baracuda rev A silverdog bad performance

[nonkapo]

Yes, thats exactly the case i think. Does it matter which setting the pot is on?

[waltr]

Hmz, yeah, but than we have no coolprit for the bad performance....accept the coil again?!?
Please look at the pics below. Measurements done at 2V/div & 20uS/div ,50uS/div for SSD and 10us/div for MSPW. Regarding the behaviour i'll try to upload video on youtube soon. Unfortunatelly i have no us nickel in hand.

The Tek 453 is a Dual trace scope. So I would like to see the Sampling pulse on second channel and the trace of your DMP image that looks to show the Pre-amp output.

What to look for is the first Sampling starts near the end of the rising coil decay.
Then look at the second sample timing which should take place a bit later.

Also while looking at the pre-amp output (DMP image) move a metal object near the coil and you should see the shape the the decay curve change. It will not change by much but should be see-able.

[Andi68]

The last photo - at which point was there measured?

[nonkapo]

Hmz, yeah, but than we have no coolprit for the bad performance....accept the coil again?!?
Please look at the pics below. Measurements done at 2V/div & 20uS/div ,50uS/div for SSD and 10us/div for MSPW. Regarding the behaviour i'll try to upload video on youtube soon. Unfortunatelly i have no us nickel in hand.

[Qiaozhi]

Impression is MSP is wider than the SSP marginally and SSD is 60us wider. What do you think about that?

As it says in the Build Document:
"Due to the way the Baracuda generates the sample pulses, there is some variation in sample width between the main and EFE samples as the sample delay is adjusted. However, this doesn't appear to produce any real problems in practice."

[nonkapo]

The photos are ready but i have no time to upload now so will do later. As per what i see and as far as my Tek 453 is calibrated properly i have the following:
MSdelay U4 pin 6 20us wit PL2 at 0ohm;
MSpulse width U4 pin 10 45us;
SSdelay U4 pin8 460us
SS pulse width 43Us
The 5534 offset despite adjusted with multimeter seems ok on the scope too. Damping looks ok as well.

Impression is MSP is wider than the SSP marginally and SSD is 60us wider. What do you think about that?

[nonkapo]

Thanks for the response,however i can only confirm the sample width. It changes when i'm turning both the trimmer and the pot. However, due to the triggering i can see only one sweep(or i'm a noob and don't know how to do it properly). Meantime the coil is not suspect any more as on the surf it gives if not decent at least better performance than the mono coil from magnet wire.

[Qiaozhi]

Seems I get in to similar issue. Detector is working but the dept is low. When doing step by step I did not manage -2.1 volts and thinking it may be mistake I set it at +2.1. Will post osciloscope pics soon. It's a bit hard to measure the delay when not triggering. Sample pulse width looks more or less accurate. There might be something wrong with my scope though(born circa 1960-1970).

If you have an oscilloscope, then you should adjust R14 as described in step 6. The dc level adjustment of -2.1V in step 7 is only a rough guide to get you into the right ballpark. R14 sets the minimum sample delay, and getting this adjustment wrong could easily result in poor depth.

[nonkapo]

Seems I get in to similar issue. Detector is working but the dept is low. When doing step by step I did not manage -2.1 volts and thinking it may be mistake I set it at +2.1. Will post osciloscope pics soon. It's a bit hard to measure the delay when not triggering. Sample pulse width looks more or less accurate. There might be something wrong with my scope though(born circa 1960-1970).

[rdz28]

I do not understand why

[rdz28]

copper does not find it

[kt315]

of 1 cent European to 10cm
---
euro cents 1 2 5 are ferrous metal. NOT COPPER.

[rdz28]

volume low at 17 cm and 12 cm high

[rdz28]

guys I have updates, r14 I tried to adjust it by ear, now I find myself with search depth of 1 cent European to 10cm and a 17cm silver ring.. Now can I lower the damping resistance value from 330 or leave it like this?

[Andi68]

If it does not supply clean DC voltage, this can lead to disturbances