CP4 is definitely NOT water tight - VERY suseptible to DEW flooding


Joe Zeglinski
 

Hi,
 
    At long last, this is a heads-up ... “PRECAUTIONS to take” and easy FIXES for CP4 owners – after my TWO water-logged disasters.
 
    At the very least, check the (white) CP4 backside lower edge, for presence of two drain holes, or  (unwisely) “rubber-stoppered” by default, on the (black) Mach-1 style case.
 
    Back in April,  I had mentioned in a post here,  the demise of my “first” Replacement CP4 - about which Marj asked me – (quite understandably):

QUOTE:   “......  I am aware that on at least two recent occasions on the AP-GTO group, you discussed the problems that you have had with your CP4. I would appreciate it if you would clarify that the issues with the unit that you returned last year was not defective and that it had sustained corrosion as a result of water damage.”

    I am glad comply and to state that indeed the ... electronics failure was entirely caused by “Dew, from  CP4 case panel leakage”.
In spite of this “initial design” oversight, in my opinion and of many others,  AP makes the finest mounts and scopes on the market. Support and response to user problems is very good, perhaps exceptional. I would never choose to own any other brands.
 
    Certainly, the first TWO dew drownings of my CP4 stock units were NOT “electronically” defective, until damaged by dew water forming on clear nights ... and as such – ONLY the (original, white) CASE design was defective,  the black MACH-1 version is corrected, but drains-plugged at the factory!
 
     This made the original CP4’s  far too susceptible to dew infiltration, shorting out of the electronics, under “reasonable observing conditions”, and which could have been easily remedied, and prevented a lot sooner.
With heated dew-free optics, imaging was always fine, and there was never a warning that my CP4 were slowly drowning – over a short time – until disaster and eventual burn out.
 
    But, as with any new product, there are “growing pains”, and lessons to be learned from problems discovered only through vast user experience. My own circumstance is having the CP4 UPGRADE ... specifically, being “attached to the RA axis” to replace the CP3 on my old AP-1200 ...  permanently set up in the backyard. My scope and in particular its new CP4 Upgrade,  are exceptionally well protected when not in use, in a  temperature and humidity tightly controlled climate year round, under a well secured top-to-ground level waterproofed nylon tarp. It has NEVER been exposed to rain showers, nor been hit by a sprinkler system while uncovered during observations.
 
    My first CP4 was purchased on the product’s ... “introductory first ship date” ... and lasted less than 11 months of VERY occasional use of maybe a dozen nights, before it drowned from dew. Its (identical) replacement lasted a mere 5 nights of observing,  through winter, for about 4 months – when it too drowned. The first unit’s actual failure was mis-identified by AP as “Non-water related” ... in spite of an obvious solid white, inch high, swath of dried water residue along the CP4 circuit board backside bottom, in an AP photo.
 
    Had I known otherwise, I would have taken the counter-measures, I outline below – and certainly will implement  on the .. “replacement, of the previous replacement,  CP4” – now that we discovered how a large volume of dew managed to leak inside, and had absolutely NO safe and rapid means of draining right back out as water entered. The two CP4’s  nearly caused permanent scope damage by an uncontrolled runaway mount - both times.
 
    Therefore, I offer the following suggestions, to help other users who have not yet experienced this problem.
 
    Dew entry into the CP4 case, does NOT seem to have yet been reported, as I was told, by either “Domed,  or by Roll-off Roof”  observatory owners.
I suggest that is because the large amount of retained daytime HEAT radiated by such building’s thick concrete floor, elevates the ambient indoor temperature directly around the scope, more than that of a mount planted on just “bare ground” surrounded by cold ambient. This extra,  slowly dissipating observatory heat,  may be enough to WIDEN the difference between ambient temperature and the local DEW point inside the observatory, over a longer time.  A dome would trap more of this “helpful”, though optically undesired heat,  longer than for a mount inside a roll-off’s, fully retracted roof, building. Ideally, users in both types of observatories try to cool down their building to ambient, as quickly as possible, before starting an observing session. This rapid cool down could cause CP4 dew problems to start sooner.  Meanwhile, the gap between ambient and dew point temperatures out in an “open field” can be much narrower, drop quicker, even though typical observatories eventually cool down, and then soon, they too become susceptible to this very same “dew flood” problem. But for those buildings, the “remaining observing hours” after equilibrium, before exposure to normal dewing, might be far fewer before the end of session, or none at all. Therefor less, if any, dew penetrates their CP4 case, or accumulates inside, over months or years.
 
