Coolant Leak on Mitsubishi WS-A65 CRT RPTV

[dick_barton]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

When everything is connected and 9VS is jumping around do you have the 110V supply which is needed according to page3-4 of V20B chassis pdf.

It's part of the feedback loop controlling the transistor between pins 9,10 of the Opto which in turn increase or decreases the feeback to IC9A50.

[stj]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

isolate B+ from the lopt and load it with a 60w mains lamp to ground.

then power up the tv.

[SurrealMustard]

stand-by

When everything is connected and 9VS is jumping around do you have the 110V supply which is needed according to page3-4 of V20B chassis pdf.

It's part of the feedback loop controlling the transistor between pins 9,10 of the Opto which in turn increase or decreases the feeback to IC9A50.

Would you recommend double checking to make sure that the 110 is there? If so, where would be best to check it?

isolate B+ from the lopt and load it with a 60w mains lamp to ground.

then power up the tv.

That sounds tricky. Even if I could do that, how would I be able to power it up without the microprocessor getting proper standby voltage in order to boot up and send the p-on command?

[dick_barton]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

You could take P_On up to the 9VS supply using a 1K resistor very briefly and see if it attemps to power up. Other than that I have no further suggestions and perhaps someone else could offer some assistance.

[mrbob84]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

white wire goes down into the transformer, you cant desolder it - from that end anyway.
it runs at several KV so dont cut it - it's the focus or grid wire.

This is correct.

That medium thick white wire carries several thousand volts to the focus and screen controls, which operate grids inside the tube, and unplugs from its own dedicated rear recessed prong of the focus block. It does NOT come off of the FBT, it is internally anchored and sealed in there in production.

If this is the only wire you disco from the focus block, you won't have to mark it as there will be nowhere else for it to go when you plug it back in. And it should be. No other wires at the FB should be disturbed, as each is going exactly where it should as we speak and that should not be changed.

HV is not something you want to allow to get loose, so again, as stated later, DO NOT cut that wire! Unplug it at the focus block by pulling it straight out, allowing its length to stay undisturbed.

To plug it back in, pull the rubber boot up and away from the end, plug in the exposed female clip to the recessed male prong on the focus block, then slide that boot back down on top of the plug and over the recess.

[mrbob84]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

That kind of voltage fluctuation is definitely a sign that the coolant has spread farther than just that one connector. If it is the board beneath the red gun it's a brown one, with only 1 layer. Examine it again, using the bounce of a flashlight off the board and into your eyes. This will pick up the gleam of liquid more easily.

Remember, this fluid is not water, and when it drips it "plops" when delivered from a foot or 2 away, and thus has probably splattered elsewhere after bouncing off the connector.

It's coolant, sometimes ethylen glycol - like anti-freeze - sometimes glycine, that has escaped from the coolant chamber. This coolant is partially conductive and will over time cause corrosion, usually blue-green in color.

Rarely does enough escape to lower the visible level of the coolant inside that chamber, tho I have seen that happen. (Just once, and the entire gun had to be replaced - Mit does not allow for just replacing the coolant, it's all or nothing with Mit when it comes to the guns.) Usually it's just spillage caused by the pressure of the natural heating of the gun and inadequate seals on the part of Mitsubishi. Since nothing visible ever usually happens, just cleaning whatever it hit is all that's usually necessary. When I replaced the gun it was because it had leaked a full third out of it, and the picture was hosed, as this coolant chamber with its transparent coolant cover forms the primary objective lens. The upper third of the lens just wasn't there anymore.


All such drippage, even what has already dried, has to be removed very thoroughly from the board and any parts it has come in contact with - and the board in between that has gotten wet - or partial conductivity will be the result, causing partial shorting of the circuit. And fluctuation of the voltages. In many cases I have had to desolder one end of a resistor and clean both it and under it, and solder it back in place. Sometimes it has gone too far, has eaten away the leg of a resistor or diode, and I have to replace that part entirely.

That hole in the connector could be causing partial conductivity between the lines on either side of it, so it needs to be dealt with. I would cut away any of the discolored part, plus some to spare just for good measure. It's OK to have the wires inside exposed, they are low voltage and you won't need to worry about arc'ing. Just so they don't touch each other.

