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Sansui 771 fuse question (F01-F04)

W

Wolf359

New Member
Hello! I recently inherited a Sansui 771, which had only one channel working. Upon closer inspection, I found that two of the QA fuses (F01 and F03 to be exact) were blown. F04 and F02 were ok. If I moved the the "good" fuses over to the F01/F03 positions, the other channel came up fine.

So I'm now trying to find replacement fuses. The problem is, 5A 250V QA (which was what was in there) are impossible to find. I can find larger size QA fuses (1-1/4"x1/4") with 5A/250V, but I can only find slow-blow fuses 5A/250V in the proper size (5x20mm). There are 5A/125V QA fuses in the proper size, however.

The service manual only states that a 5A fuse is needed--there is no mention of voltage.

Please forgive my ignorance here, but given that I am in the US where we operate on 120/110V, can I replace the 250V fuses with the 125V ones?

I've done a lot of searching here and elsewhere, and can't find a definitive answer. Many thanks for anyone who can help!

EDIT: I see the same type of fuses (Toyo, red dot) here. There's not mention of voltage, though. Is this what I need? Not something I'll be able to find locally I assume.
 
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Wolf359 said:
Hello! I recently inherited a Sansui 771, which had only one channel working. Upon closer inspection, I found that two of the QA fuses (F01 and F03 to be exact) were blown. F04 and F02 were ok. If I moved the the "good" fuses over to the F01/F03 positions, the other channel came up fine.

So I'm now trying to find replacement fuses. The problem is, 5A 250V QA (which was what was in there) are impossible to find. I can find larger size QA fuses (1-1/4"x1/4") with 5A/250V, but I can only find slow-blow fuses 5A/250V in the proper size (5x20mm). There are 5A/125V QA fuses in the proper size, however.

The service manual only states that a 5A fuse is needed--there is no mention of voltage.

Please forgive my ignorance here, but given that I am in the US where we operate on 120/110V, can I replace the 250V fuses with the 125V ones?

I've done a lot of searching here and elsewhere, and can't find a definitive answer. Many thanks for anyone who can help!

EDIT: I see the same type of fuses (Toyo, red dot) here. There's not mention of voltage, though. Is this what I need? Not something I'll be able to find locally I assume.
Click to expand...
Fuses work on amperage only. The voltage rating tells you how much voltage the fuse will stop when the fuse is blown.

The Toyo Fuses are the original type Sansui used
 
Stene said:
Fuses work on amperage only. The voltage rating tells you how much voltage the fuse will stop when the fuse is blown.

The Toyo Fuses are the original type Sansui used
Click to expand...

thanks for the quick response!
Are there other manufacturers of these kinds of fuses? Or is Toyo the only one? Bussman, for instance, doesn't appear to have this fuse in the correct size.

Also, are these considered very fast acting as opposed to just "fast-acting"? Is this critical?

I guess the real question is: What are my options? Buy those Toyos from Woodang? Are there any other sources for these types of fuses? Will any other type of fuse work?

Thanks again!
 
Wolf359 said:
thanks for the quick response!
Are there other manufacturers of these kinds of fuses? Or is Toyo the only one? Bussman, for instance, doesn't appear to have this fuse in the correct size.

Also, are these considered very fast acting as opposed to just "fast-acting"? Is this critical?

I guess the real question is: What are my options? Buy those Toyos from Woodang? Are there any other sources for these types of fuses? Will any other type of fuse work?
f
Thanks again!
Click to expand...
Little Fuse also produce these very fast uses but I don't know where you can get it.
 
blhagstrom said:
Assuming you have the spec right (5A, 5x20mm)

Do you have a Radio Shack close by?
http://www.radioshack.com/product/index.jsp?productId=2103768

If you have to order, Mouser.com.
http://www.mouser.com/ProductDetail...=sGAEpiMZZMseCiJT91fwIpCS8D8NVahFyBHUBXqnnAo=

576-0217005.HXP $0.20 each.
The cheapest postage is mail and about $6.50
Click to expand...


I do have a RS nearby and I saw those in stock. I didnt get them because they are 125V and not 250V.

But, would these be OK to use anyway?

thanks!
 
Stene said:
Both of them seems to be fast acting and not very fast acting
Click to expand...

Right, it seems the only "very" fast acting ones are the original Toyos--the Mouser site doesnt seem to have a distinction beyond "Fast Acting".

Again, how critical is Very Fast Acting vs Fast Acting for this purpose?

Has anyone replaced these fuses with anything other than the original Toyo fuses?
 