    Open field conditions are worse, but still, observatories nevertheless remain somewhat susceptible to ... one significant CP4 “case design fault”. Also, as with dew formation in humid climates, in temperate regions such as Arizona, there is similar risk for desert sand particles dropping into the case, through the same openings, forming electrically conductive “mini-dunes” between component pins. I have seen that on a different type controller.
My “Easy Fixes” should eliminate the risk of dew (and dust) exposure for the CP4 electronics – until AP gets around to finally sealing the Ethernet connector panel leaks, or using rugged leak proof RJ-type connectors, in future runs.
 
    Joe Z. – Continued below ...
 
**************************************************************
 
From the “original” -  CP4 release webpage description:
 
From:    “ASTRO-PHYSICS GTOCP4 Control Box for Servo Drive “
Mechanical Features:
  • Machined aluminum housing provides “robust protection for electronics”
  • All input lines are protected against heavy static discharge with transorbs
  • Dovetail construction allows quick removal from all GTO mounts
  • 12V DC receptacle (2-pin male) for locking power cable. All upgrades from previous GTO control boxes will require a new cable
  • USB 2.0, ruggedized version for extended temperature range, “dust-tight and water resistant
  • Ethernet receptacle
***************
   I feel that last claim - “dust-tight and water resistant” - was overly optimistic, without  NEMA Industrial Level IP-65 or even a minimal IP-63 water penetration testing and corresponding certification. 
 
 
    The recent Sept. 2018,  considerably expanded second revision of the product document, updated right after the “replacement of my original CP4” was ALSO declared to be yet another drowning fatality -  now has an added  ENVIRONMENTAL (legal) escape section on page-6, emphasizing the following:
 
(Extracted):
Wet and Humid Climates
 
    The GTOCP4 control box and optional Keypad are “not waterproof” and should be protected from rain and excessive condensation.
(See second Rev. 2018): 
  
http://www.astro-physics.com/tech_support/mounts/servo/GTOCP4-Servo-Control-System-manual2.pdf
 
    That is fair warning, but I assume that even the former claim of EVEN being  “water RESISTANT” in the initial document version, is no longer true (???)
– especially if considering exposure to acts of God or the Devil -  (i.e.  Rain, and Sprinkler Systems, respectively). There is a distinction between “water resistant and water proof”, the latter implying full immersion.  However, excessive dew condensation, (short of actual falling rain) during a night in perfectly clear skies, is unavoidable, and a natural part of our hobby. Observatory rain detectors do fail, domes and roofs do not always close fast enough, or can even jamb when closing, while those of us who “take a snooze”,  while doing hours of unattended imaging, should all be able to better rely on more robust expensive electronics.
 
    That latest document doesn’t commit to defining what AP considers “excessive” condensation, never mind a reasonable one – not even a “safe dew point temperature difference” from ambient – one we could continually check the weather office and compare our ambient during a session. The worst night, that of my second CP4 washout, my TEMP & RH% logs indicated the ambient was safely still about 6F to 8 F above dew point, measured right on the mount. But then, breezes can cause momentary variations, as automatically logged during my 5 minute interval sampling cycles, so dew still forms on the OTA and slides down, off its slick surface, DIRECTLY onto the CP4 panel beneath it.
 
    Likewise, these same problems exist  using AP’s  “Mounting to Pier Bracket (CBAPT)” as when attaching the CP4 to the RA axis position in a CP3 Upgrade.
The CBAPT adapter has an (optional) bolt-on eyelet which if chosen, conveniently angles the bracket outward at 45 degrees from the pier. Then likewise, for an attached CP4,  dew can  and very likely will seep in along the SIDES of the ETHERNET connector, flooding the case and its electronics with “rust contaminated” water produced from the connector’s steel “centering brace”. Rust, just as copper,  is a near perfect shorting conductor between the circuit board’s soaked pins.
 
