Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Telrad pulser install notes and question

  • Please log in to reply
3 replies to this topic

#1 GunArm

GunArm

    Sputnik

  • -----
  • topic starter
  • Posts: 27
  • Joined: 16 Jul 2018
  • Loc: North Texas

Posted 12 October 2019 - 03:33 PM

I bought the pulser upgrade for my telrad when I bought the telrad.  Honestly I hadn't even used the telrad yet so it was it wasn't a purchase of tested need, more of an impulse buy when picking up a ton of other bits and bobs I did need.

 

I have some comments that might be helpful to someone installing it or thinking of getting it, and then I have a question.

 

Install notes:

The kit comes with a piece of paper with instructions at the top and a drill template on the bottom.  The template is not great.  For one thing the template has an incorrect width of the actual telrad by about 1/8 of an inch, and secondly it has inches in decimal which is just odd.

 

I used a poker and made careful holes in the template targets, lined the telrad up behind the template (as best as possible given the height mismatch) and put a silver sharpie dot through the poked holes onto the telrad.  Then I drilled them out.  The recommended drill size of 9/32 is incorrect as that is not big enough for the threaded part of the knob stem to come through, so you'll have to go a step up from that.

 

Feeding the knob stem from the inside through the hole you drilled is tricky.  Until the tip of the stem goes into the hole slightly there is not enough space diagonally to comfortably wedge the circuit board down into the body of the telard.  You could probably force it but I didn't want to.  (If that sounds confusing you'll understand once you try it).  The very easy solution to this is to put the drill sorta sideways against the top edge of the inner side of the hole and mill out a small chamfer on the top side of the hole.  Once you do this the knob stem can get that millimeter of angled insertion needed for clearance and the thing drops into place very easily.  Obviously the chamfer is not visible from the outside. 

 

Finally, the threaded part of the pot stem is not long enough compared to the thickness of the telrad plastic, even with the pot body flat against the wall, there is no way to get the nut threads to catch on the other side with that tiny washer in between.  I had to ditch the washer, and then use needle nose pliers to push the nut while turning it to get it to catch the tiny bit of threads coming through.  I was able to get a half turn on the nut then, not great, but I think it will hold.

Hope this helps others trying to install this thing.

 

 

Now my question:

This isn't a big deal but I wanted to ask anyway:  The instructions say to use the new knob to cut the power.  The thing is that the second knob isn't as nice as the first lever-knob and my preferred use would be to leave the pulser knob somewhere in the middle and use the original intensity lever-knob to turn it on/off.

The instructions say "The switch on the new control turns the power to the instrument on and off and, to avoid battery drain, must be off when the instrument is not in use".  However I'm not confident they are speaking precisely.  The old knob will still cut power to the illuminator, so it might work equally well as a power switch.  However there *is* new circuitry behind the illuminator now, and I'm wondering if anyone has knowledge of the pulser circuit to know if it would leak current even when the illuminator is switched off?


  • Joe1950 likes this

#2 Joe1950

Joe1950

    Cosmos

  • *****
  • Posts: 9605
  • Joined: 22 Aug 2015

Posted 12 October 2019 - 04:50 PM

It depends on how the power lead from the pulsing circuit is wired. If the circuit goes directly to the battery pack, it will stay on, even when the light is off. If it gets power after the original pot/switch, by being connected to the pot switch itself, then the main switch will control both and nothing would stay on.

 

The problem is, looking at the main pot, which is hard to see, I can only see 3 solder contacts. That may mean that the switch is internal, which is not a good thing since you can’t get to it. I think this may be the case since I see only two wires going to the main pot.

 

So I would have to say it’s problematic to get the power off the pot connections. The main pot would be in line with the pulse circuit pot and the interaction would cause it to function oddly, if at all.

 

Eventually, I’m going to add a miniature SPST toggle switch on the side and connected between the battery + and its corresponding wire. I don’t have the pulsed circuit, but I want to leave the brightness lever more or less fixed and just turn the thing on and off.

 

If you did that, you can get your voltage off that switch and turn both on/off at the same time. Without seeing an actual schematic, that may be the best way.

 

Hope this helps.

joe


  • GunArm likes this

#3 GunArm

GunArm

    Sputnik

  • -----
  • topic starter
  • Posts: 27
  • Joined: 16 Jul 2018
  • Loc: North Texas

Posted 14 October 2019 - 12:30 PM

Thanks for the response.  I had been considering a toggle switch also and after considering it I think I'm going to go that route.  Rather than SPST I'll probably throw in a DPDT wired so the 3 positions would be off, pulser, no pulser.


  • Joe1950 likes this

#4 Joe1950

Joe1950

    Cosmos

  • *****
  • Posts: 9605
  • Joined: 22 Aug 2015

Posted 14 October 2019 - 01:47 PM

I forgot the pulser. Good idea. I don’t have the pulser on mine. Good option especially for skies where you can see a lot. Here, only bright stuff. 


Edited by Joe1950, 14 October 2019 - 02:01 PM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics