[Video] Hitachi Oscilloscope V-1085 100MHz problem - Page 1
Forum section: electronics / repair

author: felixd
author_rank: Regular Contributor
timestamp: October 12, 2015, 10:23:20 pm
content: Hello all. This topic is to log all my steps while I'm trying to fix my problems with Hitachi Oscilloscope V-1085 100MHzI've bought this oscilloscope two years ago and now it's high time to try to fix it.Well, as I've find out later on it was not working like a charmhttps://www.eevblog.com/forum/chat/hitachi-oscilloscope-owners/msg304227/#msg304227First problem I faced is time base related. It looks like it's jumping all around on initial turn on and settles down after 10-15 minutes (but not completely, it can re-appear).Second problem is with "screen width". I wasn't able to get on video yet but sometimes trace/screen is being squeezed (looks like it's same timebase/display issue).I wasn't able to find correct service manual for this scope but I've managed to find one for V-1060 model (same boards numbers).*Please find below videos. More coming*I'll keep you updated(it's high time to go to bed, 0:30 AM in Poland).Edit: Just found this EEVBlog thread:https://www.eevblog.com/forum/testgear/teardown-hitachi-v1065/Edit2:Photos:https://goo.gl/photos/Y2wRDrj5QpKJX2xo9

author: singapol
author_rank: Frequent Contributor
timestamp: October 13, 2015, 04:38:20 am
content: Old scope, recap all the electroylytics and it will come back to life miraculously.

author: oldway
author_rank: Super Contributor
timestamp: October 13, 2015, 09:11:17 am
content: I don't agree....only replace what is really necessary.I am in favor of the minimum replacement except if some electrolytics are known and proven to be of bad quality.It often creates new failures by removing and replacing parts that should not be changed.Check power supplies for ripple and if the ripple is good, do not replace the electrolytic.The intermittent failure seems to come from bad contacts or cold solders.Hit the circuit with an insulated tool to see if you can cause failure.Clean all contacts.Inspect capacitors (leakage) and solders.Check connectors.Resolder all the ground connexions and components with high thermal inertia.Cold spray can also help to locate the failure.NB: don't use cold spray on HV circuits.

author: felixd
author_rank: Regular Contributor
timestamp: October 13, 2015, 07:06:55 pm
content: Quote from: oldway on October 13, 2015, 09:11:17 amPart 3 of my investigation. I was hitting table to check if it affects the problem. It was.Than I opened device and after some minutes I thought to check part of board where calibration is done. BANG!Found little cap that's really sensitive for touchingCap is located on PEF-902 board. Let me check manual I have for it.Now it's high time to take it all apart and have a closer look.Edit:Photos:https://goo.gl/photos/Y2wRDrj5QpKJX2xo9First repair candidate attached.

author: oldway
author_rank: Super Contributor
timestamp: October 13, 2015, 07:32:10 pm
content: Look also for defective trimpots...It happen often.

author: tautech
author_rank: Super Contributor
timestamp: October 13, 2015, 07:40:34 pm
content: Quote from: oldway on October 13, 2015, 07:32:10 pmAre they the open skeletal type oldway?

author: German_EE
author_rank: Super Contributor
timestamp: October 13, 2015, 07:46:14 pm
content: Twenty years ago when I was a young field service engineer I had one of these instruments as my scope. They might say 100 MHz on the front but they work well beyond that.

author: felixd
author_rank: Regular Contributor
timestamp: October 13, 2015, 08:07:16 pm
content: This looks like a crack joint for me R813 next to cap that I touched.

author: tautech
author_rank: Super Contributor
timestamp: October 13, 2015, 08:15:47 pm
content: Quote from: felixd on October 13, 2015, 08:07:16 pmThat wouldn't worry me, look more, especially around power connections and inter-connects.

author: felixd
author_rank: Regular Contributor
timestamp: October 13, 2015, 09:44:19 pm
content: Quote from: tautech on October 13, 2015, 08:15:47 pmWell I've investigated PEF-902 board for about 30 minutes. This resistor had worst joint on whole board. I've resoldered it and neighbouring cap (as I don't have 47uF one for replace - I have to order one) and problem seems to be "fixed" for a while. Time base (horizontal size) was jumping for few second when I powered oscilloscope but I settled down afterwards. Looks fine now, it doesn't react for touching and when I hit table

author: g3
author_rank: Newbie
timestamp: February 01, 2018, 06:32:40 pm
content: Hello,I recently disassembled a Hitachi V-1085 oscilloscope. No chance to repair, CRT has a crack and possibly the high-voltage transformer is also defective.So I thought I'll announce that I have some spare parts. Tell me if you need anything.

author: TonyLangley
author_rank: Newbie
timestamp: March 30, 2018, 07:55:30 pm
content: Hello Felixed:By any chance have you come across working LOPT ( Fly-back) transformer actually needed for a V-1060 which is in need of repair.Thank youTony

author: Moonbase
author_rank: Contributor
timestamp: October 27, 2018, 02:47:43 pm
content: Hey g3,just saw you maybe have some spares. I know this is an old thread, but maybe … I’m desperately looking for S1603 (the selector switch) for my V-1065C, is there any chance maybe the switch or the front assy is still available?