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Dean Markley CD120

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  • #16
    I would still ohm out and check those jacks to see if when closed the tip is making a strong contact.
    When the going gets weird... The weird turn pro!

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    • #17
      Ok, I will double check them.

      Originally posted by DrGonz78 View Post
      I would still ohm out and check those jacks to see if when closed the tip is making a strong contact.

      Comment


      • #18
        My bet is a problem with that FET on the input side of your drawing in post #5. If I'm looking at the schematic correctly, when you plug a cable from send to return, the input is rerouted through the lower FET and U1B. With nothing in the return, the path should be through the top FET to U1A. Is the FET on? See if you have signal on both source and drain of the FET or at pin 2 of the op amp.
        "Yeah, well, you know, that's just, like, your opinion, man."

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        • #19
          I will check that out...thank you! One thing I didn't try that I'm thinking of now is disconnecting the F/S then check to see if I get a signal from the effects send and if I get a signal into the effects return. I think that's basically what you just said however...lol. I will check it out. Try to do it tomorrow... Thanks again!!

          Originally posted by The Dude View Post
          My bet is a problem with that FET on the input side of your drawing in post #5. If I'm looking at the schematic correctly, when you plug a cable from send to return, the input is rerouted through the lower FET and U1B. With nothing in the return, the path should be through the top FET to U1A. Is the FET on? See if you have signal on both source and drain of the FET or at pin 2 of the op amp.

          Comment


          • #20
            What I see id that Dean went trigger happy with FET gates and mutes all over the place.
            2N/PN-4393
            Fine with me.
            I count
            * 2 on Page 1 , the lower one triggered by leaf switches in the input jacks, the top one from the "overdrive FS" (hint hint)
            * 1 on page 2 , muting reverb recovery and triggered from "reverb FS"
            * 2 on page 3, alternatively muting/bypassing the effects loop, in this case triggered by an "effects switch" ,which might be a footswitch or a panel switch, the OP can answer that.

            I don't see a (panel) "channel switch" although there can be one, simply in parallel with the proper FS contacts.
            So it might need a FS after all.

            FWIW I once got a much needed cash input when cheap imports were killing me (same is happening now ) , the Peavey importer bought a shipload of "grey" Peavey stuff (not exactly illegal or stolen but from some mystery guy who happens to have it, often from Panama, Miami or Iquique, Chile) .
            It included a bunch of rackmount Peavey Rockmaster tube preamps , killer clean/crunch/5150 class distortion (in fact, I think they were its predecessors) but without channel selection switches, you *needed* the FS ... which was specific for that model and could not be ordered from Peavey at all.
            How would they explain ordering 100 footswitches for a model they never (officially) bought?
            As a side note, the preamp could have been somewhat usable as-is if it defaulted to the intermediate "crunch" setting (imagine something halfway between a Plexi and a JCM800) but no, it defaulted to the "ULTRA" channel.

            Oh well.

            Fine with me, I made and sold footswitches and offered a 100W 2x12" SS powered cabinet, with a 2U rack slot on top (for the preamp, plus 1 U free for effects, usually some Digital Reverb) .
            Sold a lot and it saved my bacon more than once.

            EDIT: I almost forgot:
            1) there's a typo on page 1 , the bottom PN4393 gate must go to -15V, not +15V as shown.

            *Maybe* it came out right from Factory (which has the right schematic or no amp would work properly), but somebody "corrected the error" and sent it to +15V ... in that case the bottom channel (distortion?) will never be enabled (hint hint).

            so
            2) check that you get a negative voltage on the Fet gate when you plug something in the input jacks
            3) worst case, and just for diagnostic, unsolder and pull the lower Fet, you should recover that channel.
            Last edited by J M Fahey; 07-11-2015, 03:29 AM.
            Juan Manuel Fahey

            Comment


            • #21
              I would be that without the FS, it defaults to FX loop ON. And there is no pass through. I looked at the schematic and don't recall seeing any pass through contacts.
              Education is what you're left with after you have forgotten what you have learned.

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              • #22
                So when you say for diagnostic unsolder and pull the lower fet which page are you talking about? Page 3 effects loop schematic? And that would be the 4393 connected to the effects return jack. Am I correct? Thanks!!

                Originally posted by J M Fahey View Post
                What I see id that Dean went trigger happy with FET gates and mutes all over the place.
                2N/PN-4393
                Fine with me.
                I count
                * 2 on Page 1 , the lower one triggered by leaf switches in the input jacks, the top one from the "overdrive FS" (hint hint)
                * 1 on page 2 , muting reverb recovery and triggered from "reverb FS"
                * 2 on page 3, alternatively muting/bypassing the effects loop, in this case triggered by an "effects switch" ,which might be a footswitch or a panel switch, the OP can answer that.

                I don't see a (panel) "channel switch" although there can be one, simply in parallel with the proper FS contacts.
                So it might need a FS after all.

