Creative Gigaworks S750

[brogdan]

Re: Creative Gigaworks S750

the problem is i don't have an oscilloscope, to check the waveform.
on the TDA all voltage rails measured and OK.
Mode pin is OK, i have 4.5v when in operation mode. and it dropps to 1.4v when muted.
HOW can i check the audio input pins?
i think that the amp is in somekind of power off , or muted because i can not hear anything is speckers...although if mode pin is ok, and TDA power rails are also ok...what elese should i check?

[Agent24]

Re: Creative Gigaworks S750

the problem is i don't have an oscilloscope, to check the waveform.
on the TDA all voltage rails measured and OK.
Mode pin is OK, i have 4.5v when in operation mode. and it dropps to 1.4v when muted.
HOW can i check the audio input pins?
i think that the amp is in somekind of power off , or muted because i can not hear anything is speckers...although if mode pin is ok, and TDA power rails are also ok...what elese should i check?

OK, if you can't check the OSC pin, check the audio inputs. Give the G500 an audio input and then you can use another amp or headphones or whatever to listen to what is at the TDA input pins.

If you get no signal there, you need to trace back through the circuit and find where the signal stops.

[brogdan]

Re: Creative Gigaworks S750

i checked the audio in on the tda and i get no sinal. i thnk the audio board MS0730A is the problem...any ideea what to check?

[brogdan]

Re: Creative Gigaworks S750

i checked the audio in on the tda and i get no sinal. i thnk the audio board MS0730A is the problem...any ideea what to check?

SORRY!! MY BAD. i do have audio signal at TDA input. i just had tu turn the volume all the way to Max, because it was very low signal, as it passes the resistors on the audio board.

SO if i have audio signal at TDA imput, I have all volgates ok t the TDA...what else?

[brogdan]

Re: Creative Gigaworks S750

i saw that all OSC pins of the 4 TDA are connected together, i i isolated(CUT) that circuit and connected it to the Vssa1 pin with a 30 Kohm resistor, as told in tha TDA datasheet, to force the TDA to work on the internal oscillator, but still no sound at the speackers

[Agent24]

Re: Creative Gigaworks S750

If the TDAs are indeed not working, it might be tricky without a scope to troubleshoot a Class-D amp...

I doubt though that all of the chips have gone bad at once, that would be strange.

If you had to turn an external amplifier up to maximum to get any signal, I wonder if the input signal is too low for them to amplify?

I notice you seem to have replaced the output capacitors in the amp board. Have you checked to make sure you have not caused any shorts on the output with solder bridges or anything? That may cause the amps to go into protection shutdown.

[momaka]

Re: Creative Gigaworks S750

on the TDA all voltage rails measured and OK.

But what are they? If less than 12.5V or over 30V, the amps may enter under-voltage (UVP) or over-voltage protection (OVP).

SO if i have audio signal at TDA imput, I have all volgates ok t the TDA...what else?

Did you check the outputs on each amp (pins OUT1 and OUT2) for short circuit to ground and to any other rails?

i saw that all OSC pins of the 4 TDA are connected together, i i isolated(CUT) that circuit and connected it to the Vssa1 pin with a 30 Kohm resistor, as told in tha TDA datasheet, to force the TDA to work on the internal oscillator, but still no sound at the speackers

Interesting.
Could very well be that the chip is bad. Or perhaps the default frequency won't work with the circuit in your Gagaworks G500. at's the wrong frequency for it.

According to datasheet, a 30 KOhm resistor will set the internal oscillator frequency around 317 KHz. However, allowable frequency for internal oscillator is between 210 and 600 KHz. But they didn't include a formula for how to change the internal frequency

If you want to try an experiment, you can try changing that 30 KOhm resistor to see what happens. *Assuming* (and that's a big ASSumption on my part) the internal oscillator uses some kind of RC circuit, then a 22 KOhm *or* a 47 KOhm resistor should set the frequency at 482 KHz, depending on how the RC circuit is set (if it is RC at all!)

Another thing you can try is provide a steady 5V on the MODE pin, just to rule out that the amp is somehow not stuck in Standby or Mute mode.
Without an RC circuit on the MODE pin, though, you might get a loud pop on the speaker outputs (but at least you will know if the amp outputs are working then ). However, if you want to avoid that, build a RC low-pass circuit with a 1 KOhm resistor and 100 uF capacitor. Hook the 100 uF cap between ground and MODE pins and 1 KOhm resistor between 5V supply and MODE pin. That should make the amp come out slowly out of standby/mute.