Wolf359 said:
Right, it seems the only "very" fast acting ones are the original Toyos--the Mouser site doesnt seem to have a distinction beyond "Fast Acting".

Again, how critical is Very Fast Acting vs Fast Acting for this purpose?

Has anyone replaced these fuses with anything other than the original Toyo fuses?
Click to expand...
A Quick Acting Fuse is about 10 times faster than an ordinary Fast Fuse.
At 2.7 times rated current a QA will blow in appr 50ms compared to 600ms for a fast type fuse. There are also Time Lag Fuses which can stand a surge current much better, in other words, useless for protection but very good as AC input main fuse.
 
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Stene said:
A Quick Acting Fuse is about 10 times faster than an ordinary Fast Fuse.
At 2.7 times rated current a QA will blow in appr 50ms compared to 600ms for a fast type fuse. There are also Time Lag Fuses which can stand a surge current much better, in other words, useless for protection but very good as AC input main fuse.
Click to expand...

How critical is the 550ms difference between the two, in terms of this particular application?

Do other Sansui amps/receivers use QA fuses, and if so, has anyone replaced them with ordinary fast-type fuses?
 
limb

Hmmm, I only worry about normal and fast acting. But if you really want exactly very fast acting 250V 5A 5x20mm. Mouser has those. Using their site is tricky.

http://www.mouser.com/Circuit-Prote...Z1z0x73eZ1z0s76fZ1z0vl8v&Keyword=fuse&FS=True

Spendy puppies, $2+ and up

They only show 5 of 576-23015000021 in stock. $3.37 each

Digikey shows a bunch of fast acting but I think you need to do more digging to find out the actual response time based on type. They don't sort to Quick or Very Fast acting.
 
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Does the fact that the "very fast acting" fuses are ceramic and not glass matter in this situation?

I've placed an order with Woodang for the Toyo fuses. I asked him specifically if they were 250V or 125V. He responded to me that they are 250V but that "the voltage is not mentioned on the web page as it doesn't matter".

This brings me back to my original question--if the amp rating is the important part, what's the point of the voltage rating? Will the radioshack fast-acting 5A 125V fuses work in this situation?
 
Wolf359 said:
Does the fact that the "very fast acting" fuses are ceramic and not glass matter in this situation?
Click to expand...
No

Wolf359 said:
-if the amp rating is the important part, what's the point of the voltage rating? Will the radioshack fast-acting 5A 125V fuses work in this situation?
Click to expand...

The amp rating is the important part and in protection case, the speed for the melting time. The voltage rating tells you how much voltage the fuse will stop when the fuse is blown. If the rail voltage is higher than voltage marking on the fuse it could arc across the fuse contacts. The rail voltage in 771 is 35V so you can use any fuse having higher voltage marking than 35.

Radioshack fast acting 5A 125V fuse will work but not good enough for protection depending on melting speed.
 
Stene said:
No



The amp rating is the important part and in protection case, the speed for the melting time. The voltage rating tells you how much voltage the fuse will stop when the fuse is blown. If the rail voltage is higher than voltage marking on the fuse it could arc across the fuse contacts. The rail voltage in 771 is 35V so you can use any fuse having higher voltage marking than 35.

Radioshack fast acting 5A 125V fuse will work but not good enough for protection depending on melting speed.
Click to expand...

ahh, ok, that makes sense. Thanks for the explanation. I think I will try the RS fuse to make sure it works OK and then use the Toyo fuses from Woodang for long term use.

thanks for your help Stene, as well as everyone else in the thread! You guys rock!
 
Rehashing a 9 year old thread! Anybody on this still rockin in the (kinda) free world?! Got the hood popped on a 771 here and could use some advice. Signal only coming out of the left side, right side sounds a-ok. Fuses F 02 & 04 are both blown. Dug into my stach and surprisingly had no prob finding some of the smaller size 5A 250v fuses. Holly ****! I thought to myself. Things are going to go smoothly for once! NNNNNNNNOPE! They both blew immediately.
Any clues on what I should be looking for? Don’t have a multimeter, or any other testing really. Jus my trusty ol solderin iron, a bag o’ capacitors, and a chop stick to poke around with. Any advice would be appreciated
Thanks.
 
Zombie alert
12-houses-that-will-get-you-through-a-zombie-apoc-1-30966-1338397830-10_big.jpg

Tflapjacks said:
Don’t have a multimeter,
Click to expand...

Be real handy about now. You need to check the output transistors.
 
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