You're right it's 48. I was looking at the M board and didn't notice the other large IC tucked away and assumed that was it.
I'll take a close look at the M board when I take everything apart to install the FBT I ordered. Which pins specifically are the likely culprits? Q601/Q602?
Anything I should know about installing the FBT?
Looks like mel's getting tired of this thread. Sorry...
Which pins specifically are the likely culprits? Q601/Q602?
You said in an earlier post that you did not feel any HV on the CRT face...(Post #89).. Then in post #91 , you said that the 130 vdc was there... Q601 & Q602 HAVE to be OK & some or all of the power supply is working... So Q601 & Q602 are ruled out... The pins I was referring to would be on T604 , the big transformer that sits next to Q601 & Q602 ... Also the 9 vdc regulator IC , "IC606"...
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Anything I should know about installing the FBT?
Short the anode connection to ground to discharge any residual charge... That's the heavy red wire that goes into the side of the CRT... Make sure your ground wire is well connected to a good chassis ground & you get the other end under the rubber cup..
BTW;.. Which flyback did you order ???
mel's "RIP" was refering to the TV & not the thread...
Later...Ron.M...... Veteran & Retired TV technician
I checked IC606 for shorts but didn't find any. Not that that necessarily means anything.
78xx regulators are dirt cheap so replacing it would be trivial. That transformer is a little bit hard to come by though. I only found one source so far and they want to quote it. Hopefully that part isn't the culprit. I'm still optimistic that it was just a fluke and won't reoccur (fingers crossed).
I bought the -21 FBT. Got a good deal, too!
For reference:
T604 1-423-615-11 IC606 RC7809FA - actual part installed says 7809CT
I checked IC606 for shorts but didn't find any. Not that that necessarily means anything.
You're right !!!.. Doesn't mean anything !!!.. You should have looked at the PC connections for bad solder connections.. NOT shorts...
Concerning T604;=>..
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Oftentimes , it's due to the power transformer pins being/going bad...
The same thing here... I guess I have to make myself clearer... Check the pin connections for bad connections , i.e. , bad solder connections... Transformer (T604) most likely GOOD !!!... Go back & check both T604 & IC606 for bad PC (Foil) connections..
Those older regulator ICs usually had "78" with the voltage after... The one you have is most likely OK & could have bad PC connections..(Foil)..
Later..Ron.M...... Veteran & Retired TV technician
Yeah, the joints look fine but I just noticed today that IC605 has breaks in the solder. That's a 12V regulator feeding into IC606, so that could possibly be the source of the problem.
I've made a note to resolder that guy when I do the FBT.
Easier said than done, Ron! Let's hold off on that for now. I've investigated further and found a problem that might be the cause. See below.
> Q591 sounds okay. Regarding the sound, I just meant that it's making the usual squeal as normal and I don't hear anything suspicious.
Today I checked D502 and it seems okay. But R501 seems to have gone bad. Unless I'm reading the schematic wrong it should be less than an ohm but it's in the megaohm region.
That conflicts with my earlier measurements: D502 ohmage 2.69M |<| 1.2 wrt gnd
That's of D502 BUT since there's nothing but a jumper wire between R501 and the anode of D502, I tells me I should be reading very low ohmage on the other side of R501 but I'm getting megaohms instead.
Remember a week ago how I said something was burning? The area around R501 looks discolored, like it may have burned a bit.
So R501 seems to have been destroyed. I don't understand the purpose of that resistor since it's such a low resistance. Is it safe to jumper it? The note for R501 says "FPRD" but I don't know what that means.
That's of D502 BUT since there's nothing but a jumper wire between R501 and the anode of D502,
There should be another resistor between R501 & D502... On the schematic R510 is between R501 & D502... That is a 7.5 ohm resistor probably the same size as R501..
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Is it safe to jumper it?
Hold off on that for a bit... I need some info about R510 first...
Read ohms from the anode of D502 to ground & post results... Thanks...
"FPRD" means Flame Proof Resistive Device..
Later...Ron.M..... Veteran & Retired TV technician
Speaking of glitches, I thought I successfully posted a response last night but it's nowhere to be seen this morning...
The gist of my missing post was that R510 is a factory installed jumper wire on my board and D502 anode measures mega ohms wrt ground (as well as every point between it and R501). The "R510" wire has no significant amount of resistance.
Flying Piranha Research & Development?
(This post was edited by CRT_Fan on Mar 15, 2014, 4:16 PM)
I thought I successfully posted a response last night but it's nowhere to be seen this morning...
Missed taking your meds again ???... Just kidding......
That explains why R510 is not in the parts list... OK..
I need a ohms reading from the band end "+" of D502 to the non-band end of D503... Please note you are reading between diode outputs... Read with the "+" probe of your meter on one of the diodes & the "-" probe on the other diode , then reverse the leads & take another reading... Please post results... Thanks...
Here's another;=>... Floppy Peter Running Dry ???
Later...Ron.M....... Veteran & Retired TV technician
(This post was edited by Ron.M on Mar 15, 2014, 6:07 PM)
D502 -> D503 (red -> black) yields a positive megaohms reading. Reversing it gives a negative megaohms reading.
I can't give exact numbers because the values are steadily dropping either way you measure it. The negative reading (D503 -> D502) is consistently smaller than the positive reading but still in the same range.
There must be some interference from energy storing devices. I'm guessing that's not a problem, although I'm not sure what you're getting at with this test.
When you come back;... Replace R501 with a very thin jumper wire... Turn on the TV & watch carefully for any smoke or burning smell around IC501... That is the vertical output IC (TDA8172) mounted on a heatsink.... See if the "squeal" is the same or if it has changed... IF it has changed , IMMEDIATELY turn the TV OFF !!!... IF not , leave it on for a short time , turn it off & check the temp of Q591.. Post results...
Later...Ron.M...... Veteran & Retired TV technician
What did you use to replace R501 with ???? Check R505 coming off the "+" side of D503... Should be very low (0.47) ohms.. Read ohms from the "+" (band) end of D503 to chassis ground.. Then unsolder & remove IC501.. IF R501 & R505 are good , your "+" voltage should be about +15 vdc & your "-" voltage should be about -15 vdc... (12 vdc at either or both is acceptable)..
Later...Ron.M...... Veteran & Retired TV technician
I haven't taken IC501 out because the pins are too close together--I could get it out but I wouldn't be able to solder it back in at this time. This is why:
Something else is wrong now. I saw smoke coming from foil side the board. It appeared to be coming from Q503.
I have confirmed that Q503 gets extremely hot after a few seconds. It doesn't have a heatsink so it shouldn't be getting that hot. Terminals are not yet shorted and the device itself shows no signs of burning so it may still be good. I think the smoke came from leftover resin that got burned off from the heat. (Yes it's got resin residue like it had been replaced before.)
Another oddity: If I place the probe on ground the squealing sound stops or changes and sometimes won't come back until I turn the power off and back on. If I turn it on with the probe on ground it doesn't seem to affect it. Very weird and probably not good.
I saw smoke coming from foil side the board. It appeared to be coming from Q503.
That's the Vertical Pin out transistor & you did NOT have this & the wierd squealing sound till you changed the flyback... Time to put the original flyback back in & see what gives with that one... Sorry , but , I'm thinking you live over an ancient burial site & your home is haunted by gremlins !!!...
Later...Ron.M...... Veteran & Retired TV technician
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Let's hold off on that for now. I've investigated further and found a problem that might be the cause. See below. 
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