Scott A-457 will play mono but not stereo (usually). - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 12 Old 01-20-2020, 09:11 PM - Thread Starter
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Scott A-457 will play mono but not stereo (usually).

Hi again everyone,

I got the Scott amp set up and am having a problem that I really can't figure out. When I have it set on stereo it usually plays only out of the left speaker, and only the left power level pointer is active. If I set it to Left (mono) or L+R (mono) both speakers and pointers will be active. Occasionally I can set it on Stereo and both speakers and pointers will work, but the next time I turn it on I'm back to one speaker. I've tried different speakers with the same results. If it makes any difference, I'm usually streaming Pandora in stereo, so that shouldn't be the issue. Does anyone have any idea what could possibly be causing this?
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post #2 of 12 Old 01-21-2020, 06:39 AM
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Since the right works in mono it appears the problem is in the stereo switch itself OR you don't have the speakers hooked up correctly.
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post #3 of 12 Old 01-21-2020, 08:09 AM - Thread Starter
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Originally Posted by altpensacola View Post
Since the right works in mono it appears the problem is in the stereo switch itself OR you don't have the speakers hooked up correctly.
Thanks altpensacola -

As I sit here typing this the amp is playing in stereo even though I haven't changed anything since my original post.

A couple of things might help with a diagnosis: If I turn on the amp and let it sit for 15 minutes or so before playing music it will start off fine in stereo. But yesterday I let it play for a couple of hours just to let the system "break in," and at some point I lost connectivity to the right speaker.

We can rule out speaker hookup or the speakers themselves. I've tried different speakers with the same results.

I took some video of my hookup while the system was running that I may post if the problem persists and I can't track down the issue. I'm trying to keep in mind that this equipment has all been in storage for at least 35 years and may just need a good break-in period. Fingers crossed.
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post #4 of 12 Old 01-21-2020, 08:14 AM
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Perhaps a bad capacitor or bad solder joint in the amp. Capacitors often get worse in behavior as they heat up. With solder, temperature changes make the board and the solder expand and contract slightly, and that can cause it to go in and out of contact.


I mean, depending on how the switch is wired, it's still technically possible that is the issue.



I doubt a break-in period will fix it though you are welcome to try.




Edit: Hey, this amp was apparently made under an hour from where I live. Cool.
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Last edited by DonoMan; 01-21-2020 at 08:33 AM.
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post #5 of 12 Old 01-21-2020, 08:54 AM - Thread Starter
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Originally Posted by DonoMan View Post
Perhaps a bad capacitor or bad solder joint in the amp. Capacitors often get worse in behavior as they heat up. With solder, temperature changes make the board and the solder expand and contract slightly, and that can cause it to go in and out of contact.


I mean, depending on how the switch is wired, it's still technically possible that is the issue.



I doubt a break-in period will fix it though you are welcome to try.




Edit: Hey, this amp was apparently made under an hour from where I live. Cool.
Thanks DonoMan -

Right now the beast is still playing just like it should but I don't have a lot of faith that that will continue. Unfortunately I think you're probably right about a bad solder or capacitor, and I don't have the equipment to check those kinds of problems. I wonder if Scott would repair it for free if I paid shipping

Poop, and I ordered new surrounds for the 188T speaker woofers that went with the original setup.
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post #6 of 12 Old 01-21-2020, 09:08 AM
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Now I'm going to be sad if it gets binned just because it was cool that it was made near me! I used to live one town away from them (though this was years later).


You could still use your speakers with another amp, though I suppose having a matching set is nice.


You could put it back in storage and repair it later

Quit on 1/23/2020 due to constant "file not found" errors on the server while trying to submit posts. It's one problem for your server to have an issue but totally different for it to, day after day, continue having issues that don't get fixed. The time we spend writing this content should not be considered so worthless that the server should feel free to destroy our content.
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post #7 of 12 Old 01-21-2020, 09:30 AM - Thread Starter
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Oh, it won't be chucked out! If it keeps giving me problems I'll tear it down and work at it until I completely run out of either time or patience. When it works it really sounds incredible - I just need to keep it working. All I have is a voltmeter, but I might be able to borrow a multimeter if I have to.
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post #8 of 12 Old 01-21-2020, 09:39 AM
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If you ever want to diagnose bad capacitors, you want an ESR meter which tests the "Equivalent Series Resistance" of a capacitor. Basically the internal resistance of the capacitor. ESR goes up when the cap goes bad. Bad capacitors can be tested with a normal capacitance meter but they often read as if they are fine this way. ESR meter catches most (not all but most) bad caps, and you can get them for about $15 shipped on Ebay. Even the ones that come with just a board and screen and no case are fine. But I personally like having a case so I paid something like $30 or $40 for a MESR-100 (also from Ebay) which is functionally equivalent to the $15 ones, but has a case.


