New project: Allen Engine analyzers, restoration?

[HWYCRZR]

Not much luck on the Photo- transistors. At least the TIL66, I am trying to do some research to see if I can find a compatible replacement. I may have to switch out both the IR LE and the Phototransistor's with a new matched set.

Here are the ones I have.

I also found a book from Texas Instruments with a 1978 copyright, that say do not use the TIL66 in any new projects. Page says revised November 1974 so likely out of production since the mid '70's

 

[3175375]

Not much luck on the Photo- transistors. At least the TIL66, I am trying to do some research to see if I can find a compatible replacement. I may have to switch out both the IR LE and the Phototransistor's with a new matched set.

Here are the ones I have.

I also found a book from Texas Instruments with a 1978 copyright, that say do not use the TIL66 in any new projects. Page says revised November 1974 so likely out of production since the mid '70's


View attachment 711661View attachment 711662

The book says to use TIL81.

appears to be available here: https://partstack.com/p/texas-instruments/til81/1435584916

And here:

TIL81,Texas Instruments ,OEMSEMI Electronic Components Distributor

 

[HWYCRZR]

The book says to use TIL81.

appears to be available here: https://partstack.com/p/texas-instruments/til81/1435584916

And here:

TIL81,Texas Instruments ,OEMSEMI Electronic Components Distributor

But I am hung up on the spec difference. And am wondering if they will still work with my Ifrared LED’s. Even with both data sheets I don’t know enough about these to know what matters.

 

[3175375]

But I am hung up on the spec difference. And am wondering if they will still work with my Ifrared LED’s. Even with both data sheets I don’t know enough about these to know what matters.

Post the data sheets here and I’ll review.

 

[MoPar~Man]

With the circuit powered up, are you able to see anything from the photo transistor (on pin 3 of the op-amp) when you shade and then shine a strong light on it? (preferably from an incandescent or tungsten bulb).

The data sheet says a tungsten lamp (color temp 2800 k) was used. It doesn't say the wavelength of light the TIL 66 is sensitive for, and the tungsten lamp puts out a lot of light in the visible and IR so that doesn't help much. Shining an LED flashlight at it might not work as well as using an incandescent. There are lots of suitable replacement phototransistors available, but it may be that to detect HC and CO you are going to need to know the correct IR wavelength?

 

[HWYCRZR]

With the circuit powered up, are you able to see anything from the photo transistor (on pin 3 of the op-amp) when you shade and then shine a strong light on it? (preferably from an incandescent or tungsten bulb).

The data sheet says a tungsten lamp (color temp 2800 k) was used. It doesn't say the wavelength of light the TIL 66 is sensitive for, and the tungsten lamp puts out a lot of light in the visible and IR so that doesn't help much. Shining an LED flashlight at it might not work as well as using an incandescent. There are lots of suitable replacement phototransistors available, but it may be that to detect HC and CO you are going to need to know the correct IR wavelength?

It likely had a little light sensitivity as the voltage seemed to go up minutely when it was shaded from the LED. Shining a bright light didn’t change anything. The photo transistor doesn’t read the gas, it is used as a switch with the chopper wheel being the switch that tells it to read either the sample tube or reference tube with different photo sensors. The photo transistor only reads the IR LED signal. The IR heat element is what projects the IR waves through the tube to the collation sensors.

 

[MoPar~Man]

If all this phototransistor is doing is getting a reading from an led through a rotating window and you're not seeing a decent signal on the op-amp output (pin 6) when the wheel is rotating (and the contraption is shielded from ambient light interference) then either the LED or photo transistor or op-amp is your problem. If you know the LED is IR type, and you know it's getting power, you're not going to see it light up with your eyes but most any camera will be able to see the IR. If you have a TV, stereo, etc, remote-control with LED output, point it at your phone camera and press a few buttons, see if the camera can detect the light to confirm your camera can see IR. Then see if your analyzer LED is putting out any light. Or shine the remote LED at your photo transistor and press a few buttons while scoping the signal.