[brogdan]

Re: Creative Gigaworks S750

OUT1 and OUT2 are not shorted to ground or any other TDA pin

Voltages are 27V, except a voltage measured at a capacitor connected between Vddp1 and Vssp1, witch is 54V

Also connected the MODE pin to a 5V supply

Still nothing

[momaka]

Re: Creative Gigaworks S750

Well, as a last resort, you could just try to directly feed the amp inputs via your computer and see if you get output. If you do that, though, my only suggestion is to first turn the sound on the computer very, very low (as in, all the way down to 1%).

I can't really think of much else to try. Maybe experiment with the resistors on the oscillator pin as I suggested in my last post. Other than that, I am all out of ideas for now. I guess the amps could be bad. However, like Agent24, I too think it would indeed be very strange if all 4 amps died at the same time.

[Agent24]

Re: Creative Gigaworks S750

Yeah, I agree with momaka - I would definitely try injecting an audio signal from some external source. The fact that you had to turn an external amp up to maximum to get anything out when signal tracing makes me think the input signal may be too low.

If that's the case, maybe your preamp circuit (if any) is bad.

Did you try any actual signal tracing from the input jack to the TDA ICs? Might pay to try it and see where the signal becomes such a low level. I reckon it should be somewhat higher that what you describe.



Otherwise - was there anything wrong with the PSU in your speakers?

I guess it's possible if the PSU was\is bad that some voltage spikes or such may have blown all the amp ICs at once.

[AVK]

Re: Creative Gigaworks S750

Hello everyone!
I am stumbled with gigaworks s750 SPS

Prehistory:
Several months ago I got this sub with blown fuse.
After unscrewing found just one visible damage, caused by spike at place of C62 and C7 just near the heat sink. Also observed bulged capacitors C59, C60, C69, C70 of different extent and a lot of darkened alien sperm covering most components.

Further examination revealed shorted diode D9 and overrated resistor R9 (measured 7 kOhm instead of 6.8 Ohm). These two were consequence of IC (TOP243Y) collapse.

Sperm was cleared and damaged parts together with all electrolytic capacitors found on PSU board were replaced by new ones with the same nominal except D9 (used diode with 1 kV threshold instead of 400 V). Also for reliability C6 filter capacitor and C63 (0.1 mkF, 50 V) electrolytic were substituted by ceramic ones.

Testing (used multimeter diode testing mode) of voltage regulators and rectifier diodes in secondary circuit revealed no short or open connections. Transformers T1-3 also seems to be intact (T3 has only 4 connected pins on IC side and 3 central are not)

After reassembling and switching on I observed periodically flashing green light at the Sub back panel and heard faint ticking sound from the PSU (possibly relay switching, not sure). No reaction from control Pod buttons.

After that I applied 220 V AC directly to the unloaded PSU board (don't know whether it is supposed to operate correctly in such regime) and tried to trace voltages on CN4, CN5, CN6. Voltage on CN6(1) was around 5V (true RMS) instead of 9V on other CN6 pins same situation, voltage on L4 pin of CN4 (+24 V) varied from 5 to 42 V (seems to be the result of feedback operation). After some time hissing sound came from C64 capacitor, caused by its gradual bulging.

I've checked components in standby secondary circuit line controlled by IC feedback everything seems to be in order.

Now I am going at least to replace C64 together with U3 voltage regulator and D6, D7 diacs (don't know how to test with multimeter).

By the way, as I understand, U6 (L7920) is accounted for -20V and not for -24V as it is indicated in electrical scheme. Is it critical?

The main question is what could be the reason of output overvoltage and/or overcurrent and feedback actuation? What components shall I check first or it will be easier to replace all MOSFETs Q1-6 together with four rectifier diodes and see what will happen then? Could it be primary rectification part problem?

I don't understand how IC controls high voltage line of Main PSU. So Is PSU supposed to work with connected CN6 and disconnected CN4 and CN5 both or one at a time? If no what dummy loads are appropriate for connection to -/+24 V and -/+70 V for testing standby section?

Will be very glad in case anybody can help me with this stuff.

[AVK]

Re: Creative Gigaworks S750

PSU electric schemes

[rsseco]

Re: Creative Gigaworks S750

Hello @all !

If I write here, you can think a have a trouble with my S750 set.

In resume, it works well for many years (~12 years) ; for a month ago, I wanted to start my set again, after so many weeks off (but it was always connected to the AC outlet and in standy mode) ; as I pressed on the power on button of the remote console, I heard a "pffff"-sound, then all switched off.
I check the fuse : it had burned. I also opened the subwoofer, and it very smells badly. Yes, a cap had explosed ! And guess what, it concerned the 4x 470uF 200V, the C70 one. The 3 others were bombed, so I decided to replace all 4.