If you ever want to solder in caps yourself, take a look at the TS100 iron from Banggood for about $50. It's respectable because it is directly compatible with Hakko direct-heat cartridges. It'll blow a $100 Weller WES-51 or Hakko FX-888 out of the water. (Sites like Banggood, ********, Aliexpress and such are basically online bazaars for mostly Chinese goods - basically kind of like Amazon zShops)


Edit: We're censoring names of Chinese stores here? Wow. That's incredible (and insulting). Why? The protectionism is real.
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post #9 of 12 Old 01-22-2020, 11:41 AM - Thread Starter
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Originally Posted by DonoMan View Post
If you ever want to diagnose bad capacitors, you want an ESR meter which tests the "Equivalent Series Resistance" of a capacitor. Basically the internal resistance of the capacitor. ESR goes up when the cap goes bad. Bad capacitors can be tested with a normal capacitance meter but they often read as if they are fine this way. ESR meter catches most (not all but most) bad caps, and you can get them for about $15 shipped on Ebay. Even the ones that come with just a board and screen and no case are fine. But I personally like having a case so I paid something like $30 or $40 for a MESR-100 (also from Ebay) which is functionally equivalent to the $15 ones, but has a case.


If you ever want to solder in caps yourself, take a look at the TS100 iron from Banggood for about $50. It's respectable because it is directly compatible with Hakko direct-heat cartridges. It'll blow a $100 Weller WES-51 or Hakko FX-888 out of the water. (Sites like Banggood, ********, Aliexpress and such are basically online bazaars for mostly Chinese goods - basically kind of like Amazon zShops)


Edit: We're censoring names of Chinese stores here? Wow. That's incredible (and insulting). Why? The protectionism is real.
Thanks again DonoMan!

I know that one of the main capacitors is going bad. When I had the unit torn apart for cleaning I noticed the top of one was just slightly bulged and could be popped up and down just a little bit, and I know that any play in the cap is too much.

I do have a solder gun with a fine tip, so hopefully can get everything torn apart and put back together. I love to tinker with this kind of stuff, but when something is "working," even if it's not working 100%, I'm leery of making things worse. Right now, the amp and speakers are kicking patootie.
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post #10 of 12 Old 01-24-2020, 09:34 AM - Thread Starter
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One more question...

Before I either try repairing this thing myself or having someone else do it, could some of you follow the (Dropbox) link to look at some photos of the Scott A-457 guts. Should there be so many spliced wires inside of this thing?!? It looks like some of it isn't even the same gauge that's butted together and shrink wrapped. If this is normal I'll consider trying to fix it, but if this was a cobble job and any one of those splices could have bad connections, then this is seeming kind of overwhelming. This was brand-new in the box when we bought it, so this would have been done at the factory. TIA

https://www.dropbox.com/sh/radg8ru4o...V8lMoWUKa?dl=0
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post #11 of 12 Old 02-02-2020, 10:12 AM - Thread Starter
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Thank you shoutout....

Hey Altpensacola and DonoMan (I hope you're still here!) ~

Thank you for your encouragement and help - the system is working and actually staying on for more than two hours.

I really also need to especially thank Stereo Rehab in Chicago for working with me through emails and letting me know that my best starting point would be to get some good contact cleaner and something like Caig DeoxIT D5 to clean all the pots and knobs and anything that moved or looked particularly grungy or oxidized. I never got the name of who I was corresponding with, but THANK YOU! Problem solved
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post #12 of 12 Old 02-03-2020, 06:07 AM
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Originally Posted by gristle54 View Post
Hey Altpensacola and DonoMan (I hope you're still here!) ~

Thank you for your encouragement and help - the system is working and actually staying on for more than two hours.

I really also need to especially thank Stereo Rehab in Chicago for working with me through emails and letting me know that my best starting point would be to get some good contact cleaner and something like Caig DeoxIT D5 to clean all the pots and knobs and anything that moved or looked particularly grungy or oxidized. I never got the name of who I was corresponding with, but THANK YOU! Problem solved
contact cleaner, I should have know that. thanks for follow up. Rock on!

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