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I Have a yamaha RXV-671, with the issue PS PRT 135:H, what

Customer Question
does that mean? JA: How long...
i Have a yamaha RXV-671, with the issue PS PRT 135:H, what does that mean?
JA: How long has this been going on?
Customer: mhhm well this issue has come up after I replaced one of the channels on the amp
JA: What's the exact make and model of your television? And how long has this been happening with the channels?
Customer: its an AV Receiver: Yamaha RXV-671, and about two days.
JA: What troubleshooting have you tried?
Customer: Do you know what the error PS PRT 135:H means?
JA: The electronics expert can solve this for you. Anything else you want him to know before I connect you two?
Customer: no thats it thanks
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Technician about your situation and then connect you two.
Submitted: 1 year ago.Category: Consumer Electronics
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Answered in 17 minutes by:
7/6/2016
Electronics Technician: Louie, Technician replied 1 year ago
Louie
Louie, Technician
Category: Consumer Electronics
Satisfied Customers: 12,810
Experience: 25+ yrs. experience in the field and 5+ yrs. online, down to component level.
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Hi and welcome to JustAnswer,

Thank you for the question and your patience. Should you still need assistance for information purposes only...

Initially, is the message "...PS PRT 135:H..." immediately displayed on plugging back in ? ...or after attempting to power on? ....or only after running Self-Diagnostic Function?

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Customer reply replied 1 year ago
when i run self-diagnostic function
Customer reply replied 1 year ago
what exactly does the H at the end indicate?
Electronics Technician: Louie, Technician replied 1 year ago

I understand; PS PRT = power supply protection; a power supply issue likely on the 5V line.

H = logic / voltage is high.

Possibly a 5V regulator that has failed.

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Customer reply replied 1 year ago
I measured around 5.07V at the output of the power supply board
Electronics Technician: Louie, Technician replied 1 year ago

Sorry, but which power supply board was checked please?

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Customer reply replied 1 year ago
Video 2 Board
Electronics Technician: Louie, Technician replied 1 year ago

I understand and this would be the standby power supply circuit.

Please note that this 5.5V is present even if the Yamaha is just plugged (but not turned on) hence the standby +5V.

Since the suspect +5V line is detected when running the diagnostics (not just plugged in), then it would be any of the other +5V supply fed from the main transformer.

Do you have access to the schematics?

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Customer reply replied 1 year ago
I do
Electronics Technician: Louie, Technician replied 1 year ago

Please see p. 142 grid L7 IC334, a +5V regulator.

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Customer reply replied 1 year ago
ok I found it
Electronics Technician: Louie, Technician replied 1 year ago

A potential suspect.

Since would be checking, it would be to your advantage to likewise check for the presence & consistency of its mate, the -5V.

...and another +5 after IC333.

As well as resistor R330.

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Customer reply replied 1 year ago
Ok now the only way to check these things is if it's powered up correct? But in order to access this board, the HDMI board has to be removed. IF the HDMI is removed, then I can't power it on ?
Electronics Technician: Louie, Technician replied 1 year ago

Technically correct; a case of the chicken and the egg.

A moment please, composing a workaround.

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Customer reply replied 1 year ago
Also there is no R330 Resistor
Electronics Technician: Louie, Technician replied 1 year ago

Sorry, that should be R3304.

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Electronics Technician: Louie, Technician replied 1 year ago

A workaround / bench test would need a small 1Ampere 6-0-6 transformer to feed AC-5/E/AC-5 pins of the connector. This is to simulate the supply from the main transformer.

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Customer reply replied 1 year ago
mmh I don't have a transformer on hand.
Electronics Technician: Louie, Technician replied 1 year ago

Unfortunately, no other easy bench test method except to use a substitute transformer.

Incidentally, there is another +5V after IC457 on p. 136 and some other +5Vs

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Customer reply replied 1 year ago
I can't really test this, until I get a small transformer?
Customer reply replied 1 year ago
Ok so How many Volts transformer do I nee?
Electronics Technician: Louie, Technician replied 1 year ago

6-0-6; i.e. 6VAC center tap

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Electronics Technician: Louie, Technician replied 1 year ago

It would also help to get some alligator clips with wires similar to the products shown HERE.