After reading so many posts, I clear all the "burned" glue everywhere I could and replace the 4 caps and the fuse.
Pluged on power outlet, switch on : the green led on the back turned on : check ! But I heard a "boom" sound. As the leds are still on (green on back, red on console), I decided to power on : it powered on, 2s... and then total black out. The fuse has burned again.

I open it again, but nothing "bad" to see.
As, when I replaced the cap, the negative "port" under the board were broken under 2 caps (I checked, all were conductive), I decide to remove all the caps and deport them, as you can see on the picture.

But again, the same story : when pluged in, the green led powered on. No more. But, when I power it on via console, after 2-3s all goes off, the fuse burn. To notice, I've glued the caps, the first one (c70, which one has explosed, had "jumped", but not explosed.

My electronic knowledge are very limited, so I don't know whats wrong. I tested the port on the caps ; I have a short circuit on the C69 and C59 (the 2nd and 4th ones). I visually check all the other component, they're seem to be OK. I tested the PSU board alone (the 2 DASH board were deconnected).

I really want to repare my set (and not throw away), can you please help me ? What can be the problem ?

I post some pictures if it can help you
















Thank you in advance,

[n3o]

Re: Creative Gigaworks S750

Hi to all, I'm new on this forum and on this topic. I have bought the creative s750 system but a channel (front left) doesn't work. I have already check the speaker and moving it to other channel it work. So the problem is the electronic inside subwoofer. Can someone tell me what components check?

Moreover I have other question to do:
1. somebody have tried to divide amplifier from subwoofer and move it to separate box?
2. I wan t prevent problems dued to glue and bad caps.... somebody can made a list of caps with number of unit, mF value and volt value?
3. somebody have found a way to fix the subwoofer so it's work for many time?

hoping that somebody help me

[babay6890]

Re: Creative Gigaworks S750

Hello everybody,

I'm new to the forum and i need your help.
I will soon finish repairing the S750 : I cleaned up all the glue and replace the caps as indicated in the forum. when I tested the subwoofer the sound was noisly and low. so I deepened my research on the audio process board and I noticed that there is a CMD component that was cracked (C66). I join you the photos.

can someone give me some information about the value of the CMD component C66 ? I think that C65 have a same value of C66. I don't find the schematic of audio process board (the model is MS0490C)

if anyone can help me that will be really nice

[batkata]

Re: Creative Gigaworks S750

Hello guys.
Before 3 days i bought a old one S750 which was used only 1.5 year at home and thay aer very wel mentained.
Unfortunately after i use them for the first tim - 15minutes i hear exploading fuse and the system stop working.

I open the subwoofer and start to investigate. Actually the glue is white and soft.Thay are really little used.

I will visual inspect the boards at the first time.

Can i ask you to give me the electric schemes of the psu , amp .. all boards if you have.
i ask already creative support to give them and if thay give me i will share with you.

i read that mr - Lex reapair them with big success and i hope i will repair mine with your help.

Can you give me start advice what to inspect also some links or good model capacitors that i probably will need to replace.

Best regards
Toni

[Macck]

Re: Creative Gigaworks S750

Hello!

I'm fighting with some nasty S750. Firsty I assumed that standard procedure of cap replacement "will do", and actually it fixed up secondary PSU.
By rush, I've blown two of 470/250V caps on primary PSU, and then it became clear on schematic that IRF740 are blown (actually mostly Q1 is getting killed) and these two caps are getting rectified 230V.
I replaced the mosfets, but the unit blew them again. I was measuring around the board to see if something is strang, but with no succes. I have 2 more of these PSU boards so there is still hope. But maybe after these years someone knows why mostly mosfets die in these units? I was suspecting these diacs and diodes, but im not really convinced, and actually these days its hard to even get IRF740, so i dont really like idea of blindly changing everything.

My friend likes this set a lot due to sound quality, I was even wondering if it wouldnt be more reliable to replace this whole switching abomination with all that nasty, soldermask etching brown goo, and just put some tailored toroidal transformer linear solution into this.

[Coldfear]

Sorry if i revive the topic, i have a Creative GigaWorks ProGamer and when i power it up from the wired remote for a 1 minute or so strange sounds comes from the sub and random sound in speakers during the sound test from windows. After that its like is alive and working ok sound is clear and from all speakers. What could it be?
Thank you!