model AV-27WF35R
chassis A134 ,
the set is dead, there is power to the stand by , and i do have my 5 volts
stand by... when pressing the power button, i can see the signal go in the micon IC201 , but nothing comes out , i have no schematic, but i do not see nothing come out of any other pins of this ic. that should turn on the power relay. is there any other stand by voltage that i am missing ?
there is power to the relay, but the micon is not grounding it to make it turn on.
if i short the relays power ,,i hear the power supply tweak on , and the yolk having a low frequency sound.
the H.O.T. is ok, and the switch mode supply is working.. i get my 135 volts.. if i disconect the base of the H.O.T.then the yolk stops sounding.
but from all that i can detect, the micon is bad,,
but then i might be wrong, since i do not have a schematic of the micon or the set.
nothing seems to be loading down the power supply either..
anyone able to help me out any, with some more ideas or a schematic?
i have had no luck with a web search.
the ic in question is made by TOSHIBA it is a 8812CSDNG5D89
IC201
JVC dead set
.
Well hellooo there monsewer.......and that's heavy on the sewer...didn't notice this post 'til just today.....it must have drifted down towards the bottom in a hurry.
You happen to be in luck, as my secretary's mother had moved up here after Katrina, and her same set was damaged. Nonetheless, I was able to repair it, it was using your same chassis, but only feeding a 20' inch kine.
I will initially extract a thumbnail of your u/p circuitry and post it here, and it will not even requre macrovision to view it !
Now I will walk through the circuit path and then you can come back if you need further info over in the SMPS or deflection circuitry.
RY951 is your power switcing relay ( has a D945 clamping zener shunted across its coil ) and is fed from 10VDC from a conventional 60~ mini line transformer...T951..that also takes that same initial 10 VDC and feeds to IC704 (3 term reg) that then regulates down to your 5V standby power supply for u/p and remote receiver..The power relay is driven by NPN Q951 which gets its base drive from Q701 ...a PNP..which requires 5VDC power on its emitter. Q701 is getting its base turn on drive from your mentioned U201's pin # 47.
On the topic of that u/p, be sure that it is getting its +5VDC analog and digital power supply sourced to its pins #46 and #9.
Consulting this J-peg'd thumbnail:
...(made up for you.... or / as well as any interested popcorn munchers up in the peanut gallery)
Check for the 5 Vdc as mentioned, scope check for remote activity at input pin # 55 on transmission of a signal from its xmitter.
You have pin #47 that will be keyed up to a high logic level on turn on, either done by front panel tact switch or your remote hand unit. Consulting the schema , you can then see that there is further circuitry tie in by the two transistor path between that point and the sole transistor shown at the very bottom of the page ...on through to the Pwr relay.
There is also a like feed off from pin # 54 to a front panel Red LED Pwr On indicator through its driver xstr.
Also, red circle referenced, are scope test points for observation of bit stream handshaking info from the Clock and Data lines on pin # 's 49, 50 as well as the initialization info' twixt the eeprom IC 702 on its u/p interconnect lines at # 51 and 53.
The green circled ref points are associated with power on functoning circuitry.
73's de Edd
[email protected] ..........(Interstellar ~~~~Warp~~~Speed)
[email protected]........(Firewalled*Spam*Cookies*Crumbs)
I'm not as dumb as you look.
.
Well hellooo there monsewer.......and that's heavy on the sewer...didn't notice this post 'til just today.....it must have drifted down towards the bottom in a hurry.
You happen to be in luck, as my secretary's mother had moved up here after Katrina, and her same set was damaged. Nonetheless, I was able to repair it, it was using your same chassis, but only feeding a 20' inch kine.
I will initially extract a thumbnail of your u/p circuitry and post it here, and it will not even requre macrovision to view it !
Now I will walk through the circuit path and then you can come back if you need further info over in the SMPS or deflection circuitry.
RY951 is your power switcing relay ( has a D945 clamping zener shunted across its coil ) and is fed from 10VDC from a conventional 60~ mini line transformer...T951..that also takes that same initial 10 VDC and feeds to IC704 (3 term reg) that then regulates down to your 5V standby power supply for u/p and remote receiver..The power relay is driven by NPN Q951 which gets its base drive from Q701 ...a PNP..which requires 5VDC power on its emitter. Q701 is getting its base turn on drive from your mentioned U201's pin # 47.
On the topic of that u/p, be sure that it is getting its +5VDC analog and digital power supply sourced to its pins #46 and #9.
