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RS Function Generator RS 435-226: RS 434-289: RS 591-124

 
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RS Function Generator RS 435-226: RS 434-289: RS 591-124

Post by crustytv » Tue May 19, 2015 1:49 pm

Thanks to Al's kindness I have a little home-build RS function Generator based on an 8038.

I'm gathering all the parts from my stock but one component has me fuddled, what should be located where I put the red dot where it states 10K. I thought it might be a 10K pres-set like the two 100K and two 1K but the foot print is different. I don't have a schematic, component list or build notes so I'm not sure.

FreqGen.jpg

bd1.jpg

 
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Re: RS Function Generator

Post by cobaltblue » Tue May 19, 2015 2:16 pm

Well according to this

Its a cermet 10K muli-turn pot

The others mentioned are not multi turn

Cheers

Mike T

 
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Re: RS Function Generator

Post by Mark Hennessy » Tue May 19, 2015 2:35 pm

Yes, you can fit a 10 turn preset there, but also you can connect a 3 way ribbon cable (or separate wires) to a front panel frequency control. You can, of course, use a Molex header if you wish.

I built that kit about 25 years back. It worked well. If memory serves, the IC is used in "wide sweep" mode, so the frequency might drift a bit (not that it matters for most purposes).

Datasheet is here: http://docs-europe.electrocomponents.co ... 01b696.pdf

 
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Re: RS Function Generator

Post by Alistair D » Tue May 19, 2015 3:28 pm

Chris, if you have 1k and 10k 1 turn pots lying around this dodge might just work.

Instead of the 10 turn pot wire a 1k instead. Instead of the L.F. pot wire the 10k pot. The new L.F. pot will act as a course frequency adjust and the 1k will act as the fine adjust.

Al

 
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Re: RS Function Generator

Post by Refugee » Tue May 19, 2015 3:34 pm

I was about to say that a front panel 10 turn pot would be wired into there.
My one of those was not the RS model but one with lots more components and an on board ramp generator allowing it to sweep the audio band and it is very useful for testing equalisation stages in tape recorders.
I posted lots of it photos back in 2012.

 
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Re: RS Function Generator

Post by crustytv » Tue May 19, 2015 6:29 pm

I have many small skeleton pre-sets but all are too big for this board, therefore I'm going to have to order some tiny ones to fit.

A pause in the proceedings until then.

bd2.jpg

 
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Re: RS Function Generator

Post by Norman Raeburn » Tue May 19, 2015 8:07 pm

Hi Chris, Can you give the pin spacing dimensions for the pots as I may have something suitable. Norman

 
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Re: RS Function Generator

Post by crustytv » Tue May 19, 2015 8:25 pm

Hi Norman,

The through hole dimensions for all the pre-sets. Does anyone know what I have to order for the wave selector switch?

bd3.jpg

 
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Re: RS Function Generator

Post by Ed Dinning » Tue May 19, 2015 8:54 pm

Hi Chris, I think the selector switch was one of the many RS 1 pole n way switches. I have plenty of them here, let me know if you want one or 2 for the various functions. I probably also have some suitable pots for the various pre-sets. Call over later in the week and you can have them.
I do have some of the RS data sheets about which included that particular PCB. If you can't get it from the RS website let me know and I'll see if I can find it.

Ed

 
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Re: RS Function Generator

Post by crustytv » Tue May 19, 2015 9:04 pm

Hi Ed thanks for the info and offer re the switch, unfortunately there's no way of me getting up to your neck of the woods for the foreseeable future. I have a very sick family member and I'm doing a daily 60mile round trip in the opposite direction to visit them in the hospice.

Regards
Chris

 
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Re: RS Function Generator

Post by Mark Hennessy » Tue May 19, 2015 9:09 pm

A link to the datasheet has been posted twice in this thread. Admittedly, I missed Mike's link before I linked to it in my post... Though it's not an especially useful sheet - of much more value is the ICL8038 datasheet: http://www.intersil.com/data/FN/FN2864.pdf

 
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Re: RS Function Generator

Post by Alistair D » Tue May 19, 2015 9:19 pm

The datasheet mentioned in post 3 gives the R.S. part numbers of all of the parts so it should be easy work out what the parts look like.

I wish I'd thought about it before I sent the package off and put some Veropins in it. They are ideal for the off board connections.

I am pleased to see it getting built. It came to me as part of a job lot auction item and it was far too good to bin. Only another 999 items of junk to find a mug to take off my hands. Only kidding. Seriously though, I bet we all have loads of 'to good to bin' that we will never use.

Al

 
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Re: RS Function Generator

Post by Refugee » Tue May 19, 2015 10:43 pm

The pot will be something like this.
http://uk.farnell.com/bourns/3386h-1-10 ... dp/9354913

 
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Re: RS Function Generator

Post by Briancuff » Tue May 19, 2015 10:57 pm

High ChrisI'm sure that I've got some pots that will do for you. I'm fairly sure about the ten-turn frequency pot. I'll look tomorrow and let you know. I can pop them in a jiffy bag.

