Lab Quality Function Generator - UK Vintage Radio Repair and Restoration Discussion Forum

Chris55000 · 19th May 2021, 11:33 am

Hi!

Most Function Generators based on the XR2206, MAX038, 8038, etc., tend to have a THD percentage of 0.5 to 1.5% thd on sine-wave ouput signals, not really good enough for audio testing!

The design presented here has typically 0.03% THD max using a d/a filtering process.

Frequency coverage 1 Hz - 99.99 kHz, Sine output 1V rms (original design) but an additional 50 ohm impedance power amplifier giving a higher voltage output will be included.

I am going to present in this thread here my version of the Project presented by Elektor Magazine during October, November and December 1991.

The Author of the original design was T. Giffard, who published quite a number of Elektor projects during this period.

The original PCBs for this, nos. 910077-1 to 910077-4 have long been unobtainable from Elektor, but I will provide replacement designs and Gerber Files, produced from my Easy PCB software.

All of the parts for this are still available at the time of writing this, altho' the Neosid 7A1s coil former kit isn't available in the UK, however I will suggest a modification to a Toko 10K coil assembly as a substitute!

There are no EPROMs, GALs, or microcontrollers requiring programming in this unit.

Circuit Diagrams and PCB layouts are my own derived from the original Elektor design.

Chris Williams

Electronpusher0 · 19th May 2021, 11:52 am

I look forward to this with interest!
If there is enough interest perhaps we could get an order together for the pcbs from JLCPCB (they have a minimum quantity of 5)

Peter

Chris55000 · 19th May 2021, 12:56 pm

Hi!

I will be ordering the PCBs for this when my designs are complete, there will be three sets available to begin with!

The design currently uses four 74HC696 up/down decade counter/shift register combination i.c. devices, I will design an adapter PCB to use separate counter/shift register devices if the 74HC696s become unobtanium – supplies of this device are currently available from Littlediode for £4.25 each – I've just had four delivered!

The design is currently being entered into "Easy PC's" Schematic Editor for laying out the PCBs even as I write this!

Chris Williams

Diabolical Artificer · 21st May 2021, 6:30 am

Sounds interesting Chris,thanks for your hard work. Will it have a square wave function? For testing audio gear a must.

Andy.

Electronpusher0 · 21st May 2021, 6:43 am

If its based on the Elektor one it will have Sine, Square and Triangle.

Peter

Chris55000 · 21st May 2021, 2:42 pm

Hi!

Yes it is Sine, Square and Triangle!

The design doesn't appear to have an external VCO input but it's quite possible to use an 16 bit A/D module on the counter inputs but this a very expensive solution, a much cheaper one is to add a buffer amplifier whose output is fed to the varicap control voltage input.

Chris Williams

Electronpusher0 · 24th May 2021, 9:45 am

I have the original Elektor Article in pdf format.
I will not post it here because of copyright but if anyone wants a copy PM me with an e-mail address and will send it for personal study.

Peter

Chris55000 · 24th May 2021, 10:12 am

Hi!

No need for anyone to worry about the wrath of the copyright moguls as I bought a "Green" Membership from Elektor themselves that includes every issue in high quality PDF scan all the way back to issue No. 1, November 1974, so I can reprint it any time!

(I have no time for them as they're wanting to use "copyright" as an excuse to make you pay for a purchased item over and over again!)

Chris Williams

Trigon. · 24th May 2021, 12:47 pm

All three parts of the article are available on the worldradiohistory site:

https://worldradiohistory.com/UK/Ele...or-1991-10.pdf
https://worldradiohistory.com/UK/Ele...or-1991-11.pdf
https://worldradiohistory.com/UK/Ele...or-1991-12.pdf

Cheers

dave cox · 24th May 2021, 1:22 pm

Sweep would be nice, with the generator producing a ramp / trigger

I only briefly looked at the Elektor schematics but a clock signal into the up/down frequency control might do something interesting? But you might be doing something totally different

dc

Electronpusher0 · 24th May 2021, 5:50 pm

Quote:

Originally Posted by Trigon.

All three parts of the article are available on the worldradiohistory site:

https://worldradiohistory.com/UK/Ele...or-1991-10.pdf
https://worldradiohistory.com/UK/Ele...or-1991-11.pdf
https://worldradiohistory.com/UK/Ele...or-1991-12.pdf

Cheers

agreed but I have just the articles in 3 parts, not the whole mag, in hi res.

as I say send a PM if you want a copy.