[mrbob84]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

[]

[mrbob84]

Re: stand-by

Would you recommend double checking to make sure that the 110 is there? If so, where would be best to check it?



That sounds tricky. Even if I could do that, how would I be able to power it up without the microprocessor getting proper standby voltage in order to boot up and send the p-on command?

None of this other troubleshooting has had to be done when there is a coolant leak and I was on the phone with Mit - which I was many times in that era - it always came down to the board in question.

The more you poke around in there taking readings and such, the more risk you take on that your VOM's probe slips and hits something it should not hit. Connects 2 things it should not connect. Troubleshooting something like this should always be kept to the absolute minimum because of this. These sets are not for experimenters. One tried that on a Pioneer Elite and whatever he did, I could not fix it afterwards without having to charge him an arm and a leg. If he had just left it alone and sent it to me for the comparatively simple resoldering op on that PS board, he would have been a lot better off.

You might want to surf the net for a replacement. I might have one here, I have kept several chassis boards from units that have been otherwise totaled.

A picture sent to my email might help. I will see if I have one. bob at imageperfection dot com.

[SurrealMustard]

troubleshooting data 2

Hey there Mr. Bob! I'm actually the same one who posted in the AVSForum thread a few days ago, (although it might be a while before I can post there again as my account was mistakenly banned and the administration still hasn't got back to me yet) so I'm glad you're able to help out here too.

Back to the topic at hand though . To recap, the fluid fell mainly on that second connector between the mainboard and the power board (both of which are brown). With all of the boards connected as normal, the fluctuation of the 9VS is between 2.5 and 8 volts, but with both ribbons disconnected (leaving the power board all alone), the 9VS still fluctuates, but now between 24 and 29 volts. To me, both the fluctuation and the oddly-high voltage (even with the other boards disconnected) tells me that something has to be hinky on the power supply, right? Is the voltage normally ever that high with the white ribbons disconnected (therefore putting no load on the standby)?

As far as unplugging the white cable from the FBT is concerned, I did figure it out successfully; it is indeed just attached to a basic connector that goes to the back of the focus block and pulls straight out. After that, it was no trouble to get the power supply board out of there for some more troubleshooting. Looking at it outside the set, nothing is visibly damaged or wet on either side however.

Regarding possible damage to the mainboard (which is a brown, single-layer board, Mitsubishi part number 930B885002, pictured here), I'd have to take a closer look at it, but it seemed fairly clean by the time I got done with it (save for the persistent grime that was there before). I treated the affected area with alcohol and dried that off with a cloth (and compressed air, especially around the connector, where a swab or cloth won't fit). I'll check for short circuits around the hole as well, but I think everything was kosher there too. Really hoping that the problem only lies on one board.

[mrbob84]

Re: troubleshooting data 2

Hey there Mr. Bob! I'm actually the same one who posted in the AVSForum thread a few days ago, (although it might be a while before I can post there again as my account was mistakenly banned and the administration still hasn't got back to me yet) so I'm glad you're able to help out here too.

Back to the topic at hand though . To recap, the fluid fell mainly on that second connector between the mainboard and the power board (both of which are brown). With all of the boards connected as normal, the fluctuation of the 9VS is between 2.5 and 8 volts, but with both ribbons disconnected (leaving the power board all alone), the 9VS still fluctuates, but now between 24 and 29 volts. To me, both the fluctuation and the oddly-high voltage (even with the other boards disconnected) tells me that something has to be hinky on the power supply, right? Is the voltage normally ever that high with the white ribbons disconnected (therefore putting no load on the standby)?

It is not uncommon for an unloaded power supply voltage to be significantly higher than when loaded properly. The voltage is left to simply float upwards, with no load to clamp it down properly.

As far as unplugging the white cable from the FBT is concerned, I did figure it out successfully; it is indeed just attached to a basic connector that goes to the back of the focus block and pulls straight out. After that, it was no trouble to get the power supply board out of there for some more troubleshooting. Looking at it outside the set, nothing is visibly damaged or wet on either side however.

