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Peavey Delta Blues issue...won't work

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  • Peavey Delta Blues issue...won't work

    I have had this long term issue with my Delta Blues 1-15". At times, after sitting, it will not power up....nothing, no sound, no lights, nada. It will work fine for the longest time and then suddenly just not work. Normally after it is on it will stay on....have had it on for 12 hours waiting for it to die, never did. The other day it died AFTER it powered up and I thought "this is great" now I can finally isolate what the problem is. I turned the amp over and all the power tubes were NOT lit but all the 12AX7's were. Problem is shortly after I turned it off and on again everything started working again. I have absolutely no confidence in this amp. It has new tubes, I have "worked" the sockets for oxidation, tried a plug in the effects send/return, spray cleaned the PCB and inputs. I am thinking cold solder joint or defective resistor but I'm no tech. I can understand why the PCB's on these things are called the "tunnel of hell" with it's 3-panel design held together by bare jumper wires. Anybody ever have this problem and had it resolved? I'm thinking the next time it happens the amp will turn into an extension speaker cabinet for my Classic 30.

  • #2
    Circuits are circuits, they all work the same.

    Your power tubes are wired heaters in series. All go dark if one opens. Look at your schematic. All the heaters run off the same winding, but the preamp tubes are series wired across the -36v supply, while the power tubes are series wired across the 24vAC. SO we know the AC is getting to the bridge because we have the -36v, the preamp tubes are lit. See the two resistors R71 R72 above and below the bridge? They are in series with your tube heaters too. They are crosswise at the end of the center board, right around the bend from the fuses. See if they are open, or have cracked solder.

    Those bare wire jumpers between boards? There is a pair of them by each end of those resistors. They carry the 24vAC from the fuses, through the resistors, then on to the tube board. Power off, and gently tug each of those wires, any break free? Actually, any time I have one of those amps open, I just go down the two rows and tug up on each and every little jumper. ANy that come free need to be repaired. Vibration sometimes cracks them and they can break.


    Now having said that, that approach deals with the power tube heaters. If the whole amp stays dark, that points to mains wiring. You have the incoming mains cord, the fuse holder on the chassis, the power switch, I forget if there is a thermistor or not, and the power transformer primary. Wiggling the wires to each thing often reveals any intermittant connections, otherwise simple continuity tests fromk neutral through and back to hot should reveal the open.

    The factory will send you the drawings, but may I suggest using the Classic 30 drawings. Other than the tremolo, the circuits are the same, and the layout very similar, but the Delta BLues layout is an outline drawing, the Classic 30 drawing shows the copper tracework, so you can follow the trace paths.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      The power tubes 'not lighting' may be the clue.
      The output tubes have there own heater circuit.
      The tubes heaters are in series.
      Yup, one goes they all go.
      So if they are not lit, it is a tube or a circuit problem.
      New tubes do not help, so it is down to the heater circuit.
      Now you get to find out what is the problem.
      I would check (resolder) any connection on the heater circuit.
      Headers, those stupid connectors, tube heater joints.

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      • #4
        thank you very much for the reply....I am understanding what you are saying just not knowledgeable enough electronically to apply it. I am printing the reply out however and if I decide to "sink" more money into the amp I will bring your response along with me.

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        • #5
          yeah, when the amp quit out after first firing up I thought I could finally "nail" the problem when seeing the power tubes dark. But as always after a while "all is well again" and she works. But I know you are right about it being in the heater circuit rather than the tubes themselves. Hopefully, I can locate a reputable repair facility not too far from the house. But as I've been told before, it's hard to fix something when it's still working. We'll see, I might give this puppy one more chance as I really like the amp...thanks

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          • #6
            It won't be the tubes themselves for this.

            Tell a repair shop: You have intermittant loss of power tube heater power. Tell them it was suggested by an authorized repair shop to look at the two 3 ohm 5 watt resistors R71 and R72 or the jumper wires at their ends. They will know what that means.

            Of course it could be something else, but experience tells me that is the first place to look.
            Education is what you're left with after you have forgotten what you have learned.