Consulting this J-peg'd thumbnail:
...(made up for you.... or / as well as any interested popcorn munchers up in the peanut gallery)
Check for the 5 Vdc as mentioned, scope check for remote activity at input pin # 55 on transmission of a signal from its xmitter.
You have pin #47 that will be keyed up to a high logic level on turn on, either done by front panel tact switch or your remote hand unit. Consulting the schema , you can then see that there is further circuitry tie in by the two transistor path between that point and the sole transistor shown at the very bottom of the page ...on through to the Pwr relay.
There is also a like feed off from pin # 54 to a front panel Red LED Pwr On indicator through its driver xstr.
Also, red circle referenced, are scope test points for observation of bit stream handshaking info from the Clock and Data lines on pin # 's 49, 50 as well as the initialization info' twixt the eeprom IC 702 on its u/p interconnect lines at # 51 and 53.
The green circled ref points are associated with power on functoning circuitry.
73's de Edd
[email protected] ..........(Interstellar ~~~~Warp~~~Speed)
[email protected]........(Firewalled*Spam*Cookies*Crumbs)
I'm not as dumb as you look.
.
-
dacflyer
- Posts: 4748
- Joined: Fri Feb 08, 2002 1:01 am
- Location: USA / North Carolina / Fayetteville
- Contact:
thanks Edd.
i do not know what i'd do with out you...
i'll e-mail you with my results. but so far now there is no communication from the eprom pins 5-6 to the micon..there is voltage but thats it.
i guess if theres no data , then that will not allow micon to turn on the set??
so now i must determin if ic201 is bad or the eprom ..
i do not know what i'd do with out you...
i'll e-mail you with my results. but so far now there is no communication from the eprom pins 5-6 to the micon..there is voltage but thats it.
i guess if theres no data , then that will not allow micon to turn on the set??
so now i must determin if ic201 is bad or the eprom ..
-
Timothy Rasch
- Posts: 142
- Joined: Mon Mar 04, 2002 1:01 am
- Location: Green Bay ,Wisconsin
- Contact:
Jvc turn on problem
Hi ,I am a service technician for >30 years and most of the time the 8 pin eeprom fails which is a cheep part [about $8] but get it only from JVC only because a blank one will play dead too. A lot of RCA's have this problem with their 8 pin eeprom. You did the right thing measuring the voltages for standby,Up,eeprom,relay. On the eeprom it should have 5v and not too much higher. A little lower than 5v is better for this eeprom.
PS: when you get the new eeprom and install it you may have to "fine tune" program it with your remote keyboard using JVC setup code to get into the service mode And then You have to be very carefull not to change the critical settings .I recomend after the tv is working [at least it turns on]to take it to a JVC service shop to have them program it for you . Sure it will cost some money but You will be happy again instead of having that funny feeling that You get when you have changed the tv to something worse.
Hope this solves your problem. Tim Rasch [email protected]
PS: when you get the new eeprom and install it you may have to "fine tune" program it with your remote keyboard using JVC setup code to get into the service mode And then You have to be very carefull not to change the critical settings .I recomend after the tv is working [at least it turns on]to take it to a JVC service shop to have them program it for you . Sure it will cost some money but You will be happy again instead of having that funny feeling that You get when you have changed the tv to something worse.
Hope this solves your problem. Tim Rasch [email protected]
-
dacflyer
- Posts: 4748
- Joined: Fri Feb 08, 2002 1:01 am
- Location: USA / North Carolina / Fayetteville
- Contact:
might be a problem, as the customer didn;t bring the remote for this set.
i will call and see if he has the remote..
i did however discover, that the flyback is powering up.when i bypass the relay..but it must be running at a higher than normal freq. either that or not at full power..because i do get HV at the anode.
but theres nothing on screen or filiment.. also noticed that the eprom, pins 5-6, and other spots on the 5v system, that it seems to be a tiny bit of neg voltage pulses. this was when i had the settings on 50mv. , i forget the divisions tho. but the neg dips, were so super slight
i was initially looking for data streams..
JWAX >> thanks , i still do what i can with what i am able too..
thanks to Edd also for sharing his schematics.
i share what i have also if i have any.
i will call and see if he has the remote..
i did however discover, that the flyback is powering up.when i bypass the relay..but it must be running at a higher than normal freq. either that or not at full power..because i do get HV at the anode.
but theres nothing on screen or filiment.. also noticed that the eprom, pins 5-6, and other spots on the 5v system, that it seems to be a tiny bit of neg voltage pulses. this was when i had the settings on 50mv. , i forget the divisions tho. but the neg dips, were so super slight
i was initially looking for data streams..
JWAX >> thanks , i still do what i can with what i am able too..
thanks to Edd also for sharing his schematics.
i share what i have also if i have any.
