Weekend Update 5/5/19

[Jim Starbuck]

What did you use to put the two parts back together ? Did you just glue them back together ?

Jane

I super glued the two halves to keep them aligned then epoxied a .025” splice plate across the joint. The new fuel and air tanks will hide all this. The two 00-90 screws are threaded up into the plastic motor holder. Before cutting it in half I milled the bottom of the frame flat. There was a block cast on there the original fuel tank fit over.

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Jim

[peteski]

I recently ordered 330uf and  470uf 16v caps from eBay. They come in an E type package size which is the same length and width as the 220uf D type package and only 1.2mm taller.

https://www.ebay.ca/itm/181684088864

Craig.

I would be careful with high capacitance tantalum caps from eBay - their quality might not be as good as the ones from electronic supply houses.  We had a thread about those cheap caps flaming up.  At least do the pre-installation burn-in I described in the past (hook them up to a high current capable voltage source close to their rated voltage and see if any of them burn up).  See https://www.therailwire.net/forum/index.php?topic=43648.0

[mark dance]

thanks for the burn in protocol Pete.

md

[Iain]

I would be careful with high capacitance tantalum caps from eBay - their quality might not be as good as the ones from electronic supply houses.  We had a thread about those cheap caps flaming up.  At least do the pre-installation burn-in I described in the past (hook them up to a high current capable voltage source close to their rated voltage and see if any of them burn up).  See https://www.therailwire.net/forum/index.php?topic=43648.0

Considering the effort that goes into these models, I'd even do that with caps from Mouser.

[coloranger]

Got some new things en route.   


https://i.imgur.com/sDayLlU.jpg

Details... trailers for the Humvees? specialized containers? 

[craigolio1]

Considering the effort that goes into these models, I'd even do that with caps from Mouser.

I never thought of testing these prior to installation. I have caps from ??? And from Digikey. I will be testing them all.

Great idea.

Craig.

[peteski]

I never thought of testing these prior to installation. I have caps from ??? And from Digikey. I will be testing them all.

Great idea.

Craig.

Yes, with all the work we put into our models, and with the volatility of tantalum caps, pre-install burn-in is a very good idea for *ALL* those caps.

[Jim Starbuck]

Yes, with all the work we put into our models, and with the volatility of tantalum caps, pre-install burn-in is a very good idea for *ALL* those caps.

Good call on the pre testing. Thank you for this valuable information.
I tested the 4 bank that I had built for the HH660 tonight. It hadn’t been connected to the decoder yet as there was still some lighting programming to do. Although the caps didn’t erupt into flames, they did trip the 2amp breaker on my power supply at about half a volt. I tossed the whole thing and built a new one which tested perfectly both on the bench and installed in the Alco.
From here out I’ll use higher voltage caps from reputable suppliers and still pre test.
The output of the Loksound 73800 to the caps measured 13.75 volts on my Digitrax system. At a 16volt rating that results in the caps operating at 85% capacity if my math is correct.

[peteski]

Good call on the pre testing. Thank you for this valuable information.
I tested the 4 bank that I had built for the HH660 tonight. It hadn’t been connected to the decoder yet as there was still some lighting programming to do. Although the caps didn’t erupt into flames, they did trip the 2amp breaker on my power supply at about half a volt. I tossed the whole thing and built a new one which tested perfectly both on the bench and installed in the Alco.
From here out I’ll use higher voltage caps from reputable suppliers and still pre test.
The output of the Loksound 73800 to the caps measured 13.75 volts on my Digitrax system. At a 16volt rating that results in the caps operating at 85% capacity if my math is correct.

You're welcome!
I would go with caps rated for at least 20V.  I'm a cautious person. I know others use 16V caps.

[Mark W]

Details... trailers for the Humvees? specialized containers?

I'm hoping to post the full announcement this weekend.   

_{(Yay, another announcement announcing and announcement!)}

[Steveruger45]

You're welcome!
I would go with caps rated for at least 20V.  I'm a cautious person. I know others use 16V caps.

Hi all
I contributed  in that earlier thread too and can say that with the quality caps from mouser/didikey I have not had any go ballistic when testing them on an 18v power tool battery to date. I’ve tested about 40 of them so far.  Although I have not had an issue with the cheapo caps that survived the burn in tests and now installed, I’m steadily replacing them for quality caps from mouser or digikey. BTW I always use 20v or 25v caps and for the very same reasons as Pete says.  IMHO  as The locos and decoders are quality so should be any additional components installed.  Anything less is a false economy.

[Steveruger45]

Oh I thought I should add that on one of the referenced posts in this thread there is a table for the recommended applied voltage vis-a-vis caps rated voltage.
In short: for a tantalum cap it is recommended to apply only 50% of rated voltage and in a poly tantalum cap 85% iirc.
I would still recommend keeping under the recommended for the little extra it costs.

[Onizukachan]

I would be careful with high capacitance tantalum caps from eBay - their quality might not be as good as the ones from electronic supply houses.  We had a thread about those cheap caps flaming up.  At least do the pre-installation burn-in I described in the past (hook them up to a high current capable voltage source close to their rated voltage and see if any of them burn up).  See https://www.therailwire.net/forum/index.php?topic=43648.0

Wish I had known about this before I installed the 25v ones in the Tavern car.
I suppose I instinctively did the next best thing. When ever I do install LEDs, caps, Other electronics, I put them on the track (or other power) and leave them running for 72 hours continuous (or more) to make sure I don’t have a premature failure.

[peteski]

Wish I had known about this before I installed the 25v ones in the Tavern car.
I suppose I instinctively did the next best thing. When ever I do install LEDs, caps, Other electronics, I put them on the track (or other power) and leave them running for 72 hours continuous (or more) to make sure I don’t have a premature failure.

25V gives you good margin of safety. That is the voltage I would recommend (instead of using 16V caps) But if you do a burn-in after installation, at least leave the shell off, so if one of the caps flames out, it will not melt the shell.  Also, a burn-in is best done using a voltage higher than what the caps will be normally exposed to (to weed out the weak caps which might fail under lower voltage later on in their life).