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Customer reply replied 1 year ago
ok so if i need to get a centre transformer because I need an earth connection as well ? http://www.jaycar.com.au/6-15v-30va-2a-multi-tapped-transformer/p/MM2004 Would this work?
Electronics Technician: Louie, Technician replied 1 year ago

Please consider HERE also from Jaycar but higher current 1Ampere not just 150mA.

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Customer reply replied 1 year ago
would 150mA work thouhg?
Customer reply replied 1 year ago
http://www.jaycar.com.au/12-6v-ct-7va-500ma-centre-tapped-type-2853-transformer/p/MM2013, so this is acceptable it's 500mA max?
Electronics Technician: Louie, Technician replied 1 year ago

Yes should work though the voltage may dip a bit.

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Customer reply replied 1 year ago
where do i connect this transformer to test IC457?
Electronics Technician: Louie, Technician replied 1 year ago

IC457 would need a 12V supply. Aside from the above transformer, an 1N4001 diode would also be needed. Use the 6-6 of the transformer to get 12V + the diode and the result would be 12VDC fed to the IN and COM of IC457.

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Customer reply replied 1 year ago
Ah fe, will a half wave rectifier do the trick, as the ripple will be pretty high ?
Electronics Technician: Louie, Technician replied 1 year ago

Agree but since we're just after the output voltage, should do the job for test purposes.

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Customer reply replied 1 year ago
Ok well apart from those, what else should I check?
Electronics Technician: Louie, Technician replied 1 year ago

There are other voltages derived from these +5V (such as the 3.3, 1.8, 1.3) but for the moment, checking these 5V would do.

Of course, please note that a short at the output of a regulator would also cause the 5V to go down or the output to short to the input.

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Customer reply replied 1 year ago
Ok I shall get the transformer and let you know. What would be the minimum acceptable value for these regulators ?
Electronics Technician: Louie, Technician replied 1 year ago

The regulator as its name/description implies would always be the same +5V output irregardless of the input voltage (as long as more than 5V) and/or the current drawn from it.

Simply, it should output 5V always (or thereabouts); no minimum/no maximum.

I have to add that it would be to your advantage likewise to re-do the solder in case of a cold solder on the pins of the regulator as well as the other components around it.

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Customer reply replied 1 year ago
Ok so just to re-iterate, check IC334, IC333 and IC457 as well as R3304?
Electronics Technician: Louie, Technician replied 1 year ago

Yes; ...R3304 of course can be checked with just the Ω function of the multi-meter.

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Customer reply replied 1 year ago
which pins should I measure between for IC334?
Electronics Technician: Louie, Technician replied 1 year ago

This is tricky; measure 12V supply between pin 1 and 3. Measure the output between pins 2 & 3. Expected is +5V but only if pin 4 is triggered with a separate +5V.

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Customer reply replied 1 year ago
Hi Louie,
For measuring IC334, should the triggered +5V be a DC value, correct?
Electronics Technician: Louie, Technician replied 1 year ago

Yes; a + or a - sign before the voltage value would denote that it is a DC voltage.

Ideally, an external +5V source but if IC333 checks good first, its +5T output would also serve the purpose of triggering pin 4 of IC334.

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Customer reply replied 1 year ago
ok well i check R3304, and it's reading a deat short.
Electronics Technician: Louie, Technician replied 1 year ago

To be expected or nearly so; it is 0.22Ω

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Customer reply replied 1 year ago
well does that mean it's the problem?
Electronics Technician: Louie, Technician replied 1 year ago

No; it's good.

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Customer reply replied 1 year ago
really because it's not reading anywhere near it's value?
Electronics Technician: Louie, Technician replied 1 year ago

It would really depend on the sensitivity of the meter; but 0.22Ω is nearly a short.

Incidentally, resistance values are preferably measured out-of-circuit.

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Customer reply replied 1 year ago
IC333 had an input of 3.89V and an output of 3.64V
Electronics Technician: Louie, Technician replied 1 year ago

What is the input AC Voltage of the bridge diode D3304 please? ...and what is its output DC Voltage?

