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  • #16
    What TYPE are all these pans?
    Education is what you're left with after you have forgotten what you have learned.

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    • #17
      I don't know what supply nodes means although I think you mean directly out of the can cap? I did replace the can cap with a new one from Antique Electronics, I should see what is coming out of it. I am pretty sure I have it wired up correctly or the amp would not be working very well? I have not done the cable tests yet and really don't know how, just a continuity test. As stated, nice clean signal at the centerpost of the input RCA jack. I was thinking of just replacing the output jack, I have tons of them. I still have to do the signal test. Once I feed a signal into pin 7 of the 7025 what am I looking for, the output amplified or just there? Please excuse these newbie questions and thank you once again for your help.
      J.D.

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      • #18
        In answer to Rizzo, two originals, one accutronics so called replacement, various others, my super reverb pan, my Gemini 6 pan and one I am not sure of.

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        • #19
          Originally posted by dragonwerx View Post
          I don't know what supply nodes means although I think you mean directly out of the can cap? I did replace the can cap with a new one from Antique Electronics, I should see what is coming out of it. I am pretty sure I have it wired up correctly or the amp would not be working very well? I have not done the cable tests yet and really don't know how, just a continuity test. As stated, nice clean signal at the centerpost of the input RCA jack. I was thinking of just replacing the output jack, I have tons of them. I still have to do the signal test. Once I feed a signal into pin 7 of the 7025 what am I looking for, the output amplified or just there? Please excuse these newbie questions and thank you once again for your help.
          J.D.
          Your supply nodes are the power supply reference points A,B,C...on the schematic. They all connect to filter caps and supply different amp stages.
          Voltage is measured from the positive terminal of the cap to ground.

          For a rough check of the rev recovery stage and cable, connect the return cable to the amp only and touch the tip of the tank side plug with your finger.
          You should get a loud hum.

          The recovery stage has lots of gain, maybe 1000 times.. So when feeding a 0.01V (10mV) signal to pin 7 with the tank disconnected you should see a large signal of several Volts on the depth control.

          Even better: Feed your 10mV signal to the recovery stage via the reverb cable (disconnected from tank). This will show if the cable and the recovery stage are good.

          Please measure and post the DCRs of your tank transducers (measured at tank input and output jacks when disconnected from amp).
          - Own Opinions Only -

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          • #20
            I just finished feeding a signal out of my generator into pin 7 of the 7025 and could hear it just fine. The volume control on channel 1 did not affect it, didn't think to try channel 2 volume. When I changed the amplitude and frequency on the signal generator I could hear the changes. I am having a busy day today and will try and get the rest of your instructions completed and up and posted at the latest tomorrow evening. I have a new cable stripped and ready to replace the original but I will wait till I do that test. The return cable is soldered into the amp, there is only an RCA jack on the tank end. At the risk of appearing stupid, which is to late, I don't know what DCR stands for. I didn't check for the signal on the depth control when I had the generator hooked up to pin 7. I will hook the generator up again and check the signal with my scope at the depth control. I am trying to do all this correctly and have to take it slowly. I was a machinist for 52 years, at least the blueprints looked like the part I was making lol. I am getting better at schematic reading bit by bit.
            Thanx again
            J.D.
            Last edited by dragonwerx; 09-18-2021, 05:08 PM.

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            • #21
              Originally posted by dragonwerx View Post
              I just finished feeding a signal out of my generator into pin 7 of the 7025 and could hear it just fine. The volume control on channel 1 did not affect it, didn't think to try channel 2 volume. The return cable is soldered into the amp, there is only an RCA jack on the tank end. At the risk of appearing stupid, which is to late, I don't know what DCR stands for. I didn't check for the signal on the depth control when I had the generator hooked up to pin 7.
              What signal level did you use?
              The input stages of channels 1 and 2 are before the rev. recovery stage and don't see a signal fed to pin 7, so volume settings don't affect anything.

              DCR means DC resistance (as opposed to impedance, which means AC resistance). It's just the Ohm value your Ohmmeter reads

              - Own Opinions Only -

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              • #22
                I am pretty new to all of this. I can see signals and tell if they are amplified or not but don't know how to read voltage with the scope yet. I am using an old HP200cd signal generator. First thing I do is test the signal coming out of the generator and make sure on the scope it is not to large. If I turn the amplitude up I can see the signal clip. So, I set the signal to a nice clean level at 1000hz and go from there. Another thing, I just moved into this house and don't have a test bench set up. I am going to try and upload pics and show you how I am working. This amp is a pain in the butt. The power supply is mounted to the bottom of the amp. To open the amp up and flip it to get at components there is not enough slack so the PS has to be removed and the amp has to be kept close to the cabinet to hook up the speakers and the reverb tank. I have the amp on a table with the PS next to it and the cab on a chair. All the test equipment I have on a rolling cart. Now, I did feed the generator into pin 7 then checked to see that I had a nice clean signal coming in which I did have. Then I checked the depth control and when I turned it up I could see the signal way larger but totally distorted, broken up and all over the place. I could hear the volume go up as I increased the depth control. Then I disconnected the RCA output from the tank and hooked the generator up to the centerpost. I could hear the signal and see it there nice and clean and if I adjusted the amplitude or frequency I could see the change.. Yet, when I went to pin 7 with the scope where the cable goes to I could not see anything no matter where I set the scope. I checked all four posts of the can cap, not sure which is which, I got 297v, 363v, 409v, and 515v. I tried checking the lettered points not sure I am in the right places, I went into the molex connector on the output side and on A I got 470V, B 342V, C 400V, D504V, that is as far as I have gotten. I don't know if you have ever worked on one of these amps but it is one of the worst rats nest I have had the pleasure to lay eyes on. I hope I am not boring you, I apologize for my lack of knowledge but I have to start somewhere?
                I tried to upload pics but this is what I get in response: Upload failed due to your usergroup's upload quota. This file will require 1.00 MB but you only have 776.6 KB of 976.6 KB remaining. I am guessing the pic files are too large.
                J.D.

