HP3325A function generator - hi-res scans of circuit diagrams available - Page 1
Forum section: electronics / repair

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: June 14, 2016, 07:16:06 am
content: Having had big problems reading details in the low-res scans of the HP3325A circuit diagrams for a recent repair, I got hold of a manual and have created high-res photomerges of all the circuit layouts as jpg files. They're too big to upload here - about 80MB all-up in 28 files at full resolution. However, I can make them available if they're useful to others faced with similar problems (I'm assuming there will be limited demand!) Have attached one example to give an idea of what they look like in hi-res cf the same circuit region from the low-res online manual.

author: johnh
author_rank: Regular Contributor
timestamp: June 14, 2016, 07:20:47 am
content: Why not upload it to one of the free manual sitesko4bbhttp://www.ko4bb.com/getsimple/index.php?id=manuals

author: JFJ
author_rank: Regular Contributor
timestamp: June 14, 2016, 07:56:59 am
content: Quote from: Lorenzo_1 on June 14, 2016, 07:16:06 amSaving the images in a different format could significantly reduce the file size, e.g. your hi-res example reduces from 876 KB to 173 KB, when re-saved as a GIF image - without too much loss of quality (please see attachment).

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: June 14, 2016, 11:43:28 am
content: Thanks for the suggestions. Tried gifs (and a bit of cropping) but several came out substantially larger then the original uncropped jpg files. I can shrink the jpegs to about half size by compressing and still leave them readable but figured it might not be worth the time and trouble for now as they'll still be fairly bulky all up. Will look at the free manual sites when I get a chance - might be the best bet.

author: SparkyBruce
author_rank: Contributor
timestamp: June 15, 2016, 03:02:25 pm
content: Hi Lorenzo,I have a poorly 3325A so these would be great. It has been sat in my garage for a number of years and these would really help me.ThanksBruce

author: PaulAm
author_rank: Frequent Contributor
timestamp: June 15, 2016, 11:30:11 pm
content: Having tracked through those bad online schematics, I had to end up buying a printed manual. If you load them up somewhere, they are sure to be appreciated.

author: David Hess
author_rank: Super Contributor
timestamp: June 16, 2016, 02:54:45 pm
content: If you spend the time, there is some processing you can do to minimize the compressed file size. After adjusting the contrast, select the white space and fill it with pure white. Otherwise the GIF or PNG compression will see an ever changing white like gray which prevents efficient compression. Usually this results is smaller file sizes than using JPG compression which will result in artifacts anyway.As far as distributing the files, put them up in a torrent which will require minimum bandwidth from you.

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: June 17, 2016, 12:07:14 am
content: Have done some quick cropping and compression and got it down to 20MB still readable. Currently uploading to KO4BB as suggested, so hopefully available there soon. I presume they'll send me some sort of link to the upload and I'll try and post that here. Thanks to all for the suggestions.

author: TerraHertz
author_rank: Super Contributor
timestamp: June 18, 2016, 08:11:36 am
content: "HP3325A - Fig 8.36 Control Circuits hi-res.jpg (876.81 kB, 2651x1174 )"Oh god, please tell me you saved the original scans in a non-lossy format like PNG, and still have them?Yes, those are huge files, but that's just the start. Because if you didn't go straight to JPG I can show you how to make them look really nice, in much smaller files. But if you only have JPGs, too late.What did you use to scan the big foldout sheets? Or did you stitch them?Stages:- Scan as gray-scale, 256 levels, save as PNG. (Assuming there is no colour in the schematics. If there is, scan in full RGB colour.)- (Stitching, in Photoshop for those with small scanners.)- Remove blotches and any other defects. (A bunch of photoshop tricks, and maybe elbow grease, depending on how good the scans were.)- White and black saturate, while retaining gray scale. The important thing is to remove *all* noise in the white background. This results in all those white areas later compressing to almost nothing in a run-length coding system like PNG. Second-most important is to not half-tone (FAX-ize) the edges - this is why gray scale must be preserved.- Crop and scale to an optimal final size that retains the nice visual detail. Probably your 2651x1174 is a bit too large.(All these stages must be done with non-lossy PNG intermediate files. NEVER ever use JPG for detailed images.)- Finally, data-compress to final images by recoding in a more compact non-lossy format, such as PNG, 16 gray-levels (ie 4 bits per pixel.) Oh, and strip all the EXIF data, which is pointless.You'll be amazed how small the files become.- Optional bundling stage: Present in html for appearance, index, thumbnails etc, then wrap in some single-file format such as a RAR-book. Makes it convenient, while still having the raw images easily accessible as files, unlike PDF.That's a simplified process description; assumes no photos, screened shading, colour overlays, etc.Here's what JPG (a lossy wavelet-based coding system) does to images (part of your posted hi-res sample.)All that gray dotty noise in the white areas is a result of the JPG scheme, and wasn't in the original scan data.Once this kind of noise is injected into an image, it can never be removed.

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: June 19, 2016, 12:25:40 am
content: Great advice - but only for the next time I try this! I only have Hi-res jpgs so can't do as you suggest. However, I was aiming to just get readable diagrams without spending too much time on it. Main problem I found with manual was reading pin connections, labels, mnemonics and the like. I scanned segments and stitched them together - stitching was not perfect but I edited in any text that went AWOL so I think they're all fully readable. Attached is the full version of one smallish one after cropping. Thanks for the suggestions - will give it a try when I get some spare time. Will be useful to see how small I can make them. Meantime the whole set is sitting in recently uploaded files on KO4BB so hopefully will be available for download soonish.

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: June 30, 2016, 10:30:43 am
content: These are now downloadable on KO4BB. Thanks to JohnH for the suggestion.

author: pinyoro
author_rank: Contributor
timestamp: June 30, 2016, 11:26:32 am
content: Thank you very much for uploading Lorenzo. I have a HP3325A that I need to repair. Greatly appreciated!

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: August 03, 2016, 06:17:07 pm
content: Very nice!Much appreciated!

author: Tektron
author_rank: Contributor
timestamp: May 07, 2017, 11:20:32 am
content: Thank you very much Lorenzo!?ne more request please.Could you scan and share page5-2from03325-90002operating and service manual?This page containe paragraphs from 5-3 to 5-10 about adjustment of power supply, D/A converter offset, VCO frequency and API.Unfortunately in the KO4BB and KEISIGHT files this page has been replaced by a duplicate page 6-2.I need to adjust my 3325A...

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 07, 2017, 02:19:30 pm
content: No problem if I have them. Can't see why they won't be in the hardcopy. Will check tmrw AM.

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 08, 2017, 12:26:23 am
content: Scan attached. Let me know of you need anything more.

author: Tektron
author_rank: Contributor
timestamp: May 08, 2017, 06:11:04 am
content: Thank you very, very much Lorenzo!

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 08, 2017, 07:18:24 am
content: Glad I could help. FWIW, when I fixed a power supply issue a while back and followed this procedure I found it quite difficult to get the rails within spec. Finally managed it but one or other setting was right on the margin of the spec whichever way I went. Got it in the end, but a close run thing. Perhaps a sign that something's drifted off spec elsewhere in the supply. However, machine is working great and I'm leaving well alone.