I am new to DIYA and am interested in learning about tuners and speakers.My recently bequithed sansui 1000a just took a _rap. Symptoms are loud buzz when i press the power button. I am not sure if the tuner had one of the black horizontal switches which are stacked moved or not.Top = 1 or IMP
Bott = PHASE
I did see where somebyproduct or packing had come out of the middle transformer and dripped down through the chassis almost like a Beeswax type material.I am a bit upset because i have waited along time for something like this and didnt realize it until it was given to me. I had a list of tubes i was going to buy and replace along with i guess what are called pots.
Any help,please.
Thank you
Bott = PHASE
I did see where somebyproduct or packing had come out of the middle transformer and dripped down through the chassis almost like a Beeswax type material.I am a bit upset because i have waited along time for something like this and didnt realize it until it was given to me. I had a list of tubes i was going to buy and replace along with i guess what are called pots.
Any help,please.
Thank you
Somewhere around ten to twenty years the electrolytic capacitors in electronic gear leak out the water and lose capacity. The cheap ones used on consumer gear are sealed with rubber that is attacked by oxygen, operating or sitting still. The good news is, amplifiers don't have very many and it can be economic to replace the caps if you do it yourself. I just change them all, without measuring; I understand others believe in taking them all out and measuring them once a month. Like a twenty year old tire, just because it holds air today doesn't mean it will hold air tomorrow. Some high end equipment after 1965 might have long life caps sealed with something other than rubber, but probably not a Sansui.
Electrolytic caps are either tall cans with circles triangles and squares for the plus terminals, aluminum cans with cardboard wrap and a plus on one end, or aluminum cans with plastic wrap with a bunch of minus's in balls pointing at one lead. Tantalum electrolytics can look like small peanut M&M's with a plus on one lead. Usually electrolytic caps are marked 1 mf or higher. New marking at the distributors turns 1 mf into 1 uf, as if a Uniform was a deformed Micro. You look them up at distributors by clicking passive components, then capacitors, then aluminum electrolytic. I like to buy the 2000 hour up expected life ones, as I have recapped my dynakit equipment 3 times in forty years and that is too often if they sell longer life caps now. 80% of the tantalums electrolytic caps I have owned or bought have been defective, so I replace tantalums with aluminum plus a 0.1 mf ceramic cap wired parallel. Time marches on, and frequently for 1-10 mf caps you can replace them with film dielectric caps, if you can make it fit. Some electrolytics are marked "NP" for non-polar. The small non-polar caps I make it a point to replace with film.
WIth your transformer showing heat stress, probably an electrolytic cap has overloaded it. It may eventually short out a rectifier or resistor in the power circuit (requires further debug). Check your components before the first big cap after the transformer .
Remove all jewelery so you don't burn your fingers off. Caps can hold charge after the power is off, and over 25V can kill you if it crosses your heart, so read aikenamps.com tech info technician safety button about proper rules for people repairing amps.
Sansui's were known for needing pots pretty much in the second year when I went to college. I wouldn't buy the tubes until I had replaced all the electrolytic caps and couldn't get enough power out. The tubes that wear out most are the high voltage rectifier, and maybe the output tubes. The signal tubes in my ST70 amp are 50 years old. I have two 50 year old signal tubes in my PAS2 preamp and the two I replaced for popping, it was probably actually solder rosin on the PCB in humid conditions. My organs have mostly 40 year old tubes, although one had the rectifier and an output tube replaced when the serviceman was in too much of a hurry to change the dried up electrolytic caps. The volume was still puny in that organ, compared to the similar model with original tubes and 70 new electrolytic caps.
Change 1 or 2 caps at a time and check your work by turning on the equipment and seeing if it sounds better or worse. The large power caps need to go first. New people often make bad solder joints, and checking your work 2 at a time focuses your eyes on the defective work without a lot of tracing with a schematic diagram and an oscilloscope.
Electrolytic caps are either tall cans with circles triangles and squares for the plus terminals, aluminum cans with cardboard wrap and a plus on one end, or aluminum cans with plastic wrap with a bunch of minus's in balls pointing at one lead. Tantalum electrolytics can look like small peanut M&M's with a plus on one lead. Usually electrolytic caps are marked 1 mf or higher. New marking at the distributors turns 1 mf into 1 uf, as if a Uniform was a deformed Micro. You look them up at distributors by clicking passive components, then capacitors, then aluminum electrolytic. I like to buy the 2000 hour up expected life ones, as I have recapped my dynakit equipment 3 times in forty years and that is too often if they sell longer life caps now. 80% of the tantalums electrolytic caps I have owned or bought have been defective, so I replace tantalums with aluminum plus a 0.1 mf ceramic cap wired parallel. Time marches on, and frequently for 1-10 mf caps you can replace them with film dielectric caps, if you can make it fit. Some electrolytics are marked "NP" for non-polar. The small non-polar caps I make it a point to replace with film.
WIth your transformer showing heat stress, probably an electrolytic cap has overloaded it. It may eventually short out a rectifier or resistor in the power circuit (requires further debug). Check your components before the first big cap after the transformer .
Remove all jewelery so you don't burn your fingers off. Caps can hold charge after the power is off, and over 25V can kill you if it crosses your heart, so read aikenamps.com tech info technician safety button about proper rules for people repairing amps.
Sansui's were known for needing pots pretty much in the second year when I went to college. I wouldn't buy the tubes until I had replaced all the electrolytic caps and couldn't get enough power out. The tubes that wear out most are the high voltage rectifier, and maybe the output tubes. The signal tubes in my ST70 amp are 50 years old. I have two 50 year old signal tubes in my PAS2 preamp and the two I replaced for popping, it was probably actually solder rosin on the PCB in humid conditions. My organs have mostly 40 year old tubes, although one had the rectifier and an output tube replaced when the serviceman was in too much of a hurry to change the dried up electrolytic caps. The volume was still puny in that organ, compared to the similar model with original tubes and 70 new electrolytic caps.
Change 1 or 2 caps at a time and check your work by turning on the equipment and seeing if it sounds better or worse. The large power caps need to go first. New people often make bad solder joints, and checking your work 2 at a time focuses your eyes on the defective work without a lot of tracing with a schematic diagram and an oscilloscope.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.