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Post by Lincoln on May 24, 2018 0:26:56 GMT
I picked up a Seeburg SB100 the other day. It has a TSA9 Amp in it that was not working. I noticed the fuse was blown so I put a new one in it, and put my dim bulb in line before plugging it in and noted the bulb shined bright. I recapped the amp, and still have the same problem, which is no sound and bulb glowing bright. Is there any way to start isolating parts to find my short? Or any parts that are know to cause problems? How about checking the main power transformer?
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Post by Ron Rich on May 24, 2018 2:41:25 GMT
Hi Lincoln,
Like any other thing with a "short" you gotta find it, and make it a "long". Could be anything--main culprits in these amps, usually are, IF, "someone" has not over fused it, nor replaced the fuse several times: Power supply, and out-put section. Ron Rich
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Post by Lincoln on May 24, 2018 3:17:46 GMT
Can I use the power supply transformer from a TSA7 in a TSA9? The one from the 7 looks slightly larger, and only has 2 wires going in. The 9 looks like it has 4 wires going in. Both have 3 coming out.
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Post by robnyc on May 24, 2018 5:56:13 GMT
Lincoln, the transformers are likely the -last--things to go out here. The power supply diodes can cause this to happen. Likely scenario is one or more of the output transistors have shorted and this will often take the driver transistor(s) with them. Your DVM can be used to test each output transistor for shorts. I found this a couple of years ago, it is perfect for what you are about to do: www.flippers.com/pdfs/HudsonsBayWholesale_SeeburgSHP&TSA_ServiceNotes.pdfIn short (pun intended) you'll likely find the problem in the output stages. The most frequent cause, outside of abuse of speaker lines, it the bias pots on the driver boards developing dead spots. The outputs are germanium and thus getting rare. For the drivers I simply use Tip 41(NPN) and Tip 42 (PNP)(both silicon and readily available) in place of the existing bolt-on types. I leave the heatsink flange free -these never get hot. When you find the defective transistor, be --sure-- to also test the drivers for that side. RobNYC |
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Post by Lincoln on May 24, 2018 14:15:48 GMT
Rob,
Thanks for the help. I remembered I had download that document a while back. One thing I noticed was the line about a shorted PRVC causing the damage . When I picked this one up, the previous owner had take the wires loose inside the remote, so all the ends were touching. Guessing this is the source of my problem.
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Post by Ron Rich on May 24, 2018 14:51:39 GMT
Lincoln,
No--a shorted PRVC will NOT cause this problem in a TSA type amp--only in an early SHP-1, that had no internal fuse, or in a SHP type amp, that has been over-fused (MAX 2AFB), internally. I glanced at that article mentioned above--found several "errors/omissions"--did not note the PRVC reference in it--perhaps I missed it, or perhaps you downloaded another similar item ? Ron Rich
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Post by Lincoln on May 24, 2018 15:58:57 GMT
Ron,
I was reading on the bottom of page 13 where its talking about why breakdowns occur. It mentions a power spike caused by a momentary short in the line that carries power to the PRVC.
I dont know enough about the internal workings of an amp to know if this is true or not.
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Post by Ron Rich on May 24, 2018 19:04:54 GMT
Hi Lincoln,
OK--I glanced at that too quickly--that is correct only for the early SHP-1, or over an over-fused SHP. The TSA's have a limiting resistor, which is supposed to handle that-- I have seen a (very) few open--I assume that's because the PRVC control was assembled, less the fish-paper, protector? Ron Rich
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