Pulsar Heat Sensor pictures

[retroleds]

G'day Ed.
Any chance of getting the images restored in this thread ? I'm thinking of experimenting with these vari-resistors under the IC lid.

http://dwf.nu/viewtopic.php?t=1837&post ... or&start=0

Also, do you know how to get this lid off ? Does it just pop off ?

Rgds,
Andrew.

Andrew:
That is not a lid over the IC, the IC is the "lid" - it faces downward with it's contacts made thru the small squares around the edge.
Hopefully the pictures will help explain the layout a little better, will show the 2 sensors, the smaller of which is easily bypassed externally, the second requiring a little more finesse. If you get the IC off successfully, replacing it is not that bad a job. I would suggest a drop of muratic acid or a quick woosh with a sandblaster(all other areas masked with a good ruber bodied tape) if one wants to remove/kill the contact thru the var-resistor(sensor). Scraping metal off ceramic circuit boards tends to leave metal residue imbedded in the board.

Pics below.

[retroleds]

General layout, note the 2 distinct sensors. I have superimposed some text, so look at this enlarged.
http://www.dwf.nu/images/HeatSensor/sensor_camera1.jpg

This shot shows where the smaller sensor exits from below the IC. I call the shot "passing to black", because the sensor is generally not at all noticible due to the black "paint" over the module face.
http://www.dwf.nu/images/HeatSensor/pas ... -black.jpg


This shot shows the wiggling line of the painted over sensor a little better http://www.dwf.nu/images/HeatSensor/Sensor_mic2.jpg

This one is a closeup of the terminating point of the smaller sensor.
http://www.dwf.nu/images/HeatSensor/Sensor_mic3.jpg

Just a closeup of the beginning of the larger sensor, under the IC. http://www.dwf.nu/images/HeatSensor/Sensor_mic4.jpg

[charger105]

Thanks Ed.
Very helpful.
Don't panic, I'm going to experiment on definately terminal modules. I got a P2 recently that still had the original Rayovac batteries inside. The case was full of white powder. The under side of the crystal screen had actually been etched by the battery acid !

Rgds,
Andrew.

[charger105]

Hi All.
I've got a P2 module that works only when heated, so is a potential candidate for this repair. I have a few questions for anyone who has done this before:

1. Can you bypass the smaller sensor without removing the IC ? It looks like you could make one end of the sensor open circuit (in the fading to black area), and then attach a fixed resistor to the appropriate IC mounting "square".

2. What is the best way to remove the IC if the larger sensor is to be "removed" ?

3. Has anyone got any appropriate resistor values for each sensor ?

4. Has anyone found a good spot to locate these extra resistors ?

Tks&Rgds,
Andrew.

[retroleds]

Hi All.
I've got a P2 module that works only when heated, so is a potential candidate for this repair. I have a few questions for anyone who has done this before:
1. Can you bypass the smaller sensor without removing the IC ? It looks like you could make one end of the sensor open circuit (in the fading to black area), and then attach a fixed resistor to the appropriate IC mounting "square".
2. What is the best way to remove the IC if the larger sensor is to be "removed" ?
3. Has anyone got any appropriate resistor values for each sensor ?
4. Has anyone found a good spot to locate these extra resistors ?
Tks&Rgds,
Andrew.

1.Yes, rarely this appears to have been done at the factory*...you will see a resistor attached straight across that area. * Or was heck of a neat job, including the paint.
2.Pry and pray - you are hoping for all of the "legs" to remain on the IC.
3.Small sensor is 85k at room temp - just breathing on it makes the value plummet quickly to 40K(continued blowing will get it down to 20k)....almost immediatly starts climbing again. Blow on it again, watch it fall again. Kind of neat, but I wish they would have left it out of the design...other manufacturers did just fine without. Large sensor is 35-37k at "room temp", drops to 12-14k at body temp.(determined by using a plastic drinking straw and blowing very gently but almost continuously on the sensor while testing.)If I had three hands or an assistant, I might be able to give you a better idea of the lower value at temps that would approximate a really hot day.
4.Mouser.com and other places....let us know how you fare.

[charger105]

Thanks Ed. Very helpful. I will let you know how I go.

The IC has 7 evenly spaced comb-like posts (excluding the corner posts), on all four sides.
Where the smaller sensor goes from the 'fading to black' area, to under the IC, it goes directly under one of these posts. In the pictures, there is no trace of this post. Does this post just 'rest' on the sensor, but make no electrical contact ? See here:

http://www.dwf.nu/images/HeatSensor/sensor_camera1.jpg

I'm not confident to pry off the IC, so I will attempt to put a resistor of appropriate value in parallel with the larger sensor, so that their combined resistance equals the value I measure when it's hot and working (perhaps 10% less so that if the sensor deteriorates further, I'll have some headroom).

