Deepstar with new capacitors

[Octopulse]

I remember that the detector fired up immediately on the very first switch on after the caps were replaced so that adds a bit of confusion as well.
Another option is when I get to the beach, I can turn on the detector and drink just one cold beer and then the detector will be ready to go

[pito]

That might be worth doing. I was very careful soldering

= not new soldering bat the old ones can be oxidized

[eduardo1979]

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.

Hi Octopulse. Did you check the +5V and -5V voltages? Measure those voltages with respect to ground at pin 4 and pin 7 of the NE5534. It's possible the charge pump isn't working properly and isn't supplying the negative or positive voltage. If so, you should carefully check the charge pump's capacitors, diodes, and transistors (if present). You should start there.

[Octopulse]

Hello Eduardo,

Before the audio kicked in = 0v

After the audio kicked in;
Pin 4 = - 4.85v
Pin 7 = + 4.89v

Looks okay.....interestingly, the detector only took 30 seconds to fire up this time.

[eduardo1979]

So it's clear it's the detector's ON/OFF switch. It probably has some rust inside and isn't making good contact.

[GeoMax]

There could also be contact problems with the battery holder or the battery connection itself.

[Detectorist#1]

According my long practice, contact problems with the batteries' connectors as result of leakage of the liquid are not rare, especially for old devices with long time rest inside elements.

[Octopulse]

So it's clear it's the detector's ON/OFF switch. It probably has some rust inside and isn't making good contact.

Brand new ON/OFF potentiometer

[Octopulse]

There could also be contact problems with the battery holder or the battery connection itself.

I will take a closer look….New LED voltmeter shows good voltage/connection when battery plugged in.

[Octopulse]

According my long practice, contact problems with the batteries' connectors as result of leakage of the liquid are not rare, especially for old devices with long time rest inside elements.

I have a new 4 x 3.7v Lithium battery

[pito]

New LED voltmeter

not good = Use oscilloscope in DC mode to observe DC voltage changing

[Octopulse]

I don’t have an oscilloscope but the mini LED voltmeter only draws about 15mA so “shouldn’t” be causing an issue?

[pito]

https://www.sillanumsoft.org/en/index.html , on LED voltmeter you can't see that, on this yes

[GeoMax]

Have you tried removing the LED display? Just to make sure that's not the cause of the problem. It's a quick job.

[Octopulse]

Did I cold solder the potentiometer eyelet ?

I took another look at the new On/Off Threshold potentiometer that I installed and thought to myself one of those power connections on the back of the potentiometer looked like I could do better. I checked the continuity and it was okay but I decided to reflow the solder and "fill" the eyelet. I also did this on the wiper connection seeing as I had the iron out and it was only seconds of work.
Anyhow.....the detector hadn't been switched on since yesterday and amazingly it fired up immediately with a good strong audio. I have since switched it on/off multiple times and (so far) can't replicate the audio delay problem that I haven't been able to solve.
I Googled whether those eyelet tabs need filling with solder and it appears the answer is YES for a full electrical signal to be delivered as well as the mechanical strength.
Early days but maybe that was the problem all along.
I really don't want to be known as a "cold solderer"......it fills with me deep shame and unworthiness I shall see how things work out and whether the problem returns or not.
Please be kind to me and hopefully Carl won't ban me from the forum....although he is well within his rights to do just that.