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Customer reply replied 1 year ago
On which board?
Electronics Technician: Louie, Technician replied 1 year ago

Please see p.145 grid I8 VIDEO (1) board.

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Customer reply replied 1 year ago
ok should I test it , with the 6VAC transformer?
Electronics Technician: Louie, Technician replied 1 year ago

Yes please; connect the transformer. The 6-0-6 transformer would power IC333 and IC334 through bridge diode D3304. 6-0-6 to be connected to AC-5/E/AC-5 pins.

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Customer reply replied 1 year ago
ok so on the input the cetnre two pins 0.650V AC and ouput 4.18V DC
Electronics Technician: Louie, Technician replied 1 year ago

Sorry, confused.

What is the ACV from first yellow wire to the white wire? ...second yellow wire to the white wire? ...first yellow wire to the the second yellow wire?

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Customer reply replied 1 year ago
ok between the first Yellow and White = 4.64V AC and between the second Yellow and White =4.61V, on the AC side of the rectifier = 6.67V AC and the output DC side = 9.23V DC
Electronics Technician: Louie, Technician replied 1 year ago

A bit low but should still work. Then the inputs of IC333 and IC334 should both be this 9.23V DC.

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Customer reply replied 1 year ago
What else could be wrong?
Electronics Technician: Louie, Technician replied 1 year ago

Witn an input of 9.23V DC, the output of both ICs should be 5VDC subject to the description above.

What are the readings please?

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Customer reply replied 1 year ago
ok on the output of IC333 i'm getting 3.36V and on the input of the regulator 4.63V
Electronics Technician: Louie, Technician replied 1 year ago

What is the DC Voltage across C3309 ? ...how about across C3310?

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Customer reply replied 1 year ago
Can I measure at J4142 with refrence to earth? Or do I have to measure at the capacitors themselves?
Customer reply replied 1 year ago
Also is there a way to disconnect connector CB02 from operation(2) board?Thanks
Electronics Technician: Louie, Technician replied 1 year ago

Yes, J4142 and J4141 links the + of bridge diode D3304 to the + of capacitor C3309 and eventually to IN pin of CIC333.

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Customer reply replied 1 year ago
Hi louie,
When i power the device now, i get the error. ps prt 61L
Electronics Technician: Louie, Technician replied 1 year ago

Voltage is low (or missing) on PS1. See p.61

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Customer reply replied 1 year ago
Ok so how do i go about it testing?
Electronics Technician: Louie, Technician replied 1 year ago

The same way the +5 were checked but this time, test for -5 and the other voltages as listed right of PS1. See p. 139

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Customer reply replied 1 year ago
Sorry what chips are those again?
Electronics Technician: Louie, Technician replied 1 year ago

Is everything connected / assembled back?

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Customer reply replied 1 year ago
Yess
Electronics Technician: Louie, Technician replied 1 year ago

I understand.

As posted above, for starters see p. 139 grid location G8, regulators IC101 and IC102.

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Customer reply replied 1 year ago
IC101 and IC102 are on the main board? So how do I power up that board?
Electronics Technician: Louie, Technician replied 1 year ago

Hi again and appreciate your kind understanding; mobile with sluggish Internet.

Use the above proposed alligator clips with wires to connect D1041 to the main transformer.

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Customer reply replied 1 year ago
Wait so power it up with the main transformer?
Customer reply replied 1 year ago
Also C3309 and C3310 had voltages of 5.27V and 5.23V respectively.
Customer reply replied 1 year ago
Ok so before this error came, we replaced one of the channels, however initially the insulator wasn't put correct and it was shorting out causing that transistor to smoke a few times. We fixed that problem and it's no longer shorting. With a quick multi metre test that transitor seems to still read, however it still has burnt marks on it. Not sure if that's the problem. Also if we just snip the leads of that, will it still work? It's the C4458 transistor on SBR channel.
Customer reply replied 1 year ago
OK plugged it back in again. PS2 PRT : 61L error still.
Electronics Technician: Louie, Technician replied 1 year ago

Appreciate the background information on the previous work done.

Still, what is more significant is the error code pinpointed that it is a power supply issue.

