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Technics SB-F1 - SSB12AB01 - Automatic overload circuit breaker

M

minister

New Member
Hello everyone,

I have a pair of old cabinets from the thread title, and I noticed change in loudness on one of them. Closer exam pointed to circuit breaker that has increased resistance. So I guess I need a new one... I tried searching for the original part but, for now, I had no luck.

I know I could override this fuse and listen to them, but It's just not my style, I'd rather have both fuses replaced with some modern replacement or buy original part if any of you can point me to where I can buy them. Model number is also from thread title (SSB12AB01).

Any help and/or advice is highly appreciated.

Thnx in advance.
 
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The manual, which can be found on hifiengine.com where signup is free, says there is a reset button on the speaker for the internal protection circuitry. Have you tried that? Otherwise, I'm not familiar with those speakers, so maybe someone will chime in who has had the same issue.
 
bberkom said:
The manual, which can be found on hifiengine.com where signup is free, says there is a reset button on the speaker for the internal protection circuitry. Have you tried that? Otherwise, I'm not familiar with those speakers, so maybe someone will chime in who has had the same issue.
Click to expand...

Thank you for your quick answer. You're absolutely right concerning a reset button on the back side of the speaker box. It's actually a button of the above mentioned circuit breaker which is sticking out of the cabinet.The thing is that this circuit breaker has malfunctioned and has increased it's resistance somehow and it causes increase in impedance of the whole speaker, causing it to have decreased loudness. I even tried to override it with plain wire, and speaker works just fine, but in this case it loses circuit protection.
 
Guys, yesterday I played a little bit, so new info is that alleged fuse is "dancing" with resistance, with no power going through it at all, so I determined that it's completely unusable. I decided to override fuses on both boxes. It may be just a placebo but it seems to me that system started "breathing" after this, the whole system sounds much better. My theory is since these are thermal switches they have mechanical parts that are worn out, so they "dance" with properties making this a choke for the system.

Anyway, I still need a little help since I know only basics.

Although system sounds much better now, I would like to leave these switches overridden, but, I'm a little afraid of burning the circuit. These protection fuses are certainly not put here for no reason. I would like to protect the circuit with normal fuse, It seems logical to me that common 1.25A fuse would protect the circuit, and not do any modification to the sound.

Can someone, please, confirm if I'm right?
 
minister said:
Guys, yesterday I played a little bit, so new info is that alleged fuse is "dancing" with resistance, with no power going through it at all, so I determined that it's completely unusable. I decided to override fuses on both boxes. It may be just a placebo but it seems to me that system started "breathing" after this, the whole system sounds much better. My theory is since these are thermal switches they have mechanical parts that are worn out, so they "dance" with properties making this a choke for the system.

Anyway, I still need a little help since I know only basics.

Although system sounds much better now, I would like to leave these switches overridden, but, I'm a little afraid of burning the circuit. These protection fuses are certainly not put here for no reason. I would like to protect the circuit with normal fuse, It seems logical to me that common 1.25A fuse would protect the circuit, and not do any modification to the sound.

Can someone, please, confirm if I'm right?
Click to expand...

Most speakers I've encountered with fuses for tweeter protection are of the fast-blow type. IIRC a normal-blow fuse must double it's rating (duty cycle) before it blows where as a fast-blow does not require that. Even with a low amp normal blow fuse you could still take out the tweeter. Make sure you verify what you have in there. All that said, the 1.25A value is probably safe but you might dial it back to 1A or farther to start. If it pops too frequently you can bump it up in value.

PS: I have SB-F1MK2's and they also have the breaker. They are in near daily use but so far I've not noticed any issue with them.
 
soundmotor said:
Most speakers I've encountered with fuses for tweeter protection are of the fast-blow type. IIRC a normal-blow fuse must double it's rating (duty cycle) before it blows where as a fast-blow does not require that. Even with a low amp normal blow fuse you could still take out the tweeter. Make sure you verify what you have in there. All that said, the 1.25A value is probably safe but you might dial it back to 1A or farther to start. If it pops too frequently you can bump it up in value.

PS: I have SB-F1MK2's and they also have the breaker. They are in near daily use but so far I've not noticed any issue with them.
Click to expand...

Thank you for your engagement with this matter. Your post is very helpful to me. If I understood you right, you claim that a fast-blowing (acting) common cartridge fuse of 1A would protect the circuit just fine on these speakers?
 
stoN_Cold said:
Click to expand...

Thank you for your post StoN_Cold. I watched the whole video with great interest. The more I'm messing with this matter, the more I get the feeling that these circuit breakers are more of a problem than a help. I'm using my SB-F1 without them for several days now, and they sound great, but I don't think I'm gonna leave it like that. Although I have a little child and I really listen to these speakers at low volume, I totally like them and I would hate to see them toasted because of ridiculously cheap fuses.

Although I came across different opinions on putting fuses in speaker enclosures, from ones that claim that they are no protection at all, to ones that claim that light bulbs protect drivers better... Some that claim that there are special circuit just for this... etc.I decided that I'm gonna put 1A fast-acting cartridge fuses in these boxes, since they are very easy to open and replacing fuses would not be much of a problem. I guess I'll be doing this just for a peace of mind.

Greatest thanks to all participants, you've been really helpful.
 
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