Home Forums GuitarPCB Build Support ColorTone Bass Fuzz (solved)

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  • #16980
    Jon
    Participant

    I am helping a friend troubleshoot this.  He used 5088’s, so those transistors are reversed from the printing on board per the build doc.  LED works, bypass works, no sound at all in effect mode.  Any help would be appreciated.

     

    https://i.imgur.com/QLrRHD7.jpg

     

    #16984
    Dave
    Participant

    I’m Jon’s friend, Dave, who built this – any suggestions would be greatly appreciated.  I get bypass and LED but no effect.  many thanks in advance!

    #16991
    Jon
    Participant

    Is this better?

    #17018
    Billy
    Moderator

    Nothing stands out apart from R22 doesn’t look like a 1K it looks like a 1M that would cause problems and T1 is 20K (203 code) albeit that would still work, it would just make it more difficult to get the required voltage on Q4 drain

    What are the voltages on Q4 pins

     

    #17036
    Dave
    Participant

    Thanks Billy – you have a great eye.  My kit came with a 1M for R22 rather than a 1k.  I swapped out R22 and put in a 1k and also replaced the T1 with a 5k rather than the 20k that came with the kit.  Still no effect (bypass and LED work)  – I’ll check the voltages on Q4 next.  thanks alot

    #17075
    Bruce R
    Moderator

    Guys, R22 was a 2k4. The top stripe was red, not brown, At some point, the value of this resistor was changed, probably when the MPF102 became unavailable and the project was changed to the J113. I’ll update my parts list for this kit. Sorry for any confusion this caused. I think the 5k trimmer will be too small to bias the J113. I’ll let Barry weigh in. Monitoring the thread.

    Bruce
    Pedal Parts and Kits

    #17079
    Barry
    Keymaster

    What is the voltage on the Drain Pin of Q4 (J113). (Google datasheet if needed)

    It needs to be biased between 4.5v to 6.5v for everything to sound right.

    Directions for biasing are in the document.

    You should have been able to Bias properly even with a 2k4 resistor and you likely needed the 20k trimmer as 5k may not be enough. If it is not Biased properly it will not work right.

    That said if you get a good Bias reading with the 5k trimmer all is well. If you cannot do not remove the Trimmer again since you can damage the board. You will have to compensate by raising the value of R22.

    One thing at a time though. What is the current voltage of the Drain Pin of Q4?

    #17080
    Dave
    Participant

    Thanks a lot guys for all the help!  I did a complete resistor check to ensure all the resistors were correct per the build document and they are now (1k is in R22).  I reflowed the solder on the in and out on the PCB and the 3PDT switch.  I have a 5k in the T1 per the build doc.  Here are my voltages:

    1. Q1 – 8.3 E, 0 B, 7.3 C
    2. Q2 – 8.6 E, 0 B, 9.2 C
    3. Q3 – 9.2 E, 152.3 B, 0 C
    4. Q4 – 9.3 E, 0 B, 0 C

    Note that the build doc references a J113 in Q4 but the kit came with a 2N3904.

    Any thoughts guys?  thanks again

    #17082
    Billy
    Moderator

    A 2N3904 won’t be any good it’s a BJT you need a FET for Q4 like the J113 Dave

    I think your transistor voltages may be mixed up the 5088 pinout looking at the pcb would be from left to right CBE

    They look way off Q2 base is obviously wrong at 152.3v

     

     

     

    #17085
    Dave
    Participant

    thanks Billy – The ColorTone Bass Fuzz build doc says to put the 5088s in backwards, which i did.  I swapped out the Q4 for a J113 and still no effect (just getting bypass and LED).  Still nothing.  Clearly, my most frustrating build in 35+ pedals and I recognize I’m a total; rookie and appreciate the help.  This one may be destined for the drawer of lost tone

    https://guitarpcb.com/wp-content/uploads/2018/06/BD_CTBassFuzz.pdf

    “The stock board used BC549’s​​​(this is our ​silkscreen transistor orientation​) but since ​*2N5088’s​​ are more available and sound fantastic ​we use those now​. As a result please note *​2N5088 transistors have anopposite pinout to the board silkscreen. Simply place them in upside down.”

