Hitachi V-202F Oscilloscope Schematics - Page 1
Forum section: electronics / repair

author: EduardoLM
author_rank: Contributor
timestamp: October 14, 2014, 07:38:27 pm
content: Hello everyone, I would like to ask for some help again. I have a broken Hitachi V-202F Oscilloscope.I still didn't even open it to investigate, because the service manuals I have found so far in the web are very low res: the text reads fine, but the schematics pages are completely unreadable.So I would like to ask: does anyone have a hardcopy or high resolution scan of the schematics of the V-202F?Thank you all very much!Eduardo

author: TerraHertz
author_rank: Super Contributor
timestamp: October 19, 2014, 06:43:39 am
content: I have an original Hitachi V-202, 352 service manual. Not yet scanned.I can scan it, but it won't happen for a few days. All the board overlays and schematics are foldouts, that take a bit of editing work to stitch together. Also it's stiff spined, and resists being flattened on the scanner.Oh that reminds me. A while ago I promised to scan a HP current probe manual for someone. I did the scans and tidied up the schematic scan, but never got around to posting the result. And I forget who that was for.Is the 202 much different from 202F? Wouldn't you know it, there's no pic of the scope front panel in the manual.And the scope I got this manual for was a V-352, which I gave to a friend after fixing it.Here's a rough scan of part of the mechanical drawing, with the front panel. Does it look the same?Incidentally, I recall the main problem with this scope was both channels had 'x1/x5' gain switches. Multi-pole, and the contacts had gone bad. Resulting in neither range working right. But they were impossible to get at without completely disassembling the scope. Also not the kind of switch that can be disassembled to clean contacts. So I just cut the tracks on the PCB to the switches, and hard wired for x1. Problem solved.

author: EduardoLM
author_rank: Contributor
timestamp: October 19, 2014, 11:06:55 pm
content: That's great, TerraHertz! I can wait until you have time to scan, no problem! And I can also "stitch" the scans together and repost the schematics here, to relieve you somewhat from the tedious work.About model numbers, I think V-202 is just like the V-352: V-202 is the 20MHz model, while the V-352 is the 35MHz model. Looking at the mechanical drawings, they look quite similar, but later I'll take a picture from mine and post here. About the F suffix, I have no clue what is means, but I hope it's a minor revision, with compatible guts (and schematics).Thanks for talking about the common problem with the gain switches, however I think mine has problems in the high voltage circuitry, since the previous owner told me the scope had no image on screen, and he claims to have tested high voltage presence on the "multiplier output" (his words), but found nothing. To tell you the truth, I still didn't try to power on the scope, I want to dismantle and examine it in detail only after getting the schematics, I don't want to blindly disassemble it, running the risk of making a fatal mistake.I have no experience with CRTs and analog electronics, so I want to read and study everything I can before going for it! That reminds me of another question: I just removed the main housing to examine the internals, and I saw no apparent flyback in the scope. Does this model use a flyback? Or no? And is there a way to test the tube to check if it is still good? My main fear here is that the tube gone bad, because it will be very hard to find a replacement if needed!Thanks a lot!Eduardo

author: Hydrawerk
author_rank: Super Contributor
timestamp: October 19, 2014, 11:28:28 pm
content: http://elektrotanya.com/hitachi_v-202f_203f_5mv_20mhz_sm.pdf/download.htmlhttp://mysharegadget.com/686027229Do you have this?

author: EduardoLM
author_rank: Contributor
timestamp: October 20, 2014, 12:05:36 am
content: Thanks for that, but this is the one I got: good quality service manual, but low-res schematics at the end. Some component names and values are readable, but some are not. If TerraHertz can make the scans in higher resolution, that will be great!Eduardo

author: tautech
author_rank: Super Contributor
timestamp: October 20, 2014, 12:23:37 am
content: Quote from: EduardoLM on October 19, 2014, 11:06:55 pmNot all CRO's do.Some have a HV winding on the mains transformer that provides the necessary tube voltages and is also multiplied for PDA.Some Hameg's do like this:

author: TerraHertz
author_rank: Super Contributor
timestamp: October 20, 2014, 01:26:28 am
content: I'll try to do it tonight. If I leave chores too long they tend to get bumped down the never-ending too-much queue.Resolution will be high.

author: Shock
author_rank: Super Contributor
timestamp: October 20, 2014, 12:41:59 pm
content: Quote from: TerraHertz on October 19, 2014, 06:43:39 amThat was me,Notsob did some rough scansof the set of 3 probes, so unless you going to do a good (or better) set for yourself I'm ok waiting, and if you do you might as well do your comparator at the same time as they are sort of from the same set really.Interestingly I ended up getting sent a 547a in something else I purchased so I've two now (as well as the comparator set).

author: TerraHertz
author_rank: Super Contributor
timestamp: October 21, 2014, 11:02:10 am
content: I've put a temporary copy up here:http://everist.org/archives/scans/Hitachi_V202-352.zip143 MB.This is a working set of the page scans at original scan resolution.Schematic sheets are stitched together, text pages are cropped to uniform size.No other processing done yet. Don't have time atm. Sorry about the huge filesize.Still to do:Fix tonal saturation of text pages.De-noise text pages.De-skew some of the pages.Reduce pages and schematic sheets to final size and optimal compression format.Bind in html, then in one RARbook file.But the schematics and board layouts are in good shape already. That's what you want.

author: EduardoLM
author_rank: Contributor
timestamp: October 21, 2014, 12:36:47 pm
content: TerraHertz, thank you very much!!! This is exactly what I needed, the quality is great, now my hopes to fix the thing are much higher! The size is completely compatible with the great scan quality!Thank you, indeed!Eduardo

author: Unknown
author_rank: Unknown
timestamp: December 18, 2014, 08:45:17 pm
content: I made an account just to say thanks TerraHertz, well and also because I like Dave's channel a lot. I literally just got home with this scope which I bought second hand, and yours is the only manual I could find online and it's of excellent quality! Thanks!Michael

author: tautech
author_rank: Super Contributor
timestamp: December 18, 2014, 09:08:09 pm
content: Quote from: mtemmerm on December 18, 2014, 08:45:17 pmWelcome to the forum Michael.Would you consider uploading it to:http://www.ko4bb.com/manuals/so it can be found from the links in the Repair board.KO4BB has a Hitachi folder, but it's hiding in Misc Test EquipmentHopefully withTerraHertz's approval.