Delta Pulse

[paku]

i have finish my DP but when i turn on my speaker silent
but i get sonic wave sound from my coil what its happen

[calebsone]

BC237 BC238 BC547 BC548

[paku]

this is My DP can someone explain this board
im missing one BC546 what i can use for replacement

[calebsone]

you know ill make a video this weekend i should have. it still has good range on coins and the silver bracelets i have been using over 30cm so far and i am still learning to set and use it. as far as the mods for coins im going to try to use sockes and test resistors last thing i want is to have to shield a coil because i already potted it.

[kt315]

very nice job Calebsone! anyone there had made the DP, wow... =) keeping the pics in special folder... thank you. waiting a video now... =)

many people wrote about how to retune DP on coins hunting via R7 and C5 decreasing... but not able to find those posts right now - geotech is not indexed in google, the moderator does not see that the forum engine was hacked.

[calebsone]

Ok heres some pictures of it working and dont laugh its the best I could do

[calebsone]

so if i lower R7 to 10 or 12 k is that good or you think 5k only wondering if you know if not ill test a few different values tomorrow .oh im done building the box and stick and coil so next sunny day i will take pictures.

[seadoggy]

ok thx alot

[porkluvr]

yea set in place of 4538,because i cant find cd 4538 in my place

Some other alternatives for CD4538 (actually CD4538B, but "B" is "understood" would be:

CD14538
MC14538
HCF4538
HEF4538

One thing you should be wary of is that these substitutions are not necessarily exact replacements. They do have the same pinouts and same timing formula but may have restrictions on the minimum value(s) for R and/or C that can be used. That equates to a minimum time delay that can be squeezed out of them.

For instance, HCF4538 needs minimum RC values of 4kΩ and 5nF and can give you a minimum delay of 20us according to its spec sheet. (I only found this out after I had already bought a couple dozen load of them.)

Either MC14538 or HEF4538 minimum delay would be 10us, but for slightly different reasons.

CD4538 and CD14538 have no such lower limits and should be your first choice.

So long as you use any of these parts for the unmodified Deltapulse there is not a problem because DP minimum delay is greater than 20us.

CD4098 and CD4528 also have same pinouts but those would require a modification of the RC components because their internal circuits are different and give different tc for the same RC component values. Use as a last resort (?!)

[kt315]

not possible. forget. try to find boards from oldest VGA, SVGA monitors (CRT type monitors), there are 4538s. I take its from the trash.

[seadoggy]

what you mean? directly to set 4047 in place of 4538 or what?
4538 is dual multivibrators, 4047 is mono. 16 pins vs 14 pins housings - pins-un-compatible.

yea set in place of 4538,because i cant find cd 4538 in my place

[kt315]

what you mean? directly to set 4047 in place of 4538 or what?
4538 is dual multivibrators, 4047 is mono. 16 pins vs 14 pins housings - pins-un-compatible.

[seadoggy]

hello guys!can i replace CD 4538 with CD 4047??

[kt315]

Um KT what is the resistor in the mod on post 2645 is it a 15k like the one it cuts off or something smaller just wondering.

R7+DISC 50K are related to PRIMARY SAMPLE DELAY 40-160 us value operative tuning. 40us is minimal value and limited by only R7 (DISC pot is at left, counterclockwise position, zero Ohm). if you want to retune DP to small targets like gold nugget you have to decrease this 40 us to maybe 10...15 value. so you have to reduce R7.

also in addition to above you have to tune damping resistor R5 more accurately. to small value.

[calebsone]

Um KT what is the resistor in the mod on post 2645 is it a 15k like the one it cuts off or something smaller just wondering.