Help diagnose Sonic Gear 2.1 woofer no bass

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Forgot to attached the 2 images.

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Hi budm,

Refer to your comment "You can also try using that speaker you show in the picture that you were going to use for Audio tracer by removing the red/black wires from woofer and connect them to that speaker instead and see if you can hear anything."
Done as above but still not able to hear anything from that external speaker (with speed logo) which replaced the red/black wires from woofer. As usual, i can hear audio from the 2 square sonic gear speakers. As attached img 101539.
Hope for your continued guidance. Thank you.

[budm]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

I forget to ask if you get normal level sound from the two Sonic gear speaker or not.
The control board do not have any active component on it so I will not look at it for now. I will have to trace out the connection from the TDA IC input pin to see where it goes to.

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Hi budm,

Yes, i am getting normal audio sound from the two sonic gear speakers. The volume and treble can be managed from the control board with no issue.
After desoldering the red and black wire from the woofer speaker, i briefly connect it to a set of 3v dc batteries, the woofer speaker gave out a light popping sound. I measured the dc resistance which is 5.1ohm. Just my two cent, i think the woofer speaker should be ok.
Appreciate your continue guidance in solving the mystery of the missing bass.

[budm]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Yes the Woofer is OK.
I just need to trace out the input pin of the woofer TDA to see where it goes too, it will be faster using the probe.

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Hi budm,

Quote from you "I just need to trace out the input pin of the woofer TDA to see where it goes too, it will be faster using the probe."
If you are referring to pin 1 of the woofer tda near c23, it goes back to a 22k ohm resistor (color red red orange gold) then to positive leg of c21(0.47uf50v).
Not sure if this info is of any help.

[budm]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

https://www.badcaps.net/forum/attach...4&d=1604289313

OK, I trace out the board, the VR3 is the Bass level control hat feeds pin 1 input of the woofer TDA.
so turn VR3 all the way clockwise, then use your finger to touch each leg of the VR3, you should hear loud hum coming through the woofer.

Can I also get straight shots of the bottom side of the Control board?
The connector P2 pins looks like they are bridged together, or may be just bad picture.
https://www.badcaps.net/forum/attach...5&d=1604289335

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Hi budm,

Your quote on "so turn VR3 all the way clockwise, then use your finger to touch each leg of the VR3, you should hear loud hum coming through the woofer."
Yes, i do hear loud hum coming through the woofer.
I am attaching straight shot of the bottom part of the control board. Refer img 152006.
When i probe my analog multimeter on the black and white wire on P2, i got continuity but
looking at the board and solder, they are not bridged together.
I also attached top shot of the control board img 152241.

Hope the above info helps.

[budm]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

It is quite loud, correct?
The black wire is circuit ground and connected to the bottom end of the Potentiometer, The White wire is connected to the Wiper of the Potentiometer which goes to the input pin 1 of the TDA through coupling capacitor, the Red wire is connected to top end of the Potentiometer which is the low audio frequency is fed to.

The resistance reading between black wire and the white wire will vary as you turn the pot from one end to the other, when at full counter clockwise it will be < 10 Ohms, at full clockwise will be in K Ohms range (this resistance will be printed on the body of the pot).
So you should hear the loud hum when touching White or Red wire when pot is in full clockwise.

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Hi budm,

Yes, the hum is quite loud.
On vr1 and vr2, there is a white sticker printed as B50k (this looks like 50k pot) but vr3 the bass level has no label whatsoever. So i do the dc resistance (without power on) on p2 black and white wire . I got reading of fluctuating figure of 44 to 50 ohm on 200 ohm scale.
The reading did not stay put but it varies jump up and down. I think this pot is sort of busted. Correct?
I did dc resistance on p1 near the volume control and got reading of 61.2k ohm on 200k ohm scale. This is the 50k pot. Is the volume pot and treble pot still acceptable?

[budm]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

If the Middle pin (wiper, White wire)) is shorted (low Ohm) to Ground pin (Black wire), then you will not be hearing any hum since input of the TDA woofer IC will be grounded out.
You can remove that P2 on the power amp board side and then you can recheck the pot resistance.
Do not worry about the 2 pots.

[budm]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

I am going to bed, it passes 1AM here in Bay area. good night.

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Hi budm,

Good night at your side.
From your earlier quote "The resistance reading between black wire and the white wire will vary as you turn the pot from one end to the other, when at full counter clockwise it will be < 10 Ohms, at full clockwise will be in K Ohms range (this resistance will be printed on the body of the pot).
I recheck the resistance by setting the ohm to 200k scale, my dmm probe goes to black and white wire, and i got almost zero ohm when the pot was at full counter clockwise.
However, when i turn the pot full clockwise, the dmm reads 48.8k ohm stable. I guessed the vr3 is a 50k pot as well.

[budm]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

At this point the Bass Pot is OK, the Woofer TDA is OK, so now we need to find out if the 4558 sitting at the edge of the board is working or not, that 4558 is setup as low pass filter to feed only low frequency to the Woofer TDA.

BTW: https://www.badcaps.net/forum/attach...0&d=1604289191
The picture is not well focused so I cannot easily see the prints and color of resistors

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Hi budm,

Attached a clear top view of the board with the vr1 and vr2 connector removed.
I can retake again if needed.

[budm]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Been busy, i will get back to you with test points to test.

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Been busy, i will get back to you with test points to test.

The subwoofers speaker system has been working fine for over 2 years till today. After i switched on main ac power, i can hear a loud irritating crackling and buzzing noise from the whole speaker system.
Opening the back case i did not noticed any loose wire or burnt component. So i go ahead and do voltage testing on all the 3 pieces woofer ic tda2030 by red positive probe on pin 5 and black probe on center tap of transformer. But all the 3 ic readings are similar at around 15.7vdc.

Next i do voltage testing on the 2 pieces 4558 op amp ic by red positive probe on pin 8 and black probe on center tap of transformer. The readings are about 9.1vdc on both op amp ic.
I did some solder touch up on the bass output wires but the crackling buzzing noise is still there whenever i switch on power.
Appreciate if anyone can share your thoughts and help to diagnose the source of the buzzing noise.

[mikey5791]

Re: Help diagnose Sonic Gear 2.1 woofer no bass

Hi forum members,

Yesterday i retouched all dry solder and make sure the bass output speaker wires are firm and in good contact. I also sprayed electrical contact cleaner on input jack connector and all the knobs on volume, treble and bass pot.

still no luck whatsoever. The speaker is still buzzing and hum noise can be heard. Is anyone still reading this old thread and possibly kind enough to share a little feedback? thank you in advance.