ESU LokSound Micro Select Direct install in Atlas GP40-2

[peteski]

Good luck with the caps.  I would never consider using a tantalum  cap rated for 16V in a DCC decoder circuit. But that is just me.  20V or higher.

[ednadolski]

Good luck with the caps.  I would never consider using a tantalum  cap rated for 16V in a DCC decoder circuit. But that is just me.  20V or higher.

[peteski]

While this shows backwards install, the same thermal event occurs with a  correctly powered cap if the voltage gets close to the rated voltage and the cap is "weak" or slightly off-specs.

[conrad]

While this shows backwards install, the same thermal event occurs with a  correctly powered cap if the voltage gets close to the rated voltage and the cap is "weak" or slightly off-specs.

Yikes!  And there are YouTube videos of correctly installed, cheap import, exploding caps at voltages lower than 16.  Looks like recommended practice is 50-75% of rated voltage, 8 to 12 in my case.

My source is SBS4DCC so I'll ask Bryan if he's had any problems with them.

Conrad

[peteski]

Yikes!  And there are YouTube videos of correctly installed, cheap import, exploding caps at voltages lower than 16.  Looks like recommended practice is 50-75% of rated voltage, 8 to 12 in my case.

My source is SBS4DCC so I'll ask Bryan if he's had any problems with them.

Conrad

Well, to me it is not whether he had any problems - it is about being extra safe.  Tantalum caps are like little fire bombs ready to go off  if they feel like it.  Using those caps at reduced voltage rating greatly increases the odds of them not blowing up.

I also recommend performing a burn-in process before installation to weed-out any that might be iffy.  There was a thread about this here on TRW.  One of the DCC guys came up with a clever way of doing this using a Lithium power pack for a cordless drill as a source of power for the burn-in.

[tehachapifan]

Yep....this is why the only caps I've purchased are still in their package and in a drawer.

[Steveruger45]

Well, to me it is not whether he had any problems - it is about being extra safe.  Tantalum caps are like little fire bombs ready to go off  if they feel like it.  Using those caps at reduced voltage rating greatly increases the odds of them not blowing up.

I also recommend performing a burn-in process before installation to weed-out any that might be iffy.  There was a thread about this here on TRW.  One of the DCC guys came up with a clever way of doing this using a Lithium power pack for a cordless drill as a source of power for the burn-in.

Conrad, like Pete said.  BTW it was me with the 18v power drill battery idea to proof test / burn in test the caps. 
I don’t use Tantalum caps any more even the 20 or 25 volt ones.  I had several cheap ones blow on my burn in tests so I got rid of all of them including some quality Brand ones too even though they all passed my burn test rig setup.   They will melt the loco shell if they go bad at the very least.
Now I use Only name brand (Panasonic or AVX or Kemet) poly tantalum caps rated for at least 20v.
Rule of thumb is don’t put more than 50% of rated volts on a tantalum cap but you can put 80% of rated colts on a poly tantalum.   I’ve never had a poly tantalum cap burn up on my power drill battery test rig or fail in service either.
A case of once burnt now twice shy.

[conrad]

Not to 'spark' a great debate, here's Bryan's quote (with permission):

"I have used this size for years with no issue but it is a very valid point.

The difference between 16v vs 20v has several considerations.  I am certain a EE can offer a hundred other reasons why they think this is all wrong.

I use the 16v because it is thinner which matters to me in n scale.  My installer also uses these successfully for many years now. 

The actual operating voltage is dependent on command station output and voltage drop through system among others.  Most systems are under 14V nominal and V at decoder is closer to 12V or less.

I buy this specific brand only because I have used others and had flaming failures in 16v and 20v.  This brand costs me more but seems to be much higher quality.  I don't recall exactly now but maybe mil-spec or tolerance

I have built several thousand light kits with six or more 16V tantalum caps per board.  I switched to this brand from the common yellow brand after melting the roof of a customers CZ Dome OBS which I now own...  I can only say I have not bought another.

We have done thousands of installs using these caps.  I can only say we don't replace thousands of caps.

Others are probably speaking from painful experiences so it is absolutely worth consideration.

Of course you mileage may vary and I would never guarantee they are fool proof.  That smoke is sneaky stuff."

Conrad

[peteski]

Now that I know who did the burn-in (Steve), here is the particular post: https://www.therailwire.net/forum/index.php?topic=50408.msg679271#msg679271 . I recommend reading the entire thread.

To me it doesn't matter what Bryan or even experts say about acceptable safe voltages for tantalum caps - I still do my thing. Better safe than have some expensive model's shell melted.

[Steveruger45]

Here is another thread on tantalum caps.
@Jbub did a video and has more or less done the same set up as I did on the same cheap caps off eBay that I got too.
The video says it all.
https://www.therailwire.net/forum/index.php?topic=43648.msg557404#msg557404

[conrad]

Ok, ok, ok, ok, I get it.

As a retired EE educated on vacuum tubes, discrete semiconductors, and analog computers I'm thinking maybe Tantalum is Latin for what my 3 year old grandson does when he doesn't get his way.

Anyway, for my third 73100 LokSound install (SD60) I'll just wire in the blue lead from +UB and dead end it at the Headlight shield.  Then I'll look for your suggested caps.

For the two locos I've already done, I'll run them sparingly just to tweak the CV's and change out the caps when they arrive.

As an aside, what's up with the 9 or so caps on the 73100 decoder?  Are they Tantalums and are they derated?

The referenced threads are very helpful.  It's been an education.

Conrad

[reinhardtjh]

And now you should understand one of the mottos of The Railwire... "Better modeling through peer pressure."   

[peteski]

As an aside, what's up with the 9 or so caps on the 73100 decoder?  Are they Tantalums and are they derated?

The referenced threads are very helpful.  It's been an education.

Conrad

Most (if not all) decoders utilize tantalum caps.  Those are usually rated for 6.3V and are used in the 3V power supply for the microprocessor.  Those look just like the ones you are using, except physically smaller. They are polarized (and the case markings show that).  If you are talking about a bank of other other (non-polarized) caps on that board, those are multilayer ceramic caps.  Probably 47uF each.  Those do not suffer thermal failures.

[Steveruger45]

@conrad
Here is a short list of poly tantalum caps from digikey
Hope it helps.

https://www.digikey.com/short/zd0pq5

[Jbub]

The other thing to keep in mind is the quality of the product. Buying cheap caps off ebay like I did vs digikey or mouser will yield different results. The product sold through reputable sites has been tested and has an extremely low failure rate if used by the manufacturers recommendations. The stuff on eBay most likely came right of the production line without testing hence why they are so cheap.