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Post by Casethecorvetteman on Mar 3, 2016 8:04:06 GMT -5
Hi all, Dummyload has stated a change was made in later controllers that reduced power dissapation in one circuit, which in turn reduced heat:
dummyload Avatar
Mar 3, 2016 21:36:40 GMT 10 dummyload said:
@ Case you can make controller board heatsink cooler , early versions controller boards have I64 (lm7905) connected to -19v line (load on I64 = 0,5A) so only that one generates 7w heat , connecting it to -9v line saves about 5w of heat , see manual later version for details.
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Post by Casethecorvetteman on Mar 3, 2016 8:06:59 GMT -5
Can you tell us more about that?
Also another issue ive seen on my newer controller that was not present on the old one is distortion of the lines down the left. This isnt normal, its reasonably significant, and i use a bit of green converence there to fix it up a bit.
What causes that issue?
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Post by Casethecorvetteman on Mar 3, 2016 8:31:04 GMT -5
My service manual here lists on page 292 the area in question and does indeed show that 7905 hooked up to -19v.
Is it as simple as cut the track feeding that 7905 and run a wire up to the -9v supply?
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Post by dummyload on Mar 3, 2016 9:14:46 GMT -5
The -19v line feeds I84 (lm7912) and I64 (lm7905) cut trace but becareful not cut deep it's a multilayer board you will be in the next layer before you know it (been there done that) stay on the surface
Leave some trace between cut and input I64 ,because you have to add an capacitor of 100uf at the input of I64 to ground (- pole to input I64 plus pole to ground!) Now connect input I64 with connector
j700 pen A15 & C15 (-9v). Be sure to not make any mistake anywhere ,it can distroy your board. The heatsink on the board will still run hot ,but it will be lesse ,at least enough to do it in the revision.
Will add picture of it later.
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Post by Casethecorvetteman on Mar 3, 2016 17:53:46 GMT -5
Thanks mate  |
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Post by gjaky on Mar 4, 2016 13:58:14 GMT -5
You should consider using Recom R78xx-1.0 line regulators, these are compatible with the UA78/79 series but they are switching regulators resulting in low power dissipation.
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Post by Casethecorvetteman on Mar 5, 2016 0:34:47 GMT -5
My concerns there initially would be how smooth their output would be compared with the older style regulators.
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Post by gjaky on Mar 5, 2016 0:59:58 GMT -5
My concerns there initially would be how smooth their output would be compared with the older style regulators. They are very good in this regard, and for the digital circuits it doesn't even matter that much. |
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Post by Casethecorvetteman on Mar 5, 2016 5:34:38 GMT -5
Ill have to try swapping it to the -9v line and see if the controller becomes stable again. Sometimes itd last for months, other times it just wouldnt stay on after a few minutes, but letting it sit for 20 minutes itd work again, so id say it was heat related.
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Post by Casethecorvetteman on Mar 6, 2016 22:40:56 GMT -5
The -19v line feeds I84 (lm7912) and I64 (lm7905) cut trace but becareful not cut deep it's a multilayer board you will be in the next layer before you know it (been there done that) stay on the surface Leave some trace between cut and input I64 ,because you have to add an capacitor of 100uf at the input of I64 to ground (- pole to input I64 plus pole to ground!) Now connect input I64 with connector j700 pen A15 & C15 (-9v). Be sure to not make any mistake anywhere ,it can distroy your board. The heatsink on the board will still run hot ,but it will be lesse ,at least enough to do it in the revision. Will add picture of it later. How did Barco actually do the mod? I just took the controller board out now, would it be better to pull the regulator out and bend up the middle leg up instead of cut the track? Or is it no problem to just cut the track and put the 100uF cap directly on the input and ground pins of the IC? I ask this because I see where it loops from I84, and it looks as though there is other components on that line that are on the far side of I64, so cutting that track would isolate those components from I84. |
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Post by dummyload on Mar 7, 2016 9:45:15 GMT -5
Barco made a new pcb design witch addresses the changes made to some circuits. You are correct there are two cuts to be made to isolate middle pin I64 and then you have to reconnect I84 to the -19v line. (forgot this ,did it some time ago) Your way is good to ,you not have to cut traces this way ,but there is not much room to connect a wire to the bend middle pin ,and the 100uf should be only be a few centimeters away of the middle pin. Sorry for the bad cam.  |
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Post by Casethecorvetteman on Mar 7, 2016 9:49:41 GMT -5
Barco made a new pcb design witch addresses the changes made to some circuits. You are correct there are two cuts to be made to isolate middle pin I64 and then you have to reconnect I84 to the -19v line. (forgot this ,did it some time ago) Your way is good to ,you not have to cut traces this way ,but there is not much room to connect a wire to the bend middle pin ,and the 100uf should be only be a few centimeters away of the middle pin. Sorry for the bad cam. What do you think of the switching regulators idea that Gábor put forward? In theory if they are suitable, it could save lots of heat in there. |
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Post by dummyload on Mar 7, 2016 10:28:04 GMT -5
Sure something to consider ,but I do not have any experience with them, considering they also applying power to analog output drivers, convergens astig and focus ,you could run in to new problems. (it`s sometime in the details)
@casey, I don`t think that the heat dissipation on the heatsink is your problem.(to big time difference ,failure after few minutes, few months)
I have don this mod because It makes the heatsink run cooler and it`s a very easy mod and it comes from barco themself.
(I have not don it to solve a problem)
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Post by Casethecorvetteman on Mar 7, 2016 10:54:44 GMT -5
Sometimes it was as quick as 3 or 4 minutes.
If i put the jumper on the KEEP SMPS ON pins, the set stays on and image stays up, but convergence and geometry goes to midpoints and the remote does not function, so it must be losing a voltage somewhere, i just dont know which one.
It makes no sense that they fed a 7809 with -19v when -9v was available and more than enough.
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Post by Casethecorvetteman on Mar 7, 2016 11:01:09 GMT -5
What do you reckon is causing the distortion on the left side of the raster? It happens only with this controller fitted, the other controller has straight lines all the way across the raster.
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