Memphis PR400

seankane · 21st November 2011, 05:08 PM

This is the first Memphis I have ever worked on know next to nothing about them.

Amp powers up goes into protect (red led lit) and pulses. Green light flashes slighlty during the pulses. The pulses are about every 2 seconds.

Any ideas where to look?

Board number is MAP-081-07E I believe the customer said she actually reversed power and ground for a second by accident on the inputs.

seankane · 21st November 2011, 05:11 PM

Here is a pic of the board.

brandes.cm · 21st November 2011, 07:07 PM

Check your supply and rail voltages, look for and check the outputs of the lm393 chip, check the signals on the 494 or equivilent heart of the amp.

seankane · 21st November 2011, 07:42 PM

I dont have a schematic for this amp so I am guessing here.

I am assuming D6, D7, D8, and D9 are the rectifiers for each channel.

They are FMU22S and FMU22R none of these have rail voltage.

I have no gate voltage to the power supply fet gate leg. During the pulse the amp does it will come up to a 1/2 volt and during the pulse I get a partial square waveform signal to the gate leg of the fet but its intermittant with the pulsing.

The only pin that had any signal was pin 5 of the tl494CN and it was a saw tooth waveform.

I dont see any LM393 unless its on the back side of the board as I have not removed the board from the sink.

TL494CN reads as follows:

Pin 1: 0.025 vdc jumps up to a 1/2 volt during the pulse
Pin 2: 4.96 vdc
Pin 3: 4.76 vdc
Pin 4: 4.95 vdc dropping to 1vdc on the pulse
Pin 5: 1.483 vdc
Pin 6: 3.436 vdc
Pin 7: 0.001 vdc
Pin 8: 13.95 vdc
Pin 9: 0.001 vdc
Pin10: 0.001 vdc
Pin11: 13.95 vdc
Pin12: 13.95 vdc
Pin13: 4.97 vdc
Pin14: 4.98 vdc
Pin15: 4.90 vdc drops to 3vdc on the pulse
Pin16: 4.97 vdc

Perry Babin · 21st November 2011, 07:51 PM

Pin 4 is likely being used as a soft start so when the voltage on it drops, the supply switches on. It's resetting to 5v because the amp shuts down.

Is pin 16 directly connected to pin 14?

Have you checked the outputs carefully. This seems like there is a shorted or leaking output.

seankane · 21st November 2011, 08:03 PM

I will let you know on pin 14 and 16 when I remove the board.

I found Q141 and Q143 to be shorted both are output fets and are the markings D718. The other two in the channel are the D688.

Should I replace all 4 or just the D718's?

I think I have seen these fets before in pioneer,jensen, and kenwood amps not sure though.

I clipped Q141 and Q143 out of the circuit and the amp powers up without going into protect.

Perry Babin · 21st November 2011, 08:08 PM

If it's a 2 channel amp, I'd suggest replacing all of the output transistors in the defective channel.

The FJA4313 and FJA4312 are what I use and recommend as subs for these transistors.

These are BJTs, not FETs.

seankane · 21st November 2011, 08:12 PM

Thanks Perry I will get some ordered up.

seankane · 21st November 2011, 08:20 PM

WILL I BE OK WITH THE SAME GATE AND SOURCE RESISTORS?

What would you think about subbing (NPN) 2SC5242 and (PNP) 2SA1962 ??

Perry Babin · 21st November 2011, 08:34 PM

Base and emitter resistors. Gate and source resistors are only for amps with FETs.

Yes. I've used these to replace all of this type transistor and have never had any problems.

The ones you listed are the same as the FJA parts. The datasheet for one has the other.
http://www.fairchildsemi.com/ds/FJ/FJA4313.pdf

21st November 2011, 05:08 PM	#1
seankane diyAudio Member Join Date: May 2010 Location: Washington State	Memphis PR400 This is the first Memphis I have ever worked on know next to nothing about them. Amp powers up goes into protect (red led lit) and pulses. Green light flashes slighlty during the pulses. The pulses are about every 2 seconds. Any ideas where to look? Board number is MAP-081-07E I believe the customer said she actually reversed power and ground for a second by accident on the inputs. __________________ Pyramid 46 Amp Power Supply----Fluke 787 Processmeter----Tektronix 465 Scope----Velleman HPS40 Scope----Soldering Iron----Desoldering Iron----Hejet HJ 500-S Heatgun----DM4070 Digital LCR Meter----Propane Torch

