Deepstar 1

[Altra]

By SAT pot, do you mean the Threshold pot?
No SAT on the original Deepstar 1

Sorry I was using CSPI6 schematic as reference. If there is no SAT control, still check for 10v. That will tell us if it is the power supply or threshold circuit. It could be oxidized control pots? Try some contact cleaner spray and work the knobs back and forth to clean.

You are very fortunate, that unit is super clean for it's age!

[Octopulse]

All pots have been cleaned and rotate smoothly....values appear within spec but I am unsure of the Threshold pot as I was getting just over 7 kΩ between outside contacts. Rotating pots gives a changing range when the wiper is tested.
I have some photo's uploaded....but I am unsure which op-amp to check. Thanks.

[Altra]

....but I am unsure which op-amp to check. Thanks.

You can check any of them. The only one I can read in your photos is the 5534. There should be 10v between pin 7 and 4. This will verify if the power supply is good.

[GeoMax]

Hello Octopulse and Altra,

The original first version of the Deepstar 1 did not have a SAT potentiometer. This was added later by Eric Foster. The version Octopulse has is the one without the SAT potentiometer and power amplifier switch. However, it is quite easy to retrofit the SAT potentiometer by replacing the fixed SAT resistor on the board with a series resistor and a potentiometer connected in series. I have seen this setup on revised Deepstar 1 PCB images.

[Octopulse]

Some testing today....should I be concerned about the 555's. The 5534 looks okay.
Just need to rule this out as a problem before going forward.
Thanks.

[kt315]

nothing on this detector. just one picture.

[Altra]

Some testing today....should I be concerned about the 555's. The 5534 looks okay.
Just need to rule this out as a problem before going forward.
Thanks.

That's good you have 9.75V on the NE5534. This means your power supply is okay. The problem is probably around U8 which is most likely a TL062? This is the threshold and SAT circuit. There is a J113 jfet transistor which clamps negative voltage swings and resets the threshold. If the reference voltage is out of whack it will mute the audio. The blue trimpot next to the word "setup" may be an adjustment for the SAT clamp? You could try adjusting this to see if it restores the audio. I would mark the the current setting with a marker before moving. If you don't have an oscilloscope or working knowledge it will be tough to repair. Good luck...

[Octopulse]

That's good you have 9.75V on the NE5534. This means your power supply is okay. The problem is probably around U8 which is most likely a TL062? This is the threshold and SAT circuit. There is a J113 jfet transistor which clamps negative voltage swings and resets the threshold. If the reference voltage is out of whack it will mute the audio. The blue trimpot next to the word "setup" may be an adjustment for the SAT clamp? You could try adjusting this to see if it restores the audio. I would mark the the current setting with a marker before moving. If you don't have an oscilloscope or working knowledge it will be tough to repair. Good luck...

Thank you for the update......what you describe sounds very much like the problem. I don't have a working knowledge or necessary test equipment which is a shame for me. If you have the time, could you possibly highlight the parts in question on one of my photo's from earlier. I am going to replace the potentiometers as I feel they are out of spec....can I assume that no PCB calibration is needed by changing pots ?

Any thoughts on the three LMC555 values that are attached few posts up.

Appreciate your help...

[Carl-NC]

It's next to impossible to troubleshoot a circuit blindly. Is there a schematic floating around for the Deepstar, or something known to be close to it?

[Octopulse]

That's good you have 9.75V on the NE5534. This means your power supply is okay. The problem is probably around U8 which is most likely a TL062? This is the threshold and SAT circuit. There is a J113 jfet transistor which clamps negative voltage swings and resets the threshold. If the reference voltage is out of whack it will mute the audio. The blue trimpot next to the word "setup" may be an adjustment for the SAT clamp? You could try adjusting this to see if it restores the audio. I would mark the the current setting with a marker before moving. If you don't have an oscilloscope or working knowledge it will be tough to repair. Good luck...

I see where you mean from one of my PCB pictures.....thank you.

[Octopulse]

It's next to impossible to troubleshoot a circuit blindly. Is there a schematic floating around for the Deepstar, or something known to be close to it?

Agree completely.....at this stage, I am only focussing on determining any faulty components.....and treading carefully in the darkness.
I wonder where Eric stored all his schematics....I hope they didn't go with him

[Altra]

I wouldn't change the pots yet. When connected to the circuit they rarely read the correct values. As a last ditch effort try adjusting these trimpots . Make reference marks with a felt pen on the sides of the pots. This will let you return the trimmer to the original setting. Turn your threshold pot to full then adjust each trimmer to see if you can get audio.

[Octopulse]

Thank you Altra.....I will try these tests next. Can you comment on the readings I got the LMC555's......I was under the assumption that all pins should give a voltage reading and none should read open loop......but interestingly it is the same across all three that I tested.