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  • Peavey grid resistor specs. ?

    I just got a Peavey Classic VTX 2x12 combo. One of the grid resistors
    is blown The main problem is I can't read the values on these's
    resistors? I'm assuming they where changed before? Cuz' I believe
    they are Military resistors? They are Black w/t a silver ban and 2 #s
    2873 8138 ?? the other is burned. No chance finding a schematic
    for free. Anybody have a clue?
    http://www.soundclick.com/whirlwindbluesrevue

  • #2
    Re: Peavey grid resistor specs. ?

    47k.....according to the schematic I have.

    Jeff Seal
    ..lots and lots of toys!

    "...swords and tequila, carry me through the fight!"

    "I am Phil"....
    www.houstonamprepair.com

    Comment


    • #3
      Re: Peavey grid resistor specs. ?

      WOW! Thanks Jeff That was fast!
      http://www.soundclick.com/whirlwindbluesrevue

      Comment


      • #4
        Re: Peavey grid resistor specs. ?

        Originally posted by kmcguitars
        I just got a Peavey Classic VTX 2x12 combo. One of the grid resistors
        is blown The main problem is I can't read the values on these's
        resistors? I'm assuming they where changed before? Cuz' I believe
        they are Military resistors? They are Black w/t a silver ban and 2 #s
        2873 8138 ?? the other is burned. No chance finding a schematic
        for free. Anybody have a clue?

        with those numbers, it seems to me, that is a 287K resistor made in the 38th week of 1981.

        but, it might not be a grid resistor that you found burnt. good luck!!

        germ
        Jeremy Ledford
        Tone Guru Extroardinaire
        Tone Shop

        Comment


        • #5
          Re: Peavey grid resistor specs. ?

          Originally posted by lastwinj
          with those numbers, it seems to me, that is a 287K resistor made in the 38th week of 1981.

          but, it might not be a grid resistor that you found burnt. good luck!!

          germ
          It's going across the base of the tube socket ? When the amp is turned
          on that tube become CHERRY RED !! What else might it be?
          1981 is consistant w/t the timeline of this amp, But it's odd that
          ever other resistor in the amp is your STD. color coded ban type.
          But the 2 going across the tube base are not? Did peavey use this
          style? or are they replacements? ( This is getting confusing )
          Maybe I should buy a new multi-meter and meter the good one out?
          If that one hasn't drifted off value to far? I'll have a Idea what the hell
          it is.
          kmcguitars
          GuitarArtologist
          Last edited by kmcguitars; 08-12-2004, 01:48 AM.
          http://www.soundclick.com/whirlwindbluesrevue

          Comment


          • #6
            Re: Peavey grid resistor specs. ?

            Originally posted by kmcguitars
            It's going across the base of the tube socket ? When the amp is turned
            on that tube become CHERRY RED !! What else might it be?
            That sounds like that tube is drawing WAY to much current, check the bias to it, it sounds like the bias it's receiving is to high (not a low enough negative voltage ... ). You could have a problem along your bias line, not sure how the screen grid is done on that, heck the tube itself could be going bad. I'm going to defer to Jeff and Germ on this one, anything else you guys can think of? If you swap the two tubes, well two from the same pair does it do it in that socket, does the same tube do it in a different position. I wouldn't leave the amp running that long like that. Jeff, Germ?

            Maybe I should buy a new multi-meter and meter the good one out?
            If that one hasn't drifted off value to far? I'll have a Idea what the hell
            it is.
            That might not be a bad idea, even if it's drifted a bit you can still match it to a standardized value. ... That tube look indictates another problem for sure though.
            ::::To sound reinforcement engineer::::
            ... What? ... ::::snicker:::: ...Yes, ... Right, ...
            Could we please have everything louder than everything else ? ...

            Comment


            • #7
              Re: Peavey grid resistor specs. ?

              Thanks Kent! it's the 2nd tube I tried in that socket ! So I'm sure it's
              that socket/or related to it. I shut the amp down right away. I'm down
              to my last set of unburnt 6L6s. I'm not putting them anywhere near
              this amp until this is resolved. This amp was a freebie,So if the problem
              is deeper than a resistor or something simple? (The trashman gets some
              more work !!)
              kmcguitars
              GuitarArtologist
              Last edited by kmcguitars; 08-12-2004, 04:54 AM.
              http://www.soundclick.com/whirlwindbluesrevue

              Comment


              • #8
                Re: Peavey grid resistor specs. ?

