Vintage radio - DUX (LW MW SW FM)

Ivan wrote:
The transistor is IMHO a MOSFET.

BR from Ivan

You are right. The MOSFET do not have an arrow.

No. Pin 2 of the LM386 connects to GND. Pin 3 must be connected to a resistive divider, which is separated by an input capacitor - the LM386 sets its voltage by itself. See typical schematics.

The transistor is IMHO a MOSFET.

BR from Ivan

Thanks Ivan,

The schematic:
http://www.cqham.ru/forum/attachment.php?attachmentid=34285&d=1241382228

The LM386 pin 2 must have V/2.

The source of the j-fet, 4u7, 1Mohm and the diode "common" must also have V/2.

Actually no (LM386 internal schematic):
https://www.ti.com/lit/ds/symlink/lm386.pdf?HQS=TI-null-null-sf-df-ds-null-wwe

Hi,
it is in the forums chapter:
Part 1
Part 2
Please follow a special thread started for KLOPIK.

BR from Ivan

Hi!

Could somebody please show me the deep link to the "Kloptik HF transciever"? I can not read russian, but can read a schematic:

http://www.cqham.ru/ (Harry's link got a "?" which confused the browser)

:-)

Hi Harry,
I expect you have seen a fragment of Glasslinger´s videos only, he has about 80 of them in his channel. Only some of them deal with antique electronics restoration.

I cannot open the cqham.ru server. It seems to be down just now. Russian ham projects are often quite complicated, no "weekend projects". I must look there when the server is on.

Russian is no problem for me. I really do not need translation. I am ready to help you with the original description provided that I open it...

VBR from Ivan

Hi Ivan,
Thank you for the link. I viewed the glasslinger video and it was really interesting.
Interresting how he has all old gear, but everything, even an audio spectrum analyser :-) (with a few "sproggies").
After this I saw a video about HiFi speakers being constructed. They even assembled the bass speaker unit with the cones and everything.
Yes, those were the days. https://www.youtube.com/watch?v=FH3mmRLjKxU

Have you seen the "Kloptik HF transciever" on www.cqham.ru?

I think that is a fantastic project and has really advanced features:

1 - Variable IF bandwidth
uses two 8MHz crystal filters, one "pulled" by varicap diodes

2 - IF amplifier is bi-directional that filters out unwanted side-band and any residual carrier

3 - IF gain is quite low, but the audio stage has a high-gain and a "constant volume" AF level control
audio output volume control is a pot in series with the speaker

4 - All discrete components; no "posh chippie-things"

5 - Complete TRX on a single board (except for linear amp and switching)

I tried so LTspice the amplifier stages and the voltage gain is very low (less than 10) but the Kloptik board has inductors on in/out that reduced the in/out load impedance to make the gain higher.

I spent a few hours reading the English translation of the document and there were several part that I had to think about to understand the original meaning. The author must be some sort of practical genious  
I was mega-impressed.

I think I will build something along those lines but with a few improvements of my own. For example, variable gain IF amplifiers (three) with more conventional AGC, fixed gain AF amplifier, but with the function of constant level. The guys elegant bi-directional amplifier may need to be a bit more complicated for me - fixed gain on TX and variable/AGC for RX.

Best regards from Harry - SM0VPO

Hi Harry,
a wonderful construction from the pre-pcb era. And those fancy air capacior trimmers!
The speaker switch is VERY unusual. I still have a cca 1966 MW radio made by Tesla (in Czechoslovakia, it has nothing to do with those electric cars). The earpiece connector is special, but it has the contacts arranged in the same manner as contemporary jacks.

A link to the glasslinger channel is here for your convenience.

VBR from Ivan

Hi Ivan,
Thank you very much. I will have a look at his YouTube channel

Here is my radio, and also the headset socket, with the "bicycle brake-cable" to the speaker switch:




BR Harry

Hi Harry,
you wrote a nice article. Look at Glasslinger on YouTube if you do not know his work. He seems to be very skilled in restoration of old radios and other electronics. He gives some uncommon advice and experience. He is even capable to make replicas of ancient tubes. I consider his videos interesting. (And he often wears a women dress in his videos. He probably feels comfortable in it.)

VBR from Ivan

Last Saturday I visited the Red Cross shop in Häggvik (N Stockholm) and I bought a transistor radio for 120 SEK (13.70 USD).

No model number on the outside, but there is a paper label intact inside it. I will try to take a few pictures of it.

Plywood wooden sides and back, covered with fire-engine red padded cloth. Two separate tuning dials: one for FM and the other for AM bands. Two drive belts (now fixed with original drive cord).

The radio has got history. It has quite possibly been the family radio in the window for many years, manufactured in 1962. There are micro spots of paint all over it, but nothing that cannot be washed off. It was probably entertaining people while they decorated / renovated their home. The front grille is plastic - one formed sheet, fixed in position with 8 stubs that fit through holes in the radio front panel. A hot iron was used to melt the inside stubs to secure it.

The headphone socket is 1/4", but inside there are two nylon plugs in calipers. When you plug in headphones these calipers separate and pull a cord, just like the brake cable on a pedal bike. The drive wire pulls a switch.

There is an incandescent lamp to illuminate the dial when you press a button.

Internally there are two RX converter modules, one for AM (465kHz IF) and one for FM (10.7MHz). The IF amplifier uses four AF117 germanium transistors. There are another two AC176-looking germanium for the audio output stage and another pair of germanium transistors in the low-level audio stage. The audio driver feeds a ring ferrite audio transformer, about 4cm diameter. The speaker is an efficient 10" speaker that gives a really full sound. It is really loud and amazing quality sound.

On the FM band I could hear a couple of stations without and antenna (yes the electronics are working). With an antenna the band is full. A "modern" commercial radio led me to believe I was in a bad coverage area, but this radio gives good solid reception. After 60 years it is still perfectly aligned. It also has 8 "beehive" trimmers and a switching system that reminds me of a telephone switch station.

The volume and tone controls are perfect and silent. No switch cleaner was used on any switches. I have removed about 50g of dust and "growth", so it now looks like new on the PCB.

This radio was not just manufactured, it was "built".

Naturally the case is a bit battered in places, but there is some spare material overlapping inside the rear cover so I have a source of the original material to patch the case and make it look like new.

I am really excited to own a radio like this. In the 60s and 70s a transistor radio was always built to a price. In the 90s they began to remove IF transformers, even the common 10mm Toko type. It is strange to hold a radio like this in your hand when you can feel the quality, even after 60 years. The radio was built by DUX, Stockholm, which was later bought up by Philips. I cannot find any data or photographs of the radio, but I will try to include some here.

It just goes to show that modern radios come and go, but older radios last a whole lifetime.

I just thought I would share some nostalgic info with you. very best regards from Harry - SM0VPO