21st November 2011, 07:42 PM	#4
seankane diyAudio Member Join Date: May 2010 Location: Washington State	I dont have a schematic for this amp so I am guessing here. I am assuming D6, D7, D8, and D9 are the rectifiers for each channel. They are FMU22S and FMU22R none of these have rail voltage. I have no gate voltage to the power supply fet gate leg. During the pulse the amp does it will come up to a 1/2 volt and during the pulse I get a partial square waveform signal to the gate leg of the fet but its intermittant with the pulsing. The only pin that had any signal was pin 5 of the tl494CN and it was a saw tooth waveform. I dont see any LM393 unless its on the back side of the board as I have not removed the board from the sink. TL494CN reads as follows: Pin 1: 0.025 vdc jumps up to a 1/2 volt during the pulse Pin 2: 4.96 vdc Pin 3: 4.76 vdc Pin 4: 4.95 vdc dropping to 1vdc on the pulse Pin 5: 1.483 vdc Pin 6: 3.436 vdc Pin 7: 0.001 vdc Pin 8: 13.95 vdc Pin 9: 0.001 vdc Pin10: 0.001 vdc Pin11: 13.95 vdc Pin12: 13.95 vdc Pin13: 4.97 vdc Pin14: 4.98 vdc Pin15: 4.90 vdc drops to 3vdc on the pulse Pin16: 4.97 vdc __________________ Pyramid 46 Amp Power Supply----Fluke 787 Processmeter----Tektronix 465 Scope----Velleman HPS40 Scope----Soldering Iron----Desoldering Iron----Hejet HJ 500-S Heatgun----DM4070 Digital LCR Meter----Propane Torch

21st November 2011, 07:51 PM	#5
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Pin 4 is likely being used as a soft start so when the voltage on it drops, the supply switches on. It's resetting to 5v because the amp shuts down. Is pin 16 directly connected to pin 14? Have you checked the outputs carefully. This seems like there is a shorted or leaking output. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

21st November 2011, 08:03 PM	#6
seankane diyAudio Member Join Date: May 2010 Location: Washington State	I will let you know on pin 14 and 16 when I remove the board. I found Q141 and Q143 to be shorted both are output fets and are the markings D718. The other two in the channel are the D688. Should I replace all 4 or just the D718's? I think I have seen these fets before in pioneer,jensen, and kenwood amps not sure though. I clipped Q141 and Q143 out of the circuit and the amp powers up without going into protect. __________________ Pyramid 46 Amp Power Supply----Fluke 787 Processmeter----Tektronix 465 Scope----Velleman HPS40 Scope----Soldering Iron----Desoldering Iron----Hejet HJ 500-S Heatgun----DM4070 Digital LCR Meter----Propane Torch

21st November 2011, 08:08 PM	#7
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If it's a 2 channel amp, I'd suggest replacing all of the output transistors in the defective channel. The FJA4313 and FJA4312 are what I use and recommend as subs for these transistors. These are BJTs, not FETs. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

21st November 2011, 07:07 PM	#3
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	Check your supply and rail voltages, look for and check the outputs of the lm393 chip, check the signals on the 494 or equivilent heart of the amp.

21st November 2011, 08:12 PM	#8
seankane diyAudio Member Join Date: May 2010 Location: Washington State	Thanks Perry I will get some ordered up. __________________ Pyramid 46 Amp Power Supply----Fluke 787 Processmeter----Tektronix 465 Scope----Velleman HPS40 Scope----Soldering Iron----Desoldering Iron----Hejet HJ 500-S Heatgun----DM4070 Digital LCR Meter----Propane Torch

21st November 2011, 08:20 PM	#9
seankane diyAudio Member Join Date: May 2010 Location: Washington State	WILL I BE OK WITH THE SAME GATE AND SOURCE RESISTORS? What would you think about subbing (NPN) 2SC5242 and (PNP) 2SA1962 ?? __________________ Pyramid 46 Amp Power Supply----Fluke 787 Processmeter----Tektronix 465 Scope----Velleman HPS40 Scope----Soldering Iron----Desoldering Iron----Hejet HJ 500-S Heatgun----DM4070 Digital LCR Meter----Propane Torch

21st November 2011, 08:34 PM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Base and emitter resistors. Gate and source resistors are only for amps with FETs. Yes. I've used these to replace all of this type transistor and have never had any problems. The ones you listed are the same as the FJA parts. The datasheet for one has the other. http://www.fairchildsemi.com/ds/FJ/FJA4313.pdf __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
memphis 1500	timwebb	Car Audio	3	8th August 2011 03:20 AM
memphis 1500d	timwebb	Car Audio	19	16th January 2011 02:21 AM
Memphis ca150	mike49504	Car Audio	5	12th September 2010 02:25 AM
memphis 1500d	timwebb	Car Audio	11	21st July 2010 09:33 PM
Memphis...?	hooverjr10	Subwoofers	0	14th December 2007 03:16 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read