Rgds.

[retroleds]

You are correct, it does just pass under there. An alternate method is to silver epoxy two very thin wires to your connection points and use a potentiometer(variable resister)....if/when the module shows you some love, check the pots value, snip your wires short and solder a resistor of correct value in . Use a small heat sink to keep the heat from the epoxied conections. Super small tweezers of the type that normally close themselves are great for that or flat jawed alligator clips(ground down to a nice small tip.)

There are a total of three of those posts that are just placeholders with no leads from the IC package - the one in question, two on the side facing the display. If anyone else is interested, I will gladly pry and photograph a few of these for posterity.

[charger105]

Thanks Ed.
I've removed the trimmer cap and attached wires to the base of the two posts in question. See below.



Larger sensor is measuring 98k (in parallel with rest of module).
Smaller sensor is measuring 95k (in parallel with rest of module).

Heating up the module until it works has no impact on these readings ? If these sensors aren't the problem, I'd expect to see these readings change. If they are the problem, I'd expect to see some change once the module was at it's working temperature. I'm a bit confused !

I think I'll replace the smaller sensor with a value you suggest, and then use a 2M variable resistor on the larger one, and wind it down until it works (hopefully!).

Rgds.

[retroleds]

You didn't forget to put the trimmer back into the circuit did you?

[charger105]

I didn't put the trimmer back in, but I would've expected the resistance readings to vary with temperature without it.

Does the trimmer need to go back in when taking these measurements ?

Rgds,
Andrew.

[retroleds]

Charger:
Sorry I was so brief, we had a tornado pass thru this area and I've been without Internet or phone for 4.5 days(back on last night), power via whole-house generator. I was reducedb to using my stepdaughter's laptop from a WI-fi connection point while we out shopping(the ladies shopped, I used the laptop ).

Anyway....I'm thinking you might be getting higher resistance readings as the sensor secotion may have already deteriorated somewhat. I pried off 5-6 of them to find the three best looking ones, and then was drawing an average of my readings. Some modules that are only lightly acid burnt will have almost no trace of the sensor under the IC, completely dissappeared in other cases. The trimmer needs to be in the circuit for it to work, the capacitance is fairly critical and within a narrow range. E.G. If you accidentially buy 18pf quartz oscillators instead of the correct 12pf., you will find few modules that will show any life. The more we go into this, the more I think it was a really bad idea to have that exposed sensor under the IC. I've often wondered about the exposure of the IC leads under the IC and how much failure is due to them being exposed to light acid or shorting out from fairly minor dust and such such. The longest living modules, over all the manufacturers, seems to be the ones that are/were sealed the best. I currently seal over the wire bonds of any and all modules that wasn't sealed at the factory. $.10 of slow set epoxy means never having to say, "darn, I just clumsily ruined a perfectly good module.".

Keep plugging away at it...and don't be put off by the lack of commentary. At this time of year forum participation typically falls to a low point as people enjoy the nicer weather in the northern hemisphere. 95%+ of our members live in the northern hemisphere.

[charger105]

Yes, I think in hindsight, Pulsar would've chose not to put these sensors into the module. As far as I know they didn't use them in later modules.

It must suck having tornados brething down your neck certain times every year. Do you get them regularly in Michigan ?

I haven't worked on this module in a few days, I've been distracted by my Synchronar, which I finally got working. I might get back to it today.......I could be on a roll !

Any advice on what brand of silver epoxy is good, and where to get it ? One of the tubes of mine has gone hard. I could only find one source locally, and it was $80 for a pair of tiny tubes.

Rgds,
Andrew.

[retroleds]

It must suck having tornados brething down your neck certain times every year. Do you get them regularly in Michigan ?
Any advice on what brand of silver epoxy is good, and where to get it ? One of the tubes of mine has gone hard. I could only find one source locally, and it was $80 for a pair of tiny tubes.
Rgds,
Andrew.

Generally more of an issue 100-200 miles(200-300 km)west of me, where the land is much flatter and there is a huge lake(Lake Michigan) there. So this storm system came from the west. A good number of trees toppled over onto cars and houses, homes & business without power. And traffic lights not working, which is always fun - my middle finger hurts from saluting my fellow drivers .

www.mouser.com for your silver epoxy...$25-ish a set of those small tubes. I personally squeeze mine out into two small glass jars, as I feel the silver settles(and clogs the tube outlet) in the brighter colored "A" component. I use a lot, so I feel I waste less by occasionally stirring it with a toothpick then by squeezing blobs out of the tubes.