Computer ATX power supply.

[SthBohemia]

Quick question-

Is it OK to join all the yellow 12v supply rails of a computer ATX power supply to a single BUS bar for the purpose of supplying various telescope mounts??

[Cosmic Geoff]

You might get away with it, but I worked with specifying instrument power supplies in my last job, and discovered that in most of these supplies, the 5 volt line is directly regulated and the other outputs just follow it, so that the +12v output is ill-defined if it is the only output loaded.  Considering that proper mains PSUs for a mount are inexpensive and better protected against water ingress, I would not risk it.   Likewise if you require more power to run sundry accessories like dew heaters, you can buy a PSU properly boxed up with terminals and output meters.

[malc-c]

The problem is that there are computer PSUs and then there are decent computer PSUs.   If your old ATX case was originally supplied with some non branded plain metal box then I would not use it as a mean of supplying 12v to the equipment.  Often these cheap units lack all the protection found on branded makes that often cost twice as much, and a branded supply could cost you more than a dedicated 13.8v regulated supply.

[ONIKKINEN]

I agree with @malc-c about the PSU quality thing. Was this a "gold" rated PSU? If its a no-brand HP something something smoke and spark machine, dont bother using it for anything, including a PC! The non branded and rated ones are quite good at starting fires though, if that's what you are after.

Its the one part that must not be saved money on when building a PC, and would imagine it wont do you any good if repurposed to run expensive astro equipment either so i would definitely take another look at the whole idea before hooking it up to something you dont want to lose.

[SthBohemia]

6 hours ago, malc-c said:

computer PSUs and then there are decent computer PSU

The unit is a Siemens/Fujitsu 250 watt. Would only require 1.5 amp max from the unit (driving a Celestron CPC fork) thus maybe the HDD rails would be sufficient to deliver that current? Have an 8A unit for the SWatcher mount, just want to have another unit more conveniently placed for the CPC.

Malc-c, as you seem to be on the 'ball' with various electronic issues, I posted an unanswered query 2 weeks ago in regard to the circuit board contained within a Celestron Ultima fork mount. As far as I am concerned the Ultima is, construction wise, head and shoulders above the CPC and the SW HEQ6.

HOWEVER, I am concerned regarding the rather dated circuit board, in particular ONE component that I would be unable to replace, being a 40 pin (contained within a socket thankfully) computer chip similar to a Z80.

What I would like to do is purchase a couple of 40 pin chips (wrote its number down somewhere or other, they are still available through Mouser) and get someone to 'burn' substitute chips. Problem being I moved to Czech Rep from Ozzieland and don't speak the lingo well. Thus not sure who to approach. Any suggestions?

The chip is used as a ROM to drive the 'engine' of the Ultima, later versions of the Ultima used a smaller Eprom...

Please do not suggest contacting Celestron for replacement parts as they are notorious for their total lack of customer support, especially as regards the older items.......

Cheers Rob.

[Cosmic Geoff]

2 hours ago, SthBohemia said:

The unit is a Siemens/Fujitsu 250 watt. Would only require 1.5 amp max from the unit (driving a Celestron CPC fork) thus maybe the HDD rails would be sufficient to deliver that current? Have an 8A unit for the SWatcher mount, just want to have another unit more conveniently placed for the CPC.

I have a CPC and there is no way I would risk using it with an improvised PSU.  I spent £40 just to replace the battery in the power tank I normally use.

I wouldn't risk using a computer PSU on an expensive Skywatcher mount either.

[SthBohemia]

1 hour ago, Cosmic Geoff said:

I wouldn't risk using a computer PSU on an expensive Skywatcher mount either.

^^ 🙂 it's not a Losmandy G11. However, since you lot above are trying to make me paranoid I dug around and found a couple of old transformers Ferguson 12-0-12 volt 60VA's and a few LM7812CZ's, thus will make a PSU and attempt not to drop such on my foot....

Thanks for your input, appreciated 🙂 

[malc-c]

Hi Rob,

I read a recent post regarding the control board in a Celestron scope, but didn't comment for a couple of reasons.  The first being I lack the tools to program a device in that package.  I'm just a hobbyist when it comes to electronics and programming, and it was only recently I was able to get a ZIF socket for 28pin SOIC packages to make programming the 16F886's used in older Skywatcher boards easier.  The second reason is that I have no experience in working with Celestron equipment, so don't know if the same workflow used with Skywatcher boards will / would work for the processors used in Celestron scopes.  

 

[SthBohemia]

22 minutes ago, malc-c said:

I read a recent post regarding the control board in a Celestron scope,

^^Might have been from me. The old Celestron  Ultima boards, late 90's, are simple compared to a modern SW!! Maybe of interest follow the link below. I am especially fond of the mechanics, the Ed Byers worm/wheel RA drive.

http://www.astrosurf.com/benschop/Ultima8PECElect.htm

Do you have some advise as to whom, a person or a company that I could bribe to burn a chip??

Rgds Rob.

[malc-c]

Must have been a different post as the chip was totally different.  

The microcontroller this board uses is the 16C57 in a Dual in line (DIL) package, which as you say looks to be socketed for replacement with a newer chip should the firmware be updated.  

I have two problems that prevents me flashing a new chip for you.  The first is that I can't find the firmware used, which seeing the board uses a one time only is quite common as once the PIC has been programmed you can't program it again so there would be little point in making the firmware available.  It's also quite possibly that Tangent Instruments own the IP of the code so won't publish it.  The second issue is that even if the code were available my programmer (PicKIT 2) doesn't support this device (or even the flash variant which replaced it) due to the age of the chip (circa late 80's / late 90's), so I wouldn't be able to program a chip if I had one.

Checking RS Components the 16C57 is in stock (single figures) at £8.30 inc VAT, but the flash version us back ordered to god knows when....

So basically, if you suspect the PIC is damaged or the code corrupted other than contacting Tangent Instruments (assuming they are still in business) to see if they can help I think you are going to be stuck.  Chances are the code is protected so it would be impossible to read it back even if you could manage to get the PIC running.

 

[SthBohemia]

8 minutes ago, malc-c said:

Chances are the code is protected so it would be impossible to read it back

I much appreciate your feedback, this has been a live and learn experience as I thought it was a simple job to unplug a chip, push a 'magic' copy button and instant clone!! How wrong I am. Probably assuming cloning was as simple as removing a Sinclair Spectrum ROM and copying that...

Guess I had best be careful with the Ultima mount and hope the mystical 40 pin chip behaves itself!

Thanks again for the help. Cheers Rob.

[malc-c]

1 hour ago, SthBohemia said:

Do you have some advise as to whom, a person or a company that I could bribe to burn a chip??

Rgds Rob.

Rob,   a bit more digging and came up with this

Tangent Instruments, 1691 Spinnaker Drive, Suite 202, Ventura, CA 93001

Phone: +1 805-642-3136

Links to a website seem to fail.... but that may just be  broken link

[malc-c]

3 minutes ago, SthBohemia said:

I thought it was a simple job to unplug a chip, push a 'magic' copy button and instant clone!! How wrong I am. Probably assuming cloning was as simple as removing a Sinclair Spectrum ROM and copying that...

 

Normally it is.  Whilst it took me a long evening to download all the SW firmware files and convert them into an unprotected HEX format to upload to the 16F886's, the actual programming takes half a minute.  Most commercial products that use microcontrollers code protect their I.P so it's very difficult to read the HEX back off the PIC and save the file to upload to a new PIC, which may well be the case with the Celestron board. 

[SthBohemia]

59 minutes ago, malc-c said:

Tangent Instruments, 1691 Spinnaker Drive, Suite 202, Ventura, CA 93001

^^They seem to have sunk into muddy waters over 10 years ago!

🙂 your explanations have left me scratching a not to well screwed on head! If its not a 12AX7 within a Williamson Amp and it happens to be an odd looking plastic thing with lots of metal legs I am at a total loss  😞 

Thanks once again 4 your help...

[malc-c]

I

3 hours ago, SthBohemia said:

^^They seem to have sunk into muddy waters over 10 years ago!

🙂 your explanations have left me scratching a not to well screwed on head! If its not a 12AX7 within a Williamson Amp and it happens to be an odd looking plastic thing with lots of metal legs I am at a total loss  😞 

Thanks once again 4 your help...

That may explain why a post on a different forum from 2017 stated there was no answer when he telephoned them...  Sorry, but I think on this occasion you've hit a wall

[SthBohemia]

11 minutes ago, malc-c said:

That may explain why a post on a different forum from 2017 stated there was no answer when he telephoned them...  Sorry, but I think on this occasion you've hit a wall

If/when failure occurs (assuming I am still alive) there always exists the possibility of the mechanical approach. Decades ago a friend within Oz made a gearbox from Meccano parts AND it actually kept the RA tracking sidereal for approx 15 mins. Canna remember the name or type of GEM he modified...

That would actually be ok with me as imaging holds no great interest.