Klaas's magnetic deflection amplifier circuit

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Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 1:00 pm

I have been working on klaas's magnetic deflection amplifier trying to fault find some problems i am having with it...
There is very little on the forum on the subject so putting it up here as a reference ...Klaas's procedure on how to test the circuit is something that should be kept .
BTW i have the original other circuit working but i am interested in using Klaas's circuit to learn about these things more than just copying a circuit and hoping for the best it works

1. - Disconnect the input signal to the 6k8 resistor,
- connect the deflection coil to the output
- power up the deflection amplifier.
- Multimeter: measure the voltage at the emitter op the first transistor 549,
- it should be - 0.6 volt.
- this is the voltage over the 1N4148 diode.

2. - Multimeter: measure the voltage at the base of the 549,
- it should be close to zero volts. Less than 0.1 volt.

3. - Multimeter: voltage at the collector of the 549,
- it should be about + 0.6 volt.
4. - Multimeter: voltage at the base of the 548: should be also + 0.6 volt.
5. - at the base of the 558 (PNP) should be - 0.6 volt.
6. - at the collector of the 548 (NPN) should be + 11.3 volts
7. - at the collector of the 558 (PNP) should be - 11.3 volts
8. - at the common collectors of the BD135-BD136 (or 137-138, or 139-140):
- should be close to zero, less than 1 volt.
9. - at the top of the 8.2 ohm: should be close to zero volts.
Attachments
Deflectionampl.GIF
Deflectionampl.GIF (5.2 KiB) Viewed 6064 times
Last edited by Harry Dalek on Tue Nov 28, 2017 4:51 pm, edited 2 times in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 2:24 pm

Deflection amplifier 1 .....Test on both yoke Vertical and horizontal coils

Yoke coil testing 7 ohm left 2 readings .....................................1 ohm yoke coil right 2 readings

input npn BC548 transistor
with 6.8k grounded below
Emitter -0.06 -0.07 -0.63 -0.63
Base -0.08 -0.09 -0.01 -0.01
collector+1.40 +1.62 steady voltage -0.20 -0.38 slowly drops in reading i think due to the 8ohm yoke
resistor heating
2nd 548 npn Transistor

Base +1.40 +162 -0.20 -0.38
collector +13.20 +14.36 +11.59 +11.60

3rd PNP BC559 Transistor

Base +0.70 +0.91 -0.50 -0.60
collector -12.43 -12.13 -7.97 -7.98

power transistors
collector -0.06 -0.21 -6.70 -735

8ohm yoke coil -0.03 -0.17 -6.56 -712

Deflection Amplifier 2 tests

7 ohm yoke 1 ohm yoke coil right readings

input npn BC548 transistor
with 6.8k grounded below
Emitter -0.65 -0.65 -0.65 -0. 65
Base 0.00 0.00 -4.86 -1.97
collector -0.65 -0.65 +4.93 +4.95

2nd 548 npn Transistor

Base -0.65 -0.65 +4.93 +4.95
collector +11.12 +11.12 +4.96 +4.96

3rd PNP BC559 Transistor
Base +0.20 +0.20 +4.24 +4.24
collector -11.81 -11.81-8.33 -8.36


power transistors
collector +2.20 )2.29 -8.00 -8.00

8ohm yoke coil +1.39 +1.39-4.77 -4.80
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 4:48 pm

I think deflection amplifier one input transistor might be a dud again looking at my readings ..

Photo 1 deflection amplifiers marked 1 ,2

High watt resistors not in use at the moment using 8 ohm ones and the height width trimmers circuits before the 6.8k input BC548 transistor also not used due to these voltage tests for now .

I also am a bit worried about the 1 ohm deflection yoke coil that's very low .looking at the yoke coil on the 1 ohm side i am wondering how its wired i will in time disconnect one side and test perhaps the 2 coils are in parallel ? find out it .
Attachments
IMG_0303.JPG
IMG_0295.JPG
IMG_0297.JPG
IMG_0296.JPG
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Robonz » Tue Nov 28, 2017 6:14 pm

HI Harry

Beware the BC548 and 558 can be very different. The will say 548A 548B and 548C This is the HFE which can imbalance things. You should really get some matched ones and test them to see what the HFE is matched or the deflection will be asymmetrical. You should also ask which one is supposed to be used.

