Infinity PS-12 Powered Subwoofer Fired Amplifier

[Mwitte]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I am not familiar with the "dim bulb tester" that Electricboyo mentioned above. Is that an incandescent bulb in series with the 120 volt input to act as a fuse?

[lti]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I don't see any burning at all. If you are referring to the brown stuff around the big caps - that's just glue used to hold down the caps at the factory.

The last few pictures show a hole burned in the board under the blown cap. You have to load the last seven pictures.

[ttatma]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

FORCED ON circuit.

My sub has problem switching from red to green. I repalced most of the capacitors although they all looked good.
C2/12/35/37/39/41/78.
I also replaced Q2 with 2N5550 equivalent and Q3 with 2N5401 since I could find the original parts. Are these the right ones?

My sub switched to green now. But no sound when I connect to the amp. If I played from my phone, I'd get sounds.
What other parts I need to replace. Also, C71/72/73/74 still have 0V.

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Yep, just bad brown glue.

[momaka]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Is this fixable? I have not seen another one that is burned this much...

I don't see any burning at all. If you are referring to the brown stuff around the big caps - that's just glue used to hold down the caps at the factory.

Should be fixable if there are no other dead components, aside from the bad cap(s). On that note, I recommend replacing all electrolytic capacitors in this unit. At least that would be the first part in the repair process for this unit.

[rxm9600]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Hi everyone,

I just acquired a PS-12 and the cap is blown(of course.), but it also burned the board...

Is this fixable? I have not seen another one that is burned this much...

https://imgur.com/gallery/mfwxtNk?fb...YF9kI2iZClRpwU

[Leroy_2000]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Got my PS-12 fixed too! Sub was humming while sitting at idle (no sound). Hum went away when I replaced the C72 capacitor.

Also the sub was making chirping noises. Noticed the light in the back flashing frequently between green and red. Could also hear internal circuitry noises (if I get up close to it), as if circuits were being activated and disabled quickly, on the order of about six times each second. Replaced the C2, C37, and C65 capacitors and all of those noises went away.

Big thanks for all the contributions to this thread! #righttorepair

[electricboyo]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Always use a “dim bulb tester” to apply mains power to these types of amplifiers. 60W or 100W conventional incandescent light bulb is about the right size. You need to get the amplifier to the point where it can play sound at low to moderate volume before applying “full” mains power to it.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Tecchris0516,
Did you get it completely repaired and working correctly?

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

R_J

that was it - under the C8 there wasn't enough of solder - now I have -71vdc

and a C5 i have +14.2vdc and at C10 I have -14.1vdc

I am going to go buy another C8 due to it bulging and I need to get Q18 / Q22 as they shorted and was originally blowing the fuse when I bought the amp broken.

Thanks to you and Budm for your assistance so far!

[R_J]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

This is a double side board and a feed-thru got damaged, likely at the c8 negative connection.

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

So if you check the resistance between the (-) of C8 and the left side leg (based on the diagram) of the R9/9A legs it shows open circuit?
May be you need to upload well focused pictures around R9/9A.

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

R-J

I did have -70vdc on C8 -- referencing your attachment

On the Red arrows = I have from Left to Right 70v 13v 13v
On the Green Arrows = I have from Left to Right @ C7 (-70v) but at the resistors I have -.74 and I cant find a break between C7 (- side) to the R9A/R9 resistors

[R_J]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

When you measure the voltage on the caps was the voltage on C8 -70.8 volts (negative voltage)
It seems like you have open R9 & R9a
The likely reason the voltage you measured was high is because the resistors are open and with no current flowing the cap charged up to peak voltage.

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Budm,

Well I re-measured the voltage at the C6 and C8 caps with ref to the circuit GND- on C6 I had 50.8VDC and on C8 I had 70.8VDC.

So for the hell of it - I reinstalled the original Caps ( replaced both due to one was slightly bulging) and rechecked - now both Caps are at approx 71vdc.

For Transistor MPSW06 (NPN) - which meter neg to ref GND
E- 11.46vdc
B- 12.02vdc
C- 13.0vdc
For Transistor MPSW56 (NPN) - which meter neg to ref GND
E- .74vdc
B- .20 vdc
C- .20 vdc

I wonder if the defective Caps I bought did further damage to other components

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

That Triangle symbol (center tap of the power transformer) that you circle in green is the circuit GND, the amplifier runs on +/- power supplies (+50V, -50V) that are ref to circuit GND.
You AC for each half of the transformer shows 53.4VAC, the the DC Voltage as measured on each main filter caps C6, C8 with ref to circuit GND should be = 53.4VAC *1.414 =about 75VDC, the caps are rated at 80VDC so are you 100% that you are getting 53.4VAC as shown in your diagram?

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

BudM,

Thank you for taking to time to stick with me. Based on your comment i guess I am incorrectly testing the component(s) - I have attached how i have been testing. Can you please enlighten me to the correct point for GND ref and i will be more than happy to supply the data to help get this working

The second image after looking at the schematic again - I green circled the GND ref- is this correct?

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

BudM,

Sorry for the delay - Busy at work

Voltage from transformer -
AC1-AC2 -53.4vac
AC3-AC2 -53.6vac
AC1-AC3 -106.8vac

After Bridge - 121.6v DC
voltage to (R6-&A) and (R9& R9) 51.5v after 10v

For Transistor MPSW06 (NPN) - which meter neg to GND( Neg side of rectifier bridge)
E- 8.82vdc
B- 9.52vdc
C- 10.12vdc
For Transistor MPSW56 (NPN) - which meter neg to GND( Neg side of rectifier bridge)
E- .54vdc
B- 0 vdc
C- 0 vdc

If it put positive meter lead to the (+) on the bridge
E- 9.6vdc
B- 10.1 vdc
C- 10.1 vdc

C4 and C9 are both brand new

I see why your Voltage readings are not right, the Negative of the bridge is for -50V power supply with ref, to circuit GND, the + of the bridge is for the +50V power supply with ref. to chassis GND. You use the wrong GND ref. for the Voltage testing.
May I ask if you know how to read schematic? If you know how to read schematic then you will know where the circuit GND is.

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

BudM,

Sorry for the delay - Busy at work

Voltage from transformer -
AC1-AC2 -53.4vac
AC3-AC2 -53.6vac
AC1-AC3 -106.8vac

After Bridge - 121.6v DC
voltage to (R6-&A) and (R9& R9) 51.5v after 10v

For Transistor MPSW06 (NPN) - which meter neg to GND( Neg side of rectifier bridge)
E- 8.82vdc
B- 9.52vdc
C- 10.12vdc
For Transistor MPSW56 (NPN) - which meter neg to GND( Neg side of rectifier bridge)
E- .54vdc
B- 0 vdc
C- 0 vdc

If it put positive meter lead to the (+) on the bridge
E- 9.6vdc
B- 10.1 vdc
C- 10.1 vdc

C4 and C9 are both brand new

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

So you are getting only +8V and -8V from the +/- power supply.
What do you have at the Emitter, Base, and Collector pin of the Transistor with ref to the circuit GND?
FBx is just simple inductor, there will be hardly any Voltage difference between the two leg of the FBx.
C4 and C9 are OK, correct?
BTW, the schematic called those two regulator circuits as 'SHUNT REGULATOR', they are not Shunt regulators, they are series regulators.
You can learn more here: https://cdn.badcaps-static.com/pdfs/...3da308ff49.pdf