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Sync problem - submitted by John Peters.

If you suspect that a monitor is missing a sync signal resulting in it going into power saving try connecting an external 6 volt supply to the crt filament. Turn on the supply first to heat the filament. Then turn the monitor on. You can then see if you have sync, one color missing etc.

Com Port Tester - submitted by Greg Stark

A simple com port tester for PC's and other DTE/DCE equipment. Verifies port activity, confirms 1488/1489 line drivers receivers are functioning ok. The reason for the led's on pin 2 and 3 is whether your connected to DTE or DCE equipment. Terminal/PC/MODEM/PLC anything. The jumpering satisfies every handshake known to RS232 communications.
DB25FM connector
Pin number
frame ground PIN 1 ---- n/c or attach to shield at one end only, not needed for short runs
Txd 2-- 1 kohm ----------- + [) red led, anode to 7 ground
Rxd 3-- 1 kohm --- + [) green led, anode to 7 ground
Rts/Cts 4--5 jumper 4 to 5
Dsr/Dcd/Dtr 6--8--20 Jumper 6 to 8 to 20
Ground 7 -- ground -- solder to anode of leds
I built a couple of these with db25fm and db9fm connectors and attached a 2 foot cable to the leds, heat shrunk it all together so I could see what was happening when working on PC's in tight places and other comm devices. This thing has never let me down when testing any COM port. It tells me everything I need to know about the com ports hardware or if its a software problem. If I see activity sending to the port, the port is OK.

Testing Power Supplies - submitted by Corey Ross

If you are having trouble with a Power Supply blowing fuses and are not sure if you got the problem fixed, here is a tip. Get a lamp socket with 2 extending leads and a light bulb. Solder alligator clips on the leads. Put the clips in place of the fuse. Power up the PS and turn on the bulb. If the bulb goes extremely bright on power up, the short is still present. If it goes dim more than likely the Power Supply will start working properly. It may take a few seconds or flicker if the power supply is a Switching Power Supply. This will save you time and money!

Test Jig - submitted by Woodie Morris

For NAP (Magnavox, Sylvania, Philco, Phillips) console TV sets, a spare 25"or 26" table model set whose chassis has been destroyed by lightning, makes a very good test jig. Just remove the customer's chassis along with the front panel control from any console model from the c5 chassis (15 years old) up to the present models and it will operate in this test jig. The only connection to connect/disconnect are vert yoke, hor yoke, speakers, degauss and dag to crt board and chassis. Two types of vert yoke connectors are used so test jig should have both vert yoke connector types. Do not try to operate this test jig with 31" or larger as the yoke mismatch as well as pinc components will cause problems.

Homemade CRT Restorer - submitted by Bruno De March.

All CRT restorers, including the most expensive, are based on the same principle appliyng discharges between RGB cathodes and G1 inside the tube to remove from the cathodes microscopical particles deposed on them during the CRT lifetime. Those particles diminish the electron emission, and by removing them the tube may be restored. The homemade device pictured here is good enough to do this work and gives a good service to the TV and monitor repairer in all cases when the tube is not totally unrecoverable (all vacuum electron emitters have a limit). I have tested it with many types of tubes and found it useful except in Samsung and some EMC tubes, in monitors. I guess Samsung tubes are the worst. I have never tested it with Trinitron tubes, but I do not see any reason for not trying it, only that I have not yet met any exhausted tube of these. The circuit is very simple, and you can make it recovering old materials. The isolation transformer is not essential, it only provides a means for more security. You can use an old tube socket to make the connections described in the picture (you must of course disconnect the tube from the rest of the monitor circuits), then apply the 6 to 9 volts to heat up the filaments for some minutes, then switch off and immediatly push and release rapidly several times the pusher switch that applies the 220 AC discharge through the light bulb, while the filaments are still hot. Do it first to one of the three cathodes, then repeat the whole procedure with the other two. You will see that when you apply the discharge, the bulb lights up and a little spark can be seen inside the tube. As the filaments get cold, the bulb flashes get dimmer as you go pushing the switch. When the light does not light anymore, the discharge cannot be made. Turn on again the filament supply and proceed with another cathode. Caution! Do not push the discharge switch while the filaments are under voltage, you could damage the cathode. For more security, you can use a double-circuit pusher switch that automatically turns off the filament supply. When the three cathodes are treated this way, test the monitor if it is still dim, repeat the procedure the times necessary, but if you do not see any improvement, let it be, the tube is unrecoverable. Note the device described, as you see, is intended for use in the countries where a 220 v. AC supply is available commonly. In USA and other countries where they have 120 volts (or other), you have to experiment if the procedure is directly applicable this way. I suppose a 120 volts discharge would do too.

