Injecting external source signal into VEF 206's amplifier. - UK Vintage Radio Repair and Restoration Discussion Forum

Feredzhanov · 18th Jan 2021, 3:41 pm

Hello,
I've started a kind of a project, but stumbled with a little problem, so I've found that forum, where I can see there are people, that know way more than me. So I've decided to just ask. Here's the thing. I have an old working VEF 206. It's working, except it doesn't have an FM reciever, and besides the standarts here have changed, so even the old Selena had to have it's chip changed to work with the western standarts. So what I've decided is, to remove the whole receiving part of the VEF, and replace it with a multifunction board, that has the FM capabilities, but also has Bluetooth, USB, TF, etc. capabilities. The problem is, that the amplifier that board has, if not strong enough to power the VEF's speaker. So here's where I've stumbled with the problem, that should be easy enough for many of you to just tell me. Where should I connect the board's output pins (3 of them, R+, L+ and GND, but since the VEF has only one speaker I'll most likely have to shorten R+ and L+) so that I "inject" that signal from the board, before the amplifier part, generally, I want to only use the amplifier of the radio, and will remove everything else, cause it's not usable for me anyway.
Sorry for the long post, hope you got what I want to do, and will be glad if you help me in modifying the VEF and turn it into a bluetooth speaker with radio capabilities. Thanks in advance.

Vladimir

Al (astral highway) · 18th Jan 2021, 4:03 pm

HI Vladimir and welcome to the forum!

There isn't a general purpose answer to your question. It depends on what you have in front of you.

It sounds like you were intending to drive the loudspeaker directly from the board and then changed your mind and are asking to output the signal to the audio-frequency amplifier of the radio?

Can you clarify?

In any case, first priority, post some good photos. Clear and detailed.

The photos needs to be detailed enough for people to see what chip/s are on board.

Take one of the whole thing from above, then the underside, at the very least. Also provide power supply voltage details.

Then we will be able to see if the board is intended to drive a loudspeaker directly. It is unlikely.

*It is also unlikely that you will be able to involve the radio's audio amplifier stage effectively unless you know what you are doing. Please can you state your level of knowledge?

P.S: why bother to remove what you don't need? You could just leave it intact. There is plenty of room to add a little bluetooth module.

Cheers

ms660 · 18th Jan 2021, 4:26 pm

Tape socket, pins 1 (signal) and 2 (ground)?

Lawrence.

Feredzhanov · 18th Jan 2021, 4:30 pm

Hi,
and yes, the board is too quiet, when connected directly to the speaker. On the picture's you'll see the VEF 206 board, also the board that I'm trying to add to the system. Removing the radio modules mainly bercause it'll make it much more lighter, but also, cause if not I'll still have noice from the radio trying th pick up signal and failing. The power supply, currently, is a DC generator, the board generally is designed for car and 12V (not sure about 24V), but works exactly the same way on 9V (I assume it actually need 5V) so I may still use the original 6 batteries to power it up, or just add a DC adaptor (that we'll see in the future). Also, the added board is currently connected through the volume potentiometer, that also turns the power down, so I use it to power both the added board and the old electronics aswell. As for my knowledge, I'd say, average. I've worked this for quite some time, but mostly on SMD boards, where everything is marked, and I'm not good with radio electronics, especially the old school ones. I'll also add the schematic of the radio.

Feredzhanov · 18th Jan 2021, 4:31 pm

Isn't the tape socket for recording radio for a tape recorder, not using the radio as speaker?

ms660 · 18th Jan 2021, 4:45 pm

Quote:

Originally Posted by Feredzhanov

Isn't the tape socket for recording radio for a tape recorder, not using the radio as speaker?

As well as being connected to the output of the detector, pin 1 on the tape socket is connected to the input of the receivers audio amplifier, disconnect the feed from the detector and feed a summed output from your device to pin 1.

Lawrence.

llama · 18th Jan 2021, 4:56 pm

On the circuit diagram it looks like "b" and "c" of the volume control are swapped.
Graham

Feredzhanov · 25th Jan 2021, 4:02 pm

Quote:

Originally Posted by ms660

Quote:

Originally Posted by Feredzhanov

Isn't the tape socket for recording radio for a tape recorder, not using the radio as speaker?

As well as being connected to the output of the detector, pin 1 on the tape socket is connected to the input of the receivers audio amplifier, disconnect the feed from the detector and feed a summed output from your device to pin 1.

Lawrence.

I just didn't got the "detector" part.

ms660 · 25th Jan 2021, 4:11 pm

C85 in the schematic.

Lawrence.

Feredzhanov · 25th Jan 2021, 4:29 pm

Quote:

Originally Posted by ms660

C85 in the schematic.

Lawrence.

Thanks, I'll have to search for it, cause I think it's somewhere on the curcuit board, between all the elements. Other than that, it worked, I'll have to clean the potentiometer a bit, cause it makes noices while turning (it's 40+ years old, no wonder it does that).

I have another question too. I think it's less related to the model this time. So I've connected the antenna pin on the new board, to the antenna of the radio (directly to the telescopic one), but I get nearly nothing with it. I get the the national radio, that most radio recievers can get even w/o pulling out the antenna, and it's also with a lot of noice. Do I have to add something on the way to that antenna, or which antena should I use, cause there are like 3 inside the radio? Thanks in advance again, and I'll post pictures, when it's completed.

ms660 · 25th Jan 2021, 7:25 pm

Disconnect the original wire to the telescopic antenna then connect a wire from the telescopic antenna to the antenna input of your FM device.

