Ross Phaser from Tonepad not phasing

[crowsmith8]

Hi all, I stumbled upon a Ross Phaser board that I populated a while back and decided to finish it up.  I wired everything up and when engaged the signal goes through, but it doesn't have the swirly goodness that is supposed to be there.   The rate and regen change the sound, but it is ever so slight.

I went through and re-touched every solder joint to make sure that I didn't have any cold joints, but that didn't help.  I don't know why, but at the time I populated the board I didn't put sockets for the ICs, so I'm worried I might have damaged one of chips.  I didn't incorporate any mods.  Here are the readings for the ICs.  I'm using a 9v power supply that when measured is on the power jack is reading 8.97.  Let me know if anyone has any ideas.  Thanks in advance.

ic1      
pin1   4.49   
pin2   4.49   
pin3   0.004   
pin4   0   
pin5   0.587   after a second or 2 then starts dropping
pin6   0.39   
pin7   4.46   
pin8   8.96   
      
ic2      
pin1   0.11   
pin2   0   
pin3   0.59   after a second or 2 then starts dropping
pin4   0.472   
pin5   0   
pin6   0   
pin7   0   
pin8   4.1   
pin9   4.15   
pin10   0   
pin11   8.97   
pin12   0   
pin13   0.47   
pin14   0.59   after a second or 2 then starts dropping
pin15   0   
pin16   0.11   
      
ic3      
pin1   0.11   
pin2   0   
pin3   0.59   after a second or 2 then starts dropping
pin4   0.466   
pin5   0.034   
pin6   0   
pin7   0.034   
pin8   4.45   
pin9   4.48   
pin10   0.034   
pin11   8.97   
pin12   0.034   
pin13   0.416   
pin14   0.592   after a second or 2 then starts dropping
pin15   0   
pin16   0.11   
      
ic4      
pin1   0   
pin2   0   
pin3   0.015   
pin4   2.454   
pin5   0.013   
pin6   0   
pin7   0.013   
pin8   0.013   
pin9   2.454   
pin10   0   
pin11   8.97   
pin12   0   
pin13   0   
pin14   0.015   
pin15   0   
pin16   0   

[Slowpoke101]

You seem to be missing the 4.5V Vb rail. You should have about 4.5V on IC1 pins 3 (supplied via 470K resistor ) and 5. Also on pins 3 and 14 of IC2 and IC3

Check out the following pictures and see if you can find why the Vb rail is so low.






If you can upload some pictures of both sides of the board (as clear and detailed as possible ), it would be very helpful.

[Mark Hammer]

Not saying this is the problem, but if you're at all like me, your parts bins contain components whose leads are a little tarnished. The result is that the solder joints may look good but actually be cold, or close to it.  These days, unless I'm making something with gleaming new parts right out of the shipping bag, I find myself scraping the leads with a blade to shine them up a bit and ensure better contact.

[crowsmith8]

Thanks for the replies.  I'll check on the Vb rail when I get home tonight.  I'll also take some pics and post them should I not be able to identify the issue with the Vb rail.

@Mark, that's good advise, some of the components I was working with have no doubt been sitting around for a while, so it could be a that the leads were tarnished.

Hopefully I'll have good news to post later... fingers crossed.

[crowsmith8]

Well I checked the Vb rail and couldn't figure our what's going on. I replaced the two 10k resistors and the 10uf cap (scraping the leads with a knife just to be safe) and no luck.  The weird thing is that when the 10k resistor just below the 10uf cap is in, it measures at 3.9k, but when I take it out it measures as 10k. I don't know if that's a clue or not, but thought it was important to mention.  Anyway, here are some pictures, I hope they're clear enough. It's definitely not the cleanest build,  that's something i'm trying to get better at.

[Slowpoke101]

The weird thing is that when the 10k resistor just below the 10uf cap is in, it measures at 3.9k, but when I take it out it measures as 10k. I don't know if that's a clue or not, but thought it was important to mention.

When measuring resistors in circuit it is normal for the resistances to measure differently from what the resistor's value actually is. So don't be too worried.

Your pictures are very good with only the PCB track side being a little blurry but not badly. Have a look at the picture below. There are a couple of connections to check. The picture did show something worrying. The component pads appear oxidised which can prevent the solder from making a good connection to the pads. You may need to remove the solder, clean the pad (carefully scraping it may work ) and resolder.

[Mark Hammer]

And not to drone on about it too much, your pic and situation illustrates why I like to keep an old toothbrush and something that dissolves flux handy.  It's not always needed, but sometimes, during troubleshooting, it's good to have a flux-free view of the copper side, so that one can more easily differentiate visually between solder-bridges and flux.  If the board has big expanses between traces, it's not as much of a necessity.   But when the board is minimally crowded (and I'd consider anything with ICs to be at least a little "crowded"), it's easy for little bits of solder to web across pads.

Personally, I use methyl hydrate to dissolve flux.  There are other chemicals available for the purpose.  I know it's not a nice chemical, but I have some, it works, so I use it.  It can produce some discoloration of the board, but the board comes out looking "dry", with no shiny webbing between pads or traces.  It lets the builder say "Nope, that's not it", or "A-HA! There it is", both of which are useful.

[crowsmith8]

Thanks for the suggestions and info on the resistor values.  I'll definitely try the those couple of connections and see if I can get those pads clean.  Question, whenever I remove a component I use a desoldering pump and it gets a lot of the solder, but there are always traces that get left behind.  Is there a trick to getting all the solder off?  Perhaps the desoldering wick is better for the little bit left over after using the pump? 

I'll also pick up something to dissolve the flux.  The fact that it will help with troubleshooting sounds like a good reason in itself to get some, but I also like the idea of having a cleaner board when all is said and done too.

It may be a couple of days before I can get back to troubleshooting, but I'll update with progress when I get the time to get back to the workbench.

I really appreciate all the help so far.