Just got myself a brand new (according to the seller) DT300 off eBay. I sure looks unused; and if it isn't, then only very gently used and stored quite a while. Got it out of the box today, plugged it into my DCS50 command station, and the display just flashes. I read that is a syptom of the "capcitor plague". Reached out to Digitrax tech support and they said the capacitors have dried out - and that they no longer do repairs on the DT300.
Anyone know of an outside company that will repair these inexpensively? Digitrax supposedly used to do it for about 35 bucks. I just don't want to end up spending the price of a new UT6 to get this thing going.
I'm also willing to give a shot at replacing them myself, but I don't know what the specs or part number for the replacement capacitors needs to be. I've read that the ones that go out are typically a surface mount 4.7uF 25V, but beyond that I can't find out anything else. A Google search for capacitors just leaves me confused with all the options.
Thanks for any help,
Wes
to the forum. You initial posts are delayed in moderations, as this one was.
I'm not a digitrax guy, but I'll give your post a bump.
Mouser has the capacitors you need, but I suspect size matters.
https://www.mouser.com/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/Aluminum-Electrolytic-Capacitors-SMD/_/N-75hqx?P=1
Henry
COB Potomac & Northern
Shenandoah Valley
Size will indeed matter.
I do run Digitrax. However, I don't have the DT300 myself, so I can't check. But most capacitors will have the values, if not a part number, on them. (I have a DT402, and the newer DT500 for my throttles.)
My small (and large) electronics repair buddy really likes Mouser for almost all his part needs. (Even got me a replacement reed switch for a BLI Mike with his one order, to cut shipping charges.) So, once the correct capacitor is known, I second them for the reccommended location to find a replacement.
NOTE: If attempting the repair yourself, a good quality soldering iron will be needed. A cheap big-box store soldering iron will most likely not help matters... And a way to remove quickly the (HOT!) de-soldered bad capacitor will also be a must. (Don't ask me how I know these things...)
Ricky W.
HO scale Proto-freelancer.
My Railroad rules:
1: It's my railroad, my rules.
2: It's for having fun and enjoyment.
3: Any objections, consult above rules.
Here's a representative page on resoldering these electrolytic caps:
https://chmanie.com/post/2020/05/09/soldering-smd-electrolytic-capacitors-using-a-soldering-iron/
I would recommend a good eutectic solder and no-clean flux -- use the 'community search' box to find and read the many threads here about good equipment and techniques for electronic soldering.
It has been my understanding that you can use a higher voltage-rated cap as a replacement (don't use a lower, though!) as this is a measure of breakdown strength, not 'capacity' when charged.
karman1970Thanks for any help,
I have a spare DT300 you can have if you can use it, Wes. It exhibits the same symptoms, alternately flashing the startup screen.
Still, you can use it to practice on or maybe salvage some parts off it. From what I recall there are two 4.7 µF 25v. caps that have to be replaced. One is tricky to get to and part of the case may have to be shaved away to get your soldering tip in there.
Send me your address through the PM system if that works for you.
Regards, Ed
gmpullman karman1970 Thanks for any help, I have a spare DT300 you can have if you can use it, Wes. It exhibits the same symptoms, alternately flashing the startup screen. Still, you can use it to practice on or maybe salvage some parts off it. From what I recall there are two 4.7 µF 25v. caps that have to be replaced. One is tricky to get to and part of the case may have to be shaved away to get your soldering tip in there. Send me your address through the PM system if that works for you. Regards, Ed
karman1970 Thanks for any help,
Thanks for the offer, but I already got this one torn apart (and didn't break anything!). Thank you all for the responses. This was in moderation so long I started the same topic on a different forum and forgot to check back in on this one. Link to that discussion below:
https://www.therailwire.net/forum/index.php?topic=51911.0
Long story short, there are indeed two silver 4.7uf 25V SMD capacitors on the board. Digitrax was of no help besides giving me the specs I had already been able to find elsewhere on the internet. I was able to get them both off the board without breaking or melting anything. Replacement caps are in the mail from Digikey (I couldn't get Mouser's website to work last week for some reason). I will be using standard through mount capacitors with shortened leads rather than trying to put SMDs back on. Apparently there is a Groups.io site for Digitrax and they have actually tackled this exact same issue before. For some reason, those topics never showed up in my Google searches. Hopefully between this thread and the duplicate I started on Railwire, someone else in the future will be able to find the info they need to repair a throttle in the future. I'll post back here in a week or so once I take a stab at getting the new capacitors mounted.
Well, it worked! Put the new caps on the board without much issue (Digikey 493-15371-ND). Test fit them in place, then bent and trimmed the leads as needed. Tinned the leads as well as the solder pads first; so, all I had to do was use the iron to stick them together on the board. I was worried for a minute; because, when I first plugged it in I got nothing - no signs of life. I unplugged it, and popped the cover off to see if anything had come loose. It all looked good; so, I plugged it in again, and it came to life. I've got several hours of use on it since then and it's working well. Saved me a nice chunk of change vs buying another newer throttle. Hope this helps someone else in the future.