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Orange Rockerverb 100 Squealing

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  • #1

    Orange Rockerverb 100 Squealing

    One of our Orange Rockerverb 100 amp heads came in for service from our rental inventory. There wasn't any mention that it was squealing....just that the Reverb was stated not working as well as when it does work, that it's too springy.

    Reverb DID work, contrary to the Guitar Dept claims, but I agree that it sounds horrible. Worse, though, is with a 100k terminator plug installed in the input jack, or an instrument plugged in the Dirty Channel oscillates if you turn the Gain and Volume pots way up. And can tune the oscillation with the tone controls, as well as the Gain and Volume pots. Sigh........

    I have it on the bench, started with the lead dress of the Output Xfmr wires. Unlike that problem I found on the AD200 bass amp, I've only had marginal change with wrapping the primary/secondary wires twisted together, and routing the wire bundle. Different wire exiting path on this amp from the AD200. I'm getting much greater variation with this oscillation positioning the power supply ribbon cable between the source end and the Preamp Receiving end. Helped sliding that cable in between the two boards, as well as bundling the Send/Return Effects Loop cables, but....thus far, the oscillation is stiff. Shielding the open bottom of the chassis (no shielding on the cabinet to close up the open steel chassis) only helps some, but will NOT kill the oscillation. So, while I've tamed it down some, I haven't yet found the magic bullet to kill the oscillation all together. Worse with my bass plugged in.

    So, chasing this one down. Photos will come when I have a working revelation.
    Logic is an organized way of going wrong with confidence
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  • #2
    You might be approaching this backwards? Maybe try a known non microphonic preamp tube in the the first position for the gain channel first. Of course I may be way off. And I'm sure you know what a microphonic tube sounds like. So if not a tube then I might suspect any unsoldered connection in the signal path or a bad ground connection. I mean, the amp DID work once upon a time, right? So what could have changed?
    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "If you're not interested in opinions and the experience of others, why even start a thread?
    You can't just expect consent." Helmholtz

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    • #3
      Sounds like mechanical/acoustic feedback to me.
      Either microphonic tube or the tank itself.

      Does the oscillation stop when you disconnect the tank input?
      - Own Opinions Only -

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      • #4
        Is it like this?


        If so, some of the video comments may help. This particular problem seems to be ribbon cable related.
        "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22
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        • #5
          Originally posted by Helmholtz View Post
          Sounds like mechanical/acoustic feedback to me.
          Either microphonic tube or the tank itself.

          Does the oscillation stop when you disconnect the tank input?
          The Tank isn't involved. I have the chassis open on the bench standing vertical. I've swapped out the two tubes in the Dirty Ch, with no difference. Very Noisy at full gain, though Full Gain (with input shorted) is very noisy. With Guitar or shielded 100k input terminator plug inserted, you can't get to full gain without full scale clipped oscillation.
          Logic is an organized way of going wrong with confidence

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          • #6
            Originally posted by Chuck H View Post
            I mean, the amp DID work once upon a time, right? So what could have changed?
            Wasn't a microphonic tube. Orange' service documents leaves a lot to be desired. As to the amp DID once work without this occurring, I can't say for certain. I had recently encountered same problem on our four Orange AD200 amps, which was mainly lead dress of the Output Xfmr Pri/Sec leads...where the Primary was exiting from nearly underneath the input tube stage. I solved it on those four amps with revising the Pri/Sec wire bundle, twisting the two sets together and routing as far away from the input jack as possible. One chassis had to have a shield laid in on the cabinet ti cure it.

            On this one, I've NOT come up with a solution. Shield helps a little, but doesn't stop it. I've moved on to the Reverb Tank, finding the original Ruby RRVS3AB2C1B tank with two of the three short springs broken out. No stock on that tank, so will have to cobble an Accutronics 8AB2D1A tank to replace it, needing to Ground the Output RCA jack. May have to rob that connector from one of my saved Broken tanks to have that little ground terminal and the short chassis screw to achieve it on those connectors.
            Logic is an organized way of going wrong with confidence
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            • #7
              Originally posted by The Dude View Post
              Is it like this?


