Savel brain dump in English!

As I mentioned in previous post, the power of my FM generator is too weak. At first I decided to build power amp from scratch, but I remembered, that I had old power amp from some ancient car mobile phone. I was lucky and I found it. The last and most powerful transistor is missing, but I don’t want to jam whole city with my small device. I checked the data sheets of transistors and found that max power of last stage is about 10W. I reverse engineered that part of the schematics. There are lots of stuff in the board. Also there is device to measure output power. I discarded them. Also I didn’t analyzed transistor base power supply (based on LM723H)- I put Vcc and received 0.7V on bases.

It is simplified schematics of RF power amplifier (Wiring diagram).

T1: 2N5944 npn Pout=2W, Pin=0.18W; T2: 2N5946 npn Pout=10W, Pin=1W. Both transistors work up to 470MHz.

First of all I needed to change the frequency of this amp. Originally it was about 400MHz and I needed about 100MHz. I increased capacity in stage connectors- just added new capacitors 18…47pF. Also squeezed the inductors (after testing I decided to change them) to increase inductance. Also, I added radiator as original was missing.

So how it looks like.

The power supply is from some computer. I needed only 5V.

The antenna is typical quarter wave. According to calculations and using 50 ohm type cable it is 70 cm size. Here is abstract from other internet page:

Another suitable antenna is the so-called “Quarter wave Ground plane”, as shown in figure. It consists of 5 elements of the same type and length as on the dipole. The center one radiates the signal, while the others make a so-called ground plane. D shows how the elements are assembled with a chassis-mount BNC socket. The middle rod is soldered to the center connector, while the lower ones are soldered in the bolt holes. They could preferable be bent under (an soldered to) the next as shown, to give mechanical strength. These rods should not point straight out, but be bent 30-45 degrees downwards. This antenna has 50 ohms impedance, and should be connected to a 50 ohms cable without a balun. It’s important that the antenna is placed high and free. At FM frequencies, the transmitting power don’t affect the range much, it’s more important to have a clear view towards the listeners. If you put a little effort in finding a good location, you can get quite far even with a small transmitter. The antenna should be placed outdoors (preferably on the roof) since both trees and buildings obstruct FM signals. If someone starts asking, remember that such an antenna is good for reception too!

I tested this transmitter and it seams working. Only I need to increase the inductance of L2 and L5. They are too small for lower side of FM band. Also, I need to make radiator work better- now transistors are too hot. Also, I need so tuning device to check the output stage-antenna matching.

As mentioned in other post, one of possible defects of plasma TV is black line of death. The cause of black line is that the one chip glued to display panel is defective. If only contact of the PCB is damaged, the lines are much narrow. If the “distribution” chip is damaged, the line are 4 times wider, or even, the rest of the screen is black. Why this chip can be damaged? The possible cause are: manufacturing defects, high temperature of electrical discharge.

Here you can see the flexible pcb (un)glued to panel. You can see four chips, four capacitors and four quite big resistors. Typically only the one chip is damaged, but you need to change whole panel. In fact, you need to buy new TV.

It is possible to detach PCB from display panel, but how to glue it back? The pitch of contact pads is very fine.

(The big blue bars are the millimeters)

Also you need some special glue. This problems is still under investigation.

From few not working LG plasma TV I made one half working. Just for fun and to test plasma technology. So here is small review of plasma display panel or plasma TV from LG.

Very old (21 years) Panasonic CRT TV and 2004 LG plasma.

Plasma display panel (PDP) is a big glass device- to plates of glass, covered with conductive transparent coating in the form of line. On one plate with horizontal lines, on other with vertical. The space between glass plates are filled with some inert gas. The back plate is covered with special luminescent coating. Put voltage to one vertical and one horizontal line and small plasma discharge is produced on line crossing- small amount of UV is radiated. The UV strikes special coating and it began glowing in basic colors. The back plane is glued to big aluminium plate. It is used to collect heat and cool the plasma display.

In the front of plasma panel there is protective plastic and glass plate. The purpose of this plate is to protect sensitive plasma panel, prevent people from touching hot device and to filter some colors.

