Help with a volume control pot

Hi everyone



I had formerly asked for help with an fm radio receiver schematic and though I asked real dumb questions, no one scolded me for that so I am back with another couple of questions. First is, I have got a volume control pot with five pins and I don't know how to wire it up. (Okay I don't even know how to wire up a 3 pin volume pot). Could someone kindly help me with that please? I am still pottering about with the old fm radio receiver circuit as before, I'll post the schematic so you can have a look at it. I would be so grateful if someone could tell me how I could wire the 5 pin pot to the schematic.
Another thing is, I am reading a book called Electronics All-in-one for Dummies which says an oscilloscope is a very useful thing to have. I would like your opinions about that please. Would one of the cheaper ones do for a beginner?

I am going to try and attach pics of the schematic and the 5 pin pot in the hope that someone will kindly help me. Please be gentle. I am an old fart trying to learn hehe. Also, if you could explain stuff in simple terms and examples, I would be so grateful.




The pins 4 and 5 are at the bottom of the pot. And there are 3 pins on the top part,not 2, sorry for the terrible photos.

It will most likely have an on/off switch included - does it click if you turn it all the way anticlockwise?
Either than or extra taps or a wiping switch for a "loudness" control.

Either way, ignore the rear connections and use the three at the side.

Looking at it along the spindle and with the connections at the bottom:
Left would be common or 0V, right would be signal input (the "top end" of the pot resistor in the schematic) and the centre is the output, the "wiper" contact.

The three pins are the pot, the two are on ON/OFF switch.

rjenkinsgb, sir, yes it does click if turned all the way anticlockwise sir. Thank you for pointing out which pins are which sir.

Nigel Goodwin, thank you for replying sir, I'll try to connect it with just the three in line pins as rjenkinsgb directed and see how it goes.

Please do say something about the oscilloscope too, please

maltesecorsair said:

Please do say something about the oscilloscope too, please

Click to expand...

Oscilloscopes are great bit of equipment, one of those things which you wonder how you ever managed without.

maltesecorsair said:

Would one of the cheaper ones do for a beginner?

Click to expand...

That all depends on how you define cheap.

Things which use a PC or laptop sound card...
A waste of time and money in my opinion.
Maybe useful if you just want to look at audio waveforms, but apart from that, no.

"USB Oscilloscopes"
Boxes which connect to a PC or laptop via a USB port can be very good.
I have a TiePie HS3, which I use infrequently.
It is very good for looking at long strings of digital data, I like to use it when debugging PICs and interfaces to various modules from China bought via EBay.
The downside is that the user interface is rather quirky on the PC screen, I would much prefer something which looks like the controls of a conventional scope.
But it does a good job when I need it.
It was not cheap, about £900 many (15+) years ago.

I have a very old Telequipment D75.
A conventional scope, works well, but quite "long in the tooth". I have had this one for about 35 years.
You could probably buy one similar for less that £100.

I also have a relatively new Agilent digital storage scope, which last week decided that its display would give up the ghost.
The scope works fine when externally controlled from a PC, just the display on the front panel is all washed out.
So far I have not had the enthusiasm to find out why.
If I decide that it is beyond economical repair, I may buy a new scope from Rigol or Siglent. Basically these are of Chinese origin but they do seem to work very well.
The "entry level" models can be bought for £250 - £350 (ish).

So how big is your oscilloscope budget?

JimB

I bought an Owon scope, which is OK, but a bit clunky some of the controls aren't very easy to use.

For working on cars I occasionally need an oscilloscope, and I've been using a Picoscope, which is a USB scope. The cheapest one is only 10 MHz and only £120, but it is much better than the Owon in a lot of ways. It far more portable, assuming you're carrying a laptop anyhow. It's much easier to save data to the computer with, and it'll do serial decoding for I2C, RS232, LIN,CANbus and a few others. It's got a lot of clever triggering modes that are easier to use than selecting with knobs.

Unless I was using a 'scope every day, I would go for a Picoscope. I might need something faster than 10 MHz, which do cost more.

I have one of these little handheld ones that I keep in my service kit, for low frequency stuff; it's somewhere around 25-30 years old now, but still works fine:
**broken link removed**

That exact one is no longer made, but this appears to be the replacement:

I've also got an old Solartron dual trace, which must be 50+ years old now and retired for the last few years - I've had for 40 or so..

It's replacement is a little Siglent 200MHz dual trace one. That is superb; as Jim mentioned, they seem to be a very good make.

Also a Salea "Logic 16" logic analyser, a tiny USB gadget which is fantastic for looking at lots of logic signals, and more recently a four input Hantek USB scope unit


For a minimal cost one, these seem to get good reviews - if you don't mind assembling it yourself.
They are only good for audio & up to a couple of hundred KHz, but seem reasonable for the price.

The 2 transistors "FM radio" will have VERY poor performance.
The amplifier output power will be only 0.45W when the 9V battery is new and will be only 0.2W when the voltage has dropped to 6V.

JimB, sir, this was the oscilloscope I was looking at:
**broken link removed**
I would like to mention that I have absolutely no idea about oscilloscopes, just read about them in the book I mentioned in my first post in this thread. I will have to learn how to use one . The above oscilloscope costs about 73 Pounds. I could get one of those with a couple of months of saving money. On the other hand, the below oscilloscope is going to require me saving up for about an year.
And that in GBP is about 272 pounds. Of course, Fluke makes an oscilloscope that is far beyond my means to buy.
I am hoping there are books on Amazon that I can buy and hopefully make sense out of on how to work an oscilloscope, seeing I am not particularly intelligent. I had started saving up for a soldering station and next February, I should have about 522 pounds in my account.
The soldering station now costs about 297 pounds btw.

