HP 3325A Function Generator- No square wave - UK Vintage Radio Repair and Restoration Discussion Forum

IsquaredR · 17th Jan 2018, 3:51 am

Recently bought a Hewlett Packard HP 3325A function/sweep generator. I've got the operator manual but cannot find any reference to the following anomaly:
When selected the square wave generator causes a "source calibration error" with no signal on the output. Any one have any ideas on where to start? I can't find any reference to the meaning of a "source calibration error" so any guidance is certainly appreciated.

Radio Wrangler · 17th Jan 2018, 4:51 am

do the other waveforms all work?

For each of the others, can you vary the amplitude over the expected rnage? and does the amplitude out of the output socket match what you've selected?

I've not got any of the function generator circuitry in my head, so I can't be a lot of help, but I did have the job of revamping the Frac-N synthesiser in the 3325 around a new chipset. It must have been around 1996/1997.

David

dave cox · 17th Jan 2018, 10:16 am

I would start by re-seating all the inter-board ribbon connectors - I don't think they used especially good quality connectors, I think there were some recalls / rework on them. There is a bonus 15V supply to one of the boards that needs a check as well. The output attenuator relays can be troublesome but again some retro-fitting way have been applied. As Radio Wrangler says work through the attenuator range as there is probably another clue in there somewhere.

Setting it to 0.02Hz sinewave and connecting up a analogue storage scope at 5s/cm is impressive

dc

peter_scott · 17th Jan 2018, 10:21 am

Service manual is here:
http://www.ko4bb.com/getsimple/index...5A_Synthesizer

Peter

IsquaredR · 17th Jan 2018, 11:17 pm

Thank you Peter, Dave and David.

My situation is that I have not received the function generator as yet but the problem with the square wave generator was described by the seller. I think he was being honest with me. He also stated that output was normal on all the other functions; only the square wave was defective and the SOURCE CALIBRATION ERROR annunciation that accompanied selection of the square wave function.

Good suggestion to reseat the ribbon connectors. That will be the first thing I try when it arrives (probably Friday of this week). I am also going to look into any retrofits and that bonus power supply. I so appreciate some areas at which to start my investigation.

I'll report back here what I find. Thanks so much, gentlemen. You guys on this forum are THE BEST.

Radio Wrangler · 18th Jan 2018, 1:18 am

Don't forget to find and read the HP Journal article on the 3325A You'll find a lot of insight into how the beastie works.

David

IsquaredR · 18th Jan 2018, 3:17 am

Many thanks again, David. I saw that HP Journal article on the Internet just last night but did not download it so I am looking for it again tonight per your recommendation. I could really use it, I am sure. This is a new game to me.

I also read some of your earlier comments here on the UK Vintage Radio forum about what you did professionally when redesigning the chip for the 3325. I am honored to be lucky enough to communicate with engineers of your stature.

IsquaredR · 18th Jan 2018, 3:21 am

Just found the HP Journal article thanks to www.holzleitner.com/el/hp-3325/index-en.html

You're right David. Lots of good info and will enjoy sitting down with it tonight.

Radio Wrangler · 18th Jan 2018, 9:42 am

I didn't redesign the Frac-N chip, The original one was HP designed (Loveland division, I think) and made by Mitsubishi. They shut down that process line and HP had to design a new device. There were quite significant differences, so each instrument using the API Frac-N needed redesigning around the new part. Each instrument using it was a different design for different FM/sweep capabilities, freq range etc.

Eventually the firm went over to a different approach to Frac-N, essentially a sort of sigma-delta ADC style. I prefer the name 'Noise Shaping' which gives an easier view of its machinations.

Me? I had the privilege of working in a labful of seriously top-end engineers, and I couldn't help pick up a bit in that environment. I picked up their attitude that most things could be done, you just had to find the way. And the way to find the way was to look at the problem from as many different directions as possible until some combination of views 'clicked'. I have no doubt that if I can do something, just about anyone can. It may take some time to build up the background knowledge, but no impossibility is involved. People limit theirselves a lot by telling themselves that they can't do things. Curiosity is the key. Oh, and I make plenty of mistakes!

David

IsquaredR · 19th Jan 2018, 2:11 pm

What an incredibly refreshing attitude, David! Thank you! I keep a file of
snip-its that includes profound quotes I run across and I have printed-out yours for inclusion.

17th Jan 2018, 3:51 am	#1
IsquaredR Tetrode Join Date: Apr 2017 Location: Minocqua, Wisconsin, USA. Posts: 86	HP 3325A Function Generator- No square wave Recently bought a Hewlett Packard HP 3325A function/sweep generator. I've got the operator manual but cannot find any reference to the following anomaly: When selected the square wave generator causes a "source calibration error" with no signal on the output. Any one have any ideas on where to start? I can't find any reference to the meaning of a "source calibration error" so any guidance is certainly appreciated.

