in place of originals. Especially when a marginality like this has been exposed by several lifetimes worth of use in the field. I hope I'm not offending any enthusiasts with my intent to apply an overkill upgrade on this cap. But it seems reasonable to me. And it's part of the hobbyist entertainment to over analyze and over think such minutia. But that's what engineering is, no?

I'm liking the Nichicon UCY2C470MPD1TD for this cap. I'll probably get 10 of them from Mouser. I'll even replace it in my working 465 once I have this one up and running. Seems a good prophylactic. But I won't be ordering it for a while. I have a lot of scope to go through before I know for sure everything I'll need. And I need to go down and make sure it'll fit too.

Dave


Stephen Hanselman
 

AGREED,

We use Mouser primarily, they have a fulfillment center at Love Field (or is it DFW?)so shipping response is great. Having said that we also us Allied, Newark, and Digikey with similar results. Arrow is OK IF you can figure out their website and they have minimums.

All of these folks have shipped one part orders without question. Here in the US, Mouser has a $7.99 shipping charge for up to 2-day so that’s a help also.

Steve
Datagate Systems, LLC

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of toby@telegraphics.com.au
Sent: Wednesday, November 25, 2020 8:47 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Choosing the right replacement cap

On 2020-11-25 11:11 a.m., Tom Phillips wrote:
Dave,

Regarding your question "How are places like Mouser and Digikey with small time onsie-twosie buyers..."

I have found that they are amazingly cooperative with small orders. I have been refurbishing many of my personal test equipment units each of which need a variety of replacement electrolytic caps. I end up ordering "kits" of parts after spending a significant amount of time using the search engines on the supplier's web site to find high quality replacements of suitable size and value. I choose only "in stock" parts because the stated manufacturers lead time for non stocked parts is just an estimate and usually requires a substantial minimum order quantity. I also want my "kit" to arrive complete so I can get on with the project. During my last order I found that Mouser didn't quite have all the parts I needed but Newark did and the Newark pricing was better. Digikey is a good supplier too. I just haven't needed to use them recently.

+1. I use Digikey constantly, they will ship a single part just as
efficiently as 10,000. I've had (free) deliveries of tiny orders within
11 hours of ordering.

Just a happy customer.
--T



Tom





adesilva_1999@...
 

Thanks to Dave and the rest who are on this thread. I am trying to restore a low serial 465 as I write. I also got good pointers from EEV blog. Some great contributors there. Some of you may be on there also. I will book mark this and if I can, I will make some comments.

That C 1419 is a common failure from what I have read. Someone also pointed to the "wet tantalum" caps like C 1534. I just found this last night as the + ve lead was surrounded by white flaky stuff where it goes in to the board. Surprisingly, it shows no leakage near the cap itself! Now I have to check for similar caps elsewhere.

My scope works for the most part except the CH 2. Some positions seem to have bad contact on those flimsy switch contacts. Before I go into the caps, I want to get that sorted out.


Dave Peterson
 

adesilva_1999,

Is C1534 the "can" at the back of A9 that's near VR1525?!

I just unmounted the + lead yesterday to check it because it had the same "white flaky stuff". I almost dove into a full tear down of dismounting A9 because of it. Cooler heads prevailed and the pulling of the + lead allowed me to check it (it was good) and get it soldered back in. Looks way better anyway.

I hadn't gotten to checking it's existence in the schematics yet.

I'd say "white flaky stuff" isn't a problem in-and-of-itself, but I would like to know what's going on there.

Dave


Dave Peterson
 

Yep, C1534: 3uF 55v supply filter cap (continuity to TP1536). At least it's not a signal cap (too large anyway?).


toby@...
 

On 2020-11-25 12:59 p.m., Dave Peterson via groups.io wrote:
Thanks everyone for the endorsements on these component suppliers. Makes me feel good about joining in, and you have given me some good ideas on how to order - like accumulating a shopping list and ordering when it's over a certain value.

That's what I do, to hit Digikey's free shipping threshold. That way I
can fool myself that I'm saving money!

--Toby


...
Dave





Dave Peterson
 

Hey adesilva_1999, please feel free to email me directly to discuss any 465 questions. We seem to be on the same path. Have you taken out the vertical preamp yet? Message me if not. I learned a few things taking it out that were not at all obvious for a first timer like myself.
Dave