Surf PI Pro

[6666]

Found a picture of pcb, this mysterious 12 ohm resistor is in audio cct
make sure you match the legs of mpsa13 b=b c=c e=e

[gojo1]

helppp now I have 5v on pin 6. replaced and still the same.

[Thomas]

Ok, now I see

[6666]

2 in series, paralleled with another 2 in series will also give 1 watt, the dissipated power adds up

[diplodus]

i am working on this pcb provided by Apberg

its the resistor on top of NE5534 and C3 it does not say its 1W but in this board its 12 ohm 1W

i used [2 in series 12 ohm 1/4W] IN PARALLEL with [2 in series 12 ohm 1/4W], so i can get 12 ohm 1W resistor but if power rating adds only in parallel the result will be 12 ohm 1/2W.
thanks for the help 6666 and Thomas

[6666]

thank you 6666 for your replay
what about the 4x1/4 W resistors will that give 1W power rated resistor?
another thing when powering up the board, are there any precautions to take so nothing gets burnt? should i put the trimmers to the highest resistance or should i leave them at the middle?

What schematic are you working from ?
Well 4x1/4 WATT in parallel = 1 watt
with powering up the board first time I would remove all chips, power up and take a few DC voltage readings, plug in 7660, measure the + and - 5 volts at each socket
if all ok and no smoke, replace the chips one by one, turning the power off each time of course., and power up
then adjust the dc off set on 5534 for 0.
rest of trimmers on maybe middle to start and work from there.

[Thomas]

"4x1/4 W resistors will that give 1W power rated resistor" How?, That looks like trouble to me. 4x 12 R parallel = 3R. 4x 12 R in series = 48R@ .25W Not sure what the 12R@ 1W is for, could you post a pic of the SCH where it is located.

[diplodus]

thank you 6666 for your replay
what about the 4x1/4 W resistors will that give 1W power rated resistor?
another thing when powering up the board, are there any precautions to take so nothing gets burnt? should i put the trimmers to the highest resistance or should i leave them at the middle?

[6666]

Match the pins of the BC517
8v could be a bit low for testing, but try it.

[diplodus]

update

yesterday i soldered components on the board (except tlc555 and R6), but i noticed that the BC517 transistor must go the other way round to match the schematic so it would be great if anyone could confirm that because paku did the same error with his board, unless he used a different transistor with different pinout (MPSA13).
this is the board if anyone can help (please check also the IC's if they are correctly positioned ):





another thing, i used 4x12 ohm 1/4 W resistors to get 12 ohm 1 W, its a little bit ugly but i hope it will get the job done.
another question, can i use a phone battery charger with about 8 v in the output just to see if the board is working when finished? i used that for the BFO MD and it worked.
sorry for my English, i am not a native speaker

[gojo1]

hi all, I have just recently bought a smpro 3 and all-tho it went together nicely and did appear to be working, with diy coil. it does have an issue, the thing keeps beeping it is not a constant hum. I had set the pin 6 to 0v and played with the offset but for the life of me I can't stop it beeping.
If I adjust the delay knob to max I get no detection, min is only detection.
Threshold is nearly to max to stop most of the beeping.
gain was at full and did try different rate but to no real difference except for detection height.

Any help would be greatly appreciated.

[diplodus]

now they are working

[6666]

attachments now work

[diplodus]

update

i waited about a month to get the components i ordered from tayda (and i am not complaining since its very cheap and Thailand is VERY far from where i live ), but i am still waiting for TLC555 which i bought separately from ebay but didn't receive it, so i had to reorder from another seller and wait again. Meanwhile i made a BFO metal detector (http://www.easytreasure.co.uk/bfo.htm) and its working ! i can detect a coin from about 13 cm (about 5 inches) and a 20 cm (8 inches) metallic dish from 40 cm (16 inches).
i used toner transfer method and this is how my pcb looks:

after etching:

populated board:


for the surf xx, today i etched my pcb after some modifications made to the layout ( i made the lines thicker ) and i will start soldering tomorrow.
i used hydrochloric acid+hydrogen peroxide to etch the board, a very effective combination i used before to make CuCl2 (WARNING! the reaction can be very violent and heat emitting, the plastic container i used the first time i made CuCl2 melted just after adding copper to the mix, so be careful if you use it to etch your boards, always use non concentrated chemicals and add them in small amounts and always add acid to water not the opposite)
after etching:

cleaning:

result:


i will post a video of the BFO MD soon and hopefully surf xx too.


layout with thicker lines in pdf format if anyone wants it (its ready to print no re sizing needed 98.4 x 66.7 mm).
Surf XX-layout.pdf

[paku]

what i can say this detector is good for beach salt water