Something to Verify on the Ethernet RJ-45 connector
 
    When I looked for causes on my second drowned CP4, I noticed there were  different width open gaps, on all 4 sides,  between the RJ-45 connector and its “oversized” panel cutout. Every CP4 unit will likely have different gap sizes, depending how it was soldered in. In my second unit, I could insert the corner of 3 standard business cards into the widest gaps (left and bottom) – the other sides took one or two. Using a feeler gauge, the two widest gaps were 0.030” wide, enough for water to easily drip into.
 
    This became even more obvious after I removed the circuit board from its CP4 case, holding it up to the sun – the huge gaps just lit up below the panel !
 
******************************
 
Points of DEW Water entry:
 
    In fact there are 3 ways for dew,  either from direct external condensation on the CP4 connector panel surface itself, or possibly in far greater volume – spilling down off the surface of the OTA, directly onto the CP4 from the saddle plate. Once this begins, water will seep inside the case.
In order of decreasing amount, from:
  1. The Ethernet connectors sides, which are considerably separated from its oversized panel cut-out, by as much as “3 business card thickness” - if the RJ-45 connector socket is not soldered perfectly vertical inside, leaving wider gaps at one or more panel opening sides.
  2. The RJ-11 Guider, USB, and Ethernet socket’s center hole – through which you can even spot the exposed circuit board’s lettering underneath
  3. Least likely, even the tightly bolted-down – hairline space between the aluminum case edge and the panel top covers – there is definitely a similar one along the case bottom. Mine was heavily stained by rusty water trying to leak out the bottom, between the two panel screws.
    On the other hand, there should be no leaks through all the remaining  “round connectors” which are either industrial or military grade, with (likely)  hermetically sealed signal pins. These may eventually corrode, providing problems for future “Accessories (AUX) or ENCODER” add-ons. There is a “Plug Kit” to cover them, only recently available for purchase.
    Things get worse for those using “portable” mounts. If you remove the CP4 during transport, or lay the mount  with its CP4 still axis-attached, into its travel luggage, then any “accumulated” dew water that leaked in over time, will then SLOSH around inside, covering not only that  one inch high swath of the circuit board’s  bottom edge, but far worse,  drench every component right to the antenna at top edge, especially the microprocessor. This wash will not be just “pure dew” water, but also floating rust particles from the Ethernet Connector’s steel panel-brace clip, which is  just nickel plated metal of some kind. I have spotted orange rust dots on my last drowned CP4.
 
CP4 Mounting positions – in order of decreasing risk of flooding:
  1. WORST possible position – on top of the RA axis – used as CP3 Upgrades.
    The panel faces upward, exposed to not only its own dew formation but also condensation streaming down from the OTA surface, and entering through the exposed points, noted above.
    ---
  2. Attached at  the (optional) 45-degree angle to the pier, below the mount. Same danger as #1.
    ---
  3. Vertically attached to the side of the mount fork on new models (Mach-1, AP-1100, AP-1600), or vertically to the pier itself
    using an adapter plate - still exposed but LEAST likely to flood. This is almost perfectly safe, so long as dew does not get through the entry points above, such as “catching an edge opening”, then “dribbling in sideways” along the Ethernet connector sides, when dewing up,  or water falls down onto it from the OTA, etc.
SIMPLE quick 2-Minute DIY-FIX  for CP4 Dew Leaks:
 
    There are actually two  things we can do ourselves, to make the CP4 very nearly “Waterproof”.
  1. Easiest,  temporary fix -  If you are like me, and ONLY use the original RS-232 ports for mount control – stick a wide strip of clear shipping tape down over the USB and/or ETHERNET ports. Water will just run past them.
    Or, if you actually DO USE either one of these ports – then use a box cuter or EXACTO Blade to cut a small opening in the Cello-tape, JUST around the cable entry hole. The cable connector’s hood itself should divert any water droplets onto the protection tape, away from the panel gaps.
    ---
  2. Second,  a better,  more “permanent alternative” fix – use RTV, or just (GE) Silicone Seal the cracks  (might even try TUB & TILE CALK) – to block the panel water entry points.
    Only needs a “finger dab” of silicone sealer pushed in, mainly along all the Ethernet connector sides,  to plug the panel gaps.
    Can’t do anything about the Guider port center hole, except filling it with either a permanently attached guider cable, or a dummy RJ-11  or RJ-45 plug (one cut off from a dead cable).
    ---
    If you perform the above preventative “countermeasures”, then CP3 UPGRADES “might” still be safe, even  if attached to the original position on top of the RA axis. However, when I offered to Beta test for a  “dew leak” using my most recent (second) CP4 replacement, management graciously declined my generous offer, thus  avoiding possible replacement with yet a fourth unit.
That would be too many “trips to the well” – pun intended :-)
 