In the back of the PDP is lots of electronics. Very big power supply, special computer for signal processing, plasma current supply and the decoders. The decoders-registers are special chips for commutating lines in PDP. With flexible PCBs these chips are glued to PDP glass. These devices are not changeable. So, if you plasma TV shows black line, this means that one of these chips are dead. And you must change all few thousand USD valued PDP if few buck valued chip is dead.

This is the line of death.

The TV has lots of connectors: VGA, Composite, S-Video, component, sound in, speaker out, RS-232, remote controller, ac power

Also there is some noise on this display. Small random dots moving on screen.

To be continued…

To make double sided PCB at home you need: double sided photoresist coated PCB material, some NaOH solution (in mine case- simple drain cleaner), some PCB etching solution (HNO3 in my case), some PCB software, good printer, some transparency foil, glue, UV box.

First design your PCB. I am using freeware Eagle. Print sides separated on transparency. Now glue transparencies and some spacer to form envelope for PCB. Align all the holes. The thickness of the spacer must be equal to thickness of PCB or slightly less.

Remove protective plastic from PCB. Place PCB into the envelope. Dispose useless protective foil.

Place envelope between two UV emitting lamps. Do not move the lamps, pcb and envelope during exposure.

After exposure, develop in NaOH solution. Develop slowly, as strong developer can clean useful parts of the image.

Place the PCB to etching solution.

And check the result. All the holes perfectly aligned. Now it is time to drill few holes.

In other post I mentioned, that my FM generator is too weak to jam radio stations. And I remembered, that I have quite powerful radio transmitter. 16P22B-1 (16Р22В-1, 16R22V-1). It is 146 – 174 MHz FM radio station – transmitter. Output is 8…15W. So it is powerful enough to jam all small town .

I opened the box of radio transmitter. And made few scans. I need to check, if I can move the frequency to more useful area.

This FM transmitter is using digital tuning with the help of PLL. This PLL is constructed using discrete parts. It is quite old radio station. Now I think, that all this strange gold chips can be replaced with single PLL chip, like TSA6057 – Radio tuning PLL frequency synthesizers. (The TSA6057 is a bipolar single chip frequency synthesizer manufactured in SUBILO-N technology (components laterally separated by oxide). It performs all the tuning functions of a PLL radio tuning system. The IC is designed for application in all types of radio receivers.) If I could have some spare time…

I tested that transmitter in his native frequency and get quite good result. I can speak from my summer country house to my home without any interference. From one side areal antenna is original big device, and from other side just small peace of wire.

For small amount of money I acquired very old high frequency generator. It is very old, it is made in ~1960. But still working. I opened the case and discovered few radio tubes. Most interesting, that some of the tubes were changed in 1978. All high frequency parts are covered with heavy solid shield. The power attenuator is some sort of moving waveguide.

The frequency of generator is from about 16MHz to 126MHz. So it covers all FM radio band. Output is max 0.1V. Quite weak for my experiments…

And now short story: Sometimes you have some stupid, morons, idiots neighbours who listen all day to some stupid fucking radio station. Especially, that station plays some vomiting musing for low brain public. And your neighbours listen to that music very loudly. You can’t do anything, because according to law they can do this.

So, take that old FM generator, plug simple wire to output, tune to that station and pump the power to jam it. And now neighbour’s radio is playing 1000Hz tone, your favorite music (if you use external modulation) or just plain silence (only carrier, no modulation).

It is quite difficult to get such generator for everybody, so you need to build radio jammer from scratch. Visit my pages in future and I’ll try to post here the schematics.

From local factory received some bad, not working, cable TV distribution, amplifying, filtering, coding and mixing modules. It take few photos of this devices. I think, these devices have too much connectors. Especially that smaller one. It is made only from passive components- no transistors or chips…

The bigger one is more complicated- lots of transistors, capacitors, diodes, various inductors and transformers. I picked up these devices as they look interesting and a bit funny. Maybe I’ll extract some useful components and the boxes are very well made.