Interestingly, that the power supply circuit has initially a fault of PS PRT 135:H and then changed to PS PRT 61:L makes me suspect more of a loose wiring/connector or even a cold solder and no real component has failed.

As posted above; "...Voltage is low (or missing) on PS1...." -> ACBL, AC12, AC5, ±7, +3.3, -5VA.

Re-check connections to the board from the transformer and the solder points of the MAIN board p. 139 and VIDEO board p.142

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Customer reply replied 1 year ago
Hi Louie,There are no cold solder joints oh no lose connections either. I have no idea what to do.
Electronics Technician: Louie, Technician replied 1 year ago

Consider a careful bench test for the different voltages cautiously using the alligator clips with wires to connect the main transformer to all the connectors of the MAIN and VIDEO boards.

A friendly reminder: voltage measurements by its very nature requires that the main transformer is powered up and therefore the circuit is LIVE! Please exercise due care and caution.

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Customer reply replied 1 year ago
Hi Louie,So the error PS PRT 135H is still present. However when I went to check the 12V rail at connector CB456 (operation 2 board p.g. 104), I measured the values -11.07V and +12.89V for the -12V and +12V rail. So clearly this isn't correct. So do you have any suggestions of how to proceed ?
Electronics Technician: Louie, Technician replied 1 year ago

These -12V and +12V are also produced by IC102 and IC101 (p.139). Measure the voltages at the output pins of these regulator. If the same then, there would be no issue.

On the other hand, if the voltage at the output pins of these regulators are different than "...-11.07V and +12.89V...", then there is an issue along the wires/connections from these 2 regulator to the Operation (2) board.

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Customer reply replied 1 year ago
ok, so how would I power up this board? As IC101 and IC102 are on the main board
Electronics Technician: Louie, Technician replied 1 year ago

Sorry, which "...power up this board..."; Operations (2) or Main (1)?

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Customer reply replied 1 year ago
How can I test IC101 N IC102?
Electronics Technician: Louie, Technician replied 1 year ago

I understand and as posted before; "...Use the above proposed alligator clips with wires to connect D1041 to the main transformer..."

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Customer reply replied 1 year ago
D1041 is already connected to the mains transformer, through CB102?
Electronics Technician: Louie, Technician replied 1 year ago

Yes; I was under the impression that the boards were disconnected.

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Customer reply replied 1 year ago
Ok, because in order to access D1041 I need to remove the HDMI board and without the HDMI board the unit wont power on. So i'm not quite sure what you mean ?
Electronics Technician: Louie, Technician replied 1 year ago

Oh....cautiously jumper the switching contacts of relay RY371 (p.143 / grid C7) . Doing so would force the main transformer to turn on hence all the secondary of the main transformer would have power including "...D104...through CB102..."

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Customer reply replied 1 year ago
Ok so if i jumper those pins together, as soon as I plug the amplifier into the wall, the system should turn on ?
Electronics Technician: Louie, Technician replied 1 year ago

Not necessarily fully turn on; BUT, there would be power to those connected thus "... test IC101 N IC102..." can be performed.

Please ensure no loose wire or any that may cause a short.

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Customer reply replied 1 year ago
ok i tried using a resistor across the switching contacts but it just smokes every time i turn on. What do u think i should use to jumper those relay switch contacts?
Electronics Technician: Louie, Technician replied 1 year ago

The resistor would expectedly burn as it is unable to carry the onrush of current drawn by the transaformer.

Jumper with short lengths of electrical wire and a 2.0 A fuse

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Customer reply replied 1 year ago
Ok IC101 is reading +12.3V and IC102 is reading 8.74V. However if I measure IC102 with respect to IC101's COM point im measuring -11.5V. But then if i measure IC102 with respect to it's own COM point im measuring -8.74V.
Electronics Technician: Louie, Technician replied 1 year ago

The pinout of IC101 is different with IC102. Please click HERE and HERE.

