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Old 2nd Feb 2017, 5:36 pm   #81
skysat2
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Default Re: Philips PM5544 Faulty

Hello Stan.

Now i have set a link on the PCB. But the "P" doesn't display...

IC20 on Pin2. What do i wrong?


Regards SkySat
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Old 2nd Feb 2017, 5:39 pm   #82
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Default Re: Philips PM5544 Faulty

The Testcard with Text result:
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Old 2nd Feb 2017, 6:58 pm   #83
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Default Re: Philips PM5544 Faulty

Hello Skysat2
You will have to fit the links on the print side of the board and this side of the board is the reverse of the link diagram I sent you. I noticed in one of the pictures you sent that the address ‘A’ numbers are marked in the reverse order. Looking at the print side of the board IC21 is just left of centre and IC16 is on the right hand side looking at the board with the connectors at the bottom. So the address lines will be A9 to A4 from left to right and pin one of the IC’s will be on the top right of the package.
At present the (?), is being decoded as all the lines are at logic level 1. Somewhere I have a photo copy of the rear of print side of a Teletext board showing the links for PAL and PM 5544. I will try and find it and see if I can scan it and high light the links for you.
Regards Stan.
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Old 2nd Feb 2017, 7:57 pm   #84
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Default Re: Philips PM5544 Faulty

Quote:
Originally Posted by valveman49 View Post
Somewhere I have a photo copy of the rear of print side of a Teletext board showing the links for PAL and PM 5544. I will try and find it and see if I can scan it and high light the links for you.
Hello Stan
Yes, I would be very grateful

Regards SkySat
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Old 2nd Feb 2017, 10:25 pm   #85
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Default Re: Philips PM5544 Faulty

Hello Skysat2
I have scanned the copy of the print side of the PM5543 Teletext PCB and added the links in colour. However I cannot print it out in colour as it was a mono picture. Have a look at the PDF of the PCB and note the position of the links, which are all black, but you may be able to follow it.
I think I may have misled you about the programming when I said you only need to program the ‘1’ in the table, this was wrong and it is necessary to program the ‘0’ as well. That why you ended up with all (?) in the text.
Regards Stan.
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Old 3rd Feb 2017, 7:04 pm   #86
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Default Re: Philips PM5544 Faulty

Hallo Stan,
I hope for skysat would be more practicable the attached version.
Regards-Karl
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Old 3rd Feb 2017, 9:43 pm   #87
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Default Re: Philips PM5544 Faulty

Hello Karl
The PDF I posted was my second attempt; I managed to delete my first attempt. The original was a photocopy of the print side of a board programmed to read PAL, PM 5544 and I had to change to read BBC1 and BBC2 in the upper and lower boxes and this had to made to only select either BBC1 or BBC2 as selected by “EXT TEXT” button on the front of the unit. But that’s another story.
My mistake was to scan the photocopy in Black and White instead of colour. I went to all the effort to mark the pin and IC numbers in yellow and the O volt links in Green and the 1 links in Red, but when I converted it to a PDF it assumed it was a Black and White document and all the high lights were converted to black. I did not have the heart to rescan in colour and do all the high lights again.
Regards Stan.
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Old 4th Feb 2017, 12:08 am   #88
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Default Re: Philips PM5544 Faulty

Hello Stan & karesz*

Thank you for your Scan. I've now solder the Print. The Text Display alright, but after 5 Minutes the lower text began to flicker.

I check the solder of the Print. But i haven't see a fault on it.

What could that be?


The Videoclip: > http://homepage.hispeed.ch/skysat/PAL.mov



Regards SkySat
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Old 4th Feb 2017, 11:49 am   #89
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Default Re: Philips PM5544 Faulty

Hello Skysat2
From your video clip it looks like the lower box (Sign Matrix) select line is being overloaded. The upper and lower box select lines are selected by IC 5 (7474) and the lines are driven by IC15/1 and IC15/2 7440 (Dual Quad Input Power Driver). It looks like the lower box driver is either faulty or is being overloaded as the upper box is not affected. It appears that it is mainly affecting the MSB’s as the symbols selected are missing the first three bits and are selecting the symbol with these missing bits. If you look at the symbol table you will see the differences in the binary word for each symbol only varies for the first three bits.
The most important thing to do first is to check all the soldering and ensure that none of the IC pins connected to lower box select line is also connected to the O volts line through the adjacent solder pad holes. Perhaps you could check this with your multi meter on the ohms range by holding a probe to the O volts line and the other probe to each pin of the IC’s connected to the lower box select line. I would expect any reading less than few hundred ohms would indicate the problem area.
Please see attached photo of the Teletext PCB showing the links in colour. The red links are the ones to check.
Regards Stan.
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Old 5th Feb 2017, 11:18 am   #90
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Default Re: Philips PM5544 Faulty

Hello Stan

Thank you for the Scan. I've now recheck again the PCB, but i see no fault on it.

The first 15min on coldstart are ok, then flicker it on the lower Box.

But i remember, as the PCB was Blank, the lower Box with the (?) was also flickering after a time.

Was should I replace on this Unit?


