Philips PM5544 Faulty

[Electrical]

Hello Skysat2
I am puzzled by R42 2k2 resistor being burnt out. This is a pull up resistor to the 5 volt rail for IC23/3 (7416) and is well within its rating of 0.125W. However this part of the Text board is mounted above the Current gate PCB and it may dis-coloured due to R2. R2 on the current gate board is the dropper resistor from the 15 volt rail for the zener diode GR1 (BZY88 5V6). The 5 volt supply is switched at line rate and is only on during the upper and lower text box intervals controlled by the vertical divider. This resistor R2 560R 0.125W is also well rated as when the 5 volt supply is off the full 15 volt supply is across the resistor due to transistor TS1 (2N2369) switching on to switch transistor TS2 off.
I think it is important to check TS1, GR1 and TS2 before you replace the resistors. With reference to the 2.7uF capacitor, as this is a switched supply it would be important to replace it with a 2.2uF capacitor, too large a value would upset the timing.
Regards Stan.

[skysat2]

Hello Stan.
After i replace some resistors on the Current Board and replaced on the Text-Board IC23, IC13, IC1, IC9, IC28, IC25 the Text is display ok again.

But now i have the problem again with the right charactets. Sometimes it display correctly for some time.

Do you know, which solder i should check for this? I can't find a fault on it...
The "5544" Displays always correct!


Regards SkySat

[Electrical]

Hello Skysat2
Have a look at Fig 2 Survey of the different characters (page 5) in the Teletext supplement.
The top box should display PAL and using the survey of different characters: -
P is binary 010000 and 0 is 110000
A is binary 000001 and ! is 100001
L is binary 001100 and , is 101100
From the above you will be able to see that the character address is gaining an extra “1” in
the A9 MSB (Most Significant Bit) of the binary word. The 5 and the 4 both use A9 in the
binary address, also the space or no character uses A9 and are therefore always decoded correctly.
The A9 part of the binary word is fed to the Read Only Memory IC26 by an Hex open collector
buffer amplifier IC25 (7417). This buffer amplifier could be faulty and you could unsolder one end of the pull up resistor R28 2K2, this will remove the 15 volt supply the A9 input to the ROM. However this will remove the spaces and upset the position of the text in the boxes. PAL should be decoded correctly but the 5544 will be decoded as UUTT.
Before you do the above can you check all the connections around IC21 which decodes the A9 signal
and ensure that only the pins that are used for spaces and numbers are linked to the correct text selector lines and that the upper and lower text select lines are not connected together.
Please see the programming table for PAL and PM 5544 and check the links are going to the correct upper and lower lines and any pin not connected these lines is connected to “0” volt line as any line left unconnected will assume a logic level “1” and may be cause of this problem.

Regards Stan.

[skysat2]

Hello Stan.
Thank you for your Help.

It seems as if the apparatus now work properly. I have replaced IC29 SN7496N.


I now observe it further

Regards SkySat

[Electrical]

Hello Skysat2
I am pleased you have sorted out the problem, I must admit I would not have suspected the Shift Register, IC29 although with an oscilloscope I am sure you would have been able to pin down the fault without having to change so many IC’s.
It will be best to give the unit a good run to make sure no other time or thermal related faults occur, as these units used to run continuously when new.
Do you have the Philips PM5532 Sync pulse generator and the Philips PM5545 PAL Encoder to go with the PM5544?
Regards Stan.

[skysat2]

Hello Stan

Yes, i have a complete System consisting of PM5532, PM5544 and PM5545


Regards SkySat

[Electrical]

Hello Skysat2
I have copies of the manuals for about three different versions of the PM5544 and also copies of the manuals for the Sync Pulse Generator PM5532 and the PAL Colour Encoder PM5545. If you ever need a copy of these I can scan them for you, although it may take some time.
Have you tried feeding the composite colour output from the video outputs on the PM5545 into a colour monitor or even the video inputs on a normal flat screen TV? It will show that the complete test card is displayed correctly and nothing has been adjusted in the PM5544.
Regards Stan.

[skysat2]

Hello Stan.

What do you mean about the Video Outputs? Which Connector do you mean? On the Back i have 3 Video Outputs, but on all comes the same Signal as of the Front of the PM5545.

I will move next time the apparatus to my Flat Screen. But it's all very heavy ;-)


Regards SkySat

[Electrical]

Hello Skysat2
Please see attached PDF of the connections of the PM5545 PAL Colour Encoder. If you connect Video I out or Video II out, to a colour monitor you should get the test pattern displayed in full colour. I assume you have all the interconnections connected correctly. If you take a photo of the rear wiring I will be able to tell if it is correct.
Regards Stan.

[skysat2]

Hello Stan

Here is the Photo from the rear wiring. I hope you see something from the cables.

[skysat2]

Hello Stan

At the Front of the PM5532 the Light bulb doesn't turn on anymore. What for a Type is it, to replace it?


Regards SkySat

[Electrical]

Hello Skysat2
I am not sure about your pictures, can you check the connections against the attached picture.
Please note this picture shows the PM5544 connected in RGB mode, but all the other connections should be the same.
Regards Stan.

[karesz*]

Hi,
your existend bulb is (usually) stamped/marked with voltage and current/wattage data...
Karl

[skysat2]

Thank you for your Help Stan & Karl. I will check this.

What Mode is better? In RGB or Y, R-Y, B-Y Mode (like my wiring) ??


Regards Skysat

[Electrical]

Hello Skysat2
The lamp is a 6 volt 50mA with a LES base and is the same part number in all the manuals.
Your PM5544 is connected up in the normal manner that is Y, R-Y, B-Y mode unfortunately I could not find a picture of this mode of connection and posted a unit connected in RGB. However the other connections are all the same regardless of which input is used.
I was wondering if you have tried to display the video output on your colour monitor and what results you have obtained. You could use a long 75R coax cable to connect to your colour monitor rather than move the rather heavy PM5544.
Regards Stan

[skysat2]

I have noticed, that light bulb is a smaller Version as the other ones. The normal light bulb Size does not fit in.
What do you mean with LES? Is that the Size?

[TonyDuell]

LES = Lilliput Edison Screw and relates to the diameter of the threaded base. I seem to remember it's also called E5.5, meaning it's 5.5mm in diameter.

[Electrical]

Hello Skysat2
Please find attached a PDF copy of a lamp catalogue showing the LES lamps and sizes.
Note the catalogue does not list a 6 volt 50mA version of the lamp, so if this is not available use a 6 volt 40mA version of the lamp instead. I think the one you need is the smaller of the two types listed.
Regards Stan.

[karesz*]

Stan,
I dont know the exact lamp situation, but what about an 5mm LED please?
Reichelt Elektronik , and Conrad too, has an(not very optimal) 6V,80mA E5,5 lamp...
I found just these annoncement on eBay/de; 6V, 50mA for good price.
Karl

[Electrical]

Hello Karl
I must admit, the last two units I repaired I did fit LED’s soldered into the old lamp base and changing the series resistor R02 from 27R to 330 or 390R, carefully observing the polarity of the LED and the lamp holder connections. If to take a look at the PDF copy of the PSU drawing Fig XIII-5 you will see that the lamp (LA1) is connected to the 5V rail via a 27R resistor; this is the resistor to change if a LED is fitted. The lamp is also used as a fault indicator should any fault develop in the power supply regulators.
The only position this modification will not work, is the crystal oven indicator on the PM5545 PAL colour encoder, as the lamp is fed with 6.3V ac.
Regards Stan.