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Customer reply replied 1 year ago
Ok IC101 is +12.03V and IC102 is -11.95V . Now if I measure CB456 (operation 2 board) I get +12.14 and -11.84V
Customer reply replied 1 year ago
But before when i measured at CB456 with everything plugged in I got -11.07V and +12.89V respectively.
Electronics Technician: Louie, Technician replied 1 year ago

It is surprising that the regulator outputs +12.03V but CB456 reads +12.89. The voltage would have to come from somewhere

or

there is a ground issue between the boards.

It is expected that voltage can go down from -11.95V to -11.84V but not -11.07V . It is either the regulator is not performing well

or

there is a load/part attached to the - supply line that is drawing too high a current thus forcing the voltage to dip.

Does the IC102 heats up faster/hotter than IC101?

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Customer reply replied 1 year ago
Ok so I bought the whole amp back together and measure the voltage at CB456 (operation 2 board) and got -11.6 and +12.3V respectively. However now I'm getting PS2 PRT : 66L. So something is going wrong here.
Electronics Technician: Louie, Technician replied 1 year ago

Based on "...has initially a fault of PS PRT 135:H and then changed to PS PRT 61:L..." and then "...PS PRT 135H is still present..." back to "...PS2 PRT : 66L...", then yes; something is wrong and as posted before, it would appear likely to be a connection, wiring or even a solder issue but definitely intermittent.

Bear with me as the only approach would be to review the wiring, connections and solder points particular of the power parts; i.e. those that carry the power/voltages (not the signal parts).

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Customer reply replied 1 year ago
Ok well If i disconnect the big grey connector (R189 from the HDMI board which connects to the Main Board), the error goes from H to L. I'm also given to understand that connector carries the signal for PS2 PRT
Electronics Technician: Louie, Technician replied 1 year ago

Let's look at the HDMI board.

Please see p. 91. These are the different regulators that would warrant checks.

Likewise of interest then would be the capacitors coupled to their outputs.

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Customer reply replied 1 year ago
Ok which ones should I check ?
Electronics Technician: Louie, Technician replied 1 year ago

All since all have their inputs from the same source.

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Customer reply replied 1 year ago
Sorry I can't find the schematic. Can u give me the name of one of the IC's?
Electronics Technician: Louie, Technician replied 1 year ago

IC65, IC6, RP130Q501D, R1172H501D, IC945, IC946, IC26 and IC930

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Customer reply replied 1 year ago
IC930 has +4.52 on the output and +5.5V on the input. Should this output not be +3.3V?
Electronics Technician: Louie, Technician replied 1 year ago

Yes, the +5.5V input would be the same to all others.

And likewise yes on the +3.3 expected output.

The +4.52 is an over-voltage hence would cause fault in the circuit that it feeds.

Strongly consider a replacement.

And further bear with me as I would be mobile again shortly; 500+KM trip.

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Customer reply replied 1 year ago
Hi Louie,
Before i purchase that IC are there anymore that i should check on that board?
Also RP130Q501D, R1172H501D are not specific ICs but simply part numbers of the already mentioned Ics correct?
Electronics Technician: Louie, Technician replied 1 year ago

Yes on RP130Q501D and R1172H501D as the Part Numbers on some of the regulators. There are others such as IC65 / NJM2888 for +5HT1

Please review pp. 127-134 of the Service Manual for the actual Part Numbers of the other regulators.

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Customer reply replied 1 year ago
Hi Louie ,I tried to measure the voltage +5A which is at connector CB944. When I measured it with respect to the case ground i got a few mV. Then I tried to measure it with respect to DGND and I still got a few mV. This value needs to be +5V correct? Also the +5A pin is the 4th pin from the right correct?
Customer reply replied 1 year ago
Also where can I measure -VP ?
Electronics Technician: Louie, Technician replied 1 year ago

+5A is produced by IC457. Please see p. 138 grid J5

-VP is produced by Q4085. See p.137 grid G6

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Customer reply replied 1 year ago
ok so IC457 is reading 0.641V. Does this mean it needs to be replaced? Also does this account for IC930 having an output voltage of +4.52 ?Thanks
Customer reply replied 1 year ago
Also note that the input V to IC457 is around 3.34V
Electronics Technician: Louie, Technician replied 1 year ago

The input of IC457 should be +12V and is fed from from the output of IC101 through resistor R4293.

