Argh! Halt and Catch Fire

[Stub Mandrel]

Well that was frustrating!

Last night was a club meet followed by observing. Only my second time and I chose a spot by a picnic table for my stuff. I started off on Jupiter then changed to Saturn not long before it hid behind a tree.

I kept getting an odd fault where guiding would suddenly cease until I sent a command with my hand control.

No one could explain the problem, but after about an hour or so it explained itself when the magic smoke came out of the EQdir dongle.

Luckily I was looking by the computer and was able to whip the dongle out once I realised what was happening. It was VERY hot - I put my thumb right on the hot spot!

Even luckier, the USB port still works and the mount went on tracking, but the dongle is toast:

This is where the magic smoke got out (and I put my thumb!):

A spot of damage by a capacitor below the board suggests the problem may have been related to the voltage multiplier, but the 'explosion' had enough force to blow two legs clean off the chip:

Edit - looking closely I think there seem to be some stray wires inside at the serial connections, looks like (unused) 3V3 and TXc may have shorted, which could have overloaded the voltage step up. ?

very strange, it seems the yellow wire (unused) in the lead had its insulation stripped  for about 10mm with 2 or 3mm protruding from the sheath and presumably despite the hot melt, at some point it was able to cause a short

The laptop was running on internal batteries and the mount was running off a 7aH battery, so not caused by a mains spike or anything like that, and as RS232 should cope with much bigger voltages across its inputs I'm not hugely worried about the mount.

What I discovered is that it is just possible to aim a scope working at an effective focal length of 3.6 metres by gently pushing and pulling the end to get a planet into view, although I suspect my subsequent efforts at focusing and aiming weren't great. As for Mars, the target at the time, it looked like a fuzzy red ball with a hint of green at top right...

[Stu]

Eeeeeek! That looks a bit dramatic Neil! Good job no other damage caused.

[JamesF]

That's nasty.  In a different situation it could have caused a far worse problem   Bit of a QC failure, perhaps?

James

[wimvb]

Glad that your mount/pc wasn't damaged. It seems that these cables are either poor quality to start with, or aren't age proof.

Last winter I blew a fuse in my power box, and the mount died. It took me quite a few fuses until I tracked the fault to a short circuit in the (blue hitecastro) eqdir cable. It turned out that two poorly stripped and soldered leads caused the short circuit. Fortunately I had a backup cable (the newer black, lynx astro version). Meanwhile, I've resoldered the hitecastro and used it on my eq3. I'm just glad it didn't fry the electronics in my mount.

[RayD]

Holy cow that's not good!!

I have one of these as my "back-up" so will be sure to keep a close eye if it ever needs to be used.  Glad you didn't seem to suffer any other damage but thanks for sharing this.

[Dr_Ju_ju]

The quality control of some manufacturers, leave a lot.... that's why I make my own, using standard parts (RJ45 lead & FTDI USB to serial adaptor), never had any issues.....

[Stub Mandrel]

I found this on the EQmod website. Looks like the yellow wire is connected to the Mount's 12V. Hardly surprising sticking 12V up the wrong pin killed the chip. Luckily the seller included a spare EQdir lead but it's a bit short. Luckily I've found a pre-wired FTDI chip lead in my goodie box (I bought a few because they were little more expensive than buying FTDI chips and they have a proper case and strain relief, so a full length replacement was a five minute job.

The cable to cable join worried me a bit, so I used heat shrink on all joints, than an outer layer of heat shrink, then I took a ferrite filter out of its case and filled it with a particularly gooey fast setting epoxy and clipped it over the joint.

I then adjusted the DEC worm on the HEQ5, as explained to me last night (and turned the scope holder through 90 degrees so its aligned with the polar scope, the previous owner used it in an ROR obsy so had it crosswise. Saves a lot of angst being able to speak to someone who has already done the job.

[wimvb]

4 hours ago, Dr_Ju_ju said:

The quality control of some manufacturers, leave a lot.... that's why I make my own, using standard parts (RJ45 lead & FTDI USB to serial adaptor), never had any issues.....

So will I, if I ever need a replacement.

[Stub Mandrel]

These are so cheap and come with a nice plug ready fitted and a cable with strain relief:

https://www.ebay.co.uk/itm/1PCS-6Pin-FTDI-FT232RL-USB-to-Serial-adapter-module-USB-TO-TTL-RS232-NEW-/191736103524?hash=item2ca45cc264

[Dr_Ju_ju]

The problem with those is trying to put an RJ45 on the end, that's why I use a Cat5e cable & replace the supplied cable 

[Stub Mandrel]

9 hours ago, Dr_Ju_ju said:

The problem with those is trying to put an RJ45 on the end, that's why I use a Cat5e cable & replace the supplied cable 

I spliced the two cables together using heath shrink on the individual ways and the whole thing, then epoxy encapsulated the joint inside the shell from a clip-on ferrite ?

Otherwise, I'd probably do the same as you. Sugru is good for making strain reliefs.

[Jkulin]

If this helps, I have just ordered 5 off here at just over £4 each: -

https://www.banggood.com/6Pin-FTDI-FT232RL-USB-To-Serial-Adapter-Module-USB-TO-TTL-RS232-Arduino-Cable-p-1035802.html?rmmds=myorder&cur_warehouse=CN

If ordering make sure you add the faster postage service, got here in 5 days, these are the FTDI 232 Chip.

HTH

[bottletopburly]

I had ones of those cables , wasn’t impressed with build quality changed it to a lynx eqdirect cable , lot better build quality. 

[Stub Mandrel]

12 hours ago, Jkulin said:

If this helps, I have just ordered 5 off here at just over £4 each: -

https://www.banggood.com/6Pin-FTDI-FT232RL-USB-To-Serial-Adapter-Module-USB-TO-TTL-RS232-Arduino-Cable-p-1035802.html?rmmds=myorder&cur_warehouse=CN

If ordering make sure you add the faster postage service, got here in 5 days, these are the FTDI 232 Chip.

HTH

The ones I got of the bay look identical, are UK stock and are about 2/3 the price ?

11 hours ago, bottletopburly said:

I had ones of those cables , wasn’t impressed with build quality changed it to a lynx eqdirect cable , lot better build quality. 

Hmm... I opened up mine to check it and in my case the cheap and cheerful was better assembled than the 'specialist' item  -which I note is no longer  made.