So I just finished up the low rider build. had a few problems with the board creating traces between two components, or maybe it was me revealing a trace that was already there. anyway, I had components making contact, but the schematic showed they were supposed to make contact so that was okay. does anyone know what i'm talking about here? i got like a little silver trace in between two resistors in places I had to desolder components.
here's the real problem... this is my first build with PCB mounted pots. I got the short ones from mammoth and as I began to mount them on the board- they are showed on the drilling template that they need to be mounted back over the top of the board. i took this to mean the pots on top of the component side of the board. this did not work well at all! there's a big 14 pin chip with a socket right below one of the pots, and even the trim pot forced me to lean the pot forward. so now all the pots are leaning forward and the board definitely wont fit into a 1590bb.
Can i install the pots so they're hovering over the trace side of the board? How am I supposed to know in the future? there's no numbering on this build pdf or anything! I'd really appreciate some insight on this
Hey there- sorry you are having troubles- I'm sure the folks here can help you sort them out.
If you could link some pics that would be helpful. You can post them on Flickr or Picasaweb (google) and insert the links or just link to the external pics (easier but pics wont show here in the post)
C
The pots are supposed to be mounted on the solder side of the board. The pot holes are labeled in the doc.
Quote from: Loztboy on January 31, 2012, 10:39:15 PM
The pots are supposed to be mounted on the solder side of the board. The pot holes are labeled in the doc.
thanks man! I woulda never saw those tiny little numbers there
claytushaywood ,
I'm sorry that you've had a frustrating time with the build. For future reference: all the MBP projects that allow for PCB mounted pots are fitted underneath the PCB. I could have more explicitly stated this in the document, but I relied on the pot numbers on the silkscreen in this case. I will try to remember to state that more clearly in future documents.
I'm a little unclear as to what you are describing in the first paragraph as far as the "board creating traces between two components". Can you clarify that a bit more?
Check out this cool idea for using normal pots in a board mounted style... props to Lacesensor
http://www.madbeanpedals.com/forum/index.php?topic=3222.0 (http://www.madbeanpedals.com/forum/index.php?topic=3222.0)
thanks for the help guys... that tutorial is actually what i was gonna do with the .50 cent tayda pots originally, then i was thinking about sanding down the pins to fit into the holes on teh pcb.
now, i started trying to desolder the pots from this board, and for the life of my i cannot get all of the solder out. I absolutely cannot get them out, i already broke one pot in the process of it, i've had problems desoldering anything on this board really though. i'm in fear of losing my whole board. I might have to cut off the pots and try to jerry rig the other ones through... if only i had 4 right hands and 3 soldering irons
anyone got any tips on how to do this without ruining the board. i am really fearing im screwed at this point, never had this much trouble desoldering
You need a desolder pump or solder sucker... heat the join then suck it out. Be careful with the board, the right tools and patience will mean you can desolder a number of times no problem... good luck
here's a video demo
http://www.youtube.com/watch?v=Aw4lZGk90i4 (http://www.youtube.com/watch?v=Aw4lZGk90i4)
I find it easier to cut off the pins before removing pots. rather lose a couple bucks in parts than the whole board. plus the pots can be used again lug style.
oh i have a solder sucker which i use most of the time without a problem, i busted out the desoldering braid and desoldering iron with pump for this with no avail!
Oh bummer, I hate those tricky spots.... :(
Sometimes if you reflow the joint with solder and start again it can come loose. Also you can try using a toothpick to poke out any fragments in there while the joint is heated by your iron. Even if you tear up a pad you can save the pcb, don't give up.
Good luck
Quote from: lloyd17 on February 01, 2012, 04:40:33 AM
I find it easier to cut off the pins before removing pots. rather lose a couple bucks in parts than the whole board. plus the pots can be used again lug style.
do you cut off the tabs from the bottom and top? i was thinking i could do that then maybe somehow poke something through the holes while applying heat to clear them out. could you explain a little more, tricks are definitely welcome, id hate to lose such a large board
Quote from: nzCdog on February 01, 2012, 05:11:10 AM
Oh bummer, I hate those tricky spots.... :(
Sometimes if you reflow the joint with solder and start again it can come loose. Also you can try using a toothpick to poke out any fragments in there while the joint is heated by your iron. Even if you tear up a pad you can save the pcb, don't give up.
Good luck
nice! reflowing solder seriously crossed my mind 5 minutes before i read this, must have caught it in the universal subconciousness. those are exactly the kinda tips im looking for.
i was thinking that it has been more difficult to resolder lately, not just on this board now that i think about it. ive been using a hotter setting on my iron and a lot less time heating the joint. i also switched from plain 60/40 to solder with silver content. which has been great for drying quicker and the higher heat has really kept my component heating to a minimum (i also use a heatsink clip where possible) but i have been putting transistors in without sockets where i want to and not using sockets on diodes or chips with 100% success, until it comes time to desolder a wrong component. could this be causing my difficulty? or is it the double sided pcb?