Lawrence.

Feredzhanov · 25th Jan 2021, 10:05 pm

Quote:

Originally Posted by ms660

Disconnect the original wire to the telescopic antenna then connect a wire from the telescopic antenna to the antenna input of your FM device.

Lawrence.

Yeah, that's what I did (it was easier to disconnect it from the whole system, then solder another one in place)

Feredzhanov · 26th Jan 2021, 11:25 pm

Ok, screw the last one. Guess I didn't solder it well, now it worked quite fine. Follows some cleaning and putting the new board in place. Also thinking on doing such modding for some old radio recievers, cause it'll look kind of cool. One of them is made 1925 and it's Bulgarian, that will be an interesting project since most likely, I won't be able to even find schematics

18th Jan 2021, 3:41 pm	#1
Feredzhanov Diode Join Date: Jan 2021 Location: Sofia, Bulgaria Posts: 7	Injecting external source signal into VEF 206's amplifier. Hello, I've started a kind of a project, but stumbled with a little problem, so I've found that forum, where I can see there are people, that know way more than me. So I've decided to just ask. Here's the thing. I have an old working VEF 206. It's working, except it doesn't have an FM reciever, and besides the standarts here have changed, so even the old Selena had to have it's chip changed to work with the western standarts. So what I've decided is, to remove the whole receiving part of the VEF, and replace it with a multifunction board, that has the FM capabilities, but also has Bluetooth, USB, TF, etc. capabilities. The problem is, that the amplifier that board has, if not strong enough to power the VEF's speaker. So here's where I've stumbled with the problem, that should be easy enough for many of you to just tell me. Where should I connect the board's output pins (3 of them, R+, L+ and GND, but since the VEF has only one speaker I'll most likely have to shorten R+ and L+) so that I "inject" that signal from the board, before the amplifier part, generally, I want to only use the amplifier of the radio, and will remove everything else, cause it's not usable for me anyway. Sorry for the long post, hope you got what I want to do, and will be glad if you help me in modifying the VEF and turn it into a bluetooth speaker with radio capabilities. Thanks in advance. Vladimir

18th Jan 2021, 4:03 pm	#2
Al (astral highway) Dekatron Join Date: Nov 2006 Location: London, UK. Posts: 3,496	Re: Injecting external source signal into VEF 206's amplifier. HI Vladimir and welcome to the forum! There isn't a general purpose answer to your question. It depends on what you have in front of you. It sounds like you were intending to drive the loudspeaker directly from the board and then changed your mind and are asking to output the signal to the audio-frequency amplifier of the radio? Can you clarify? In any case, first priority, post some good photos. Clear and detailed. The photos needs to be detailed enough for people to see what chip/s are on board. Take one of the whole thing from above, then the underside, at the very least. Also provide power supply voltage details. Then we will be able to see if the board is intended to drive a loudspeaker directly. It is unlikely. It is also unlikely that you will be able to involve the radio's audio amplifier stage effectively unless you know what you are doing. Please can you state your level of knowledge? P.S: why bother to remove what you don't need? You could just leave it intact. There is plenty of room to add a little bluetooth module. Cheers __________________ Al Last edited by Al (astral highway); 18th Jan 2021 at 4:08 pm.*

18th Jan 2021, 4:26 pm	#3
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Injecting external source signal into VEF 206's amplifier. Tape socket, pins 1 (signal) and 2 (ground)? Lawrence. Last edited by ms660; 18th Jan 2021 at 4:35 pm. Reason: extra info

18th Jan 2021, 4:31 pm	#5
Feredzhanov Diode Join Date: Jan 2021 Location: Sofia, Bulgaria Posts: 7	Re: Injecting external source signal into VEF 206's amplifier. Isn't the tape socket for recording radio for a tape recorder, not using the radio as speaker?

18th Jan 2021, 4:56 pm	#7
llama Octode Join Date: Jun 2006 Location: St Osyth, Nr Clacton, Essex, UK. Posts: 1,482	Re: Injecting external source signal into VEF 206's amplifier. On the circuit diagram it looks like "b" and "c" of the volume control are swapped. Graham __________________ Half my stuff is junk - trouble is, I don't know which half!

25th Jan 2021, 4:11 pm	#9
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Injecting external source signal into VEF 206's amplifier. C85 in the schematic. Lawrence.

25th Jan 2021, 7:25 pm	#11
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Injecting external source signal into VEF 206's amplifier. Disconnect the original wire to the telescopic antenna then connect a wire from the telescopic antenna to the antenna input of your FM device. Lawrence.

26th Jan 2021, 11:25 pm	#13
Feredzhanov Diode Join Date: Jan 2021 Location: Sofia, Bulgaria Posts: 7	Re: Injecting external source signal into VEF 206's amplifier. Ok, screw the last one. Guess I didn't solder it well, now it worked quite fine. Follows some cleaning and putting the new board in place. Also thinking on doing such modding for some old radio recievers, cause it'll look kind of cool. One of them is made 1925 and it's Bulgarian, that will be an interesting project since most likely, I won't be able to even find schematics