No, the input of IC930 is a different +5V source. If present, then its output should be +3.3V

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Customer reply replied 1 year ago
I've measured IC101 before and gave me a voltage of +12.03V
Electronics Technician: Louie, Technician replied 1 year ago

If "... IC101...+12.03V...", then "...input V to IC457..." should be +12.03V also.

If not and as measured 3.34V, then a connection issue or resistor R4293 as posted above may have failed or went high value.

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Customer reply replied 1 year ago
I just measured R4293 and it was 21.5 ohms. So that's good as well.
Customer reply replied 1 year ago
the voltage across that resistor is 3.34V.
Electronics Technician: Louie, Technician replied 1 year ago

I understand;...then likely a connection issue.

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Customer reply replied 1 year ago
How do you suggest I verify this?
Electronics Technician: Louie, Technician replied 1 year ago

What is the voltage before and after the resistor please?

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Customer reply replied 1 year ago
Ok so before meaning, I measure it at IC101 ? And after I measure across the input of IC457 ?
Electronics Technician: Louie, Technician replied 1 year ago

The easiest would be to measure the voltages at the 2 ends of the resistor itself.

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Customer reply replied 1 year ago
Ah so you mean measure across it ?
Electronics Technician: Louie, Technician replied 1 year ago

Sorry but no; that was done already "...voltage across that resistor is 3.34V...".

Black probe to common ground, red prove to 1 end of the resistor __V?

Black probe still to common ground, red prove to the other end of the resistor __V?

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Customer reply replied 1 year ago
12.17V at one end and 3.34V at the other end
Electronics Technician: Louie, Technician replied 1 year ago

Is the resistor hot?

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Customer reply replied 1 year ago
I can't tell as I'm only measuring behind it.
Customer reply replied 1 year ago
Tomorrow I'll take the HDMI board and force power it on, and confirm if its getting hot. From what we measured it sounds like that resistor has gone.
Electronics Technician: Louie, Technician replied 1 year ago

I would beg to differ based on "... R4293 and it was 21.5 ohms..."

I am more inclined to suspect IC457 (most likely) and/or +12A is loading the resistor/+12V line (least likely) or C4288 (just a possibility).

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Customer reply replied 1 year ago
OK. How would you suggest I proceed, to get a definite cause for this issue ?Thanks
Electronics Technician: Louie, Technician replied 1 year ago

Disconnect jumper J4186 or de-solder / remove IC457. Then re-test the voltages of the resistor. If the 3.34V shoots up to 12, then IC457 is faulty.

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Customer reply replied 1 year ago
Ok thanks. I shall try this tomorrow. Also since the +5A voltage is monitored by PS2 PRT. Should this solve the problem of PS2 PS PRT 61L ?Thanks
Electronics Technician: Louie, Technician replied 1 year ago

Likely yes as 61L is indicative of a low or missing +5V

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Customer reply replied 1 year ago
ok . Hopefully this solves the problem.Thanks
Electronics Technician: Louie, Technician replied 1 year ago

Cheers.

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Customer reply replied 1 year ago
Now, when I remove IC457 and measure the voltage across the resistor. Should I plug the HDMI board back in ?
Electronics Technician: Louie, Technician replied 1 year ago

I was under the impression that the voltage measurements done on IC457 and resistor R4293 were without the HDMI board installed/connected.

Is this not so?

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Customer reply replied 1 year ago
No. I made this measurements with everything connected and the unit powered on. (Well i had to remove the protection to do so). Should I remove the HDMI board and repeat these measurements ?
Electronics Technician: Louie, Technician replied 1 year ago

Repeat please. The same as how it was done now; with everything connected except the regulator or jumper.

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Customer reply replied 1 year ago
ok. I shall remove the HDMI board and force the relay on, then repeat the measurements.
Electronics Technician: Louie, Technician replied 1 year ago

...and would look forward to an update when able.