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                • #23
                  I am done with this. Soldered two new cables in today, no go. I have put way too much time into it and have gotten nowhere. I just don't have the expertise yet and am in over my head. I haven't practiced an of my instruments in days because of it and I need the room in the basement. I packed it up and put it back together. I will bring it to an amp tech when I find one. Maybe if I am lucky and it can be fixed whoever does the work will tell me what the heck it is.
                  Thanx for those that helped along the way.
                  J.D.

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                  • #24
                    I have reverb now, and too much of it. As I turn it too high she starts feeding back.

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                    • #25
                      Originally posted by dragonwerx View Post
                      I have reverb now, and too much of it. As I turn it too high she starts feeding back.
                      Wow, what did you change since your last post?

                      The feedback you have is acoustic feedback. It means that tank and reverb circuit are working fine but the tank needs better acoustic insulation against speaker and cabinet vibrations.
                      How is the tank mounted?


                      - Own Opinions Only -

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                      • #26
                        The tank was not mounted, just sitting on top of the amp. Now for the juicy details. I probably went all through this for nothing. I replaced both connectors, the .01uf @400v cap and the 270K resistor on pin 1 of the 7025. Before I had done that, I needed the room in the one side of the basement, so I moved the amp to the other side. Before I had the cabinet facing down. Now I have the cabinet facing up. I noticed one of the speakers was not working. I started checking. There is a knob for a switch for internal or external speakers. That knob was missing. The knob for the on and off/polarity switch keeps falling off when the amp is upside down. I didn't realize it was set to external speakers. As soon as I set it for internal speakers both speakers started working and the reverb kicked in. Now, I have to look and see why once speaker cuts out when it is switched to external speakers. I am guessing the reverb cuts out if that speaker is not working since the return only goes through one channel. One other thing, when switched to internal speakers, there is considerably more hum in the amp. At one time while changing electrolytics ect., while I had the amp upside down the knob probably fell off, I must have put it back on the internal/external switch and switched the external speakers on and much of the hum went away and I probably thought I had turned the polarity switch which is right next to it. I don't really know. This is a weird amp if you read the literature. I don't know if that is normal or not. I will also have to look at the schematic and see if I can figure out if that is the normal operation of the amp or if there is something wrong with the internal/external switch. Why would the amp only work with one speaker and the reverb cut out when switched to external? If I were within driving distance of you, I would come over and let you kick me in the ass. The reverb was feeding back before all of this with the original tank anchored in the cab. I was using the accutronics reverb which I had sitting on top of the amp. I hooked up my "Ruby" tank which is about half the physical length of the accutronics an it doesn't feed back but doesn't sound as good. The hum that is introduced when turning on the internal speakers is unacceptable. It may be just that the hum that is driving the reverb into feeding back? We live and we learn or we get electrocuted. I am pretty sure that is how I am going to go at this rate, but I could think of worse ways.

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                        • #27
                          While working with the cabinet upside down, although it didn't have far to go, the thought of both speakers not working did cross my mind, but I couldn't really tell because the cabinet was upside down. In the heat of the moment I forgot about that and didn't catch it until I moved everything and had the cabinet facing up. Then I thought, let me check and see if both speakers are working, doh. After looking at the schematic there must be something wrong with that switch (rotary knob), it appears that both speakers should still be working with the external speakers turned on.

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                          • #28
                            Originally posted by dragonwerx View Post
                            After looking at the schematic there must be something wrong with that switch (rotary knob), it appears that both speakers should still be working with the external speakers turned on.
                            The ext. spkr. jacks also have switch contacts in them. Those contacts should close when nothing plugged into the jacks. If the contacts are oxidized or bent, the internal spkr. will not work with the switch in one position.
                            The idea seems to be to have the ability to turn internal speakers off when ext. spkrs. are in use.

                            "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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                            • #29
                              I have never plugged a jack into them and they look almost as clean as the day they were installed. The contacts appear open, I can see between them. Even when I plug a jack in they appear open unless they are making contact somewhere below the insulator where I can't see it. The problem now is, why is hum being introduced when the rotary switch is turned to internal. Either something with the switch or something when the other channel amp comes on line? I have two of these amps, the other one has lots of problems like a
                              burnt connection in the twelve pin molex connector from the power supply to the amp. I have never tried to fire it up. I could switch out the rotary switch between them but I don't believe that is the problem. It is probably when the other amp comes on comes on line and problem there. I will switch them out to see anyway. Only two wire easily accessible.
                              Last edited by dragonwerx; 09-22-2021, 11:58 AM.

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                              • #30
                                I see the contacts now. They are closed and they do open when a jack is inserted. This amp is such a pain in the butt. I don't see how I am going to get the rotary switch out without taking the whole amp cover off. You can't get a socket or nut driver down in there. There is not enough clearance to fit one in. I am going to give my smallest needle nose pliers a shot but I don't think that is going to do it. I would unsolder the four leads and try unscrewing the pot out from the back but the on/off switch is in the way.

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