Infinity PS-12 Powered Subwoofer Fired Amplifier

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Hello All,

New to hear - but a huge wealth of information - I just got a PS-10 from a Garage sale - that didnt power up - Internal fuse was blown - replaced the fuse and immediately blew- did some preliminary checking and form the Q18-22 MOSFETS were bad - replaced and powered up but lasted for about 3 sec and fuse blew again - check and mosfets bad again !

I began checking some voltages and i have some questions

What is the output voltage (DC) from the bridge- i have over 100vDC
What is the voltage After the (R6-&A) and (R9& R9) I have about 10v
What controls the 15V rails - I checked C5 and i have approx 8v but on C10 it is less then 1V

I also replaced TIP31C with the orig Q18,22 to be safe
There were also a list of CAPS that were know issues - replaced all of them as well
and Q2 and Q3

And help would be appreciated

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Hello all,

I was wondering if someone can help me out with the above post

Thank you

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Tecchris,
Have you located the service manual? The schematic and parts list are included at least for the PS-12. With the parts list you can get data sheets to determine if the voltage makes sense. I didn't have to mess with the power supply circuitry or transformer so I don't have any specific data that I can recall without digging into the documentation mentioned.

Do you know for sure the fuse rating including voltage, amperage, and speed are correct?

It seems like there was some discussion on here about the expected bridge output, but would need to search for it. Maybe this weekend a couple of the others can jump in and help.

Wanted to let you know we saw your post and to encourage you to stick with it. It should sound good when it's repaired.

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I asked about the fuse due to some similar klipche subs being shipped with incorrect/faulty fuses. The service manual and probably users manual should state the correct size fuse.

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Hello JR,

Yes I do have the service manual and have been going through it until my eyes crossed, along with reviewing the data sheets for components - the fuse it correct (2.0a/250v) slow blow)

the voltage out of the rect bridge is 121v DC - the voltages at the MOSFET's are 70v along with the same voltage at the MOSFET driver - (IR2111)

I am trying to find out what controls +15v - MOD and -15v - MOD and +15VSW

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

It is linear bi-polar power supply to produce +/- 60VDC with ref. to circuit GND as shown in service manual PDF page 33.
Q2 and Q3 are for linear regulator circuits (they take +/- 60VDC input to produce +/- 15V outputs) to produce +/- 15VDC for running the OP-AMPs as you can see in same page number. So do you still have the + and - 15V as shown in the schematic? or it is still blowing the main fuse?.
So look at the schematic then you will see what/where the circuit GND is for your meter.
Page 32) +15Mod is fed by the +15V through Ferrite Bead inductor FB1.
Page 32) -15Mod is fed by the - 15V through Ferrite Bead inductor FB2.

Q18. 22 are blown is probably due to drive circuits are bad and not switching the MOSFET's ON and off bu they are stuck fully on, there are many parts in the GATE drive circuits that you need to test. This is class D amplifier not linear amplifier.

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Bud, - JR

Thank you for the response - the fuse is not blowing right now due to me removing the Mosfets. But the 15v is not anywhere near 15V - I will check Q2 and Q3 as I did replace those as well with a cross NTE128P (NPN) & NTE129P (PNP). The only reason why i chenged them as to multiple posts about issues with them. I might put the old ones back and see what I get.

[Tecchris0516]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Hello All,

Well I reinstalled the old Q2 and Q3 with the original ones - when I measure between C5 (+) and C10 (-) i only get about 8v.

If i measure the voltage after the (R6-&A) and (R9& R9) I have about 10v ( before the resisitors (51.6V)

I also checked the voltage through the FB1 and FB2 an it is the same on both sides..

[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

[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

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,

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

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,

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

[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

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

[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.

[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.

[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!

[Jr_ece]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

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