Alan28 - How to remove the modulation limitation on Alan 28.

Question

Greetings to everyone, sorry for the grammatical errors I use a translator. I read on the net that the Alan 28 leaves the factory with a limitation to the modulator in fact my Alan 28 has a very bad modulation, you have to remove the components that cause the limitation to have a good modulation...

SP5IT · Answer

Remove Q510 to disable limiter. Replace dynamic microphone with electret capsule.

Asterix5867 · Answer

OK SP5IT thanks for answering me.

Asterix5867 · Answer

I am sending you attached photos. Could you kindly tell me where the Q510 and R650 are located? I have the scheme, but it looks bad if I try to enlarge the image it grains.

SP5IT · Answer

Sorry, I don't remember.

HD-VIDEO · Answer

Q510: And R650 >> R580 has a value of 6k8 - I do not know why the replacement

SP5IT · Answer

That there would be a slightly stronger signal from the dynamic cartridge. As it has a microphone with amplification, you can not move it.
Anyway, I recommend replacing the cartridge with an electret one, if it is still on the original one.

HD-VIDEO · Answer

But the R580 is an attenuator parallel to the incoming signal, and the R650 doesn't know where it is.

Asterix5867 · Answer

I found the Q510, but I can't find the R650.

SP5IT · Answer

Please share a clearer diagram, it looks like 650 for me, but I don't have a readable one.

gumisie · Answer

@ HD-VIDEO Do you have a service shop with a clear diagram? Not only the author of the topic has a problem with it (clear diagram). Regards.

Asterix5867 · Answer

the problem is this, that there is no clear pattern on the net, the best I could find is this. Send the link:

HD-VIDEO · Answer

I have an org. instructions, the diagram also blends a little but is it a parallel resistor to the pot. modulation and cannot be reduced

Asterix5867 · Answer

HD-VIDEO I don't understand your message, you could be clearer. Unfortunately, when using the translator, certain phrases and words are not translated well.

Added after 1 [minutes]:

HD-VIDEO I don't understand your message, you could be clearer. Unfortunately, when using the translator, certain phrases and words are not translated well.

SP5IT · Answer

Leave resistor, remove only transistor. What microphone are you using?

Asterix5867 · Answer

SP5IT friend, I have carefully checked the parts list of the manual and the R650 resistor does not exist, there is the R690 and R691 but the R650 is not in the list and in the schematic. Maybe you wrote wrong?

Added after 2 [minutes]:

SP5IT friend, I'm using the original microphone.

SP5IT · Answer

Put electret capsule instead of dynamic and mod radio inside as on attached schematic. ele.jpg Download (23.38 kB) 8V is present in many places inside radio. Mike

Asterix5867 · Answer

ok which of these mics is right? I send attached photos.

Asterix5867 · Answer

or maybe I have to fit one of these into a microphone? I send attached photos

gumisie · Answer

I would call the F-16. EDIT: In the case of such a microphone insert, the CB should be modified in accordance with the diagram in # 17

Asterix5867 · Answer

if I understand correctly I have to remove the TR510 and mount the microphone Alan F-16 . if, on the other hand, I want to mount a microphone that needs power supply like the one in the photo I sent, I have to make the change according to the scheme in # 17.

gumisie · Answer

You don't necessarily have to disassemble the Q510. The F-16 microphone has a battery-powered preamplifier. I would connect this microphone and check the AM modulation level.

Asterix5867 · Answer

I was wrong I wanted to write remove TR 510 and use the original microphone, it is clear that the Alan F-16 microphone is internally amplified.

SP5IT · Answer

The F16 has a toilet-like modulation and the limiter in the 28 is kicked and spoiled the audio.

gumisie · Answer

In the sense that he has so factory, is it damaged?

Asterix5867 · Answer

I take off the limiter and use the original microphone, and let's see how it goes. I'll let you know. I take this opportunity to ask you, how do you control the modulation? Do you need a spectrum analyzer or just an oscilloscope?

gumisie · Answer

I don't know what Kol. Michał (SP5IT) uses, I used the oscilloscope when I was still repairing CB_radia.

SP5IT · Answer

I use oscilloscope and signal generator.

Asterix5867 · Answer

what kind of low frequency or high frequency generator? where do you get the signal to be analyzed on the oscilloscope?

SP5IT · Answer

I use the PC application Dual Function Generator mV, 1 kHz tone.

Alan28 - How to remove the modulation limitation on Alan 28.

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