Deepstar with new capacitors

[Octopulse]

I have finally finished my overhaul of the Deepstar 1 detector. The detector now runs very well and the circuit feels more responsive and performance has increased.
I replaced all 12 electrolytic capacitors (as well as new potentiometers) which were now over 28 years old. Some older caps had leaked a small amount of black "tar" but they all came out and I gave everything a very good clean with isopropyl alcohol before and after replacing with nice new Japanese caps.

Now to my question........When I power on the detector (from a cold start), there is no audio for about 2-3 minutes. After this time, the detectors audio kicks in and operation is perfect. If the machine has been running for 10-15 minutes then an ON/OFF cycle will have the machine fire up straight away. Do these capacitors need "forming" or a break in period before things become normal. I only have about 2-3 hours run time so far on these new caps. All caps have exact same specifications as the old ones except rated to 105C. All capacitors have correct polarity and well soldered.

I was curious to know if the NE3354 needs calibrating for any DC bias (as a result of new caps)?

Thanks for any ideas.

[GeoMax]

Hello,

It's possible that a semiconductor component (IC, diode, transistor, etc.) is faulty and needs to reach its operating temperature. I would also check on the new inserted capacitors to be sure. To locate this component in the circuit, I would apply freeze spray (for electronics) to each component one by one and check if the audio tone changes. If the audio tone disappears when a component is sprayed with freeze spray, I would replace that component and then check if there are any other such components in the circuit.

[Octopulse]

Hello,

It's possible that a semiconductor component (IC, diode, transistor, etc.) is faulty and needs to reach its operating temperature. I would also check on the new inserted capacitors to be sure. To locate this component in the circuit, I would apply freeze spray (for electronics) to each component one by one and check if the audio tone changes. If the audio tone disappears when a component is sprayed with freeze spray, I would replace that component and then check if there are any other such components in the circuit.

That is some great guidance.....all I know is that when the circuit is fully warmed up then there are no issues when switching off to on.
This problem wasn't around when using the older (and mostly dead) caps ?

[pito]

12 electrolytic capacitors = you change them = they have a problem, check which one is charging slowly especially those with large volume, if you find that tell as

[nejdet]

Could it be that you have a capacitor installed the wrong way around by mistake? Check the polarity!

[Octopulse]

I double checked all caps prior to soldering and even after installation. All polarities are correct.✅

[Octopulse]

12 electrolytic capacitors = you change them = they have a problem, check which one is charging slowly especially those with large volume, if you find that tell as

I will check the main 4700uf and 1000uf

[Carl-NC]

Some Foster designs have an audio blanking circuit gated with an RC circuit that enables the audio when it charges past a threshold voltage. Usually a few seconds, to prevent a big audio blast on start-up.

[GeoMax]

Some Foster designs have an audio blanking circuit gated with an RC circuit that enables the audio when it charges past a threshold voltage. Usually a few seconds, to prevent a big audio blast on start-up.

Hi Carl,

With my Deepstar 1, audio is available immediately after switching it on. It doesn't matter whether it's a "cold start" or not. Do you perhaps have an example or circuit diagram where Eric Foster incorporated a blanking circuit like the one you described into his detector? Or maybe another example from another detector?

[Detectorist#1]

Hi,
Where is published the schematic of Deepstar 1?

[Altra]

Hi Carl,

With my Deepstar 1, audio is available immediately after switching it on. It doesn't matter whether it's a "cold start" or not. Do you perhaps have an example or circuit diagram where Eric Foster incorporated a blanking circuit like the one you described into his detector? Or maybe another example from another detector?

Here's an example

The GS5 had a power on muting circuit. In the schematic look for the CD4001 quad nand gate. The early TDI had something similar. The GS5 schematic has a mistake in the DC to DC converter. One of the diodes is connected wrong.

[Octopulse]

Caps are good….Could it be that the new capacitors require something in the chain to be recalibrated such as the NE3354. It does feel like there is an audio clamping going on and at some point unlatches and the detector runs just fine. The detector performance after its warm up phase is better since the old and leaky caps were replaced. All new caps meet original specs except one or two that are rated to 25V instead of 16V. I might run the detector for 4 or 5 hours continuous and see if that has any benefit. Thanks for the replies.

[Octopulse]

On the NE3354…..tested Pin 6 to ground and got 1.36V. Online resources suggest this value is too high and should be below 1V. Please excuse my limited technological know how in these matters. I am mostly an end user of detectors but like to try and know how things “work under the hood”.

[pito]

Caps are good

That we know they are new yet behave in the described manner, this indicates that one of them is charging slowly not due to a defect, but because of insufficient charging current—caused by oxidation at a solder joint. To identify the specific joint, you need to locate the capacitor or resistor and touch the solder connections with the soldering iron tip to reflow the solder.

[Octopulse]

That might be worth doing. I was very careful soldering….tiny dab of flux on each capacitor leg then cleaned with IPA before and after. Checked all my work after under magnification but an error could be possible?