PROCO RAT Unity Gain

[rmfroyd]

Morning everybody.  Quick question about my ProCo Rat build.  I used this layout:



Everything works, volume, filter, distortion, BUT it is about 20-30% quieter than unity.   I can't imagine this is normal for this pedal.  I have built some pedals in the past that needed a boost in front to open them up(sabra cadabra), but I didn't think this would be the case with the rat.

I forgot to take pics this morning, but I will try to take some tonight.

I have replaced the volume pot, the IC and the transistor without any noticeable difference.

Thanks

[Ciaran Haslett]

Can you post some hi res pics of the front/back and off board wiring?  I've built this and it's plenty loud so I think there's an error somewhere.  Maybe a wrong value component.

[rmfroyd]

Thanks for the help!

[rocket88]

hey man. the pic you posted is way too small to see anything. when you upload a pic click the option that says "Large Size." also, don't forget to upload a pic of the bottom of the board.

in the mean time go through the board with something sharp, like a knife, between the copper tracks to make sure you don't have any tiny solder bridges you can't really see.

you will also want to measure the voltages at each leg of the IC and the transistor and upload that info. it will help out tremendously in trying to diagnose the problem. the voltages can tell you a lot about what's going on in the circuit.

[rmfroyd]

Dang, sorry about that, I thought I did that.  Maybe because I uploaded from my phone?  



Voltages are as follows
IC
1--8.69
2--8.43
3--7.85
4--8.35
5--0
6--8.43
7--9.24
8--7.76

D--9.24
S--2.09
G--0

Knifed the back of the board, but didn't take a pic.  No solder bridges.

Thanks again.

[Beaker]

Thanks for the larger picture, it helps a lot. A photo of the copper side is always a good idea, as it helps us to see any problems with the sodering - not just track shorts. it also helps with checking component positions, when they are not obvious from the top-side photo, as well as hidden links and cuts.

Just looking at the top though, your transistor socket is sitting very high off the board.
I have serious doubts about whether you have a proper solder conection between the copper tracks and the pins. Check for continuity, and re-flow the solder and re-seat the socket if needed.
You are getting voltage on the JFET pins, but it might be intermittent.

[rmfroyd]

After doing some research, shouldn't I be getting 0 voltage out of Pin 4?

[Beaker]

Correct, pin 4 should be zero Volts.

Two other things to check - have you got the link wire from pin 8 to one row higher (under the IC) as it is not visible on the photo.

Check the link from pin 4 to the bottom row is not shorting on the leg of the big 1uF box cap at the bottom.

[rmfroyd]

The link is there, will check shorting on leg of box cap when I get home.  

Thanks.

[Ciaran Haslett]

On the surface everything looks good.  Correct values/placement etc.  So as the lads say...check every cut for unwanted bridges, every track for stray solder.  Make sure every link is touching only what its supposed to...not accidentally shorted to another component/IC socket etc.  I'd definitely seat that transistor socket a bit better.  The pins seem very high I'm wondering if some of them are even soldered to the tracks on the other side.

Hi res pics of the track side and offboard wiring will also help.  Don't worry about how big they appear in the post.  The bigger the better

[rmfroyd]

Reseated Transistor socket.  Nothing is shorting.  STILL getting voltage at Pin 4.  Distortion pot acts weird, when going from one side to the other fuzzy nasty static in the middle.  I had this happen before, and it was a bad IC.  But what are the chances the I would get 3 bad LM308s from Mammoth?  

Can anyone with a working one send me the correct voltages?  All I can find are people posting ones that don't work.  I will send you a virtual 6 pack of the beer of your choice if you do.

Ugggghhh, last two builds have been bad news for me, gotta get out of the rut.

Here is a pic of the back.  Looks like the south end of a north bound donkey.

[rocket88]

hey man, I see a lot of joints I'm not happy with, either look cold or incomplete to me. For instance looking from the bottom pic you just posted the top right, 5th hole in isn't solid. I would check them all with your DMM in continuity setting. Side note, looks like you're using the "silver" stripboards. Based on my own experience I find these boards to be nothing but trouble.

[nocentelli]

Do you do your track cuts with a power drill? You only need to take the top layer of copper off, a drill bit twisted lightly with your fingers will do it, no need to go through the board.

[rmfroyd]

Fixed that one.  Still getting voltage out of pin 4.  Can someone find/post proper voltages for me?

[rmfroyd]

I am giving up on this one, until I can see some voltages from a working board.

Something with the distortion pot is wonky.  I have replaced it, but no change.  Sounds fine at lowest setting, moving it up it sort of pulses in and out, and is really compressed at full range.  

