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Looking for Information on Seeburg SHP3 amplifier

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    #1

    Looking for Information on Seeburg SHP3 amplifier

    I have been restoring some Seeburg SHP3 amplifiers for a customer. I have repaired wiring and replaced caps and done a ton of cleaning. Not used to working on this older audio gear, so I am basically a noob. It seems pretty straight forward, but I am missing some important schematics. I have both board schematics and most of the chassis schematics. I also have a PARTIAL parts list, but no information on the resistors. I am nearly ready to power this up(on bench) and I believe the customer has all the schematics, but he is a little old school and I thought I might ask here(as you guys have been very helpful in the past. Right now, I have an issue where it looks like someone replaced a 180 Ohm resistor with a 220 Ohm resistor in the dead bug section of the chassis(mute trip switch). Not a huge deal, I can't verify what is supposed to be where. Only guess. I am familiar with Tony Miller's book, and I can find a few places where I purchase them, but I can just get the manual from the owner and convert them to PDF. Also, if there is interest in this, I will start a detailed restoration thread. If I manage to slow start this amp and none of the magic smoke escapes, I will start the process of setting the bias and tracking down any problems, including distortion. I will also be(here it comes) stuffing new lytics in the old filter caps Thanks!
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    #2
    Re: Looking for Information on Seeburg SHP3 amplifier

    May be providing the pictures and the schematic will help.
    http://www.cparso.com/2017/07/seeburg-shp3.html
    http://4tubes.com/SCHEMATICS/Music-amps/Seeburg/
    http://arcarc.xmission.com/PDF_Jukeb...rg/Schematics/
    Last edited by budm; 09-27-2018, 10:03 AM.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

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      #3
      Re: Looking for Information on Seeburg SHP3 amplifier

      I got a hold of the customer and he will be dropping off an actual set of original Seeburg schematics. I can turn them into PDFs at that point. Should I upload them somewhere for the next guy? If so, where?

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        #4
        Re: Looking for Information on Seeburg SHP3 amplifier

        You can upload them here (on badcaps.net). Just click on the "Post Reply" button near the bottom of the page, then on the new page, click "Manage Attachments" button and upload here.

        Regarding the amplifier releasing the magic smoke - you can avoid that by hooking up a 60-150 Watt incandescent light bulb in series with the live power line. This will limit current to the amp, should something major on the output stage decide to do funny business.

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          #5
          Re: Looking for Information on Seeburg SHP3 amplifier

          So, it's been a minute. In fact, I forgot I posted this. I'll make a quick breakdown of what has happened. After replacing some wires with solder iron burns and thoroughly testing the driver and preamp boards, I powered it up slowly with a Variac(with a dim bulb and isolation transformer of course). Around 30 Volts, the bulbs started to glow and just as I was reaching to turn off the power a main filter cap exploded in my face. After replacing all the electrolytics, I tried it again and still had a short. Left channel output transistors were hot. I checked the transistors out of circuit and had a short. Replaced. Still drawing current. Traced again. Stabistors(two small signal diodes in series) on same channel were leaking. Replaced in both channels. Still drawing current. After much gnashing of teeth as I still had a short, realized I had put the diodes in backwards. FINALLY, I was able to power up the amp without fault. Attempted to set the bias with the meter before placing on the scope. No response from the bias pots. I had already flushed them with deoxit and followed with contact cleaner. Now armed with the book, realized the correct value should have been 75k. We were only getting about 38k on the "bad" channel. I open the resistor and confirmed someone had put it back together incorrectly. The rotation of the adjuster was being impeded by the stop tab on the rear case of the pot. After cleaning and reassembling the pot, 81k. I was able to put a signal in and confirmed MUCH amplification on the 8ohm load resistors. Hooked up the scope and while I was able to bring the gain up to matching waveforms, they were distorted exactly the same. The bias adjustment was unresponsive on both channels. I have not had time to get to it, but I believe hard driving the driver transistors has caused them to leak. I will upload schematics as soon as I have time to scan them(I haven't had time to wipe correctly since September) and update you on the finished result. I have actually fixed a few of them since starting this one, but the others were mainly cap issues. This one has been a figgin' wreck since the get go.