Regards SkySat
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Old 5th Feb 2017, 11:30 am   #91
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Default Re: Philips PM5544 Faulty

After a Hour, the upper Box is also flickering...
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Old 6th Feb 2017, 12:28 pm   #92
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Default Re: Philips PM5544 Faulty

Hello Skysat2
This may be a problem with Unit 18, Current Gate PCB, this is a small PCB mounted on the back plane of the PCB rack. The current gate only switches the 5 volt supply to the Text Generator Unit 17 during the upper bar V5-7 and lower bar V23-25 to save power supply loading. You should use an oscilloscope to see if the 5 volts is being switched on and off at the correct time and is of the correct amplitude. However as you only have a multi-meter perhaps you could try monitoring the voltage from switching the unit on until the fault occurs and note any changes in the voltage level. I would guess that the voltage indicated will be around half, that is 2.5 to 2.8 volts. The voltage can be measured at 17-53’. Another way to test this could be to switch the Text off when the fault occurs and wait, say five minuets and the switch the Text back on again. If the text is displayed correctly it may point to a fault on the current gate board driver transistor. If the fault remains the same it may be a timing fault on the vertical divider PCB. The current gate is part of the PDF attachment I posted earlier on the Teletext board Unit 17 pages 174-175.
Please try these tests and I will look into other possibilities.
Regards Stan.
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Old 6th Feb 2017, 3:37 pm   #93
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Default Re: Philips PM5544 Faulty

Hello Stan.

The +5 Volt Votage is OK, on the terminals from the Current gate. It stay constant on +5 Volt, also when the Text-fault comes occurs.

If I press the "EXT TEXT" Button (an wait 5 minutes), the faulty Text comes instantly back. I don't think it's a fault on the current gate PCB.

I think the fault must be on the Text Board... Should i replace some IC's on the TeleText PCB? IC5 & IC15 are now are ordered. Maybe i should also order IC25, IC28 and IC29 ??


Regards SkySat

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Old 6th Feb 2017, 5:44 pm   #94
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Default Re: Philips PM5544 Faulty

Hello Skysat2
I am still not convinced that one of the clock oscillators is drifting off frequency as the temperature of the instrument warms up or the there is another faulty IC. If my memory serves me correctly you already have some spare 7400 and 7410 IC’s and there are a number of possibilities, which without the correct test gear is going to make this nothing more than a guess.
When first switched on the unit displays PAL and PM5544 and after a short time the lower box starts the get corrupted and a short time after this the upper box is corrupted. From the manual Fig 2 (Survey of the different characters) it would appear that the first three most significant bits of the binary address are being lost and the result is the displayed characters, not the programmed characters. Working back from the Text output 17-60’ the Shift Register output is controlled by the (Pre-Set Gate) and the (Clock Gate) IC 6 7400, IC27 7410, IC24 7450 and IC 28 7404. A fault on any of these IC’s would not give the symptoms we have, I think it would be more jumbled up characters. The buffers driving the address lines would not give the symptoms either.
Working back still further, the ROM input address is controlled by the hex buffer amps IC25 7417 and the address lines by IC23 7416. The symptoms would suggest that the ROM inputs are being corrupted or the address lines are being corrupted. However timing of all these signals is all important and the input data and output data will only be read at the correct time by signals from the (Read Out Gate) and the (Read In Gate). The only IC you could change hear would be IC6 7400 which may not be decoding the signals from the 7:1 divider IC’s 5, 7 and 8. I am sure that the inputs to the ROM are OK and the error is in the timing of the in and out signals.
To sum up try and change IC 6 and see what happens.
Regards Stan.
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Old 6th Feb 2017, 11:44 pm   #95
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Default Re: Philips PM5544 Faulty

Hello Stan.

After I replace IC6 (SN7400) see the Photo in the attachment:

Regards SkySat
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Old 7th Feb 2017, 9:35 pm   #96
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Default Re: Philips PM5544 Faulty

Hello Skysat2
The reason I suggested changing IC6 was because its four gates are used in all the parts I mentioned in my last post IC6/1 is used in the “Clock Gate” IC6/2 in the “Read out Gate” and IC6/3,4 are used in the “7 : 1 divider”. Looking at the results it would appear that shift register is not being clocked correctly and can only be due to the IC you have just fitted, or perhaps a solder bridge on the IC pins when replacing it. Please check for any solder bridges around the pins of the IC on both sides of the PCB and for any poor soldered joints or damaged print. If you cannot find any may I suggest that you replace the IC again?
Regards Stan
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Old 7th Feb 2017, 10:40 pm   #97
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Default Re: Philips PM5544 Faulty

Hello Stan.

I've replaced the old IC again, but it's stays exactly on the same symptom. I've checked the solder of the IC6, it's all alright. I'm now really confused...

Hmm, i think i could try to replace the capicators on this Unit...

I have filmed a Videoclip, when I start the Unit from coldstart: http://homepage.hispeed.ch/skysat/faulty.mov


Regards SkySat
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Old 8th Feb 2017, 8:47 pm   #98
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Default Re: Philips PM5544 Faulty

Hello Skysat2
Can you connect the test amplifier to Unit 17 Terminal 60’ (text-signal) and see if you get a blank screen with PAL at the top and PM 5544 at the bottom and see if the characters get corrupted, this will prove that the fault is on the board.
Looking at your video clip it would appear that line address A1 to A3 are varying with time (see circuit diagram page 171) these signals come from IC13 (7474) and IC14 (7473) and are controlled by IC11/1 and 2 and the start stop circuit is part controlled by IC11/3 and 4. IC11 is a Quad Two Input NOR Gate type 7402, if you have one of these IC’s you could change it and see if it improves matters.
Regards Stan.
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Old 9th Feb 2017, 9:35 pm   #99
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Default Re: Philips PM5544 Faulty

Hello Stan

Something is strange happen.
When I noticed during the operation that a smell came from the text unit. I looked like a resistance burnt. It was R42. I replaced him today. Then I noticed on the current-PCB that the resistor R2 is also burned. I have replaced him. But unfortunately I have no more +5Volt voltage on Terminal 53 'of Unit17. I'll buy the R4 tomorrow. I hope it work again.


Regards SkySat
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Old 9th Feb 2017, 10:46 pm   #100
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Default Re: Philips PM5544 Faulty

Short question:

Is it critical if I replace the original capacitor with capacitance 2.7uF by an 33uF? Is that too high?
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