New project: Allen Engine analyzers, restoration?

[HWYCRZR]

I think I found and amplifier issue, but I need to check a couple of things down stream. Amp 301 and 302 should have the same readings as the circuits are twins that are run off each of the phototransistors. Both inputs are the same, but the output of pin 6 on amp 302 is only -14V with no PpV. Pin 6 on 301 is 28.8Vpp which is correct. Considering all inputs match and grounds good I am suspecting that the 302 amp is bad.
I do need to check a couple of diodes upstream. But pretty sure that may be my next fix.

 

[3175375]

I think I found and amplifier issue, but I need to check a couple of things down stream. Amp 301 and 302 should have the same readings as the circuits are twins that are run off each of the phototransistors. Both inputs are the same, but the output of pin 6 on amp 302 is only -14V with no PpV. Pin 6 on 301 is 28.8Vpp which is correct. Considering all inputs match and grounds good I am suspecting that the 302 amp is bad.
I do need to check a couple of diodes upstream. But pretty sure that may be my next fix. View attachment 712231View attachment 712232

Looks like you’re close to finding the smoking gun. Good work!

 

[HWYCRZR]

I broke down and bought a cheap ESR meter to test the capacitors in circuit. (I already replaced all the 10uF ones). And I found a couple of bad capacitors. Good news is that I ordered the remaining sizes Sunday and they should arrive tomorrow.

 

[MoPar~Man]

I own several capacitance and inductance meters, but not an ESR meter. I am scratching my head over your use of it here. ESR is more important for caps that handle large current flows, such as in power supplies or speaker cross-overs. If you suspect that an electrolytic cap is bad, test it's capacitance first, clip one leg (if axial type) so it can be tested while "not in circuit". A little harder to isolate one leg if radial type.

 

[HWYCRZR]

This supplies a little square wave power through the capacitor to to measure the impedance. This one references based on 25volt but can do different voltage. When I pull out the two that it’s telling that they are bad I will test it out of Circut and see.
I was searching info on testing capacitors in Circut and found this. Seems quick and easy.

 

[HWYCRZR]

Waiting for more parts on the exhaust analyzer. I replaced the bad amplifier and now have the correct pattern and my CO gauge moves now. But not HC. The nice thing is they’re twin circuits so can compare. I found a resistor that was shorted. R201 is supposed to be 249K 1% per the schematics but the actual on the board which is likely original is 261K. Found them and the “hi performance” Raytheon amplifiers online so am waiting for them still. One part at a time, I keep going through the circuit until I hit the next roadblock. I did also replace all the capacitors.

 

[HWYCRZR]

While waiting for parts for the exhaust analyzer, I decided to try and replace my timing amp dwell gauge that snapped the needle. I already charged out voltage meter with the one from the blue machine as the rating on the gauges were the same. However for my amp gauge it is labeled differently.
My original says FS=1ma. Whereas the gauge I want to replace it with says ES=182-818 ua. Can I assume correctly that this may not work due to the rating. I am not too familiar with gauge ratings.
I would like to replace the needle, but not sure if that is possible. Easier to switch the gauges and keep the original face.

 

[HWYCRZR]

After some research I think the ES= is a mistake and maybe should be FS=. Google didn’t do very well with ES. So if it is FS=212 - 818 uA and my other gauge is FS=1 ma which equals 1000 uA. Then they are not that far apart. The internals look identical, but I didn’t count the windings I am going to try it. My other choice is to learn how to rebuild a graphite needle. I don’t think my hands are small enough or have the dexterity to try.

 

[3175375]

After some research I think the ES= is a mistake and maybe should be FS=. Google didn’t do very well with ES. So if it is FS=212 - 818 uA and my other gauge is FS=1 ma which equals 1000 uA. Then they are not that far apart. The internals look identical, but I didn’t count the windings I am going to try it. My other choice is to learn how to rebuild a graphite needle. I don’t think my hands are small enough or have the dexterity to try.
View attachment 714736View attachment 714737

I’m glad that you discovered the range of the two meters is close.
Looks like you are making great progress! Keep up the great work!