Regarding possible damage to the mainboard (which is a brown, single-layer board, Mitsubishi part number 930B885002, pictured here), I'd have to take a closer look at it, but it seemed fairly clean by the time I got done with it (save for the persistent grime that was there before). I treated the affected area with alcohol and dried that off with a cloth (and compressed air, especially around the connector, where a swab or cloth won't fit). I'll check for short circuits around the hole as well, but I think everything was kosher there too. Really hoping that the problem only lies on one board.

Usually the case, however your model is only 2 years away from final model year for Mit CRT RPTVs. Mine was the final year, and it ends in 17. Yours ends in 13. Meaning 2 years before, as there were 2 numbers between model years. A fairly late model, not an early one.

As such your set would seem to have a DM module, so it's still possible that either 4 or 7 caps are bad in the DM module, depending on how many your set has in there. If so be sure and observe my info straight from Mit about the change in value for those caps when you replace them. 680uF rather than the 1000's that are in there, all else the same.

[SurrealMustard]

HDTV model clarification

It is not uncommon for an unloaded power supply voltage to be significantly higher than when loaded properly. The voltage is left to simply float upwards, with no load to clamp it down properly.

That makes sense. Even with that accounted for, it shouldn't be jumping all around though, right?

Usually the case, however your model is only 2 years away from final model year for Mit CRT RPTVs. Mine was the final year, and it ends in 17. Yours ends in 13. Meaning 2 years before, as there were 2 numbers between model years. A fairly late model, not an early one.

As such your set would seem to have a DM module, so it's still possible that either 4 or 7 caps are bad in the DM module, depending on how many your set has in there. If so be sure and observe my info straight from Mit about the change in value for those caps when you replace them. 680uF rather than the 1000's that are in there, all else the same.

The WS-A65 is basically a repackaged WS-65311 as far as I can tell and it definitely does not have a DM or the telltale digital inputs.

[mrbob84]

Re: HDTV model clarification

That makes sense. Even with that accounted for, it shouldn't be jumping all around though, right?

Right. The partially conductive coolant is somewhere it should not be, causing that. Sometimes you can actually hear a splutter of conduction in this kind of scenario. It might have crawled under an IC, causing partial conductivity at many legs. Erratic, unpredictable operation is one of the characteristic signs of coolant invasion.

The WS-A65 is basically a repackaged WS-65311 as far as I can tell and it definitely does not have a DM or the telltale digital inputs.

Ah, ending in 11, not 13. Makes it 3 years older than mine. If it does not have a DM module then you're right, the 4 or 7 caps do not factor in.

Luckily those sets are very modular, and replacing that board might be the ticket, if you can't find any more coolant loose anywhere.

Many things can cause protection to kick in tho. Have you checked all fuses and IC protectors? In the Mit's they are usually green and look like resistors with rounded edges. They will have a number plus an A to signify how many amps. IC protectors are simply fuses in different cases.

[SurrealMustard]

diagnostic evaluation

Right. The partially conductive coolant is somewhere it should not be, causing that. Sometimes you can actually hear a splutter of conduction in this kind of scenario. ...
Many things can cause protection to kick in tho. Have you checked all fuses and IC protectors? In the Mit's they are usually green and look like resistors with rounded edges. They will have a number plus an A to signify how many amps. IC protectors are simply fuses in different cases.

I located a whole cluster of those, but they all test good. No unusual audible noises either when the board was plugged in to mains power.

Right. The partially conductive coolant is somewhere it should not be, causing that. Sometimes you can actually hear a splutter of conduction in this kind of scenario. It might have crawled under an IC, causing partial conductivity at many legs. Erratic, unpredictable operation is one of the characteristic signs of coolant invasion.

Luckily those sets are very modular, and replacing that board might be the ticket, if you can't find any more coolant loose anywhere.

I took a closer look at the power board now that it is out of the set and can't see or feel any errant liquid anymore. It may still be hiding somewhere, but I can't spot any. Given how long it was left plugged in after the leak, I get the feeling that something (or things) on the power board might be toast. Do you think it would be more cost/time-effective to try to troubleshoot the culprit on this board or to just buy a replacement? I can get one right now for less than $38 shipped.

