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Old 11th Nov 2020, 10:33 pm   #21
cathoderay57
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Default Re: First project (mini mod)

Hi Barry, You can get an illuminated magnifier on a sort of angle-poise mount for between 25 - 30 that would really help. I am seriously thinking about getting one myself since even with reading glasses on I am struggling with stripboard soldering. Just google it - seem to be available from several sources. Cheers, Jerry
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Old 12th Nov 2020, 7:28 pm   #22
Ian - G4JQT
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Default Re: First project (mini mod)

The OP should make sure the fet Q1 has the gds in the right holes. I'd recommend the BF256 rather than the original 2N3819. But they have different pin outs! Beware!!

Good luck.

Ian
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Old 12th Nov 2020, 8:51 pm   #23
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Default Re: First project (mini mod)

Is this a good idea making my own circuit board so that I can see to solder. Do i carry on or do i give it up as a bad job? My plan is to cut out where it needs to be after I have soldered it together and placed hot glue between the wires to stop them shorting. Am I mad or what?

Thanks Barry
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Old 12th Nov 2020, 9:42 pm   #24
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Is this a good idea making my own circuit board so that I can see to solder. ... Am I mad or what?
Hello again Barry, I'd say that's inventive! There used to be a style of construction called 'breadboard' which beginners started with, and could involve nails and bits of wire and literally, a bread-board! I started like this in my early teens before I owned a soldering iron.

Your parallel wires idea is similar in some ways.

It's worth a try, although it has drawbacks. One is that it will be tricky to solder an integrated circuit into all that. The other one is to do with the stability of a radio frequency circuit laid out like that.

But it looks like you are on the exciting first steps of a path...

So there is nothing to lose by trying and seeing what happens! It's much preferable to you walking away from it! Keep us posted, there's plenty of support here!
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Old 12th Nov 2020, 10:48 pm   #25
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Is this a good idea making my own circuit board so that I can see to solder. Do i carry on or do i give it up as a bad job? My plan is to cut out where it needs to be after I have soldered it together and placed hot glue between the wires to stop them shorting. Am I mad or what?

Thanks Barry
That's one way Barry.

But to make things easier, try and get hold of a bit of printed circuit board - single sided will be all you need, but double sided is just as good in this case.

Google images of "electronics ugly construction" and you can see what can be achieved, especially if you also cut some small 5mm x 5mm-ish bits of copper board and super glue them down as needed. This is often called Manhattan construction.

But all I do is use single-sided copper board and use a PCB layout to wire the components underneath and the copper surface as the ground plane and negative, with countersunk holes though the top for leads to pass through. Photo of top of board attached. I can't find one of the underneath, but just imagine printed copper tracks replaced by wires.
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Old 12th Nov 2020, 11:22 pm   #26
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I wrote up this alternative to a PCB technique in September 1995 HRT magazine. Unfortunately that issue is missing from worldradiohistory.com/

So if anyone has a copy...
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Old 13th Nov 2020, 12:43 am   #27
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Default Re: First project (mini mod)

Very neat build indeed. I would have been interested in your write up. I use Manhattan style construction all the time, it’s great.

I wonder though if the OP is needing to keep things simple and clear for the time being. It’s great to have a challenge and there’s also a line which feels enough but not overwhelming. I hope Barry can find that line
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Old 15th Nov 2020, 11:55 am   #28
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Hello, got all the components on apart from L1 and L2. L1 number 2 pin has to be stretched out and put in the hole next to it. Then in between 3 and 4 there is a pin comes out but I do not know what number this goes to, is it the actual metal surround pin? For L2 the number 2 pin seems to go in between the circuits and the wire coming from 1 and 6 where has this come from?
Tried to explain this as best as i can. Hope I have not confused you.

Thanks Barry
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Old 16th Nov 2020, 9:05 pm   #29
baza100
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Default Re: First project (mini mod)

Don't laugh as you look at my effort but still struggling to find where the pins go on L1 and L2. As soon as I get them in I can try it. Very much doubt it will work first time but you never know. Thanks Barry
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Old 17th Nov 2020, 12:14 pm   #30
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Default Re: First project (mini mod)

Barry, pin 2 on L2 isn't used, so I think you could drill a larger hole for it on the board between the two tracks, neither of which appear to be used also. The link between 1 and 6 appears to be connecting L2's metal case to earth - there's a similar link on L1 between 3 and 4. You'll need to make a link to pin2 on L1, as your drawing shows.

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Old 19th Nov 2020, 9:44 pm   #31
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Hello it works in a fashion. I only get it to play through the radio when I am touching the round thing i have marked in the picture with the pen. Any ideas? When I touch the wire where the aerial is there is nothing at all. Thanks Barry
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Old 20th Nov 2020, 10:22 am   #32
Ian - G4JQT
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Hello it works in a fashion. I only get it to play through the radio when I am touching the round thing i have marked in the picture with the pen. Any ideas? When I touch the wire where the aerial is there is nothing at all. Thanks Barry
The component pointed at is Q1. Sounds like you're close but not there yet. You need a yard/meter of so of wire from the non-earthed junction of C13 and the secondary of L2 - the side where there are three pins but the centre one isn't connected to anything.