 

[HWYCRZR]

Already determined the photo transistor is the issue. Now trying to find a replacement one that has been out of production since 1974. There is a video above that shows how I tested it to determine that the Photo Transistor is bad.

 

[HWYCRZR]

Here are the Data sheets for the Infrared LED emitter an the Phototransistor.

Monsanto Infrared Emitter ME 60 - tested and working

Texas Instruments TIL66 NPN Planar Silicon Phototransistor -one not working.

 

[MoPar~Man]

BPV11
Data sheet: https://www.vishay.com/docs/81504/bpv11.pdf
Digikey PN: 751-1003-ND ($1)

I'd buy that for a dollar.

 

[3175375]

Here are the Data sheets for the Infrared LED emitter an the Phototransistor.

Monsanto Infrared Emitter ME 60 - tested and working
View attachment 711720View attachment 711722

Texas Instruments TIL66 NPN Planar Silicon Phototransistor -one not working.
View attachment 711723View attachment 711724View attachment 711725View attachment 711726View attachment 711727

I will look at these.

Here’s a source for the TIL81:

TIL 81 TIL81 PHOTOTRANSISTOR DETECTOR KOREA NOS Vintage electronics | eBay

 

[HWYCRZR]

BPV11
Data sheet: https://www.vishay.com/docs/81504/bpv11.pdf
Digikey PN: 751-1003-ND ($1)

I'd buy that for a dollar

Thanks for a $1 and probably another $ 5 shipping, I may have to try it out. I may check out the TL81 @3175375 posted above as well.

So mine does not have the Base pin and is only 2 pin. In my online reading it says the base pin doesn't have to be used. Any thoughts on that?

 

[MoPar~Man]

Yea don't connect anything to the base. Might need to just cut it right off so it doesn't pick up stray static.

The options you're going to have with these are where the peak wavelength sensitivity is, and the radiation angle pickup, and that's a bit of a guess here.

 

[3175375]

Clip the base. Test circuit:

 

[HWYCRZR]

Thanks guys. I ordered 2 of the TL81 from Canada. The body looks a lot like my original and has a 25C higher temp rating than the plastic one from Vishay. Since it is in a higher temp area better safe than sorry.
Says a week to 10 days will see.

Its worth a shot, At least in that TI book it has the suggestion of what TI emitters work with the TL81 in case my Monsanto ME 60 doesn't excite it.

 

[MoPar~Man]

Choose the BPW77NA as a backup.
Digikey 751-1020-ND. $3.60

 

[HWYCRZR]

I got the Visas BPW77NA off Amazon yesterday. Soldered it in today. At first I didn’t think it was working, until I shined my light at it and saw the voltage change, but wasn’t picking up the IR LED. I staked the other LED on top and saw it open up (voltage change to around 15V) so hooked the voltage meter to it and started moving the phototransistor and moved it into place until I had 14.79 volts. Was pretty finicky. Was easy to get 12 volts, but to get above 14 was some real light adjustments. Didn’t fix my meter not reading issues but at least I know the sync signal is good and the chopper wheel is doing its job.
Here’s a video.

 

[HWYCRZR]

Question on capacitor testing. Do they need to be removed from the board to get an accurate reading? Or can they be tested on board?

 

[3175375]

Question on capacitor testing. Do they need to be removed from the board to get an accurate reading? Or can they be tested on board?

I believe that you have to remove one side to measure the capacitance.

 

[HWYCRZR]

I believe that you have to remove one side to measure the capacitance.

I did some reading and yes you should. You can use an ESR meter in circuit to measure the resistance. But I don’t have them yet. Since I ordered some new 10uF capacitors, and since I had to take them off to measure. I went ahead and replaced 13 of them that were 10uF. The old ones were labeled 10uF, but the schematics listed 10/15uF. All the ones I removed measured 15-17UF. So maybe not so far apart.