I have trouble getting components out of double sided boards with any solder type lol. RE the pot legs I'd just cut t hem at the angle leaving enough to grab the pin with hemostats (my tool of choice for these tasks) and enough terminal on the pot for later recycling. I never try to remove solder until after the component leg is out. Actually I add solder when pulling components to ensure the whole joint gets gooey, then remove the lead, then clean up the hole.
How to remove the pots without breaking anything or even using a desolder braid: Secure the PCB so that it does not move when gently tugging the pots. Melt the solder on the right pin while very gently pulling the pot away. Quickly repeat with the middle then the left pin. If you do this gently the pot will start to pull away from the PCB without damaging it in any way. Just keep melting each pin for one or two seconds and then gently pull. Eventually the pot will come out. Don't force it or you may damage the actual pad. If any solder is left in the pad after removal, use a combination of solder sucker and poking the tip of your iron through it to remove it.
I do this all the time when my actual desolder pump won't fit in a tight space.
I just did a combo of all the stuff listed and actually didnt see madbeans last post until just now. wish i woulda thought about leaving solder in there so I wouldnt have ruined so many pads. i only had to cut off one pot though.
but it looks like I lost some pads, which ive never dealt with on a double sided board. i usually just follow the trace and it's super easy, i was using guitar pcb boards so i havent had to deal with this for a while.
how do i go about fixing this? I lost the following pads
component side- upoc1 #2 maybe doct 2 #1
trace side- Doct2 #3 up oct #1 & 2
and maybe a few others, that are still partially connected but look like they could still make contact if pushed down and soldered in. major bummer, am I gonna have to solder wires to where they go to components on the board?
okay, i dont really need it all spelled out completely. here's a couple concise quesitons.
if the pad is okay on the top and gone on the bottom (trace side of the board) or vice versa, do I need to jumper it to where it's supposed to go? Cuz if one of the sides will work I'll only maybe have to do Uoct1's 2nd terminal to R49 which is right next to it.
if i do need to hardwire all these bad pads, i know where they need to go for the most part. only question is on Doct2 terminal 3 makes a connection with VR+ can I just tap that from anywhere on the board or should I make a jumper to the 9v pad on the board?
regarding the two pads in the 9V solder pads on the upper right corner of the board. is the square pad V+ and the circle pad ground?
Good that you got them off... Bummer that it ruined some pads. :(
Quoteif the pad is okay on the top and gone on the bottom (trace side of the board) or vice versa, do I need to jumper it to where it's supposed to go? Cuz if one of the sides will work I'll only maybe have to do Uoct1's 2nd terminal to R49 which is right next to it.
If you make a good solder connection, it should make continuity between the top and bottom if the pads aren't completely removed
Quoteif i do need to hardwire all these bad pads, i know where they need to go for the most part. only question is on Doct2 terminal 3 makes a connection with VR+ can I just tap that from anywhere on the board or should I make a jumper to the 9v pad on the board?
VR will be different from 9V. If you have a DMM (Digital Multi Meter) you can check continuity to determine where intervention will be needed... You may consider wiring the pots to the board rather than soldering directly, which will give you the option of connecting to equivalent points other than the busted pads...
Quoteregarding the two pads in the 9V solder pads on the upper right corner of the board. is the square pad V+ and the circle pad ground?
From memory the Square one is 9V... not sure about the circle...
Good luck
so... I'm not understanding your answer if the pad is missing on one side completely, the other side wont make a connection to where it is supposed to go?
i guess i dont really understand how double sided pcb's work. it looks as though the pots are only connected to individual traces
-Where is VR then? i'm a noob.
also is there a chance these pots are ruined due to a little bit of excessive bending? everything is still connected and whatnot.
Quoteso... I'm not understanding your answer if the pad is missing on one side completely, the other side wont make a connection to where it is supposed to go?
i guess i dont really understand how double sided pcb's work. it looks as though the pots are only connected to individual traces
The dual layer pcb pad-holes have 3 sides; top, inside and bottom. There may be enough conductive matter left in the pad hole still to complete the connection if a good enough solder joint is made.
Quote-Where is VR then? i'm a noob.
VR is a voltage reference in the schematic. Just like all the GNDs (ground)are connected, all the VRs are connected too. However VR is not neccesarily the same as 9V.
Quotealso is there a chance these pots are ruined due to a little bit of excessive bending? everything is still connected and whatnot.
Yes, you can test it with a DMM, using the Ohms/resistance measuring function. Measure lug 1 and 2 whilst turning the pot a full rotation. The readings should change relative to the turn of the pot from '0' the maximum value of the pot (in this case 100k)... do the same with lugs 2 and 3...
i'm still a little confused on how I tap a VR if the pad is missing.
I see all the VR points on the schematic, but I'm not really sure how I would go about tapping into it for the broken solder pads.
Could I for example: Lug 1 of the Clean pot is connected to VR- Can I just wire my missing solder pad of Lug 1 of Up Oct 1 to lug 1 of clean pot? that's all i'm trying to figure out... but it seems like that would also be connecting the two lugs together, but i guess they are pretty much connected... correct?
If the bottom pad is completely gone, do you think i should just try to solder the pots in normally (correctly) and make a good connection or do you think i should just go ahead and tap the points where they are connecting.