    #17088
    Billy
    Moderator

    You’re correct Dave my mistake  I’m forgetting the original was BC549s I was looking at the build doc not your image so never accounted for them being opposite the silkscreen

    It was just to make sure your pin labelling was right for EBC albeit not put across very well by me apologies for adding confusion

    Pinout backwards as it should be for 5088s, left to right would be EBC, is that how you noted the voltages

    What are Q4 DSG pin voltages with the J113

    You will get it going just takes a little time as you know to figure out what’s failing

    #17090
    Bruce R
    Moderator

    Dave and Jon,

    I spoke with Barry about your issue briefly this morning. Please provide the voltages you have now as requested above. If the moderators here can’t get this working, then I propose plan B:

    I am sending a package today to Dave (I assume he’s the Dave in Texas). It will contain an MPF102 transistor, 3 – BC549C, a couple 1k resistors (since you used your own for R22), transistor sockets and a 20k trim pot.

    The J113 is unlikely to bias with the 5k trimmer. The MPF102 can be used in that Q4 location and will possibly bias with a 5k trimmer. The MPF102 was the original transistor for this location, but about 2 years ago, they became unavailable for 9 months or a year. Since then, some have become available again, but GuitarPCB switched all the designs that used the MPF102 to use J113 instead.

    If you still cannot bias the Q4 transistor, please swap in the 20k trimmer (sending a new one in case the old one was damaged during removal). I am almost 100% positive you’ll be unable to bias a J113 with a 5k trimmer; it just doesn’t have enough resistance.

    If this does not get the pedal working, then an audio probe might be the next step.

    Bruce
    Pedal Parts and Kits

    #17091
    Dave
    Participant

    Thanks everyone for the help once again!  Here are my voltages with the j113 in Q4

    1. Q1 8.0 E, 0 B, 6.5 C
    2. Q2 8.4 E, 0 B, 8.3 C
    3. Q3 8.8 E, 0 B, 0 C
    4. Q4 0 E, 0 B, 0 C [this is the j113

    I’ve got a 5k trim pot loaded and it appears to do nothing when adjusted.  Thanks all – “Texas Dave”

    #17093
    Bruce R
    Moderator

    Dave,

    I’ll send you a new kit minus the enclosure, knobs, pots, jacks and wire. It probably won’t go out until tomorrow though. I suspect the PCB may be damaged from the removal of the trimmer. I’ll email you a tracking number tonight.

    Thanks,
    Bruce
    Pedal Parts and Kits

    #17094
    Barry
    Keymaster

    Yah don’t give up yet.

    Apparently Bruce is going to take care of you.

    So I suggest using sockets when populating and do them right after populating the resistors since they are the next in line regarding height. This way it is easier to populate and to test for issues and also make substitutions.

    Also I suggest using the 20k trimmer as it will work better for J113 or MPF102 and the difference in turn is negligible.

     

    #17277
    Dave
    Participant

    Bruce, Barry & Billy – Thanks for all the help.  Bruce – thank you especially for sending me the new parts. I can’t thank you enough for your professionalism and customer service.  This pedal had me scratching my head but you guys, along with friend Jon, straightened me out.  I live in Houston and we’ve had some seriously delayed mail due to the weather hit we took down here.  I got the parts package yesterday and built the pedal this morning with no hiccups or problems.  It fired right up and its for a friend of mine who I’m sure will love it.  Thanks and look forward to more builds as I’m a huge fan of yours – Best, Dave

    #17279
    Bruce R
    Moderator

    Dave,

    Glad you got the kit and it fired right up. We have a lot more kits available so come by the Pedal Parts and Kits website anytime. Congrats on your success!

    Bruce

    Pedal Parts and Kits

     

     

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