Zetagi B47 Amplifier Issue: Signal Weakening Despite Power Amplifier Replacement & Relay Activation

Name: Zetagi B47 Amplifier Issue: Signal Weakening Despite Power Amplifier Replacement & Relay Activation
Uploaded: 2014-12-27T20:37:52+01:00
Description: Hello, I have an amplifier zetagi b47 which does not amplify the signal even makes it worse. I changed the power amplifier nothing changed, everything works. The relay activates the amplifier when pressing the pager and the power lack. I connected the median Watt with the amplifier switched on,...

Question

Hello, I have an amplifier zetagi b47 which does not amplify the signal even makes it worse. I changed the power amplifier nothing changed, everything works. The relay activates the amplifier when pressing the pager and the power lack. I connected the median Watt with the amplifier switched on,...

SP5IT · Answer

Do you have a HF probe?

kisiol · Answer

No, I only have a meter.

kriss51 · Answer

Which transistors you inserted and on which the amplifier originally worked, because there were several versions.

mickemaster · Answer

It is possible that the original was 2SC1969 and the friend put in a MOSFET.

kisiol · Answer

was put in c1969 although I do not know if it was the original because it does not have it since the news but earlier it worked and I bought the same after the exchange is still not working.

RAFPOL5 · Answer

You bought a so-called red peach or counterfeit, you have to organize a certain transistor from old stocks. Measure this old transistor in omomuja.

kisiol · Answer

I measured the old one and it turns out that it is good

RAFPOL5 · Answer

Without probe in advance You do not have to do anything. You need to check if the control signal comes on the base. Is the relay is good, i.e. when you press the microphone, it should close the contacts, that is, wox before. it works.

kisiol · Answer

the relay works, because it knocks and the plaque drops on the back Added after 7 [minutes]: after pressing the pear and turning the relay on, the transistor gets warm.

RAFPOL5 · Answer

The reception is correct after connecting the amplifier between the radio and the antenna.

kisiol · Answer

The receipt is correct.

kriss51 · Answer

The diagram on this theme fits? It's a multi-emitter transistor. On the meter will show that it is ok. But when it comes to amplifying the signal in advance. it will not do it. If you bought a new 2SC1969 in the shop, it's probably a coloring book and you will not get any reinforcement on it. Such a transistor is only suitable for the basket. Measure at least the quiescent current of course without control from the radio. You can insert IRF520 there, but you need to slightly change the divider setting the quiescent current.

kisiol · Answer

The other parts are used a little differently. I took a picture of the middle.

kriss51 · Answer

This transistor, however, looks like the so-called Coloring. The amplifier will not work on it. I suggest inserting IRF520 and measure the quiescent current in the drain circuit. It will be above 100mA so you have to adjust the pre-gate control circuit a bit. Please see how it looks in such an amplifier on two IRFs. It's about two resistors R3, R4. They ensure proper control of the goal. As R3, you can insert a perek to set the quiescent current.

http://elektrotanya.com/PREVIEWS/63463243/23432455/egyeb/zetagi_b47_sch.pdf_1.png

kisiol · Answer

Thank you for your help when I buy a new transistor I will appeal.

Anonymous · Answer

Only where you can buy? Did you read it? How to buy it in Because they at least give a guarantee of quality.

kisiol · Answer

Hello, I bought the transistor original and not painted and the amplifier works. Thanks for help. Maybe someone will tell you how to entrust this quiescent current and exactly at which points to take measurements.

kriss51 · Answer

It's a slightly different model of the amplifier, but the principle of measuring the quiescent current is the same. You have to disconnect in your case the collector supply of the final transistor and connect the Ammeter exactly as in the picture. You can even directly disconnect the collector from the rest of the system and connect the meter there. Only do the measurement without turning on the radio, and preferably do not connect it to the radio. The amplifier must be without control.

SP5IT · Answer

A bit not so kriss. Bias here is determined by the divisor r3 / r4 Poor solution, better to do on zenerce or LM317. In addition, the colleague has 1969 and the taste probably works in class C. M

kriss51 · Answer

I guess it works linearly because its model is probably from SSB. If not then class C.

The second thing is:

kisiol wrote:
Maybe someone will tell you how to entrust this quiescent current and exactly at which points to take measurements.

So I showed. Another thing is the fact that Bias in the presented diagram is implemented on the divider, and not more professionally on LM or zenerka. Let the author write if his amplifier has an SSB switch then everything will become clear. Best wishes and happy new year wish you.

Zetagi B47 Amplifier Issue: Signal Weakening Despite Power Amplifier Replacement & Relay Activation

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