I understand the basic concept of a double sided pcb. but i'm curious as to the purpose of the 3 solder pads, when the schematic appears to show that each point i'm looking at is only connected to one other point. i thought it was more for arranging components in paralell and points with multiple connections more easily on a pcb.
Sorry this thread has become so long! I really appreciate all the help guys!
QuoteCould I for example: Lug 1 of the Clean pot is connected to VR- Can I just wire my missing solder pad of Lug 1 of Up Oct 1 to lug 1 of clean pot? that's all i'm trying to figure out... but it seems like that would also be connecting the two lugs together, but i guess they are pretty much connected... correct?
Yes that will work, you could just run a wire between the two pots
QuoteIf the bottom pad is completely gone, do you think i should just try to solder the pots in normally (correctly) and make a good connection or do you think i should just go ahead and tap the points where they are connecting.
You'll have to decide that... but I would try the pots in the correct spot first... My preference is to use wire and make a really good connection... get it hot, and load that sucker with all the solder it can eat, whilst keeping the wire and board completely still. A good joint will protrude healthily both sides of the board (without becoming a big mess) Do that, and hopefully the connection will 'self repair' and work out fine.
If that fails, run a wire from the pot to the next component down from the busted lug, and share that hole with the other component. (Meaning more careful desoldering first)
QuoteI understand the basic concept of a double sided pcb. but i'm curious as to the purpose of the 3 solder pads, when the schematic appears to show that each point i'm looking at is only connected to one other point. i thought it was more for arranging components in paralell and points with multiple connections more easily on a pcb.
Depending what the pot is used for, it can sometimes use either 2 or 3 lugs. When designing the pcb for board mounted you have all 3 for rigidity in assembly, there are other reasons also but all the madbean pcbs have all 3 pads per pot, even the non mounted or single sided designs. I don't really know if that answered your question or not... lol
QuoteSorry this thread has become so long! I really appreciate all the help guys!
Your welcome :)
Quote from: nzCdog on February 02, 2012, 07:33:08 PM
QuoteI understand the basic concept of a double sided pcb. but i'm curious as to the purpose of the 3 solder pads, when the schematic appears to show that each point i'm looking at is only connected to one other point. i thought it was more for arranging components in paralell and points with multiple connections more easily on a pcb.
Depending what the pot is used for, it can sometimes use either 2 or 3 lugs. When designing the pcb for board mounted you have all 3 for rigidity in assembly, there are other reasons also but all the madbean pcbs have all 3 pads per pot, even the non mounted or single sided designs. I don't really know if that answered your question or not... lol
Here, I'm not talking about the 3 lugs on the pot... I'm talking about the apparent 3 pads you mentioned inside of each individual pad of the double sided pcb. I'm saying- I thought a double sided pcb would allow for multiple connections to made, like parallel components or something. but on this schematic it seems that my broken solder pads are only connected to one other place. Why would I need all of the solder pads (as in the top and bottom and apparent pad inside the board) to connect?
again, not talking about lugs 1,2,3 of a potentiometer---solder pads individually
Let me see if I can clarify: each pad you see on the PCB is a singular pad. It connects to either components on the top side of the board or bottom side through traces. The traces on the top and bottom usually go to different places, so a top trace may connect the pad to one end of a resistor (via another pad), and the bottom may connect to a capacitor somewhere else. The pads themselves are "plated though". This means whenever you solder an actual lead or wire to the pad, it makes all the connections at once because the top and bottom portion of each pad is connected via s small amount of plating in each pad hole.
So, if you rip up or melt off a pad on the top, for instance, you may lose the connection to whichever component the top trace routes to. But, the bottom connection should be okay, because assuming the pad is intact on the bottom, the trace attached to it is also still in place.
However, it's much simpler than that. Whenever you lift a pad, top or bottom, all that is required is to figure out what trace that pad connected to, and then use a wire to jumper from the lead on the lifted pad to the "end of the line".
Here's a pictorial example from the LaVache. The green area I've highlighted is where we are going to make the example. The pad that the end of D2 goes in is routed on both the top and bottom to different places. On the top (red) it goes to D1 and C3. On the bottom (grey) it goes to the middle pad for the Shape switch.
If you lifted the pad on the top, then you would run a wire (on the bottom of the board) from that D2 pad to where the top trace connects to D1 or C3 (meaning their pads). If you lifted the bottom instead, then you would connect the wire from the lead of D2 on the bottom to the middle pad on the Shape switch. If you managed to lift top and bottom, you would need to run wires to BOTH places (always do it on the bottom of the PCB--it's easier).
Hopefully, that makes it clear. BTW: the large grey areas on the bottom are all part of the ground plance. The connect to grounded pads via little tiny slivers of traces (called Thermals) which you can just make out in the pic.
Let me know if there is still any confusion :)
I just noticed the LR doc doesn't have a pic of the trace layouts. I've been including these more recently. Here it is...will probably help you a lot!
Ballin! I get it! I get it! You guys are amazing people! I have been inspired to help when I can. I hope one day I can be of 1/100 as helpful as the people on this forum! Thanks!