 
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Re: RS Function Generator

Post by Norman Raeburn » Wed May 20, 2015 8:27 am

Hi Chris, I have the 1k pots with the RS part number on them, I don't have the 100k ones or a pc fit multiturn that size. I do have a panel mount multiturn pot, please let me know if you would like any of them. Brian may be able to turn up a set. I have had a look on the RS website and they are listing equivalents for all the pots if we can't dig them up between us. Norman

 
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Re: RS Function Generator

Post by Terrykc » Wed May 20, 2015 10:11 am

Chris, if you fit a preset, you are going to end up with a very strange generator!

You will have two externally accessible controls for level and waveform type but no way of changing the frequency without dismantling it!

Fit an external pot.

A one turn pot will do for starters - just use anything to hand. You can always fit an expensive multi-turn pot later.

If you are going to calibrated it and fit a scale, a one turn pot will be better, anyway. You can always fit a drum and drive cord, just like tuning on a radio!

Just make sure that the cord arrangement allows for 270° rotation rather than the 180° of a radio tuning gang.

 
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Re: RS Function Generator

Post by Mark Hennessy » Wed May 20, 2015 12:53 pm

Just remembered that I had a photograph of mine. Apologies for the quality - this is a crop from a scan of a 35mm photo, taken with a cheap fixed-focus "point and shoot" camera. I was 16 or 17 when this picture was taken (circa 1990). The original shot is here, if anyone is interested.

The generator is the grey box. The large knob sets the frequency, and the smaller knobs would be for amplitude and waveform. The outputs are on red and black 4mm terminals, and the green one is mains earth (function generators are far more useful if they float from mains earth). I suppose a BNC would have been better, but it was a case of using whatever was to hand. A toggle switch and LED were for power.

The black box on top was a power amplifier. The kit as supplied is a bit weedy, as a TL084 can only source a few milliamps (and should have provided a series output resistor, BTW). The amplifier would have been based around a TDA2002 or similar, and was used to drive loudspeakers and motors and solenoids and similar things. A useful thing - think I still have the guts somewhere in the attic.

Some TV folk will recognise the thing on top of the DIY amplifier :bba
Attachments
Function generator.jpg

 
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Re: RS Function Generator

Post by Briancuff » Wed May 20, 2015 6:08 pm

Chris
These are the pots I could find. The large ones are 100k (moulded track), the tiny cermet is 1k and the blue 10T one is 1k.
I can post them tomorrow if they're OK.
P5200007web.jpg

 
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Re: RS Function Generator

Post by crustytv » Wed May 20, 2015 6:58 pm

Hi Brian,

Thanks for the offer but I think I'm almost sorted now.

Taking the advice offered I will be fitting this into a project box ( yet to be found) with panel controls.

yesterday I ordered 2 x 100K & 2 x 1K trim pots
trim.JPG
2 x 100K & 2 x 1K trim pots

In my spares I found a three-way slider switch for the wave select. That just leaves me to source 1 x 4k7 panel pot, 1 x 10k Multi-turn Panel pot for frequency.

Norman If your multi-turn panel pot is suitable I would be interested.

Regards
Chris

 
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Re: RS Function Generator

Post by Norman Raeburn » Wed May 20, 2015 7:48 pm

Hi Chris, I will post the multiturn pot to you tomorrow. Norman

 
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Re: RS Function Generator

Post by Ed Dinning » Wed May 20, 2015 9:07 pm

Hi Chris, if all else fails, drop me a PM and I'll stick some multi turn pots/ switches in the post.
If you let me know what size project box you need I may have one.

Ed

 
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Re: RS Function Generator

Post by Alistair D » Wed May 20, 2015 9:24 pm

Since you are going to use a 10 turn pot for frequency, bring the pre-switch sine out to a bnc socket for a frequency counter.

Al

 
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Re: RS Function Generator

Post by Mark Hennessy » Wed May 20, 2015 9:42 pm

Alistair D wrote:Since you are going to use a 10 turn pot for frequency, bring the pre-switch sine out to a bnc socket for a frequency counter.

Al


Or if there is space in the chosen box you could really go to town: http://www.ebay.co.uk/itm/Digital-Frequ ... 1640374044

Though a separate "sync" output is often handy for other tasks, such as triggering the 'scope. It's usual in my experience for the sync output to be a TTL signal, but some Farnell oscillators were sine wave.

 
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Re: RS Function Generator

Post by Refugee » Wed May 20, 2015 11:15 pm

That at a glance looks like it also has a crystal testing oscillator built in.

 
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Re: RS Function Generator

Post by Alistair D » Wed May 20, 2015 11:24 pm

OMG £5.55 for a frequency counter I can remember a time when £255.55 would have been nearer the mark.

Indeed the square wave output may be a better option.

Al

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