Another option is to use a common audio amplifier chip starting with TDAxxxx, these are well known for deflection amplifiers.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 6:39 pm

Robonz wrote:HI Harry

Beware the BC548 and 558 can be very different. The will say 548A 548B and 548C This is the HFE which can imbalance things. You should really get some matched ones and test them to see what the HFE is matched or the deflection will be asymmetrical. You should also ask which one is supposed to be used.

Another option is to use a common audio amplifier chip starting with TDAxxxx, these are well known for deflection amplifiers.


I didn't think of that here but in the past checking the same transistors i did find they varied as you say must be the reason if any thing there is a difference in the same 2 circuits .
I will ask Klaas about the npn BC 548 549 or pnp 559 if they are a problem i will have a look what they are .
Yes i do have those audio amps but here i am interested in just getting this transistor one going to learn ..,,,i find getting a crt with magnetic deflection working correctly much harder than electrostatic another thing to learn on my endless list .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 6:56 pm

Looked into the 1 ohm yoke coil 4 wires each side of the coil so its around 2 ohm 2 ohm or 4 ohm either side so it looks like it could be wired for an increased resistance another thing to ask Klaas here ..can get 8 ohms if needed .
EDIT
mistake in the drawing its pins 5 and 8 also 4 ohms not 5 and 6 i will correct the drawing soon
Attachments
IMG_0317.JPG
IMG_0316.JPG
IMG_0315.JPG
Last edited by Harry Dalek on Tue Nov 28, 2017 7:54 pm, edited 2 times in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Klaas Robers » Tue Nov 28, 2017 7:08 pm

There is no point in the difference of the amplification factor of the transistors. The amplifier is so heavily feeded back, that this will eliminate all (relatively small) transistor differences. That is the strength of these amplifiers.

Also the coil resistance should do little to nothing to the static measurements, that is with the input (resistor of 6k8) floating or grounded. The only thing I can think of is that in one situation (coil of 1 ohm) the amplifier is wildly oscillating. You can see that with your oscilloscope. If that happens a small capacitor (1 nF) from the collector of the input transistor to ground will eliminate that. Make that capacitor as low as possible, just eliminating oscillations.

Any way, do these tests firstly with the preset potentiometer of 2k2 in the shorted position. The voltage between the bases of the 548 and 558 should be about 1 volt. Later you may preset that to a setting that will give the least distortion.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Klaas Robers » Tue Nov 28, 2017 7:16 pm

What is the resistance of one of these windings? Is it 4 ohm?

If the 4 parallel windings was 1 ohm, I would say one winding = 4 ohm.
- All 4 in series will be 16 ohm,
- two of them in parallel will be 2 ohm
- these two parallel circuits in series will be 4 ohm.
- That will be suitable.
So 1 ohm, 4 ohm or 16 ohm. Make your choise!
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Re: Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 7:42 pm

Klaas Robers wrote:There is no point in the difference of the amplification factor of the transistors. The amplifier is so heavily feeded back, that this will eliminate all (relatively small) transistor differences. That is the strength of these amplifiers.


So does not matter what type of transistor that's good to know .

Also the coil resistance should do little to nothing to the static measurements, that is with the input (resistor of 6k8) floating or grounded. The only thing I can think of is that in one situation (coil of 1 ohm) the amplifier is wildly oscillating. You can see that with your oscilloscope. If that happens a small capacitor (1 nF) from the collector of the input transistor to ground will eliminate that. Make that capacitor as low as possible, just eliminating oscillations.


Here is a Question should i use the 1 ohm coil as is or rewire to a higher resistance ?
I can check the oscillation if its there on the 1 ohm coil next time i hook it up ..

Any way, do these tests firstly with the preset potentiometer of 2k2 in the shorted position. The voltage between the bases of the 548 and 558 should be about 1 volt. Later you may preset that to a setting that will give the least distortion.