.
OH...Tay, since you have now found that the u/p is powered up at its digital and analog supply power points, time to move on to other areas for analysis . You did mention that the unit would initially do a short power up with a growling when the set was void of power for a long enough time for all caps to zero out their static charges. When you said that the sets sweep "growled" on for just an instant upon an initial turn on.That would be indicitaive of an initial burst of hoz drive at the u/p's pin 19 hoz drive output. Scope it and see how long it lasts....probably agrees with the power relays on and then off time. I would suspect that the sets shut down sensing circuitry is now being engaged due to an excess current consumption from the 135VDC main sweep supply or else that the voltage might be going higher than that.
Refer now to the supplemal thumbnail schema:
CURRENT SENSING
There is a current sensing series resistor in line with the 135VDC supply as R516...2 ohm resistor and is sampled by a voltage divider resistor pair across it and an accompanying delayed/ lag response provided by C 971/ 100ufd. Their derived voltage reference then is feeding the base of Q971. If current consumption is within tolerance , the base voltage will not rise to the level to turn on the sense transistor, in turn, if the threshold is reached, the transistor will start conduction and will then engage a transistor circuit loop thru another voltage divider bridge on the transistor collector line with an adjunct C972...47ufd providing a delay/lag response upon that junction. As sensed current rises above the design threshold, the voltage at the latter emitter junction will track it accordingly. At the threshold of D972 zener's knee, voltage in excess of ~15 Vdc will be routed towards series isolation/steering diode D973, with an intermediate loading resistor of R 978.The voltage that passes thru D773 will then zip straight for Q531 only encountering another voltage divider bridge / DC interstage coupling media between the two xstrs of a discrete latch. When the base voltage build up is at the threshold of conduction at Q 531, it will then enact conduction and cause its collector voltage to diminish towards the low/sole voltage level of its semi junctions. That action will then affect the connection to D 535.... which in turn is tied into the voltage that is fed into the base circuitry of Q 951 which is the relay driver that initially powered up the set. With all of the base drive of Q 951 now effectively shunted off to ground through the D-535 / Q531 collector-emitter loop, the set then turns its self off. Never to run again until the CURRENT / OVERLOAD condition(s) are corrected...OR....until the sets caps are "drained" down to permit a repeating of the same "cycle".
VOLTAGE SENSING
There is a voltage sensing of the sweep circuitry that is acquired by a sampling of flyback voltage derived from itskine filament winding and is then rectified filterd and fed to a voltage divider bridge of R535 / R 537 which is sampled at their common node by zener D531. In the same manner as mentioned for the zener breakover threshold for the curent sensing functon, this zener will feed over into the same base supply line of Q531, where the same shut down procedure will be triggered, this time, it being a response to overvoltage.
It now seems that you need to go back to the anode side of D973, for the isolation that it provides, and do some DC coupled mode / scope probe monitoring of that node to see if , that upon initial turn on, that 15+ V comes down that line, and on to trip your shut down circuitry. If it wasn't at that point, then you can move on over to the base of Q 531 and expect the voltage to have originated from a threshold flowover of D 531 zener.
That set is probably new enough to not have a wholesale worry of esr'd out caps, unless in critical sweep filtering applications or unless dressed up towards thermal areas, but take note to the referenced circles , as they would speed up sensing trip times and not have a proper circuit response if deficient units were in those points.
If you have isolated it as a shut down problem, it might then be permissible...within centi-milliseconds operation.. to have a scope probe connected to a suspect voltage supply point and be merely using the scope in its vert DC coupled mode...set up wih vert DC level to at least the expected experienced DC level and then watch the DC trace baseline for its attained DC level. In this manner one can power up the set just for an instance and immediately see what voltage is there. Using an analog meter can take just a second to get a reading and .....Lord forbid.....an auto ranging DVM could have a circuit reduced to toast before it even ramps up and displays its reading.
I was thinking of this application in the case of the opening of one lead of the D535 loop to disengage its function for a very SHORT turn on testing burst.
Lastly,on your comment on being able to turn on the set with the switch or the remote, initially. The EEPROM only makes a comparison with the u/p on an initialization...in case you were monitoring the pins 5 and 6 and expecting constant activity. Its in the like order of booting up a 'puter...you don't have to do it every time. The program is on the EEPROM.
73's de Edd
[email protected] ..........(Interstellar ~~~~Warp~~~Speed)
[email protected]........(Firewalled*Spam*Cookies*Crumbs)
Anytime you have a 50-50 chance of getting something
right..........there's a 90% probability you'll get it wrong.
