My Seeburg 160 with a TSU 5 started doing the dreaded two scans/no record pick ups after working flawlessly for over a decade. Here’s what I noticed: both OA2 tubes were unlit. There was a blow electrolytic cap (10MF/450V) nearby (blown in the sense that the positive end is bulging with some white crud deposits). It looks like it’s C512. All the other caps visually look fine. Someone did a cap job on the unit before I acquired it 25 years ago.
I happened to have a similar electrolytic cap with the same specs so I replaced it to see if the OA2s would relit. I also replaced the 6X4 with one from a working guitar amp in case that was the issue. The new cap & the fuse blew in less than a minute. (Note that I had run the unit with the original bulging cap for a lot longer earlier while trying to figure out what was wrong and the fuse didn’t blow. The new cap is shorted/The original cap is not shorted.) Any suggestions on where to start on this issue? I could replace the cap and fuse and try again but that seems like risking more damage. Start testing all the nearby resistors? Put the original cap back in and see if a new fuse wouldn't blow so I could start testing voltages? (Note: The OA2s and 6X4 have never been changed.) Replace all the electrolytics?
Any help trouble shooting will be greatly appreciated.
jerold k
Dumb question. The electrolytic cap you are describing is polarity sensitive. Did you put it in backwards perhaps? That certainly would make it blow immediately.
Additionally the “crud” coming out of the cap means it’s leaking not blown but certainly should be replaced.
Your OA2’s should emit a purple glow and should pulse as the mech scans
Regards Rick
On Fri, Jan 6, 2023 at 6:48 PM Jerold Kress via Jukebox-list < jukebox-list@lists.netlojix.com> wrote:
My Seeburg 160 with a TSU 5 started doing the dreaded two scans/no record pick ups after working flawlessly for over a decade. Here’s what I noticed: both OA2 tubes were unlit. There was a blow electrolytic cap (10MF/450V) nearby (blown in the sense that the positive end is bulging with some white crud deposits). It looks like it’s C512. All the other caps visually look fine. Someone did a cap job on the unit before I acquired it 25 years ago.
I happened to have a similar electrolytic cap with the same specs so I replaced it to see if the OA2s would relit. I also replaced the 6X4 with one from a working guitar amp in case that was the issue. The new cap & the fuse blew in less than a minute. (Note that I had run the unit with the original bulging cap for a lot longer earlier while trying to figure out what was wrong and the fuse didn’t blow. The new cap is shorted/The original cap is not shorted.) Any suggestions on where to start on this issue? I could replace the cap and fuse and try again but that seems like risking more damage. Start testing all the nearby resistors? Put the original cap back in and see if a new fuse wouldn't blow so I could start testing voltages? (Note: The OA2s and 6X4 have never been changed.) Replace all the electrolytics?
Any help trouble shooting will be greatly appreciated.
jerold k
Jukebox-list mailing list Jukebox-list@lists.netlojix.com http://lists.netlojix.com/mailman/listinfo/jukebox-list Searchable Archives: http://jukebox.markmail.org/
On 1/6/23 15:47, Jerold Kress via Jukebox-list wrote:
I happened to have a similar electrolytic cap with the same specs so I replaced it to see if the OA2s would relit. I also replaced the 6X4 with one from a working guitar amp in case that was the issue. The new cap & the fuse blew in less than a minute. (Note that I had run the unit with the original bulging cap for a lot longer earlier while trying to figure out what was wrong and the fuse didn’t blow. The new cap is shorted/The original cap is not shorted.)
Electrolytic capacitors rarely fail catastrophically unless subjected to reverse polarity or substantial overvoltage. Note that this is a negative supply and C512, C514, C515, and C521 are installed with the positive to ground.
In many circuits heater-to-cathode shorts of 6X4 rectifiers can cause issues but this isn't the case with how it's wired here.
I'd replace all of the electrolytics and ensure they're installed with the correct polarity.
If the OA2 weren’t lighting your missing the grid voltage. If you have a schematic follow/test the components going to the grid….
On Sat, Jan 7, 2023 at 1:45 AM Jay Hennigan via Jukebox-list < jukebox-list@lists.netlojix.com> wrote:
On 1/6/23 15:47, Jerold Kress via Jukebox-list wrote:
I happened to have a similar electrolytic cap with the same specs so I
replaced it to see if the OA2s would relit. I also replaced the 6X4 with one from a working guitar amp in case that was the issue. The new cap & the fuse blew in less than a minute. (Note that I had run the unit with the original bulging cap for a lot longer earlier while trying to figure out what was wrong and the fuse didn’t blow. The new cap is shorted/The original cap is not shorted.)
Electrolytic capacitors rarely fail catastrophically unless subjected to reverse polarity or substantial overvoltage. Note that this is a negative supply and C512, C514, C515, and C521 are installed with the positive to ground.
In many circuits heater-to-cathode shorts of 6X4 rectifiers can cause issues but this isn't the case with how it's wired here.
I'd replace all of the electrolytics and ensure they're installed with the correct polarity.
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
Jukebox-list mailing list Jukebox-list@lists.netlojix.com http://lists.netlojix.com/mailman/listinfo/jukebox-list Searchable Archives: http://jukebox.markmail.org/
IDK but if it keeps blowing fuses I'd be afraid it's going to fry a transformer testing it over and over. Best to have someone else familiar with them service it.
Tony
On 1/7/2023 7:07 AM, Donald Whiting via Jukebox-list wrote:
If the OA2 weren’t lighting your missing the grid voltage. If you have a schematic follow/test the components going to the grid….
On Sat, Jan 7, 2023 at 1:45 AM Jay Hennigan via Jukebox-list < jukebox-list@lists.netlojix.com> wrote:
On 1/6/23 15:47, Jerold Kress via Jukebox-list wrote:
I happened to have a similar electrolytic cap with the same specs so I
replaced it to see if the OA2s would relit. I also replaced the 6X4 with one from a working guitar amp in case that was the issue. The new cap & the fuse blew in less than a minute. (Note that I had run the unit with the original bulging cap for a lot longer earlier while trying to figure out what was wrong and the fuse didn’t blow. The new cap is shorted/The original cap is not shorted.)
Electrolytic capacitors rarely fail catastrophically unless subjected to reverse polarity or substantial overvoltage. Note that this is a negative supply and C512, C514, C515, and C521 are installed with the positive to ground.
In many circuits heater-to-cathode shorts of 6X4 rectifiers can cause issues but this isn't the case with how it's wired here.
I'd replace all of the electrolytics and ensure they're installed with the correct polarity.
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
Jukebox-list mailing list Jukebox-list@lists.netlojix.com http://lists.netlojix.com/mailman/listinfo/jukebox-list Searchable Archives: http://jukebox.markmail.org/
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