SMPS Test Jig - submitted by Ron Reyn

Here is a little item that I use all the time to test power supplies. Most supplies will not start without a load. I use an automotive brake light bulb. The bulb has two filaments, one I connect to the 5Volt line (Brake filament) and the other to the 12 volt line (running light filament). This bulb is connected to a standard connector. I used an extender cable cut the male end off and soldered the bulb to the Yellow and red wires. Both blacks are attached to the sleeve if the bulb. If the supply is good, both filaments will light up almost the same brilliance. I found it great for debugging supplies. Make sure all the other lines to the computer and hardware are disconnected for this test.

An adapter to operate an Apple monitor from a PC - submitted by Glenn Wilson. Glen is a member of our email discussion groups.. All subscribers have access to his, as well as over one hundred other technician's comments and expertise.

Its connections are:

IBM 15 pin 3 row to Apple 15 pin 2 row
IBM 3 row Apple 2 row Signal Name
1 2 Red Video
2 5 Green Video
3 9 Blue Video
4 nc
5 nc
6 1 Red Video Return
7 6 Green Video Return
8 13 Blue Video Return
9 nc
10 11 & 14 Grounds
11 nc
12 nc
13 3 & 15 3=Composite Sync, 15=H Sync
14 12 V Sync
15 nc
nc 4 Monitor ID #1
nc 7 Monitor ID #2
nc 10 Monitor ID #3
The three monitor IDs tell the Apple / Mac
video controller what frequencies or scan rates to output - but the PC computer doesn't need them.

10 amp Power Supply - submitted by Ron Reyn

Had a need for a low voltage power supply today with high current, and since it was after 5.30 and tomorrow being Sunday, I decided to build one. So I got a few parts that I had laying around and built it. Except for the 15 amp transformer, 50 amp bridge and 40,000 Ufd capacitor, I figure the parts would cost about 3 or 4 bucks. The supply is ROCK stable and variable from 3 volts to 18 volts. The supply is over voltage and over current protected as a bonus. See figure below.

Power Supply - submitted by Michael Ernst

Years ago, I built a similar power supply like Ron but needed higher output. It works when using 2N3773 transistors instead of 2N3055. The limit is then 40 Volts and lots of Amps.

High-Current Transformer - submitted by Ken Hull

For a surprise FREE high current transformer look to your 'junk' microwave ovens. Most shops have some laying around with bad control boards, not repairable (I have nine of them). Just remove the power transformer, chisel away the 1000vac winding and take some #12 romex wire, single and wrap that around the core where the old hv winding was. Formula= 1 turn per volt. Secure and glue it and you have a transformer capable of MANY amps.

G2 Pot Bypass - submitted by Luc Degrande. Luc is a member of our email discussion groups.. All subscribers have access to his, as well as over one hundred other technician's comments and expertise.

To eliminate a possible bad G2 pot (or to repair it), I have been using following little circuit (5 components). It uses the pulses from the HOT to create approximately 1000VDC. Feed this into a pot and then to G2. You only need three wires from this module:
1 HOT collector
3 G2
The circuit (copied from several monitors) from the Hot collector two 1000V fast diodes (BYV96E or equiv.) in serie, to a 10n 2KV cap, then to the top of a 2M HV pot, the bottom of the pot via 1M resistor to ground. The wiper of the pot goes to the G2 input on the neck pcb. If you want to connect directly to G2 on the tube (eliminating the resistor and cap already on the neck) you should add on the wiper a 1M resistor to a 10n 2KV cap (as filter). Of course be VERY carefull when handling, also take care how you mount it it carries over 1KV!! See figure below.