.
OH...Tay, since you have now found that the u/p is powered up at its digital and analog supply power points, time to move on to other areas for analysis . You did mention that the unit would initially do a short power up with a growling when the set was void of power for a long enough time for all caps to zero out their static charges. When you said that the sets sweep "growled" on for just an instant upon an initial turn on.That would be indicitaive of an initial burst of hoz drive at the u/p's pin 19 hoz drive output. Scope it and see how long it lasts....probably agrees with the power relays on and then off time. I would suspect that the sets shut down sensing circuitry is now being engaged due to an excess current consumption from the 135VDC main sweep supply or else that the voltage might be going higher than that.
Refer now to the supplemal thumbnail schema:
CURRENT SENSING
There is a current sensing series resistor in line with the 135VDC supply as R516...2 ohm resistor and is sampled by a voltage divider resistor pair across it and an accompanying delayed/ lag response provided by C 971/ 100ufd. Their derived voltage reference then is feeding the base of Q971. If current consumption is within tolerance , the base voltage will not rise to the level to turn on the sense transistor, in turn, if the threshold is reached, the transistor will start conduction and will then engage a transistor circuit loop thru another voltage divider bridge on the transistor collector line with an adjunct C972...47ufd providing a delay/lag response upon that junction. As sensed current rises above the design threshold, the voltage at the latter emitter junction will track it accordingly. At the threshold of D972 zener's knee, voltage in excess of ~15 Vdc will be routed towards series isolation/steering diode D973, with an intermediate loading resistor of R 978.The voltage that passes thru D773 will then zip straight for Q531 only encountering another voltage divider bridge / DC interstage coupling media between the two xstrs of a discrete latch. When the base voltage build up is at the threshold of conduction at Q 531, it will then enact conduction and cause its collector voltage to diminish towards the low/sole voltage level of its semi junctions. That action will then affect the connection to D 535.... which in turn is tied into the voltage that is fed into the base circuitry of Q 951 which is the relay driver that initially powered up the set. With all of the base drive of Q 951 now effectively shunted off to ground through the D-535 / Q531 collector-emitter loop, the set then turns its self off. Never to run again until the CURRENT / OVERLOAD condition(s) are corrected...OR....until the sets caps are "drained" down to permit a repeating of the same "cycle".
VOLTAGE SENSING
There is a voltage sensing of the sweep circuitry that is acquired by a sampling of flyback voltage derived from itskine filament winding and is then rectified filterd and fed to a voltage divider bridge of R535 / R 537 which is sampled at their common node by zener D531. In the same manner as mentioned for the zener breakover threshold for the curent sensing functon, this zener will feed over into the same base supply line of Q531, where the same shut down procedure will be triggered, this time, it being a response to overvoltage.
It now seems that you need to go back to the anode side of D973, for the isolation that it provides, and do some DC coupled mode / scope probe monitoring of that node to see if , that upon initial turn on, that 15+ V comes down that line, and on to trip your shut down circuitry. If it wasn't at that point, then you can move on over to the base of Q 531 and expect the voltage to have originated from a threshold flowover of D 531 zener.
That set is probably new enough to not have a wholesale worry of esr'd out caps, unless in critical sweep filtering applications or unless dressed up towards thermal areas, but take note to the referenced circles , as they would speed up sensing trip times and not have a proper circuit response if deficient units were in those points.
If you have isolated it as a shut down problem, it might then be permissible...within centi-milliseconds operation.. to have a scope probe connected to a suspect voltage supply point and be merely using the scope in its vert DC coupled mode...set up wih vert DC level to at least the expected experienced DC level and then watch the DC trace baseline for its attained DC level. In this manner one can power up the set just for an instance and immediately see what voltage is there. Using an analog meter can take just a second to get a reading and .....Lord forbid.....an auto ranging DVM could have a circuit reduced to toast before it even ramps up and displays its reading.
I was thinking of this application in the case of the opening of one lead of the D535 loop to disengage its function for a very SHORT turn on testing burst.
Lastly,on your comment on being able to turn on the set with the switch or the remote, initially. The EEPROM only makes a comparison with the u/p on an initialization...in case you were monitoring the pins 5 and 6 and expecting constant activity. Its in the like order of booting up a 'puter...you don't have to do it every time. The program is on the EEPROM.
73's de Edd
[email protected] ..........(Interstellar ~~~~Warp~~~Speed)
[email protected]........(Firewalled*Spam*Cookies*Crumbs)
Anytime you have a 50-50 chance of getting something
right..........there's a 90% probability you'll get it wrong.
.
