Internal Shots of the Logitech Z313

[kaboom]

Re: Internal Shots of the Logitech Z313

Here ya go.

My only gripe is that the spkr coupling caps should be bigger. 2200u for the 4 ohm speakers usually plugged into these amps. Wanna get the -3dB point nice n low.

That card came out of a 233MMX clone that I junked. It was upgraded from one of the many 486 clones from the glory days. It didn't belong to me- belongs to the same people the LCS1020's do. That stuff's been here since September, as well as a system I built for them...

When I dug out my XT back in '05, I put an SB card in it. I figured if I stay within the limits of the 8-bit ISA slots, that 16-bit card could 'hang over.' Got the OPL2/3 to work with some old DOS demos and could also play 8-bit WAVs. Also found a prog to remap/convert MIDIs for custom Adlib banks and played 'em. I'd convert, check, and play them on an 'emulated' XT in DOSbox, then put 'em on a floppy and play them on the real XT.

LOUDSP30 also ran on that XT, as did 'DOSSHELL.' Fun for a week, then the MFM hdd finally died.

-Paul

[Th3_uN1Qu3]

Re: Internal Shots of the Logitech Z313

Don't worry, though. Those baby speex are/were good for 250W 'PMPO.'

The 2025 can do a honest 5 watts when bridged at 14 volts, and about 2W/ch in stereo mode. When coupled with a bass crossover the soft clipping circuit makes it sound decent even when loud, especially combined with the fact that the 2822 doesn't ever distort driving those little sats. That is valid for the speakers that my dad had.

Somewhere along the line they figured that they risk blowing the 2025 by running it at max rated supply and they installed a protection. That is a fancy way of saying they downsized the transformer. I remember the power LED blinking in time with the beats on my cousin's A4Tech speakers. With those, it was all about who had the highest output on their soundcard...

Who remembers ASOUND 'speakers'? TigerIndirect was giving these away back in late '99.

They weren't ASOUND in here, but i do remember the white boxes. When i was like 10, i used to have a pair of unpowered walkman type speakers connected to the speaker out of my soundcard (btw, do you remember soundcards with onboard amps?). They walked all over the white boxes.

[kaboom]

Re: Internal Shots of the Logitech Z313

2025 bridged on sub

Like in 'ASOUND'/POWMAX speakers? My Fisher-Price tape recorder from ninteen-eighty-something was more honestly rated- at half a watt!

Don't worry, though. Those baby speex are/were good for 250W 'PMPO.'

Reason being the power supply was 15 volts - the maximum rating of the chip.

Depending on local line voltage, you'll have a bit more- maybe you'll get 251W PMPO.

Who remembers ASOUND 'speakers'? TigerIndirect was giving these away back in late '99. Upgrade to a 17" crt and they threw in a sound card and the tin cans. Sound card had a Crystal CS4281 or something, and the .INFs were 'broken' in such a way as to install NT4 drivers on the 98/ME systems. Guaran-damn-teed BSODs on reboot! Don't ask me how I know- that's *not* funny...

The solder side on my Logitech board was absolutely atrocious.

In those damn ASOUNDs, I've seen as much corrosion as solder as well as the usual sloppy lead dress. Line cords were all of two feet- no strain relief except a knot. Cord movement was then transferred to transformer lead wires. So many untrimmed leads on the boards, it's a wonder they didn't short out. No fusing of any kind in the primary, shit caps, sloppy mechanical alignment, 'microphone wire' speaker leads, etc... Supply voltage rejection? No way- enjoy the hum!

Of course, the power switch switched the tx secondary. If you ever get one of those boards, you'll notice a silkscreen for a DC input jack. At some point, these things were powered by a wall wart. Must've been too ex$pensive, so they put the pig inside. At least the little transformers had a split bobbin for 'damage control' when the smoke came out.

-Paul

[Th3_uN1Qu3]

Re: Internal Shots of the Logitech Z313

By far, the worst I've seen for 'puter speakers was in Labtec LCS1020s.

The power IC was a TDA2004.l

TDA2004... that can be called good. You haven't seen the TDA2822 and TEA2025 affairs. They are laughable.

Dad's old computer speakers had the 2822 on satellites/2025 bridged on sub, and was about the only pair of speakers done with this combo that were actually done good. Proper crossovers, good speaker drivers, and adequate power transformer. When the TEA2025 blew up after over 10 years of use, i went thru 3 brand new chips till i found one that worked. Reason being the power supply was 15 volts - the maximum rating of the chip. The new ICs were probably fake and croaked one after another when run at maximum power.

[TheLaw]

Re: Internal Shots of the Logitech Z313

Wow you did a good job not ripping off the solder pads. The solder side on my Logitech board was absolutely atrocious. I think I've learned my lesson to not mess with things that are already crap to begin with.

[kaboom]

Re: Internal Shots of the Logitech Z313

These are waiting to be picked up, so I got some pix...

This thing looked like one of those baby boom boxes with all the untrimmed leads. But it'll never be the same- I mean it actually has a reasonable heatsink and sounds good now.

The new tone control is just a few resistors and caps, high-current traces were jumpered, and a reverse polarity protection diode was added. This takes a 15v, tip *negative* adapter. The cable from the other speaker was shielded #28, like the cable for a PC mike but more brittle. It's 18/2 now.

That was nice when Logitech had Labtec over a barrel and bought 'em out back in' 01, cash, debt and all. Not that it matters to me. I'll build my own stuff, thank you.