                Originally posted by kmcguitars
                Thanks Kent! it's the 2nd tube I tried in that socket ! So I'm sure it's
                that socket/or related to it. I shut the amp down right away. I'm down
                to my last set of unburnt 6L6s. I'm not putting them anywhere near
                this amp until this is resolved. This amp was a freebie,So if the problem
                is deeper than a resistor or something simple? (The trashman gets some
                more work !!)


                if you can get me a pic of the innards i would be most appreciative. it will help me out. be sure to indicate, if i cant saee it, where the key is on the tube socket.

                also, now that i know what it is doin, i think it is a screen resistor (not a grid resistor) that went south on you. change both of them, with whatever the schem shows. probably a 470 ohm 2 watter. somethgin like that.

                germ
                Jeremy Ledford
                Tone Guru Extroardinaire
                Tone Shop

                Comment


                • #9
                  Re: Peavey grid resistor specs. ?

                  Germ, this one's all yours!!!.... This one must be an early one...... VTX series runs the 6L6's neither fixed or cathode biased, but instead use transistor pre-drivers for both the bias and audio feeds. Grids (pin 5) are tied together through 1.5k resistors and run to a fixed + 15v supply. (no audio). Plates are standard push/pull wired to either side of the OT. Screen grid's are wired to a tap in the OT between the CT and the plate, thus running at lower voltage. Suppresor grid and cathodes are tied, so basically whereas the older Fender Vibrato circuits modulated bias for volume shifts, this design modulates the entire cathode feed for the signal.......weird stuff...huh?

                  kmc, if you know which pins the resistor in question are attached to, it would help tremendously.....by the way I now doubt they're 47k's....
                  These are the few amps that defy "common" circuit design.... Do you know if it has the 6465 Pre-drivers? (located at the top left corner of the PCB or corner closest to AC cord) If it has these, they are still available....But the T0-220 package transistors aren't.....all in all you're only hope is just to check every component for well within tolerance........or chunk it in the dumpster and grab a beer!

                  good luck!...hopefully germ can help you more!

                  Jeff Seal
                  ..lots and lots of toys!

                  "...swords and tequila, carry me through the fight!"

                  "I am Phil"....
                  www.houstonamprepair.com

                  Comment


                  • #10
                    Re: Peavey grid resistor specs. ?

                    hmmm this is a VTX ? Does the chip read " '75 Classic ". If it does i may have the same exact amp.
                    2004 50th Anniversary Deluxe American Strat, SETH-N BRIDGE, ANT 2 SURFER MIDDLE, ANT 2 DLX MINI HUM NECK

                    280K RS guitarworks volume pot, 250k cts tone pots, .047uf paper in oil Jensen aluminum capacitor, running D'addario Chromes 13's with wound g > Analogman Orange Juicer>Acoustic 200H Bass head> Alesis Picoverb> unknown 12'' JBL Orange car speaker

                    Comment


                    • #11
                      Re: Peavey grid resistor specs. ?

                      O.K. here's some pics. Thanks guys for all the input Jeff, At a quick
                      glance I didn't see a 6465 chip? ( But I'm gonna get a better look in
                      the daylight) It's a Peavey Classic VTX series. That's all it says and
                      I believe its 65 watts.The resistor in ? runs from pins 3 to 7. Thanks again Hope the pics help.
                      BTW, If you look next to the filter cap there's a 1 amp fuse missing.
                      It poped the 1st time I fired it up. I took the one from my Princeton
                      to get it working again. (It's now back in the princeton) Ah, yes good
                      ole' Point to point wiring in that baby !! I hate this PCB IC chip crap
                      Makes a Cold beer and the trashman look that much better!


                      kmcguitars
                      GuitarArtologist
                      Last edited by kmcguitars; 08-12-2004, 10:08 PM.
                      http://www.soundclick.com/whirlwindbluesrevue

                      Comment


                      • #12
                        Re: Peavey grid resistor specs. ?

                        Pics helped.... The transistors mounted on that corner (again closest to AC cord) are the discontinued TO-220's... If they're bad, it's almost next to impossible to find them.