 
Extra protection step – ADD DRAIN HOLES - but may take over an hour:
 
( View Tony’s - a.k.a. Harley Davidson – excellent video at:  https://www.youtube.com/watch?v=HwU5ibObflw
Posted on 02/10/2018 – [ap-gto] Drain holes in CP4 )
 
        If you have already taken the above quick remedies offered above, there is still one other essential thing that can be done, to almost guarantee water won’t short out the electronics inside the case, if dew SOMEHOW still finds a way in.
 
    Unlike the old reliable CP3, without Ethernet & USB panel gaps – there was a case design “oversight” (... Hej ... stuff happens).
The new (WHITE) CP4 case, shipped during the  first few years,  lacks the TWO “water DRAIN” holes, that the CP3 has along its case bottom, backside edge. The holes on my old CP3 backside were about 3/32” (call it 1/8”), based on measuring by poking a drill bit into the hole. This still might be too tight for “water bubble cohesion” to break through the opening fast enough, without the added weight of more dew and thus a heavier weight, volume of water. A slightly larger diameter hole might be better, depending on the size of bugs you  expect to enter the CP4 case - (Really ??? I never found one dead bug inside,  in all my years of CPx use)

    So, if you don’t perform the quick & simple DYI  “Sealing” suggestions, above, then at the very least opening up DRAIN holes will prevent upto about TWO “shot-glasses” of water accumulating inside, (over time, perhaps months) - covering the circuit board right upto the bottom edge Ethernet connector panel opening, where it will finally flow back out, when the case’s bottom water capacity is full. There is little likelihood that it would otherwise  easily evaporate from inside the case.
For RA attached CP4’s lying flatter - at lower Latitudes, the amount of retained case flood water can be even deeper, and spread out covering more IC’s  at the upper circuit board.
Worst case: observatories nearer to the Equator using old model mounts – where the RA axis attached CP4 lies nearly horizontal, completely inundated with rusty water.

**** PROCEDURE – nicely demonstrated in Tony’s Video ****

    This ADDED SAFETY measure requires first unbolting the top case cover, flipping it up, backside onto a table above the case - to avoid the risk of unplugging the ultra thin WiFi antenna (pull-up) coax cable plug with its delicate miniscule (possibly bendable) gold center pin.
 
    Next, unbolt the 4 bolts of the panel section, and the 3 power IC screws from the case sides - (do NOT lose their lock washers, next to the panel surface) ... holding the power IC’s thermal sink tabs to the aluminum case upper sides. Lift out the connector panel with its circuit board as a unit, as you “pull aside” the now empty aluminum case, leaving the electronics safely resting flat on the table and its upper top cover with antenna,  positioned above it.

    NOW ...  you can easily DRILL at least two holes on the backside, one at each bottom edge end, in the milled,  rounded-out corners – perhaps a third one at upper right and/or upper left, if you think you might need to attach the CP4 rotated by 90 degrees, such as on an AP-900 RA axis, or likewise on an AP-1200 at sites below 37 deg. Latitude, (using a CBAPT adapter). The extra pair of unused (upper) rear DRAIN hole(s) can be covered, with black electrical tape, unseen from the front – or with a special rubber plug, as done on recent (Black) CP4’s. The new ones come with “Drains plugged” by default, looking like “case flat rubber feet” – so, it is far wiser to remove the plugs and store them away.
 
    N.B. Tony’s (video) additional Mach-1 CP4 case two holes may be unnecessary – at least pull out the existing rubber stoppers.
Certainly need to drill a pair in the original white CP4 case, since there were none at all.


    In fact, most of the water ... assuming any still gets in after making the above simple fixes – will drip out MAINLY from “ONLY one” DRAIN hole, not likely both, since the pier/tripod attached mount and its CP4 will likely never stand “perfectly” vertical, especially in the field, so the drops will gradually drift toward just one end drain hole.
----
 
    With this longer, more difficult task completed, re-assemble the CP4,  (carefully) reversing the disassembly steps taken above – do NOT forget those three lock washers.
******** END *****
 

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