-Paul

[Scenic]

Re: Internal Shots of the Logitech Z313

Labtec = Logitech
Logitech sells outdated stuff under the labtec label. usually with a slightly different/cheaper casing.

a bunch of webcams my brother had were labtecs. internals were all logitech, but very old hardware designs. hell.. even the driver installed itself in c:\program files\logitech, despite the fact it had labtec logos all over the place lol

edit: the .inf files were also (c) Logitech

[kaboom]

Re: Internal Shots of the Logitech Z313

By far, the worst I've seen for 'puter speakers was in Labtec LCS1020s.

The power IC was a TDA2004. There was a 2SC945 in each channel, attempting to play preamp, but no decoupling whatsoever. Biasing? You're kidding!

The final was set up for some ridiculous gain- 48 or 50-odd dB, in an attempt to recover the low level, humming, distorted, NASTY signal from the 'preamp.' That's right, a negative gain preamp.

I cleared all that junk and redid the whole damn thing. I kept the TDA2004 and changed the resistors in its feedback loop, lowering the gain to around 34dB. That was to match the insertion loss of the new passive tone control I designed for it. The loss was 8dB. Not having that stupid preamp anymore and increasing the size of the SVR cap, the amp was nice and quiet. Headphone output before was a joke with all the hum. I made a bigger heatsink, too. The one it had was making accidental contact with the IC.

I changed the caps too

Pix coming soon
-Paul

[TheLaw]

Re: Internal Shots of the Logitech Z313

It's junk, but it's cheap as heck...so it has to be.

[Krankshaft]

Re: Internal Shots of the Logitech Z313

Kind of crappy to see those two op amps one for each channel. They're there for preamplification since the input signal isn't strong enough to drive those heatsunk audio amps.

Opamps aren't the best for preamplification. They get the job done but they're not a top choice by any means.

There are specific preamp ICs made for this. There are even integrated audio amp ICs that handle the preamplification and final amplification on one IC.

On the positive side very simple circuit design and very easy to service should it be required.

[TheLaw]

Re: Internal Shots of the Logitech Z313

Well, I recapped about 75% of the caps. The other 25% I didn't even bother with. The traces/pads on the bottom of the board were so small that I would rip the pad off every time. So I decided to suck it up, and deal with a few SamXons/CapXons. They stink but I recapped all of the more important ones. The caps I didn't replace were of the small variety. 2.2uF and 0.22uF: So I doubt it will really matter in the end.

The caps I did replace work well though I struggled a lot with desoldering. This board clearly wasn't meant for any time of rework and thus I wound up ripping off about 50% of the pads that I worked with. It's unfortunate, but luckily I was able to jumper all of the connections that were lost during desoldering.

It works!...somehow. I attached a picture of the back of the board and it looks bad. It actually looks much better in person, but from the picture it looks terrible.

Caps include Nichicon FW & FG and Panasonic FM. Also replaced the fuse with a ceramic type.

[Trinite]

Re: Internal Shots of the Logitech Z313

Can't be much worse than what you would find in a "high end" Bose unit, I would imagine...

[TheLaw]

Re: Internal Shots of the Logitech Z313

It is a piece of crap. There's no way of getting around that...but for the price, the quality is par for the course.

[Scenic]

Re: Internal Shots of the Logitech Z313

Panasonic FC is what i usually use for audio stuff.
this thing doesn't really look too bad considering the price.. i've seen (far) worse than this..

[TheLaw]

Re: Internal Shots of the Logitech Z313

Run it with the covers off. If there's no heat then the bad caps aren't much at risk.

Uh well easier said than done...Anyway, I wanted some decent audio caps. I think alot of that is bogus, but they are better for audio than this garbage.

[severach]

Re: Internal Shots of the Logitech Z313

Run it with the covers off. If there's no heat then the bad caps aren't much at risk.

[TheLaw]

Re: Internal Shots of the Logitech Z313

Yeah....it's a shame. The speakers don't sound too bad, but the parts are pretty junky. But really, when you get down to it: These things are almost always on sale for <$35. They really have to go cheap on parts if they'd like to make any money. But really, even some general purpose United Chemicons are like $0.10 more...I guess those are $0.10 too much.

I'm actually recapping it with some Panasonic FMs and Some Nichicon Muse FGs/KWs.

The sub is only a 4ohm. I'm also replacing that with a decent 8ohm.

Spent about $30 on parts and hopefully breath some life into it. I kind of destroyed the sub box while opening it...so I'll need to build a new one of those....not like that's hard at all.

[Trinite]

Re: Internal Shots of the Logitech Z313

Looks like Logitech has gone downhill in quality. I have their X-530 5.1 set that I got a few years ago and it is actually rather decent. I am not a fan of their newer setups, though.

[TheLaw]

Re: Internal Shots of the Logitech Z313

Sorry...I didn't know the images are hidden if you aren't a member of the forum. If you'd like to view them and are not a part of this site, you can see the pictures here:

http://s288.photobucket.com/albums/l...view=slideshow

I'd recommend making a Badcaps.net account anyway....but, if not, you can see the album there.

[TheLaw]

Re: Internal Shots of the Logitech Z313

Tags: Logitech Z313 Circuit Board, Amplifier Board, Amplifier, Capacitor, Internals, Guts, Circuitry, Fuse, 4ATL, Transformer, Logic Board, Subwoofer, Powered Sub, Amp