When you turn the centre ferrite slug of L2 (just use a flattened cocktail stick as it will break with anything metallic) the signal should increase in volume in the radio. If not there is something wrong around Q2 and associated components. Obvious question, but is Q2 in the right way?

What voltage readings have you made? The RF might affect your meter, but assuming you're using a 9V battery, you should be getting something like this:

Q2C 4V
Q2B 0V
Q2E 0V
IC1 pin 5, 4.5V

If you're getting some modulated signal I expect you have correct voltages around Q1 and the IC.

L1 sets the frequency and L2 matches the output transistor to that frequency. If they are not both tuned to the same frequency you'll get hardly any output.

I find it hard to get my head around Veroboard layouts, that's why I use any of the other construction methods previously mentioned in this thread. Check again that all the tracks you think are cut really are, with no shavings shorted to adjacent tracks.

Let us know how you get on.

Ian
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Old 20th Nov 2020, 11:16 pm   #33
baza100
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Tried it again today and it worked for about 20seconds. then it has died completely. Can I have blown anything by any of the tracks touching. Can't see any but if it had would it have blown anything? Thanks barry
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Old 20th Nov 2020, 11:17 pm   #34
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Hello it works in a fashion. I only get it to play through the radio when I am touching the round thing i have marked in the picture with the pen.
Hey Barry, congrats for getting some response out after your first attempt! Im just dropping by to say that as Ian has covered all the bases...
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Old 21st Nov 2020, 10:20 am   #35
Ian - G4JQT
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Tried it again today and it worked for about 20seconds. then it has died completely. Can I have blown anything by any of the tracks touching. Can't see any but if it had would it have blown anything? Thanks barry
Please take some DC voltage readings and post them here so we can have a look.

Ian
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Old 21st Nov 2020, 4:16 pm   #36
Ian - G4JQT
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Just found the instructions I supplied with the MiniMods I sold.

It might be useful to post them here.

Ian
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Old 22nd Nov 2020, 12:27 am   #37
baza100
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Quote:
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Hello it works in a fashion. I only get it to play through the radio when I am touching the round thing i have marked in the picture with the pen. Any ideas? When I touch the wire where the aerial is there is nothing at all. Thanks Barry
The component pointed at is Q1. Sounds like you're close but not there yet. You need a yard/meter of so of wire from the non-earthed junction of C13 and the secondary of L2 - the side where there are three pins but the centre one isn't connected to anything.

When you turn the centre ferrite slug of L2 (just use a flattened cocktail stick as it will break with anything metallic) the signal should increase in volume in the radio. If not there is something wrong around Q2 and associated components. Obvious question, but is Q2 in the right way?

What voltage readings have you made? The RF might affect your meter, but assuming you're using a 9V battery, you should be getting something like this:

Q2C 4V
Q2B 0V
Q2E 0V
IC1 pin 5, 4.5V

If you're getting some modulated signal I expect you have correct voltages around Q1 and the IC.

L1 sets the frequency and L2 matches the output transistor to that frequency. If they are not both tuned to the same frequency you'll get hardly any output.

I find it hard to get my head around Veroboard layouts, that's why I use any of the other construction methods previously mentioned in this thread. Check again that all the tracks you think are cut really are, with no shavings shorted to adjacent tracks.

Let us know how you get on.

Ian
Hello again, Sorry for being a complete novice and pain, but i have checked the Q2C and the voltage is 4.9 and for the IC1 pin 5, 4.5V I have no idea where this is. I have been checking some of the resistors, one seems to be really low. R7 should be 100R and showing 21. Few others are a bit low. Hope this helps.
Sorry I really new to all this. thank you for your patience.
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Old 22nd Nov 2020, 11:25 am   #38
Ian - G4JQT
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Q2C at 4.9V is a good sign, suggesting the voltage at the output of IC1 is about half the supply voltage.

You can't measure the actual value of most components in situ because other components and semiconductor junctions around them will change the apparent values. For example R1 won't measure 100k because that has D1 and part of Q1 across it which are also likely to cause it to measure differently depending on the polarity of your meter leads.

However, R7 should measure 100R as long as you have nothing connected to the L/R input. R7 is isolated from any resistive effects of IC1 by C12, so 21R means something is wrong.

IC1 pin five is pin 5 of the LM386 chip. Just look up the LM386 data sheet, but the image is here

In case you haven't found the circuit diagram of the MiniMod it's in the original article link below. Remember I changed Q1 to a BF256 which has different pinout to the original 2N3819.

Other than very carefully checking the values of each component - by lifting on end if necessary to remove it from the effect of other components - I'm not sure what else to suggest, except you posting a list of voltage measurements from the negative battery terminal to all the active device terminals.

Unfortunately during this lock down, I'm not in Fakenham where my workshop is and I don't have a MiniMod to hand to exactly compare voltages, but I should be able to suggest what's wrong from your list of voltage measurements.

Ian
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Old Today, 12:32 am   #39
baza100
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Default Re: First project (mini mod)

Hello quick question Inductors L1 and L2 are both 90 H but mine are 90 uol are they the same thanks
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