Peter

19th May 2021, 11:33 am	#1
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Lab Quality Function Generator Hi! Most Function Generators based on the XR2206, MAX038, 8038, etc., tend to have a THD percentage of 0.5 to 1.5% thd on sine-wave ouput signals, not really good enough for audio testing! The design presented here has typically 0.03% THD max using a d/a filtering process. Frequency coverage 1 Hz - 99.99 kHz, Sine output 1V rms (original design) but an additional 50 ohm impedance power amplifier giving a higher voltage output will be included. I am going to present in this thread here my version of the Project presented by Elektor Magazine during October, November and December 1991. The Author of the original design was T. Giffard, who published quite a number of Elektor projects during this period. The original PCBs for this, nos. 910077-1 to 910077-4 have long been unobtainable from Elektor, but I will provide replacement designs and Gerber Files, produced from my Easy PCB software. All of the parts for this are still available at the time of writing this, altho' the Neosid 7A1s coil former kit isn't available in the UK, however I will suggest a modification to a Toko 10K coil assembly as a substitute! There are no EPROMs, GALs, or microcontrollers requiring programming in this unit. Circuit Diagrams and PCB layouts are my own derived from the original Elektor design. Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

19th May 2021, 11:52 am	#2
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,296	Re: Lab Quality Function Generator I look forward to this with interest! If there is enough interest perhaps we could get an order together for the pcbs from JLCPCB (they have a minimum quantity of 5) Peter

19th May 2021, 12:56 pm	#3
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Re: Lab Quality Function Generator Hi! I will be ordering the PCBs for this when my designs are complete, there will be three sets available to begin with! The design currently uses four 74HC696 up/down decade counter/shift register combination i.c. devices, I will design an adapter PCB to use separate counter/shift register devices if the 74HC696s become unobtanium – supplies of this device are currently available from Littlediode for £4.25 each – I've just had four delivered! The design is currently being entered into "Easy PC's" Schematic Editor for laying out the PCBs even as I write this! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

21st May 2021, 6:30 am	#4
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,658	Re: Lab Quality Function Generator Sounds interesting Chris,thanks for your hard work. Will it have a square wave function? For testing audio gear a must. Andy. __________________ Curiosity hasn't killed this cat...so far.

21st May 2021, 6:43 am	#5
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,296	Re: Lab Quality Function Generator If its based on the Elektor one it will have Sine, Square and Triangle. Peter

21st May 2021, 2:42 pm	#6
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Re: Lab Quality Function Generator Hi! Yes it is Sine, Square and Triangle! The design doesn't appear to have an external VCO input but it's quite possible to use an 16 bit A/D module on the counter inputs but this a very expensive solution, a much cheaper one is to add a buffer amplifier whose output is fed to the varicap control voltage input. Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

24th May 2021, 9:45 am	#7
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,296	Re: Lab Quality Function Generator I have the original Elektor Article in pdf format. I will not post it here because of copyright but if anyone wants a copy PM me with an e-mail address and will send it for personal study. Peter

24th May 2021, 10:12 am	#8
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Re: Lab Quality Function Generator Hi! No need for anyone to worry about the wrath of the copyright moguls as I bought a "Green" Membership from Elektor themselves that includes every issue in high quality PDF scan all the way back to issue No. 1, November 1974, so I can reprint it any time! (I have no time for them as they're wanting to use "copyright" as an excuse to make you pay for a purchased item over and over again!) Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

24th May 2021, 12:47 pm	#9
Trigon. Hexode Join Date: Jun 2018 Location: Buckinghamshire, UK. Posts: 387	Re: Lab Quality Function Generator All three parts of the article are available on the worldradiohistory site: https://worldradiohistory.com/UK/Ele...or-1991-10.pdf https://worldradiohistory.com/UK/Ele...or-1991-11.pdf https://worldradiohistory.com/UK/Ele...or-1991-12.pdf Cheers

24th May 2021, 1:22 pm	#10
dave cox Nonode Join Date: Jan 2009 Location: Bristol, UK. Posts: 2,062	Re: Lab Quality Function Generator Sweep would be nice, with the generator producing a ramp / trigger I only briefly looked at the Elektor schematics but a clock signal into the up/down frequency control might do something interesting? But you might be doing something totally different dc