I will start from scratch.  I keep thinking it is the lm308, but three in a row from same supplier seems really suspect.

[Frank_NH]

Your voltages appear to be wrong for your LM308 IC.  

Pin 7 should be 9V (supply voltage).  Pin 4 should be ground (0 V).  Pins 2, 3 and 7 should all be at the bias voltage of 4.5V (half the supply).  Pin 5 is not connected, and Pins 1 and 8 are connected to the compensation capacitor.

It may be a good idea to build it again.  Check all your connections as you go.  In particular, before you begin to solder, check all of your cuts with the continuity function on your DVM.  Then, once you install the links, check those for continuity.  As you proceed, visually inspect each joint and make sure no obvious solder bridges are apparent.  Good luck!

[Beaker]

I don't want to sound as though I am criticising you, but if you build it again, slow right down, and build it as carefully and neatly as you possibly can. Check EVERYTHING as you go along, to ensure your build is correct, and as good as you can make it.

We have all started off badly, and got better with time and practise. These are skills that need time, patience, perseverance and repeated practise to learn.
Treat every mistake and every failure as an opportunity to learn from, in order to improve.

Have a look at the "Show your pedal guts" thread. Try to get your board looking as neat as some of the builds on there. You might not succeed, but there are loads of clues to getting a tidy looking board.

Your solder technique looks suspect - brown residue on the solder suggests you are overheating your joints, which can lead to "cold" solder joints. Either your iron is far too hot, which is cooking off the flux, or more likely, it is too cold, meaning you need to have the iron on the board for far too long before the solder melts, which perversely, has exactly the same effect. Remember that overheating not only produces bad joins, but can and will kill components too.

I come from a toolmaking background, and a couple of saying were drummed into me as an apprentice. "Build it right or build it twice" was one, the other being " Don't waste an hour trying to save a minute."

In other words try your absolute best to get it right first time, and work slowly, carefully and methodically as it's quicker in the long run - not to mention a whole lot better for your sanity.

Finally, while it is entirely possible that you have a batch of bad, or more likely fake ICs, it's better to assume that the mistake is somehow yours, until you can definately prove otherwise. (I have had to learn this one the hard way myself).

If you need any hints, tips or tricks, or are unsure of anything, please ask. There is no such thing as a stupid question, and any one of us will be happy to help if we can.

[rmfroyd]

Beaker and Frank, thanks for the replies.

Frank, that is exactly the kind of answer I was looking for.

Beaker, I am soldering at around 700 degrees on my solder station.  Never had a problem in the past.  Probably looks extra crappy because I have reflowed the solder 5-6 times.  

Rocket88 mentioned the silver stripboard, and I am also not a fan, I will try the copper kind next.

Unless Mammoth started selling fake IC's I don't think they are fake.  

I will try again in a couple days and get back to this thread.

Thanks again.

[rocket88]

Hey man. You're iron is way, way, way, did I say way yet? too hot. You're iron doesn't need to be more then like 325 degrees F. While it may not be the source of the problem, it's definitely contributing to it and can lead to many more as beaker mentioned.

If you're in the US I can send you small board of plain copper vero that I use for you to try out. This way you don't have to order a hole bunch or pay through the nose in shipping.

Just to add to what beaker mentioned about taking it slow and being methodical. If you check out the pedal guts thread you're going to see a lot of builds, including a few of my own. One think you'll notice on builds done by those of us who've been building while is that the components sit nicely, flat as possible, and as straight as possible. Same thing with your wiring, which takes awhile to get down. By taking you're time to make it neat when you do have a build error it's easier to spot and correct.

I learned this early on as my first build was a russian big muff and it was a mess. I couldn't trace all the problems I had going on and took forever to figure out. I actually want to rebuild it just so I can have it looking better, and wired the way I do now. I hate that it's a birdsnest in there. Sounds epic though.

[rmfroyd]

Thanks Rocket88, that is very generous to send a board out, I appreciate it!  I am going to hold off for now, I have about 5 builds in the next 6 weeks, and I am sure I will be ordering for one or more places and I will toss one in on my orders.  

Again, I appreciate all the help you guys have given me, but I think I am going to step away from strip board builds for a bit.  I gotta stick with stuff I know.

I machined this Rat Board this morning:



Thankfully, I got outta work and picked my folks up at the airport, and they watched the little ones so I could build this up for a friend.  And it actually worked first shot.



I had the enclosure done a couple days ago, my buddies a big Skyrim fan





I did turn my soldering iron down, but it wouldn't melt solder at 325, I must need a new tip.

Thanks for the help and advice, catch you guys later.