              If so, some of the video comments may help. This particular problem seems to be ribbon cable related.
              My desk computer's Sound Card isn't responding, and haven't figured that out, so I'll have to listen to this YouTube file when I get home. That power supply ribbon is one of several cables inside involved with the degree of onset of the full oscillation.
              Logic is an organized way of going wrong with confidence

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              • #8
                The opening post stated the problem is worse with the dirty channel. This latest post is focused more on the reverb issue (I think?). Just to stay on track, does the oscillation issue seem to be separate of the reverb issue? That is, are we solving two problems or does the oscillation issue seem to be related to the reverb issue?

                Also, a schematic might help for further discussion. Assessing drive levels between the channels on the reverb or anything else, etc.
                "Take two placebos, works twice as well." Enzo

                "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                "If you're not interested in opinions and the experience of others, why even start a thread?
                You can't just expect consent." Helmholtz

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                • #9
                  Orange Rockverb 50 is the only one I can help with
                  Attached Files

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                  • #10
                    Originally posted by Chuck H View Post
                    The opening post stated the problem is worse with the dirty channel. This latest post is focused more on the reverb issue (I think?). Just to stay on track, does the oscillation issue seem to be separate of the reverb issue? That is, are we solving two problems or does the oscillation issue seem to be related to the reverb issue?

                    Also, a schematic might help for further discussion. Assessing drive levels between the channels on the reverb or anything else, etc.
                    I just got to listen to the The Dude's YouTube attachment, and yes....that's the problem. The Reverb is turned all the way off, so it's not involved. With the amp standing up on the Power Xfmr end braced so I have access to the internal harnessing, There are multiple cables involved in the sensitivity of the oscillation starting. The 10-pin ribbon cable from the Power Supply to the Preamp board at the other end of the chassis is very sensitive to orientation. I was able to slip it in between the two PCB's. There's a blue wire...not yet sure it's role...that runs the same span that also is involved. The cable harness that carries the Effects Loop signal from the jacks to the opposite corner of the chassis is involved. The Primary of the O/T is involved.

                    At present, you cannot turn the Dirty Ch to full volume (both Gain and Volume at max) without full clipped oscillation. Turning either Gain or Volume down will get to killing it. Tone circuits as well as either Gain or Volume are involved in tuning the oscillation. Just what a great amp needs!

                    I haven't looked at any of our other Rockerverb amps yet, but based on what I have here, I need to look at those amps as well. I'll post what schematics Orange provides when I get back to the shop. Watching the MLB playoffs today and probably tomorrow.

                    This amp thus far is much worse than the AD200 was, which was relatively easy to correct. I've swapped the two tubes in the preamp path of the Dirty Ch circuit with no difference.

                    Presently replacing the short 3-spring Reverb tank, unable to find any Ruby RRVS3AB2C1B replacement tanks. So, this amp will be apart for a few days.
                    Logic is an organized way of going wrong with confidence

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                    • #11
                      I can't upload the schem right now (my bandwidth is intermittently terrible) but here's what I'm thinking...

                      If the amps are made this way I have to assume MOST of them work. Now, even with some futzing, this one you have cannot be made to work as it is. Perhaps there is an issue like some of the Fender HR models where like phase circuits share a common HT source. Maybe when the decoupling capacitors are in top working order the amp works? That might explain why more care wasn't taken with the layout? They may not have known it was necessary. If there are like phase circuits sharing a power supply node you might at least try paralleling a good capacitor across the one in circuit just to see what happens.
                      "Take two placebos, works twice as well." Enzo

                      "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                      "If you're not interested in opinions and the experience of others, why even start a thread?
                      You can't just expect consent." Helmholtz

                      Comment

                      • #12
                        Ok. I was able to see the schematic this morning. It doesn't appear that like phase stages are shared on PS nodes with the exception that first preamp tube for either channel is on the same node and the channel switching arrangement grounds the unused channel through 47 ohm resistors. I would think this is sufficient to limit interaction BUT I would try pulling the first tube for the normal channel (V10 on the schematic) and see if the oscillation in the gain channel changes at all. If it does I might suspect the F node decoupling cap and/or I might try shorting the 47 ohm to ground resistors on the relays. The 47 ohm resistors are probably there for a reason I don't understand so that may cause some other problem, but maybe not.
                        "Take two placebos, works twice as well." Enzo

