Yamaha RXV 465 no display and power problem

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

Dear R_J,

I think the missing transistor Q201 should be in place, as there is no indication for IT to be meant for a different model number of the receiver.

The &2 is just for interchangeable parts from the manufacturer, as mentioned in different sections of the schematic. Also, the dashed lines symbolises a complete digital low power transistor, as per the datasheet of DTA144.

will try finding the same part or will make it by using a simple PNP transistor.

If there are any inputs from your side, kindly do let me know,

Regards,

[R_J]

Re: Yamaha RXV 465 no display and power problem

The only reason for the Q201 is to turn +3.3S on and off, Check Q200 If it has 3.4 volts on its source and 3.4 volts on its drain then maybe they don't require +3.3S to be controlled
Does it look like it was removed?

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

Hi R_J,

The Q201 was made with KMPSA92 PNP transistor with 47Ks, as per the datasheet of DTA144EKA, a little progress is achieved i guess , now with the very first press of the standby switch, the unit turns ON.

The Relays RY100 and RY371 show drop in voltage across their coils, i guess this is also OK, now.

In total i hear 3 relay click one after another. Now the whole board is to be turned upside down to take measurements at the power supply capacitor.

Further, the STKs pin number 123 & 8 are floating.

I will update the voltage measurements across power capacitor, stk input in the evening.

NOTE : The display is still OFF, no single sign of illumination.

Regards,
Hemant.

[R_J]

Re: Yamaha RXV 465 no display and power problem

Could it be that someone else worked on this unit? If installing that missing part restored function, what else is missing?
You should have reported that the transistor was missing, this would have saved a lot of time
Check for missing +3.3dsp likely missing Q401, Q403 & Q404

electronicspoint/threads/yamaha-rxv-465-no-display-and-no-power.288290/
Please note,

I removed the μp board while tracing the +3.3S supply and found that the transistor Q201 is missing.

I think this unit is already worked by someone but thats not my problem, as i am trying to learn more of these recievers of today.

Regards,


Hemant Choudhary, Jun 18, 2018

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

Hey R_J,

It was during my troubleshooting, that i found about the missing Q201. Sorry if my post was confusing.

Summary of todays work,

I soldered the pins 123 &8 of both stk's and the problem reappeared then i undid what was done but to no avail.

The amp has returned into its previous state. SAD.

One thing is for sure, i was tracing the pin 96 of the micro and found that there is 3.34v when the power switch is pressed and this voltage remains for 5 to 7 seconds then drops to zero, which is guess turns ON the Q201.

Further details along with your suggestions will be posted tommorow.

Thanks for your reply,

Regards,

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

The only reason for the Q201 is to turn +3.3S on and off, Check Q200 If it has 3.4 volts on its source and 3.4 volts on its drain then maybe they don't require +3.3S to be controlled
Does it look like it was removed?

The GATE and SOURCE of Q200 has 3.3 volts but not the drain, before the new transistor mpsa92 was placed in place of Q201.

There is 3.34v at the base of Q201, when the power switch is pressed and this voltage remains for 5 to 7 seconds then drops to zero.

Will check today, if 3.3v is switched from emitter to collector of Q201.

let me know, if this is has become confusing, may be summary would be of help.

Regards,
Hemant.

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

Hi R_J,

Some observations made today,

Voltage at the gate was held at 3.3v all the time so i re-soldered all the pins of Q200 and now its is giving me 0v all the time, which is as per the schematic.

Now back i am getting the three relay click one after another with some time lags.

The display remains off. All the relays were confirmed to be working by touching them.

If initially, RY100 is at AC_BL then now with the second relay click, it should give me AC_BH, hopefully i will get it ( i will confirm this )

Both STK Pins 123&8 still are floating.

Regards,

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

Check for missing +3.3dsp likely missing Q401, Q403 & Q404

This will be done today.

Thanks for your help,

Hemant.

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

Q401,Q403 &Q404 are present. Shall i go ahead and solder the stks one by one.

Approx 50v plus and minus appear at the big power capacitors.

Or there are other things to be checked before.

Kindly advise.

Regards,

[R_J]

Re: Yamaha RXV 465 no display and power problem

You can solder the ic's back, I would solder all the pins on one first, then test, if it is not shutting down, solder the other ic.
You did not mention if you have the display yet, so check if you have +3.3DSP for the display ic.

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

Hi R_J,

For finding the +3.3DSP : i am not getting 3.3 v at the connector CB20, pin 24 infact it is shorted to DGND. Then tracing back i also found that the drain Q400 is also shorted to DGND ( before tracing, i also found that the Q400 was loosely fixed to the board, so i removed it and resoldered it)

The Q400 was checked outside the ckt and there was no short between source to Drain and Gate to drain.

The gate and source, both are at 3.3 volts in circuit.

I should have not overlooked your suggestion to check for the +3.3DSP before, my BAD.

i will be tracing the short to ground problem but do you have any suggesstion to look for the comman area, where this can happen most probably.

NOTE : The STKs are still floating.

Regards,

[R_J]

Re: Yamaha RXV 465 no display and power problem

If you unplug CB20 where is the short? on the digital board or on the operation board? If its on the operation board (page 115) it could be ic402, or one of the caps like C4012, C4016, C4017
If it's on the digital board it will be harder to track down.

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

if i remove the connector from CB20 the short is still there, so it is on the digital board.
i was suspecting R479 but is it ok and now out of the ckt.

now C470 is the suspect.

Before pulling C470 out is will first arrange the smds.

I will update this thread.

Thanks for your help, R_J.

Regards,

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

C470 also shows short, in fact few el caps too show short and at the last almost all the smd capacitors back side of DTS ic are short.

So now this is becoming difficult to track down.
The digital board has been totally removed from the rest of the unit. So, shall i inject external voltage close to 3 v to check which ic gets hot.

As this is somewhat extrem, i require your asistance..

Kindly do suggest.

Thanks,

[R_J]

Re: Yamaha RXV 465 no display and power problem

There are a few coils that might be removed to aid in isolating the short, Like L409, L405, L401 etc. If you are going to inject a voltage, I would keep it to a volt or two, and limit the current if possible, even at 1 volt the shorted component should heat up.

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

I am trying to get ways to remove the coils out of the board but as i dont have a smd rework station.

Finding techniques to achieve the same.

Will keep you updated.

Regards,

[R_J]

Re: Yamaha RXV 465 no display and power problem

I did'nt know they were smd, what about applying a small voltage, were you able to find any over heating parts?

[hemant_2222]

Re: Yamaha RXV 465 no display and power problem

Hey R_J,

i haven't tried injecting the voltage yet, as it could create further problems, because i dont have any PS that can give me small fixed current. I have a homemade LM317 supply but not sure of its ampere rating.

I agree with your isolation technique methode to locate the fault but then trying to arrange the rework station.

I will update you, in between, is there any alternative to such soldering.

I have seen halogen lamps used to remove smd components but not sure of its heat quantum.

Regards,

[R_J]

Re: Yamaha RXV 465 no display and power problem

The line is 3.3 volts, you can use a 1.5 volt aa or aaa battery, Just connect it for a second or two and check the suspected parts. DON'T leave it connected.

[manfriend]

Re: Yamaha RXV 465 no display and power problem

I'm also working on a Yamaha receiver but it's a RX-V479. I need a relay for it. A TV-8. Service manual sayeth replace with a DG5D1-O(M)-II. I cannot find one of these to save my life. Best I could do was find a place that was out of stock but might ship August 3rd. Is there anything I can use to replace this? It's a TV-8, 5V DC, 5V coil, 8A 250V AC, 8A 30V DC. See image for details. I appreciate any help!