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            • #7
              OK, I will do that....I appreciate the info. It's a little frustrating that I don't feel confident enough to do this myself but I'm afraid I might do more harm than good....thanks again

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              • #8
                Those are the most miserable amps to work on because of those stupid jumpers. Designed to be manufactured, but not serviced. I appreciate Leo more every time I have to open one of these up.
                It's weird, because it WAS working fine.....

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                • #9
                  well, tomorrow she goes to a legitimate Peavey repair facility. I'm not messing with it. But as usual it's working fine right now. I just hope they can actually find something wrong with it and repair it so maybe I can develop a little more confidence in it....

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                  • #10
                    Tell them about the intermittent heaters and they will know. It is a VERY common problem and can be repaired as to not happen again by adding more flexible jumpers between the boards at the ends of R71 and R72, bypassing or replacing the two current un-insulated jumper wires. To do it right, the 4 pc boards have to come out(the U boards and the speaker jack PC board) but that is not hard or time consuming.

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                    • #11
                      I think I'll print out your reply and tape it to the amp....some of these guys are touchy though and I don't want them to think I'm telling them how to do the job. I can't believe I'm getting replies from all the way from Russia! thanks.....

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                      • #12
                        just wanted to inform those who helped me that I did have the amp serviced and the tech indicated that he did re-solder some cold solder connections on the "heater lines". So, hopefully all is well....thanks again

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                        • #13
                          Congratulations on getting your amp working and playing again. Depending on how he repaired it, it will probably happen some time in the future again. If you have a soldering iron and a screwdriver, we can talk you through taking care of it again.

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                          • #14
                            yes...he probably just re-soldered the existing bare wire jumper cables...I remember you saying about putting some flexible wire jumpers to do it right but I'm sure this is the most cost effective way....at least it works. It's not moved that much so maybe she'll hold for a while. I'm just wondering if the original owner "bounced" this thing around a little, jarred something loose.
                            Appreciate the offer about the online tutoring....will keep it in mind.

                            Comment


                            • #15
                              Hi all, sorry for digging this up from the depths but Google brought me here and I have had a problem similar and wanted to see what everyone thinks.

                              Bought the amp new in '94 and have used it a fair amount, retubed it several times, new speaker a few years back, it's generally in good shape. I have an electronics background, including repair of tube gear (worked in repair dept. of Sam Ash for several years fixing this kinda stuff) so I have a decent clue about this stuff lol.

                              Last night first tune of the gig, semi full house and the amp quits, no sound. Pilot light on, all tubes appear to be lit just not as bright as normal. Switch from creative brain to technical brain and begin troubleshooting:
                              -Plug straight into amp, bypassing pedalboard/wireless unit. Nothing.
                              -Plug into effects return to bypass preamp section, nothing.
                              -Backup guitar, nothing.
                              -Spare cable, nothing.

                              Start wiggling tubes around to see if any weren't fully seated and noticed they were lit up more than before and not only that, I had sound! Thinking something wasn't seated, I plugged back in and away I went.
                              First song, halfway thru the sound fades and dies out. Look in back, tubes barely lit again. At this point I recall two things:
                              -These amps have the tube heaters wired in series.
                              -I have old spares in my gig bag.

                              I quickly replace the power tubes, everything lights up and we have sound!!! Play the rest of the 3 hour gig with no issues except that the old tubes sound worn but not horrible. Ordered new tubes as soon as I get home from gig at 3am.

                              Popped it open yesterday and just took a quick look for any hotspots or burn marks around connectors and resistors etc... (didn't pull the pcb's out) but everything looked fine. Next step would be to check solder joints. After I put it all back together I played the snot out of it for a good 90 minutes at gig volume (and beyond) trying to make it cut out but couldn't.

                              My questions to those out there that have experience with this platform of amp:
                              -Since the amp worked fine after replacing the power tubes, could there be anything else to look at that caused it? Power tubes are in my opinion the weakest link of the chain and do go wonky, so maybe it was just a bad tube.
                              - Thermal cycling? Cold car to warming up to hot at gig and back to cold car.....
                              -Good time to swap out filter caps? It is close to 25 years old and all original, however they all appear to be fine, no bulges or ooze anywhere.
                              -Any tips for extracting the pcb assy. out of this amp? I hear they can be tricky.

                              Apologies again for revisiting this and sorry for the long post. Thanks in advance, I appreciate it.

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