VSX-74TXVi MCACC Flashing

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

Okay here is the results from testing output from the power Amp Block after power on the Amplifier.

White CN4006= -40v
Purple CN4005 = -14v
Orange CN4004 = -17v
Green CN4003 = -16v
Brown CN4006 = -17v
Gray CN4005= +29v
Yellow CN4003 = -18v

Reading from the Output is intermittent plus or minus I just record the highest voltage output.

[R_J]

Re: VSX-74TXVi MCACC Flashing

Those voltages do not look good, You need to relate the color to the pin number. CN 4006 and CN4005 have big problems but they all seem to have an issue.
If you look at the service manual, page 75 for example, I would check each of the output transistors, on ic5001, check for shorts between pins 3 and 4, On IC5002, check between 3 and 2.
Then check both emitter resistors in R5027 and check R5025, R5026, R5023 and R5024.
You will need to check these components in ALL the channels
I also see IC5601 and R5292 and IC5602 and R5592, these need to be checked as well.

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

Those voltages do not look good, You need to relate the color to the pin number. CN 4006 and CN4005 have big problems but they all seem to have an issue.
If you look at the service manual, page 75 for example, I would check each of the output transistors, on ic5001, check for shorts between pins 3 and 4, On IC5002, check between 3 and 2.
Then check both emitter resistors in R5027 and check R5025, R5026, R5023 and R5024.
You will need to check these components in ALL the channels
I also see IC5601 and R5292 and IC5602 and R5592, these need to be checked as well.

I test all the resistors and they all in the specs. Is these Diode D5041, D5042, D5241, D5242, D5141 and D5142 are Normal read from Both direction? At diode mode on Multimeter I have these reading 1.801v and 0.547v at reverse? This is the Left Power Amp I didn't check the Right power amp yet.

[R_J]

Re: VSX-74TXVi MCACC Flashing

Why bother checking those diodes? the chances of them being bad is highly unlikey. Check the output transistors, in ALL CHANNELS. they are what are likely shorted.

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

Why bother checking those diodes? the chances of them being bad is highly unlikey. Check the output transistors, in ALL CHANNELS. they are what are likely shorted.

Okay! I will Order all of them and replace all the IC transistor then we go from there.

[mmartell]

Re: VSX-74TXVi MCACC Flashing

Okay! I will Order all of them and replace all the IC transistor then we go from there.

If you do that and power it up you're likely to hear a BANG! again if one was shorted in the first place. I don't see where you tested all the output transistors ? It's not necessary to replace them all you only have to repair the blown channel - output transistors and associated failed components in that channel.

[R_J]

Re: VSX-74TXVi MCACC Flashing

Find the bad components first, If one channels outputs are shorted, then you need to check the driver section for that channel as well. The output transistors may be ok and it's just a driver that is bad, You can't just throw a bunch of parts in it and expect to to start working.

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

Find the bad components first, If one channels outputs are shorted, then you need to check the driver section for that channel as well. The output transistors may be ok and it's just a driver that is bad, You can't just throw a bunch of parts in it and expect to to start working.

On AWX8658 Pages 241 Can I do that so I can start testing to bypass the protection circuit? Is not going blow on me

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

Sorry to tell you that I do have experience in Macbook Pro Logic board repair component level but I don't have experience in repairing AVR. This is my first time to fix my Own AVR so please pardon me if don't have idea where to start.

This is the equipment I have for my Logic board repair.
1. HP DC Power Supply 6632A
2. Hakko FR-802
3. Hakko FX-951
4. Infrared Thermal Camera for short circuit detection
5. Fluke 15B Digital Multimeter.
6 Amscope ( Stereo Microscope)
7. RIGOL DS1102D Digital Oscilloscope ( i don't use to much)

I know I can fix this one with your humble help step by step.

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

Okay! I pull out all the transistors both Power Amp L and Power amp R. Can someone assist me how to check these transistors/IC with my multimeter. I would really appreciate. Thanks.

[mmartell]

Re: VSX-74TXVi MCACC Flashing

You didn't have to pull them you could have checked them in circuit. Actually you've complicated things because if one is shorted you won't know which channel it came from.

Anyway all you're looking for is a short between any two legs of the output transistors. No leg of any transistor should be shorted to another leg.

[mmartell]

Re: VSX-74TXVi MCACC Flashing

Wait. Left and right channel ? Isn't this an avr ? Should have more than two channels... Test the rest without removing them.

[madan1]

Re: VSX-74TXVi MCACC Flashing

Wait. Left and right channel ? Isn't this an avr ? Should have more than two channels... Test the rest without removing them.

Nope - left channels on one amp board, right channels on other.. "audiophile" stuff you know .. still this does not change the thing that the op has no idea what he is doing and totally refuses to follow our advises.

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

You didn't have to pull them you could have checked them in circuit. Actually you've complicated things because if one is shorted you won't know which channel it came from.

Anyway all you're looking for is a short between any two legs of the output transistors. No leg of any transistor should be shorted to another leg.

So far so good I don't see one of them are shorted.Problem is not on the transistors.

[tibimakai]

Re: VSX-74TXVi MCACC Flashing

Now remove all the driver transistors.
Joking aside, you should follow these people advise, if you want to get some help.

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

Now remove all the driver transistors.
Joking aside, you should follow these people advise, if you want to get some help.

Sorry but I don't have any idea where the transistors driver is. Sorry for my ignorance this my first time to fix a receiver so I don't have any clue.

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

Sorry but I don't have any idea where the transistors driver is. Sorry for my ignorance this my first time to fix a receiver so I don't have any clue.

Thank you all you guys for all your input support i get it to fixed with the reset Combination now its working.

One more thing I would like to install a Fan to make it more cooler because i know this thing come get very hot sometimes. I already have the fan and install below the Protection circuit perfect fit 80mmx25mm fan but my questions is where can i get a safe 12V dc connector for fan. I like the fan start once i power up the receiver.

[madan1]

Re: VSX-74TXVi MCACC Flashing

page 60-61 from the sm show the power rails .. pick one.

[R_J]

Re: VSX-74TXVi MCACC Flashing

The local supply board has +12 volts, The non N.A. models have a fan but the this model does'nt have the fan control components installed.
Or find CN5706 on the power protect board, Pin2 should have -12v, so connect your fan (-) lead there and (+) lead to ground

[MobileXT]

Re: VSX-74TXVi MCACC Flashing

The local supply board has +12 volts, The non N.A. models have a fan but the this model does'nt have the fan control components installed.
Or find CN5706 on the power protect board, Pin2 should have -12v, so connect your fan (-) lead there and (+) lead to ground

Thanks R_J yes it's working! My receiver will run much cooler now than before. Thank you very much guys and sorry if can't follow you guys instructions during troubleshooting i'm a new to this kind of troubleshooting but i've learn a lot from you guys. Maybe next time I can follow better. PEACE!