                        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                        "If you're not interested in opinions and the experience of others, why even start a thread?
                        You can't just expect consent." Helmholtz

                        Comment

                        • #13
                          Schematics for the Orange Rocerverb 100 that I have on hand:

                          Rockerverb 100W Power Board.pdf
                          Rockerverb Preamp Sheet 1.pdf
                          Rockerverb Preamp Sheet 2.pdf
                          RK50MK2.pdf

                          Rockerverb100-Manual.pdf

                          I'll dig back into this amp either later today or tomorrow. I have a scope on the bench trying to find why I don't have internal triggering on the mainframe. Still dealing with my main bench scope NOT having a CRT display, and the potential backup is still not yet functional. Shops are NOT supposed to have Lab Gear Failures!
                          Logic is an organized way of going wrong with confidence
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                          • #14
                            After I got the substitution Reverb in, and robbed the Output connector assy from another Accutronics RED Plastic connector assy that HAD the GND'd tab which the tank I bought in place of the Ruby tank that wasn't available, I played with the Preamp tubes, but didn't achieve any improvements. I instead had the next Rockerverb 100 brought over from our inventory to see if this first one was just a fluke, or a design issue.

                            It appears to be a design issue. This next Rockerberb 100 squeals just as badly as the first one. I haven't yet pulled this one apart, but will be doing so until it's time to pull the plug and go watch Game 1 of the World Series coming out of Houston. What happened to that great choo-choo train at Minute Maid Field that ran along the rim of the stadium out past the outfield and that great locomotive horn that rang out when the Astro's hit a homer??

                            Logic is an organized way of going wrong with confidence

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                            • #15
                              The past couple days, with this second Orange Rockerverb 100 on the bench, which oscillates beautifully when you turn up both the Volume and Gain pots in the Dirty Ch mode, I looked thru the Orange Forum (no longer active, but all of the posts are present). I was very surprised NOT to find this problem reported in the first 100 pgs of posts (dating back to 2007. I didn't look beyond that, as most of the posts are really NON-technical with respect to those we deal with here on this forum. So far, looking on line, the only mention of this oscillation problem is that which The Dude found in Post # 4. That, however, didn't point to a solution. Just posted the problem that we could hear.

                              So, I looked for R10, which on this amp is a 4.7k Feedback resistor from the 8 ohm tap of the output xmfr secondary. Found that resistor, parked right between C9, the Feedback side of the LTPI output and C8, which is the input cap from the feedback resistor. Both of those 100nF epoxy box caps tightly mounted with the feedback resistor sitting between them seemed like asking for oscillation. BUT, there is NONE in the Clean Ch mode.

                              I first tack-soldered a 100k resistor across R10 so I had a place to both hang my decade box across it, as well as tack-solder a lower value resistor, to see if I could tune out this oscillation by applying more feedback. I took it down to 1k (1.3k across the 4.7k), which barely made any difference. Still oscillates beautifully when turned up. Sigh....

                              I then tried placing a copper shield around C9, having some 1/2" wide adhesive-backed copper shielding, fully enclosed C9 and tack-soldered a ground wire from that shield to the base of R31 100 ohm resistor at GND (bottom of the LTPI cathode string). That too made no difference.

                              At least with the AD200, I was able to null out the oscillation by lead dress of the Pri/Sec O/T wires placement. NOT SO on this Rockerverb layout. The only time I got NO Feedback was when I draped the output load cable across the open bottom of the chassis. But, with a shield plate there instead, it oscillates/squeals just fine...if that's what you want. I can also stop the feedback with my hand placed inside the chassis. I doubt if obtaining body parts to place in the chassis would work though.

                              So, temporarily out of ideas here.

                              I tried swapping out the LTPI tube V5 (ECC83) with an ECC81/12AT7. Made no difference.

                              Seems odd that with low source impedance on the input jack, there's no squealing/oscillation. Plug in a guitar, passive pickups, or what I've been using...a shielded 100k resistor to raise the input impedance, it feeds back just fine. AND, it ONLY squeals in the Dirty Ch mode. I've tightened down the pot mounting nuts, finding some loose, and the case of the pots weren't exactly at GND potential. Made no difference there either.



                              Last edited by nevetslab; 11-01-2022, 08:33 PM.
                              Logic is an organized way of going wrong with confidence

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