Mr Bills Mod Help Please.

[keith777]

Hi again guys.

i am doing the Mr bills mod to a Whites Classic 3. i have done the mod before to a Classic 2 and all went fine. on this machine the Threshold doesn't work. all i get when i use the trigger switch is a consent loud signal tone no matter wear i adjust the potentiometer. before i took off the original small blue oblong potentiometer. it did the same thing. before i did anything to the machine it had a fixed Threshold. i assumed once i swopped it with the new 100k potentiometer. i would be able to adjust the Threshold like i could on the Classic 2
any ideas guys. any help would be so much appreciated.

[kt315]

can you show your pcb? i want to see a number of series. whites used through numbers for whole pcbs.

[Carl-NC]

I can't find my mod schematic, you'll have to show me what you're doing.

[keith777]

I can't find my mod schematic, you'll have to show me what you're doing.

no bother. i will take some photos some time today. this is the instructions same as ones as i used on the Classic 2 model.


Instructions

Remove VR1 Trimmer off the board. Replace with a 50k linear taper, single turn potentiometer. (Ground balance).

Remove VR4 trimmer off the board replacing it with a 100k linear taper, single turn potentiometer. (threshold).

Mount these potentiometer?s externally on the top of the case.

Replace resistor R24 with a 2.2 Meg. You could have either a 470k or a 1.5 Meg there depending on when the unit was manufactured.
Check resistor R7. If it?s not a 51 ohm resistor, replace it with one of that value. It?s most likely a 100 ohm from factory. Later manufactured units had 51 ohms.

For potentiometer wiring, I use flat multi wire such as type used in computers for component connection to the board. I cut a 2 wire, 7.5? piece for the 50k ground balance pot, and a 3 wire
7.5? one for the 100k threshold pot. I secure these wires with a wire tie to the head phone & speaker wire near the connectors. I used one other wire tie to secure the pot wires together up near the pots.
Caution. Be sure that the pot closest to the end of the case doesn?t short out against the installed board components.

S.A.T changes. R32 220k resistor can be changed out. Raising the value slows the SAT. I have been installing a 375k running it through a toggle switch with the 220k. Giving a high & low setting of the SAT. One could use a potentiometer for variable results.

[Carl-NC]

I have these instructions but my Classic schematic did not have a VR4 trimmer. I just found a newer Classic schematic that does. So before you removed the trimmer did the unit have a reasonable threshold in AM mode? Did you check to see if the trimmer altered the threshold? If the problems began when you replaced the trimmer with a pot then I would revisit the pot wiring. The wires might be swapped.

[keith777]

firsti replaced the VR1 Trimmer with the 50k potentiometer. i i couldn't do the VR4 trimmer next as i was still waiting for the 100k potentiometer coming in the post. so i next replaced the R24 resister with a 2.2 Meg one. then i did the S.A.T. switch. before i remvoed the VR4 trimmer off the board. i did test the machine and the detector didn't have a fixed threshold any more at this point. which i did think was a bit strange. i assumed once i swapped it with the new 100k potentiometer. i would be able to adjust it.

[keith777]

here is some photos guys as promised. not perfect but i tried my best. it defiantly looks the part mind in pic 0. pic number 1 is before i even did anything to the board.

[Carl-NC]

Can you show a pic of the threshold pot (back side)? Try putting a voltmeter from the center lug of the threshold pot to ground. It should vary from 0V to 0.85V.

[kt315]

505-0210-D revision board.
not Bills mod. just a mod. thx for the pics.

[keith777]

Can you show a pic of the threshold pot (back side)? Try putting a voltmeter from the center lug of the threshold pot to ground. It should vary from 0V to 0.85V.

is this what you needed to see.
when i bought the B100k potentiometer it came as a pack of two. i have checked the resistance of both of them. one measured 74 and the other 85 ? i tried each of them on the board, but neither make any difference. ware is MR Bill when you need him.lol

[kt315]

the pot.

[keith777]

so does anyone think they may know what the problem may be with the threshold not working. has anyone else had this problem before when they have done the mod to a Classic 3

[Carl-NC]

So far I don't see the problem. Pots are often 20-25% tolerance so the values aren't surprising and should be OK. Again, try measuring the voltage at the pot's center lug.

[keith777]

So far I don't see the problem. Pots are often 20-25% tolerance so the values aren't surprising and should be OK. Again, try measuring the voltage at the pot's center lug.

Hi again Carl.
i have tested the voltage on the pot. it was measuring from 0v to 0.55v the battery is only showing at 11.24v due to using it over the last two day on testing. it has got me stuck on what i can do. every thing else works fine just i have no all metal mode with a loud constant tone. plus no working threshold. i followed the mod steps which are not that many to be honest. which i did to a classic 2 once before. that all went strait forwards, but this machine just wont have it.

[kt315]

connect 6 pin of U5 on GND (lower pin of R32, C18 etc). disconnect C16. measure voltage on 7 pin U5 and write the value
and do you hear a sound or not, in ALL METAL mode.