Ok i will check on my scope for oscillation and follow the suggestions,
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 7:49 pm

Klaas Robers wrote:What is the resistance of one of these windings? Is it 4 ohm?

If the 4 parallel windings was 1 ohm, I would say one winding = 4 ohm.
- All 4 in series will be 16 ohm,
- two of them in parallel will be 2 ohm
- these two parallel circuits in series will be 4 ohm.
- That will be suitable.
So 1 ohm, 4 ohm or 16 ohm. Make your choise!

[/quote]

One side of the coils has 4 wires two 2 ohm readings and a 4 ohm on that side.... same on the other side.

So its pretty much 4 ohm or 8 ohm depending on wiring if it does not mater that's good i can test what works better .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Robonz » Tue Nov 28, 2017 7:55 pm

I was not worried about the mismatched transistors not working. I have had it where the scan becomes asymmetrical with badly miss-matched hfe's.

You can also measure the BD135 and BD136 base to emitter. They should be around 0.7 volts with no signal running.

If you start off with 8 ohms it is safer as it will be less load until you get this thing running.

Harry, did you add the two 10uF caps?, It won't stop it working but its good to complete the circuit
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Re: Klaas's magnetic deflection amplifier circuit

Postby Klaas Robers » Tue Nov 28, 2017 10:11 pm

Harry I don't understand your measurements on the deflection yoke.

Now you have numbered the wires, after you desoldered the lugs that had each 4 wires connected, isn't it?

I assume wires 1, 2, 3 and 4 were at the left lug,
and wires 5, 6, 7 and 8 on the right lug, yes?
Or is it differently? How?

Because if wire 4, came from the left lug, measured to wire 5, which came from the right lug, shows a shortage, that is zero ohms, then I don't understand it any more...... Shorted will say: connected, as if it were a short wire.
This is opposed to "open", no connection at all.

I should assume, if wires 1, 2, 3 and 4 came from the left solder-lug and 5, 6, 7 and 8 from the right solder lug, that after desoldering them:
1 is not connected to 2, or to 3, or 4,
but e.g 1 is having 4 ohms to 5,
2 is having 2 ohms to 6
and the same for 3 to 7 and for 4 to 8

Can you still restore the original situation? Or did you so many changes that you don't know any more how it all was?
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Re: Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 10:13 pm

Robonz wrote:I was not worried about the mismatched transistors not working. I have had it where the scan becomes asymmetrical with badly miss-matched hfe's.

You can also measure the BD135 and BD136 base to emitter. They should be around 0.7 volts with no signal running.

If you start off with 8 ohms it is safer as it will be less load until you get this thing running.

Harry, did you add the two 10uF caps?, It won't stop it working but its good to complete the circuit



Yes Keith Klaas got me to do a reading on the collectors of the BC 458 and BC559 which go to the bases of the power transistors but they do read near power supply voltages below klaas mentions that's correct in range ..my readings below and klaas procedure range readings//
I rather a higher coil resistance i will try that for a start and see what happens but first i need to find out why the difference in deflection amplifier test readings nice to get them close to identical or close as i can /
No not the 10uf caps yet on circuit or the 100 ohm across the yoke coil but i did try them on on crt test ..yes i need to do that solder them in and i will for the next testing.

Deflection amp one... left 7 ohm yoke coil readings right 1 ohm yoke coil ...left also with floating input ist input transistor right 6.8k to input transistor gives a slight voltage difference when its grounded ...
2nd 548 npn Transistor
Base +1.40 +162 -0.20 -0.38
collector +13.20 +14.36 +11.59 +11.60
3rd PNP BC559 Transistor
Base +0.70 +0.91 -0.50 -0.60
collector -12.43 -12.13 -7.97 -7.98
.............................................
Deflection amplifier 2
2nd 548 npn Transistor
Base -0.65 -0.65 +4.93 +4.95
collector +11.12 +11.12 +4.96 +4.96
3rd PNP BC559 Transistor
Base +0.20 +0.20 +4.24 +4.24
collector -11.81 -11.81-8.33 -8.36

1. - Disconnect the input signal to the 6k8 resistor,
- connect the deflection coil to the output
- power up the deflection amplifier.
- Multimeter: measure the voltage at the emitter op the first transistor 549,
- it should be - 0.6 volt.
- this is the voltage over the 1N4148 diode.

