Sanyo 920 or M9998...which is better??

[MasterBlaster84]

I'll admit my preference leaned slightly to the 9998 on looks but I love them both and don't think you'd go wrong with good working examples of either one.

 

[Superduper]

Here is the RECAP of the Amp Module in the 920 that Melly took home with him:

Here is amp board, removed from boombox, and ready for transformation.

Here the amp board, recapped, including the cluster under the amp heat sinks. The two horizontal rows labeled 532 on the right hand side is for the amp IC's, which will first be mounted to the heatsink before being soldered back on. All the components between those two rows will be completely boxed and hidden beneath the heatsink. Good quality components are a must here.

Here is the completed module. Amps back in. Also, because one IC was suspected bad, I have added additional heatsinking, the two new heatsinks alone should normally be enough for those ROHM IC's because it's a very high efficiency design that transfers heat better than the simple aluminum plates. I eventually had to snip off a couple of fins on the top right due to interference, and then bend the remainder. Eventually, I modified the mounting posts so the board would sit a bit lower (about 1/5"). All's good. BTW, LOOK at that pre-amp board I left that one alone since I didn't see any symptoms suggesting it needed work but you know -- if one goes, and they are all manufactured the same time, they all should be replaced. Anyone got $$$'s

Ok, it's back into the boombox.

Finally, while the re-capping did take an afternoon to do, imagine how much work is involved in an entire re-capping. There are many more boards besides the amp. The bigge is the Main-Preamp board and you are seeing 1/2 of it to the left of the amp PCB which it dwarfs ! Then there is also the tuner, Power Supply, and a few minor boards. Enjoy!

 

[mellymelsr]

A big thanks goes out to Norm for sharing his time, his boxes, and his incredible knowledge with me. This is what this site is all about and why I love this hobby...and many thanks for hooking me up with an incredibly restored grail!!...it will receive much love and lots of usage...

 

[Fatdog]

I say we start pooling our money now to bring Norm and all of his tools to the 2011 meet. Of course, the meet would then have to be spread out over three or four days.

 

[Superduper]

Melly. In case you were wondering what the innards look like, here it is! It's NOT a beginner boombox to tinker with and not for the faint of heart. Look at how the amp module is tethered It looked simple outside of the boombox, didn't it?

 

[mellymelsr]

Melly. In case you were wondering what the innards look like, here it is! It's NOT a beginner boombox to tinker with and not for the faint of heart. Look at how the amp module is tethered It looked simple outside of the boombox, didn't it?

...wow, you were not kidding Norm...I think I'm gonna need a service manual...or a whole lot of pictures... ...and I agree with FD, gotta get Norm to the next meet, cause I know I am gonna go....

 

[Superduper]

Melly. Redbenjoe can blame the Bombeat delay............ ON YOU!

 

[redbenjoe]

agree with ampledog --

i wish i knew how to re-cap EVERYTHING !!!!

 

[Superduper]

When you own 100 boomboxes, and you recap something that doesn't appear to need it, you might be wasting your money. BUT if you own 4 boomboxes, you should recap them all to improve reliability and restore like-new performance. OR if your boombox has symptoms that suggest weird operational or circuitry issues, it should be recapped.

ONE thing that is not clearly understood is that most amplifier stages are capacitor coupled. Capacitors will pass AC but block DC. I won't get into the technical aspects of how it works but suffice it to say that the capacitors protect the varying amplifier stages from DC signals which if not operating properly, could take out all the stages of an amplifier when one stage fails. Therefore, if a capacitor fails open, then you are OK in that while the boombox might not work, the other stages should remain intact. If a cap fails short and another amplifier stage fails, it could create an avalanche effect and take out everything.

 

[redbenjoe]

will USING our boxes --instead of 'just saving' then on a shelf ....
enhance the life and performance of the caps ????

 

[Superduper]

No. Heat and usage will shorten their life. There are many types of capacitors but electrolytic capacitors are the only ones that needs replacement and cause problems. That is because by design, they are filled with an electrolytic solution. Over time, the solution dries out and that's when problems occur. The others fail too and are replaced on an as-needed basis. But the electrolytics -- they all fail eventually. Time is NOT on their side.

 

[redbenjoe]

ok - thanks

 

[Reli]

Outstanding thread............. But personally my vote still goes out to the 9998 ........simply because of looks...........It's got a low-slung look....... I don't like tall radios, for the same reason I don't like tall cars.....They look slow ).

Also it's got those cool legs, like a lunar lander. Kind of sets it apart I think. True, it's not a box you would take outside, because it doesn't have the right "look" for that...........But that's fine with me. The black chassis and the legs make it look like serious home audio gear.

The int. + ext. speaker switch is useful as well. Does the 920 have that?

 

[Blasterpunk]

if you do not like the 920 let me know

Me too! I would like to have another 920

 

[monchito]

,,good comparo for both boxes i still have to finish my 920 cap change part of it is done but still have a bit of a ways to go ,, but i still love the 9998 looks and really they all look good

 

[vladi123456]

thats very surprising --
so --the big news is --that a :super: capped box is the only way to go

norm --did you agree with melly re this comparo ?

Here ya go:

My (2) M-X920. Melly left the nicer/mintier one for you richer guys.

Are you selling the second one as well? I might be interested

 

[MasterBlaster84]

Sellers remorse Vladi.
You've sold some nice boxes, do you miss many of them?

 

[vladi123456]

Ya, I was pretty broke - sold almost everything, including my bimmer. But now I'm expecting a small tex refund - not enough to start a harem, but enough to buy a couple of boomboxes - including some of the ones I've sold in the last couple of years

 

[MasterBlaster84]

Gotcha Vladi, a lack of funds can sure mess up our collections.

 

[shane higgins]

When you own 100 boomboxes, and you recap something that doesn't appear to need it, you might be wasting your money. BUT if you own 4 boomboxes, you should recap them all to improve reliability and restore like-new performance. OR if your boombox has symptoms that suggest weird operational or circuitry issues, it should be recapped.

ONE thing that is not clearly understood is that most amplifier stages are capacitor coupled. Capacitors will pass AC but block DC. I won't get into the technical aspects of how it works but suffice it to say that the capacitors protect the varying amplifier stages from DC signals which if not operating properly, could take out all the stages of an amplifier when one stage fails. Therefore, if a capacitor fails open, then you are OK in that while the boombox might not work, the other stages should remain intact. If a cap fails short and another amplifier stage fails, it could create an avalanche effect and take out everything.

oh yes of cause
hay NASA just rung need you back at work