                        The componenets mounted to the tube sockets aren't resistors at all, they are "spike suppression" diodes, (thus why they're black and have a silver band denoting cathode) cut them out and do not replace them. (the slight benefit they provide is greatly outwieghed by the fact they will fail even under normal power-up conditions) The only current production amps that still use them besides Peavey is Crate and Ampeg and it's well known they wish they wouldn't have! No other amps use them...so I can guarantee you they're not that important.... If anyone would like to disagree, that's fine and I'll find you a suitable replacement diode for it..... this explains the weird numbers as the factory designation is 2873.

                        Jeff Seal
                        ..lots and lots of toys!

                        "...swords and tequila, carry me through the fight!"

                        "I am Phil"....
                        www.houstonamprepair.com

                        Comment


                        • #13
                          Re: Peavey grid resistor specs. ?

                          Thanks Jeff So my true grid resistors are the ceramic pairs mounted
                          on the PCB ? I just checked, I don't see a TO-220 chip? Is it on the main
                          PCB or the power supply board? Maybe it was changed to a different
                          spec.? I think Someone was inside this amp before ? If the 220 is not
                          avilable is there a subsititute? This is all weird to me I'm used
                          to the insides of BF/SF Fender amps. I may be getting in over my head
                          with this thing? And to make matters worse no luck finding a schmatic
                          for this thing?? I found one for a Duece and Mace ( I wish it was one
                          of them ) You where right on them the grid resistor is 47k. But this
                          is most likely a whole different beast. May be time for that Beer
                          http://www.soundclick.com/whirlwindbluesrevue

                          Comment


                          • #14
                            Re: Peavey grid resistor specs. ?

                            My bad, for not explaining...... TO-220 is a description of a transistor, not a part number and not a chip at all! (where did that come from?). The two transistors next to the ceramic resistors attached to the metal "plates" are the transistors I was referring to. Because they have the three legs on one side and the metal "tab on the other.... this is a TO-220 transistor, most of the VTX's had the TO-3 transistors, which look entirely different (round "can" looking transistor's)....

                            Your actual grid resistors are the 1.5k (brown, green, red and either gold or silver), but a better idea would be to turn the amp on without the 6L6's and check pin 5 for about 15v....

                            JS
                            ..lots and lots of toys!

                            "...swords and tequila, carry me through the fight!"

                            "I am Phil"....
                            www.houstonamprepair.com

                            Comment


                            • #15
                              Re: Peavey grid resistor specs. ?

                              Originally posted by Jeff Seal
                              Germ, this one's all yours!!!.... This one must be an early one...... VTX series runs the 6L6's neither fixed or cathode biased, but instead use transistor pre-drivers for both the bias and audio feeds. Grids (pin 5) are tied together through 1.5k resistors and run to a fixed + 15v supply. (no audio). Plates are standard push/pull wired to either side of the OT. Screen grid's are wired to a tap in the OT between the CT and the plate, thus running at lower voltage. Suppresor grid and cathodes are tied, so basically whereas the older Fender Vibrato circuits modulated bias for volume shifts, this design modulates the entire cathode feed for the signal.......weird stuff...huh?
                              Ya got that right, BTW I love the original Fender Tremolo ... what did they call it ... Harmonic Tremolo I think, it's the simplest of there designs and it sounds better than the LED/LDR designs ... cool.

                              kmc, if you know which pins the resistor in question are attached to, it would help tremendously.....by the way I now doubt they're 47k's....
                              These are the few amps that defy "common" circuit design.... Do you know if it has the 6465 Pre-drivers? (located at the top left corner of the PCB or corner closest to AC cord) If it has these, they are still available....But the T0-220 package transistors aren't.....all in all you're only hope is just to check every component for well within tolerance........or chunk it in the dumpster and grab a beer!

                              good luck!...hopefully germ can help you more!

                              Jeff Seal
                              One place you might look ... www.chipdocs.com as that site will find places that still have obsolete parts stored, and prices. You punch in the part number, they cover lot's of semi-conductors and chip based passives.
                              ::::To sound reinforcement engineer::::
                              ... What? ... ::::snicker:::: ...Yes, ... Right, ...
                              Could we please have everything louder than everything else ? ...

                              Comment

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