-
dacflyer
- Posts: 4748
- Joined: Fri Feb 08, 2002 1:01 am
- Location: USA / North Carolina / Fayetteville
- Contact:
hi Edd.
i might not sed stuff right in the last post..
i ment that, if i short the relay. the ps will fire up..and i do get HV.
at the anode..and i can draw a arc ... screwdriver + lead to crt gnd.
but thats only if i short the relay, it will not turn on via front side buttons. buttons work all the way to the input of ic201
all parts to the relay and the power led check out good.
and the inital static i heard was good,, does this set operate at a higher freq? then most sets ? most tv's i hear operate around 17khz.. at the flyback...this one must be higher, because i cannot hear it, yet it is working.. the growel i told you of is the vert. yolk
i seem to have all my voltages.. i just cannot see nothng on pins 5-6 of eprom,, i scoped them at start up etc, i just get a 5volts.. never see any data....
tritronics wants $70.00 for the ic201..phuuu :O
and $10.00 for the eprom...
as much splaining you reply with,, its a great help...
i might not sed stuff right in the last post..
i ment that, if i short the relay. the ps will fire up..and i do get HV.
at the anode..and i can draw a arc ... screwdriver + lead to crt gnd.
but thats only if i short the relay, it will not turn on via front side buttons. buttons work all the way to the input of ic201
all parts to the relay and the power led check out good.
and the inital static i heard was good,, does this set operate at a higher freq? then most sets ? most tv's i hear operate around 17khz.. at the flyback...this one must be higher, because i cannot hear it, yet it is working.. the growel i told you of is the vert. yolk
i seem to have all my voltages.. i just cannot see nothng on pins 5-6 of eprom,, i scoped them at start up etc, i just get a 5volts.. never see any data....
tritronics wants $70.00 for the ic201..phuuu :O
and $10.00 for the eprom...
as much splaining you reply with,, its a great help...
JCV AV-27WF35 dead set
Wanted to pay it back to others who post helpful info on line. I am an EET, not a tv service tech (so I needed help with how this TV worked). I had a dead set, turned out to be D708 (5.6v zeener diode) was pulling down pin 53 of IC201 (uP) to a 2.5v level with + & - spikes. 3 out of 50 times the set would work. Sikes brought the illogic level up to an acceptable level randomly.
Thanks to all who posted.
mmalf_mi
Thanks to all who posted.
mmalf_mi
Re: JCV AV-27WF35 dead set
Which begs the question, how did that zener die?mmalf_mi wrote: I had a dead set, turned out to be D708 (5.6v zeener diode) was pulling down pin 53 of IC201 (uP) to a 2.5v level with + & - spikes.
Zeners on the I2C bus pins are there for protection
against over voltage (or ground bounce), I wonder
where the hostile spikes come from?
What killed the zener??
Bigglez,
A reasonable and viable question... The connector (cnooc) is not connected to anything and is internal to the cabinet of the TV. The set has never been serviced and is about 4 yrs old. The bad diode was on the SCL1 line of the connector. If not a spike on the connector, then a huge spike on the 5v line, which I would assume would have destroyed the digtal IC's first. Then again, maybe the power supply failed to surpress or filter (7805 regulator), and the diode took one for the team. Open to other ideas...
A reasonable and viable question... The connector (cnooc) is not connected to anything and is internal to the cabinet of the TV. The set has never been serviced and is about 4 yrs old. The bad diode was on the SCL1 line of the connector. If not a spike on the connector, then a huge spike on the 5v line, which I would assume would have destroyed the digtal IC's first. Then again, maybe the power supply failed to surpress or filter (7805 regulator), and the diode took one for the team. Open to other ideas...
Re: What killed the zener??
Good reasoning, and we'll never really know.mmalf_mi wrote:The bad diode was on the SCL1 line of the connector. If not a spike on the connector, then a huge spike on the 5v line, which I would assume would have destroyed the digtal IC's first. Then again, maybe the power supply failed to surpress or filter (7805 regulator), and the diode took one for the team. Open to other ideas...
Its possible that the factory doesn't know
either. Someone either attached diodes for
protection as a result of a lesson learned
elsewhere, or putting in the diodes by trial
and error fixed the "problem of the day".
Generally, parts are only included if really
needed on consumer high volume curcuits.
I alway remind myself that the most reliable
components (of any system) are the ones
you leave out.
Your thread on TV repair stands out in these
discussions as most of the circuits that hobby
forums post run from five volts and have
digital interconnects. Good to see some
analog is still alive, even if in this case it
was digital circuit element (EEPROM) that
was to blame.
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