Diver300, sir, I see a few Owon scopes in my Amazon which I could buy in February or March, but can't find anything called Picoscope sadly.

rjenkinsgb, sir, I tried to look at the Amazon link you provided but sadly it says not available currently. And seriously, I am not very adept at electronics, so I would probably mess it up if I were to try to assemble it myself.

audioguru, sir, um um, perhaps you might have a better schematic that I can try please?

maltesecorsair said:

Diver300, sir, I see a few Owon scopes in my Amazon which I could buy in February or March, but can't find anything called Picoscope sadly.

Click to expand...

https://www.picotech.com/

https://uk.rs-online.com/web/c/?sra=oss&r=t&searchTerm=picoscope[/QUOTE]

An oscilloscope is used to see the waveform of one steady frequency, not the thousands of audio frequencies at the same time from a radio.
If you build an oscillator that has one steady frequency, then an oscilloscope can be used to see its waveform or the waveform of an amplifier fed from the oscillator.

A half-decent FM radio has at least 5 transistors and 5 tuned LC circuits plus an audio amplifier. It is called a super-heterodyne FM radio circuit and can be seen in Google.

maltesecorsair said:

The soldering station now costs about 297 pounds

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Ouch!! That is very expensive!

An Antex TCS230 digital temperature controlled iron costs about £60:
**broken link removed**

And you can get a pretty reasonable soldering station with a temperature controlled iron and hot air tool, for about £40
I have one of these, I've only used the hot air side but that does work well:
**broken link removed**

And the Velleman scopes seem readily available on ebay at reasonable prices - eg. this is identical to one I have:
**broken link removed**

Or this is the new version:

They are only single trace, but look like a bargain to me at those prices; they are 10MHz rated, vs. 200 KHz for a lot of the ebay kit or minimal versions.

It's down to you as to what type of instrument and what capabilities you want, vs. how much you are prepared to pay.

rjenkinsgb said:

Ouch!! That is very expensive!

An Antex TCS230 digital temperature controlled iron costs about £60:
**broken link removed**

Click to expand...

I've used Antex irons for decades now, I have a 'similar' one to that at home (but no LCD on it), I've had it many years. And I use an Antex soldering iron station at work - in fact it's on my kitchen table at the moment, as I'm still working from home.

Diver300, well those sites are UK sites sir, and I am out in the orient. I am unable to buy from foreign sites as I don't have an international debit card sir.
audioguru, I will try to google for a super-heterodyne FM circuit sir. ( I don't even know what super-heterodyne means but I will search hehe). You gotta keep in mind sir, just about the only thing I know now is that I can get a shock from electric current.

rjenkinsgb, sir, yikes those are UK sites, and I have no way of buying from those sites. We have our own version of Amazon sir, which doesn't list many of the things that are so readily available in the west. Those foreign brands available here, cost a lot too sir, possibly due to the import fee and such. I tried searching for the brands you mentioned sir but sadly, those are not on www.amazon.in

Nigel Goodwin, sir, sadly Antex is not a brand that my Amazon has. *sniffle*

Oooh, maybe somebody would look into www.amazon.in and see if there are any soldering iron stations or oscilloscopes they like the look of and tell me? Just a thought, that's all, as I don't have the knowledge or experience. I would be able to buy a soldering station and an oscilloscope, each with a budget of around Rs 25000-30000. Just saying, in case someone is bored enough to look into my Amazon site hehe

There are quite a few places selling this iron, under different names; it seems to be a temperature controlled one:

I'd get one that comes with a full range of bits, as those on their own seem to be almost as much as the iron with them!

rjenkinsgb, omg sir, you actually took the time to look into www.amazon.in. I am so grateful and happy for that. I'll get that first one, which has extra bits, as you said, sir. I will get it as soon as I possibly can. I do not want to seem pushy or sorta misusing your kindness, but sir, could you also look at the oscilloscopes please? If you are busy or something, don't worry sir, I'll understand.





Does the above schematic look better than the first schematic I posted, everyone? anyone? Or is it incomplete or bad? Please do express your opinions.
Edit: TDA7000 is a chip I can buy online in one of our online stores.

The TDA7000 IC is very old and is obsolete. It is garbage. Philips invented it but made better replacements later.
The TDA7088 is one of the replacements but it is also obsolete and not made in The West anymore. There are cheap Chinese copies available online but they might be fakes.

I bought an "FM" radio with a cheap Chinese TDA7088. It is overloaded by local FM stations and does not receive weaker stations that any better FM radio has no problem receiving. It is noisy and distorted. It "scans" to the next station but the scanning misses some local stations. The "radio" cost $1.00 and came with earphones and a battery that are worth more than $1.00 so the actual radio was free. It is garbage.

audioguru: Yikes sir, sorry, I will keep trying to find a better schematic then. I had seen a TDA7088 one but that chip is not available in my shops.

Sadly, the circuits I find have IC's that are not available to me probably because they are very old models. The TDA7000 IC, is available and I actually bought two, but audioguru warned me against trying to use one of those, so presently, I am thinking of buying a DIY fm radio kit from Amazon. Thank you everyone for the replies, I am so grateful to all of you.