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            #6
            Re: Looking for Information on Seeburg SHP3 amplifier

            Also, I was under the impression these amps had been in service while owned by this customer. Turns out, he bought them because someone else "didn't have time to fix them". I.e., guessing the same guy that put the pot back together incorrectly had no idea what was wrong.

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              #7
              Re: Looking for Information on Seeburg SHP3 amplifier

              Ok. So I have been busy and this amp was placed to the back burner until I had a bit more time to figure this out. In my sleep deprived state, I used the wrong diodes. What Seeburg called "Stabistors" are really just two graded 1N4148 switching diodes(they were blue, and that thew me for a loop). I had one of those "Oh, duh." Moments while working in an AMI control computer board that had corroded switching diodes and realized my mistake in the Seeburg bias circuit. After replacing all four diodes, the bias adjustment pots worked normally. all though the floor of one channel is still high(39mV) where the recommended setting is 2-20mV as measured from test point to collector of the power transistors. No more current draw after the initial in-rush current. The wave form is stable on both channels, but the amp sounds "muddy". I am thinking it is in the per-amp board as all the electrolytics have been replaced. I will finish the thread in case someone needs the info later with pics and I still have not had time to scan up all the schematics. There are a lot and it is a work in progress. Will upload them as soon as I finish. Thanks again for the input.

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                #8
                Re: Looking for Information on Seeburg SHP3 amplifier

                Thanks for following up on the thread, circuitmonkey. I'm sure the info could come helpful to anyone trying to repair any similar issues with this amp.

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                  #9
                  Re: Looking for Information on Seeburg SHP3 amplifier

                  Ok, Sorry it took so long. I finally had time to get my pc talking to my scanner, so I was able to create a PDF that contained all the pages of the manual's amplifier section instead of each page on a separate PDF. I will upload more schematics as I have time to scan them. If you are looking for SS160 info, I may have the schematic. Post here to engage my rear and I'll post them.
                  Attached Files

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                    #10
                    Re: Looking for Information on Seeburg SHP3 amplifier

                    This PDF is for the Seeburg Digital control centers. They cover more than those listed in the file name. Check the first page of PDF for your flavor. They are more useful than some of the others I have seen and I tried my best to make them searchable. They mostly are. I think...
                    Attached Files

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                      #11
                      Re: Looking for Information on Seeburg SHP3 amplifier

                      And just because, here are the schematics for the SHFA1, SHA3, and SHFA4. Of course, the only SHFA amplifier models I have to restore are both SHFA2's....
                      Anyway, I scanned these up myself and so far they are better resolution than any I have seen on the net. The resolution holds up pretty well through a lrage amount of zoom, and I couldn't find anything that was illegible. So I hope someone finds them helpful.
                      Attached Files

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                        #12
                        Re: Looking for Information on Seeburg SHP3 amplifier

                        So the amp is finished. It actually has been finished for a few weeks,but I have been pretty busy. This amp represented the SHP I had that required the most repair. From the power supply all the way through the output signals and control boards. It was re-wired. Re-capped. All the transistors replaced, including matched transistors in the pre-amp. The bias was set (correctly) and after being tested on the bench for nearly ten hours, performed flawlessly. The customer is happy. I am happy(mostly to have it gone, but also because I fixed a non-working POS and restored it to full function). There are several videos posted to Youtube on my channel, Circuit Monkey. Thank you for helping with this project! The videos are meant to demonstrate the amount of work that goes into the amps and are intended more for beginners than vets like you, but the final video demonstrates the amp working in the last couple of minutes. I am still working on Seeburgs, but I have a lot of other amps and projects going as I type this. Thank you again. Take care.

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                          #13
                          Re: Looking for Information on Seeburg SHP3 amplifier

                          Originally posted by circuitmonkey View Post
                          This amp represented the SHP I had that required the most repair. From the power supply all the way through the output signals and control boards. It was re-wired. Re-capped. All the transistors replaced, including matched transistors in the pre-amp. The bias was set (correctly) and after being tested on the bench for nearly ten hours, performed flawlessly.
                          Wow, that's a full rebuild job right there! Nice work, though.

                          Also, great videos!

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                            #14
                            Re: Looking for Information on Seeburg SHP3 amplifier

                            Thanks!

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