2. - Multimeter: measure the voltage at the base of the 549,
- it should be close to zero volts. Less than 0.1 volt.

3. - Multimeter: voltage at the collector of the 549,
- it should be about + 0.6 volt.
4. - Multimeter: voltage at the base of the 548: should be also + 0.6 volt.
5. - at the base of the 558 (PNP) should be - 0.6 volt.
6. - at the collector of the 548 (NPN) should be + 11.3 volts
7. - at the collector of the 558 (PNP) should be - 11.3 volts
8. - at the common collectors of the BD135-BD136 (or 137-138, or 139-140):
- should be close to zero, less than 1 volt.
9. - at the top of the 8.2 ohm: should be close to zero volts.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Klaas Robers » Tue Nov 28, 2017 10:24 pm

Why are there 4 wires in parallel?

In a normal TV the horizontal deflection is running a saw tooth of 16 kHz. Then, especially during the fast fly back, there are such high frequencies running, that the current has no time to run deeper in copper wires. So they run only in the surface of the wire. This is called the "Skin Effect".

The horizontal deflection coil needs to have a low resistance. Normally this is obtained by a thick wire. But then, due to the skin effect, the current runs only in the outer part of the wire, so the copper is only partly used.

This can be overcome by using several mutually insulated wires in parallel. At both ends they are soldered together. That is why the H-coil is made up of 4 wires in parallel. They all have the same length, so they should have the same resistance after you disconnected them all, at both ends. Then you should find 4 wires that are fully insulated from each other.
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Re: Klaas's magnetic deflection amplifier circuit

Postby Harry Dalek » Tue Nov 28, 2017 10:49 pm

Klaas Robers wrote:Harry I don't understand your measurements on the deflection yoke.

Now you have numbered the wires, after you desoldered the lugs that had each 4 wires connected, isn't it?


8 wires all together

4 one side 4 the other

2 ohm 2 ohm left side so 4 ohm same readings right side

I assume wires 1, 2, 3 and 4 were at the left lug,
and wires 5, 6, 7 and 8 on the right lug, yes?
Or is it differently? How?


That's correct yoke as 1 ohm all 4 were connected in parallel one side and the other

Because if wire 4, came from the left lug, measured to wire 5, which came from the right lug, shows a shortage, that is zero ohms, then I don't understand it any more...... Shorted will say: connected, as if it were a short wire.
This is opposed to "open", no connection at all.


sorry if you have a look again i noted i made a mistake in my drawing as to the pins pins 1 to 4 left side measure 4 ohms right side 5 and 8 measure also 4 ohms so connect 4 and 5 pins i get 8 ohms on pins 1 and 8 now .

I should assume, if wires 1, 2, 3 and 4 came from the left solder-lug and 5, 6, 7 and 8 from the right solder lug, that after desoldering them:
1 is not connected to 2, or to 3, or 4,
but e.g 1 is having 4 ohms to 5,
2 is having 2 ohms to 6
and the same for 3 to 7 and for 4 to 8


Yes having 8 wires is confusing ! and wiring of the yoke i have measured left coils and right coils .. all 4 wires disconnected as you think show 4 ohms each side ....using say pins 1 and 2 i can get 2 ohms and 3 and 4 another 2 ohms ...............I don't really know if pins 1 2 3 and 4 are pins 4 2 3 or 1 back the front but best i can do since i didn't see how it was wired up .guessing here .suppose find out on a deflection screen test .

Can you still restore the original situation?


yes very easy to do just resolder 4 wires one side same the other they are all together near their lug

Or did you so many changes that you don't know any more how it all was?

[/quote]

not really a problem that i could not reverse i would not of started other wise ,,,,,,,,,,the 7 ohm coil looks more tricky if it needs work but will not touch it if i don't need to ,
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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