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Customer reply replied 1 year ago
Ok so across each end of the resistor and GND we're getting 12.31V at both ends. But measuring across the resistor we get nothing. So i assume IC457 needs to be replaced ?
Customer reply replied 1 year ago
Ok I tested IC457 with a computer power supply, and I'm getting 5.13V at the output. So thats working.
Electronics Technician: Louie, Technician replied 1 year ago

Interesting....let's recap:

  • with IC457 still soldered in, resistor R4293 shows 12.17V at one end and 3.34V on the other end;
  • input V to IC457 is around 3.34V;
  • with IC457 removed, resistor R4293 shows 12.31V at both ends;
  • tested IC457...5.13V at the output.

With the unit unplugged, test the resistance to ground of J4178 (p. 96 grid G4)

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Customer reply replied 1 year ago
ALSO that capacitor is good. And yes that's all correct. However the voltage across the resistor Is almost 0, with ic457 removed.
Electronics Technician: Louie, Technician replied 1 year ago

voltage across the resistor Is almost 0, with ic457 removed - is to be expected hence good.

J4178's resistance to common ground please?

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Customer reply replied 1 year ago
As a result the resistance bwtween the output and common terminals of IC457 is almost zero (short).
Electronics Technician: Louie, Technician replied 1 year ago

Agree a short at he load hence the input voltage is brought down;....should not be.

Please repeat/confirm resistance with jumper J4173.

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Customer reply replied 1 year ago
Should I measure it at the point indicated in the picture I sent?
Customer reply replied 1 year ago
If so the resistance is 2.8 ohms
Electronics Technician: Louie, Technician replied 1 year ago

"...the resistance is 2.8 ohms..." which please J4173?

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Customer reply replied 1 year ago
J4173. Also the resistance across C4278 is almost zero (short). Hence shorting the output to GND. Is there a replacement for that part , as its very small.
Electronics Technician: Louie, Technician replied 1 year ago

Surprising that C4278 is shorted. Was this resistance check done with C4278 out-of-circuit / de-soldered ?

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Customer reply replied 1 year ago
in circuit.
Electronics Technician: Louie, Technician replied 1 year ago

Doubtful then; still, please consider repeating the test on C4278 out-of-circuit.

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Customer reply replied 1 year ago
well if c428 isnt the problem, what else should I test?
Customer reply replied 1 year ago
Ok C428 isn't a short. But the tracks on either side of the capacitor is shorted together, for some reason.
Electronics Technician: Louie, Technician replied 1 year ago

Test / follow J4178, J4176, J4173 then to where CB460 is connected to...

...and it will lead us back to CB944 where you found out first the missing +5A. This test point if checked with resistance would most likely show very very low Ω.

Then locate and carefully de-solder / remove L9401. Test again for short where the +5A was originally found low/missing. Then test resistance of pin 11 of IC941.

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Customer reply replied 1 year ago
Ok sorry. So do I test the resistance of those links to ground ? Then I test the resistance of +5A to ground?
Electronics Technician: Louie, Technician replied 1 year ago

Yes please; always with respect to the common ground.

The fault is too low resistance or even a short of the +5A to ground and we have to find out which component causes this low Ω reading.

It is rightful to suspect the capacitors as well but must be tested always out of circuit.

Personally, I use tweezers when handling SMDs.

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Customer reply replied 1 year ago
Hi Louie,I can't seem to find the inductor L9401?
Electronics Technician: Louie, Technician replied 1 year ago

Please see p. 92 grid B3

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Customer reply replied 1 year ago
Well see there's a short between the point 5A and GND without the HDMI board even connected.
Electronics Technician: Louie, Technician replied 1 year ago

Tested on CB460?

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Electronics Technician: Louie, Technician replied 1 year ago

De-solder / remove all the jumpers; J4178, J4176, J4173 and test resistance to ground of all the now empty solder holes.

Can you also please re-check the empty solder points of the removed IC457.

Might as well check D4203.

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Customer reply replied 1 year ago
Hi Louie,Do i take of each of the links one by one and check there resistance, or do I remove all of them at once then check there resistance at each hole ?
Electronics Technician: Louie, Technician replied 1 year ago

Appreciate the image.

With J4176 & J4178 removed, then please check or even temporarily remove (also) C4252 and then J4177. After each removal, determine if the "...points...have a low resistance (short)..." would still persist.

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