Tonepad ProCo RAT problem

[w437776]

The only problem is the filter pot, when i turn it up it acts very strange - when I hit a note for a moment it is very quiet (like something is blocking the signal) and then the volume increases gradually. Hope you understand  , it's something like this oooooooo  I did no modifications to the circuit.

Here's the IC voltage chart (OP07 op-amp):

P1 = 8.32 V
P2 = 4.19 V
P3 = 2.04 V
P4 = 0
P5 = 0
P6 = 4.20 V
P7 = 8.42 V
P8 = 8.32 V

Any ideas?

[richon]

is the FET (at the end of the effect) in the right direction?

[w437776]

is the FET (at the end of the effect) in the right direction?

I tried turning the FET but then the output signal was very very very weak, barely hearable even with the volume on the amp turned all the way up... IC voltages didn't change at all.

[richon]

maybe the IC is backwards? 

[w437776]

maybe the IC is backwards? 

Hahaha, I doubt it would work at all if the IC was turned backwards.

[grolschie]

The only problem is the filter pot, when i turn it up it acts very strange - when I hit a note for a moment it is very quiet (like something is blocking the signal) and then the volume increases gradually.

Are the pickups in your guitar high output ones? Sounds like the its overloading.

[w437776]

The only problem is the filter pot, when i turn it up it acts very strange - when I hit a note for a moment it is very quiet (like something is blocking the signal) and then the volume increases gradually.

Are the pickups in your guitar high output ones? Sounds like the its overloading.

Tried it on a strat 5 minutes ago and it seems to work fine. What about the voltages? I think pin 2 and 8 should be somewhere around 4.5 volts but mine are 2 and 8.5 volts.   

[PapaHet]

Hi there 

Firstly, I know this isn't the right place to post my problem, as it concern an original ProCo Rat 2 and not an homebuilt pedal but decides to post here because the author already pretty well described the problem. I'm upping this old thread because I have exactly the same problem with my ProCo Rat 2 (the original complete pedal).  It doesn't occur all the time, but most of the time when I hit a note after series of fast palm muting. It is really hard to describe, but it seems that something is holding the note a fraction of second just before letting it ring, and it is pretty annoying as there is a kind of "hole" in the sound I really don't know what may be the cause of this. The pedal is new, a bought it a bit less than 2 month ago, and under warranty. It is one of those Chinese made (...) new ProCoRat 2. I'm using an LTD EX 400 loaded EMG active pickups. I read the answer saying the the pedal might be surcharging, and tried with my Gibson SG with passive pickups and I got the same problem. And still, the pedal isn't suppose to do that with any kind of active or passive pickups. I really don't know what to do, so I' am digging you guys to help me if you can 

I am sorry if there is any spelling mistakes, but English is not my mother tongue (I speak french) 

Have a nice day,

PapaHet.

[GGBB]

First make sure your input and output jacks are clean and you're getting good contact.  Then use an audio probe to check the signal at various points along the audio path.  That should lead you to where the problem is on the circuit board.  My suspicion is a bad connection or solder joint (or pot) or a faulty cap somewhere along the audio path.

[Pyr0]

If it's still under warranty why not bring it back and get it replaced ?

[PapaHet]

Thanks for the answers  I do checked, and everything is clean and the contact is very good. When I don't use the pedal, everything is doing fine.  As this don't seem to be a frequent problem and I don't want to loose my time doing useless things in the pedal, I am just going to directly use the warranty and exchange the pedal. Anyway, thanks for your contribution  . Even though I love my ProCo Rat 2, I have to say that I am really disappointed with Chinese material in general. My conclusion is that you get what you pay for 

Rock on ! 

[aron]

I have the same problem with my Rat. It's the smaller box one. Never took the time to figure it out.

[tubelectron]

Well,

I rebuilt a Big Box Vintage RAT RI to the original 1981 Rev. B RAT circuit, aka "Big Box RAT" some years ago : absolutely no problem, it works perfectly well...

The PCB is labelled : PRO CO SOUND INC. RAT 3 Rev. B SEC 5-0. So it is probably the same as yours...

The original chip was the OP07DP, which is WAY inferior to the LM308N - If it is not done, change it : you'll be surprised by the distortion qualities of the LM308N... I wonder why they changed it for some time.

My advice is that there is probably a faulty component in your RAT (passive or active), or maybe a bad/unsoldered joint on the PCB... That you have to discover ! 

Here is the schematic of my "returned to 1981 Rev. B specs" RAT :



A+!