                FWIW I once got a much needed cash input when cheap imports were killing me (same is happening now ) , the Peavey importer bought a shipload of "grey" Peavey stuff (not exactly illegal or stolen but from some mystery guy who happens to have it, often from Panama, Miami or Iquique, Chile) .
                It included a bunch of rackmount Peavey Rockmaster tube preamps , killer clean/crunch/5150 class distortion (in fact, I think they were its predecessors) but without channel selection switches, you *needed* the FS ... which was specific for that model and could not be ordered from Peavey at all.
                How would they explain ordering 100 footswitches for a model they never (officially) bought?
                As a side note, the preamp could have been somewhat usable as-is if it defaulted to the intermediate "crunch" setting (imagine something halfway between a Plexi and a JCM800) but no, it defaulted to the "ULTRA" channel.

                Oh well.

                Fine with me, I made and sold footswitches and offered a 100W 2x12" SS powered cabinet, with a 2U rack slot on top (for the preamp, plus 1 U free for effects, usually some Digital Reverb) .
                Sold a lot and it saved my bacon more than once.

                EDIT: I almost forgot:
                1) there's a typo on page 1 , the bottom PN4393 gate must go to -15V, not +15V as shown.

                *Maybe* it came out right from Factory (which has the right schematic or no amp would work properly), but somebody "corrected the error" and sent it to +15V ... in that case the bottom channel (distortion?) will never be enabled (hint hint).

                so
                2) check that you get a negative voltage on the Fet gate when you plug something in the input jacks
                3) worst case, and just for diagnostic, unsolder and pull the lower Fet, you should recover that channel.

                Comment


                • #23
                  I said:
                  1) there's a typo on page 1 , the bottom PN4393
                  but no problem , I'm talking about the bottom PN4393 on page 1 , the one which enables/mutes the distortion channel (the channel which seems to be silent).

                  It may be good/bad , connected to +15 or -15 , be getting the proper voltages or not, may need the FS or not, but one thing is certain , if you pull it off the board, it can mute nothing, so that's why I suggest doing so ... for diagnostics of course.

                  Just
                  1) suck solder well, so you pull it easily, not damaging PCB pads

                  2) >>>take note/ make a drawing/take a picture/mark it<<< so when you replace it it goes the exact same way.

                  Fets are somewhat confusing to measure , because some measurements demand the diode scale, some demand the ohms one , so I'd rather not need to have you measure it if you are unsure of position.

                  3) so after you pull it, distortion channel *should* work.

                  EDIT: the above applies to a missing Distortion Channel, per your post # 10 which I'm answering.

                  But now I reread the whole thread from the beginning, ans see you started worrying about *both* channels missing, so I'll change my suggestions:

                  pull no FETs to begin with, and if everything works with the pedal plugged in, then it's probably what the designer intended.

                  There are missing parts in the schematic, specially a detailed description of internal switching wiring/routing and of course the entire FS pedal is not there.
                  I saw on a YT DM60 demo (which must be probably the same) that it also has at least 1 LED, yet we ignore how it's fed/activated.

                  I'd suggest that if the amp works flawlessly with the pedal, then there's nothing wrong, it is what it is .

                  If you want to be safe and not depend on an unobtainable switch which may be lost, I'd open and copy it now thatb you have one.

                  At least post 3 or 4 clear sharp well illuminated pictures of its guts, maybe somebody can trace it.
                  No cellphone pictures please, try to borrow a real camera which can take closeups, most do.
                  Last edited by J M Fahey; 07-11-2015, 04:49 PM.
                  Juan Manuel Fahey

                  Comment


                  • #24
                    Sorry to bump an old thread. I was looking for a schematic for the CD-120 combo I have (Thanks for sharing). Mine does work on the clean channel only without the foot switch plugged in. No panel switch for the gain channel. Just adding this in case it may help someone else in the future.

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                    • #25
                      Here I hope this is what you need. Only thing is that the part designations are not labelled, only the value.

                      Edit: Scrolling through the thread I see the schematic was already posted.
                      Attached Files
                      Last edited by DrGonz78; 04-28-2020, 04:23 AM.
                      When the going gets weird... The weird turn pro!

                      Comment


                      • #26
                        I had a CD60 in last week.

                        I installed a regular 1/4" jack so the owner could use a standard single or dual footswitch to switch channels and reverb.

                        Comment


                        • #27
                          Originally posted by DrGonz78 View Post
                          Here I hope this is what you need. Only thing is that the part designations are not labelled, only the value.

                          Edit: Scrolling through the thread I see the schematic was already posted.
                          Thanks. Yeah, I see my post was a little misleading.

                          Comment


                          • #28
                            Originally posted by drewl View Post
                            I had a CD60 in last week.

                            I installed a regular 1/4" jack so the owner could use a standard single or dual footswitch to switch channels and reverb.
                            That's a good idea. My footswitch is a little jacked up.

                            Comment


                            • #29
                              I have a whole bunch of DIN connectors and cables the field techs throw away at work, and could have made a duplicate footswitch
                              But the owner just wanted it to switch channels, I wired it up to switch reverb also just for the heck of it.

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