17th Jan 2018, 4:51 am	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,857	Re: HP 3325A Function Generator- No square wave do the other waveforms all work? For each of the others, can you vary the amplitude over the expected rnage? and does the amplitude out of the output socket match what you've selected? I've not got any of the function generator circuitry in my head, so I can't be a lot of help, but I did have the job of revamping the Frac-N synthesiser in the 3325 around a new chipset. It must have been around 1996/1997. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

17th Jan 2018, 10:16 am	#3
dave cox Nonode Join Date: Jan 2009 Location: Bristol, UK. Posts: 2,061	Re: HP 3325A Function Generator- No square wave I would start by re-seating all the inter-board ribbon connectors - I don't think they used especially good quality connectors, I think there were some recalls / rework on them. There is a bonus 15V supply to one of the boards that needs a check as well. The output attenuator relays can be troublesome but again some retro-fitting way have been applied. As Radio Wrangler says work through the attenuator range as there is probably another clue in there somewhere. Setting it to 0.02Hz sinewave and connecting up a analogue storage scope at 5s/cm is impressive dc

17th Jan 2018, 10:21 am	#4
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: HP 3325A Function Generator- No square wave Service manual is here: http://www.ko4bb.com/getsimple/index...5A_Synthesizer Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

17th Jan 2018, 11:17 pm	#5
IsquaredR Tetrode Join Date: Apr 2017 Location: Minocqua, Wisconsin, USA. Posts: 86	Re: HP 3325A Function Generator- No square wave Thank you Peter, Dave and David. My situation is that I have not received the function generator as yet but the problem with the square wave generator was described by the seller. I think he was being honest with me. He also stated that output was normal on all the other functions; only the square wave was defective and the SOURCE CALIBRATION ERROR annunciation that accompanied selection of the square wave function. Good suggestion to reseat the ribbon connectors. That will be the first thing I try when it arrives (probably Friday of this week). I am also going to look into any retrofits and that bonus power supply. I so appreciate some areas at which to start my investigation. I'll report back here what I find. Thanks so much, gentlemen. You guys on this forum are THE BEST.

18th Jan 2018, 1:18 am	#6
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,857	Re: HP 3325A Function Generator- No square wave Don't forget to find and read the HP Journal article on the 3325A You'll find a lot of insight into how the beastie works. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

18th Jan 2018, 3:17 am	#7
IsquaredR Tetrode Join Date: Apr 2017 Location: Minocqua, Wisconsin, USA. Posts: 86	Re: HP 3325A Function Generator- No square wave Many thanks again, David. I saw that HP Journal article on the Internet just last night but did not download it so I am looking for it again tonight per your recommendation. I could really use it, I am sure. This is a new game to me. I also read some of your earlier comments here on the UK Vintage Radio forum about what you did professionally when redesigning the chip for the 3325. I am honored to be lucky enough to communicate with engineers of your stature.

18th Jan 2018, 3:21 am	#8
IsquaredR Tetrode Join Date: Apr 2017 Location: Minocqua, Wisconsin, USA. Posts: 86	Re: HP 3325A Function Generator- No square wave Just found the HP Journal article thanks to www.holzleitner.com/el/hp-3325/index-en.html You're right David. Lots of good info and will enjoy sitting down with it tonight.

18th Jan 2018, 9:42 am	#9
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,857	Re: HP 3325A Function Generator- No square wave I didn't redesign the Frac-N chip, The original one was HP designed (Loveland division, I think) and made by Mitsubishi. They shut down that process line and HP had to design a new device. There were quite significant differences, so each instrument using the API Frac-N needed redesigning around the new part. Each instrument using it was a different design for different FM/sweep capabilities, freq range etc. Eventually the firm went over to a different approach to Frac-N, essentially a sort of sigma-delta ADC style. I prefer the name 'Noise Shaping' which gives an easier view of its machinations. Me? I had the privilege of working in a labful of seriously top-end engineers, and I couldn't help pick up a bit in that environment. I picked up their attitude that most things could be done, you just had to find the way. And the way to find the way was to look at the problem from as many different directions as possible until some combination of views 'clicked'. I have no doubt that if I can do something, just about anyone can. It may take some time to build up the background knowledge, but no impossibility is involved. People limit theirselves a lot by telling themselves that they can't do things. Curiosity is the key. Oh, and I make plenty of mistakes! David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

19th Jan 2018, 2:11 pm	#10
IsquaredR Tetrode Join Date: Apr 2017 Location: Minocqua, Wisconsin, USA. Posts: 86	Re: HP 3325A Function Generator- No square wave What an incredibly refreshing attitude, David! Thank you! I keep a file of snip-its that includes profound quotes I run across and I have printed-out yours for inclusion.