There are capacitors and there are very big capacitors. The last ones are with heavy duty terminal connectors for high current connections, and the capacity of them are quite big. Something like 47000mkf x 80V or 100000mkf (0.1F)x 16V. Such devices can store lots of energy. They are used, when high currents are used in pulses- like large printers, high power audio amplifiers. That 0.1F cap is very old, I think about 20 years old, but still holding the charge. I charged it to 14V, and after about 2 hours, my voltmeters shows 13V (after night it is still 12.5V!).

The energy stored in capacitor is calculated in Joules:

E = CU²/2 ; E in J, c in F, U in V.

So that cap can hold 27.6J of energy. As you see, the voltage is more important in energy calculation than capacitance. So another big cap- 350mkF x 450V can hold – ~73J of energy. And it is lighter than low voltage one. Ant this 73J can kill you.

The capacitance (C) is the amount of charge per volt of potential that a capacitor holds.

C =Q/U ; where Q = coulombs (the unit of charge) and U = Volts.

The average power in watts is:

P_av = CU²/2t ; where t = time in seconds.

Using caps in pulse mode, the current is important. The ripple current is sometimes rated for a capacitor in RMS current. Remembering that

P = I²R ; where R in this case is ESR

It is plain to see, that this is a power dispassion rating. ESR is the sum of in-phase AC resistance. It includes resistance of the dielectric, plate material, electrolytic solution, and terminal leads at a particular frequency. ESR acts like a resistor in series with a capacitor (thus the name Equivalent Series Resistance). This resister can cause circuits to fail that look just fine on paper and is often the failure mode of capacitors.

How to measure the capacitance of such big caps? The formula is here:

Uc = Usupply(1-2.718-t/(RC)).

Discharge your cap by shortening the terminals, connect your cap to powerful and stabilised power supply in series with resistor, charge the cap for few seconds and measure the voltage of the capacitor. And compare to theoretical values:

In old magazine (Radio – Радио) I found small article about calculating PWM power transformers. The formulas are for toroid core transformers, but I think, they are usable in standard E core transformers too.

1. Calculate the power of transformer: P_t=1.3*ΣP_n , W. The power of transformer is sum of all output powers multiplied by 1.3.

2. The core max power: P=S_c*S_o*f*b_max/150 , W. f=Hz, S_c=area of core section in cm², S_o=area of the “hole” in cm². B_max= max induction in Teslas, from core datasheet.

3. Number of turns in primary winding: w₁=0.25*10⁴*U₁/fB_maxS_c , in turns.

4. Max current in primary winding: I_1max=P/ηU₁ , A. (η = ~0.8)

5. Diameter of wire: d₁=0.6*√I_1max , mm. diameter is equal 0.6 multiplied by square root of max current.

6. Secondary (ant other) winding: w₂=w₁*U₂/U₁ , in turns.

There are lots of antispyware – addware software. Some of them are free, some commercial and some contains addware and spyware… So every windows user must know few place in their system to check and remove malicious software.

1. Start menu, Startup folder. Remove all strange, unused software.

2. Visit control panel, add remove programs. Uninstall all unused and bad software.

3. Start regedit. (Start, Run, regedit). For novice users visit only few known places. It is:
My Computer\HKEY_CURRENT_USER\Software\Microsoft\Winodows\CurrentVersion\ and check Run and RunOne branches. Delete all unused and alien software.

Also check:
My Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ and check Run, RunOnce and RunOnceEx…

4. Also check legacy files win.ini and system.ini from windows system folder. Check for [run] section.

5. Go to your Internet explorer properties- Temporary Internet Files->Settings->View Objects. And delete suspicious and “bad” objects.

Also press Control+Alt+Delete to invoke task manager. Look in the list for alien process. Stop it and if it starts again- it is bad software. Note the software name and search for it- it can be locate anywhere in hard disk. Try to delete the file. If windows denies access to file, try to rename file or rename parent folder. Sometimes, if software is starting in more complicated way it quite interesting to change virus executable to some text file. Just create with notepad any file and rename it to virus executable. Let the f**king virus run txt file

Cool, but dangerous tool is “HijackThis.exe”. This software shows all addware starting points. You can clean the computer by selecting software by mouse.

Be careful, you can kill your system if delete too much information.