[mrbob84]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

Absolutely! Hop on that puppy. For $38 shipped??? That shoulda been hopped on yesterday. As my daddy used to say, "Immediately if not sooner."

Keep in mind tho, that ribbon connectors connect boards. You are concentrating on one board. What about the other one, on the other side of that ribbon connector? The coolant splatter from coolant hitting the connector would go in both directions.

[SurrealMustard]

power board ordered, shifting focus to mainboard

Absolutely! Hop on that puppy. For $38 shipped??? That shoulda been hopped on yesterday. As my daddy used to say, "Immediately if not sooner."

Keep in mind tho, that ribbon connectors connect boards. You are concentrating on one board. What about the other one, on the other side of that ribbon connector? The coolant splatter from coolant hitting the connector would go in both directions.

Got the power board ordered up! While I'm waiting for it to get here, I'll pull the mainboard out of there again and look at it really close. Do you think I could run it through the dishwasher or would that cause too much stress? I've seen people who have had great luck cleaning their computer motherboards that way, but those are also more even and rigid.

[mrbob84]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

Well, motherboards for 'puters are usually multi-layer boards, where these are single layer. That really shouldn't matter, tho.

I think it would be OK, but I would shy away from actually using detergent. Some of it could get lodged in there and not rinsed off, causing electrolytic conduction later on with possibly the same corrosive results as you are having now. With just water, whatever doesn't get dislodged will just evaporate. I think i heard that too, along with the dishwasher recommendation, to also not use detergent.

I have heard the same about the dishwasher cleaning ECBs, just never tried it yet. It's on you, on this one. Let us know how it turns out -

[dick_barton]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

When we had equipment that suffered considerable smoke damage as a result of a fire, the circuit boards were cleaned up by a company assigned by the insurance company. They used distilled water for washing the circuit boards so that no conductive particles were left on the boards to cause further problems.

[SurrealMustard]

cleaning and adjustment considerations

Well, I'll certainly keep those cleaning tips in mind. I won't run it through the dishwasher unless I can round up some other stuff too that could use a good cleaning as well because I don't want to clean just one item (or mix it with silverware and dishes). If not, I'll just look over that mainboard closely and maybe give it another good cleaning the manual way just to be sure that there's no more errant coolant.

While we're pondering that though, I've got another couple of questions. Firstly, Mr. Bob, is there any chance of finding a front faceplate/grille for one of these models? I searched the part number, but (predictably) nobody has them in stock. Is my best bet to just scour Craiglist for a broken set with its faceplate still intact? Is there a DIY solution that wouldn't cost too much?

Also, I've been thinking ahead to once it's up and running again and was considering trying to build one of those I2C interfaces to attempt the "red push" fix. I read the manual on CIR Engineering and it sounds doable, but I was wondering if the values that have to be changed are the same for the V20 Mitsubishis as it was for the earlier models that the author originally wrote the guide for.

[dick_barton]

Re: Coolant Leak on Mitsubishi WS-A65 CRT RPTV

My error in post#37
They used de-ionized water not distilled water to wash the circuit boards.

[mrbob84]

Re: cleaning and adjustment considerations

While we're pondering that though, I've got another couple of questions. Firstly, Mr. Bob, is there any chance of finding a front faceplate/grille for one of these models? I searched the part number, but (predictably) nobody has them in stock. Is my best bet to just scour Craiglist for a broken set with its faceplate still intact? Is there a DIY solution that wouldn't cost too much?

Yes, and I would also check out ebay. Why do you need that?

Also, I've been thinking ahead to once it's up and running again and was considering trying to build one of those I2C interfaces to attempt the "red push" fix. I read the manual on CIR Engineering and it sounds doable, but I was wondering if the values that have to be changed are the same for the V20 Mitsubishis as it was for the earlier models that the author originally wrote the guide for.

The parameters rarely changed year to year in the Mits line. You're probably safe assuming they have not changed, but always best to try new values out first, after very carefully recording the original values before changing any of them.