Author Topic: [Video] Hitachi Oscilloscope V-1085 100MHz problem  (Read 3949 times)

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Offline felixd

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[Video] Hitachi Oscilloscope V-1085 100MHz problem
« on: October 12, 2015, 10:23:20 pm »
 :popcorn: :scared:

Hello all. This topic is to log all my steps while I'm trying to fix my problems with Hitachi Oscilloscope V-1085 100MHz

I've bought this oscilloscope two years ago and now it's high time to try to fix it.  :box:

Well, as I've find out later on it was not working like a charm  :-DD
https://www.eevblog.com/forum/chat/hitachi-oscilloscope-owners/msg304227/#msg304227

First 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
« Last Edit: October 13, 2015, 07:21:31 pm by felixd »
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Offline singapol

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Re: Hitachi Oscilloscope V-1085 100MHz problem
« Reply #1 on: October 13, 2015, 04:38:20 am »
Old scope, recap all the electroylytics and it will come back to life miraculously. ;)
 

Offline oldway

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Re: Hitachi Oscilloscope V-1085 100MHz problem
« Reply #2 on: October 13, 2015, 09:11:17 am »
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.
« Last Edit: October 13, 2015, 09:48:55 am by oldway »
 

Offline felixd

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Re: Hitachi Oscilloscope V-1085 100MHz problem
« Reply #3 on: October 13, 2015, 07:06:55 pm »
I don't agree....only replace what is really necessary.
...
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.

Part 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! :)  :-BROKE :-DMM
Found little cap that's really sensitive for touching :)  :-DD

Cap 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/Y2wRDrj5QpKJX2xo9

First repair candidate attached.
« Last Edit: October 13, 2015, 07:25:15 pm by felixd »
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Offline oldway

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #4 on: October 13, 2015, 07:32:10 pm »
Look also for defective trimpots...It happen often.
 

Online tautech

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #5 on: October 13, 2015, 07:40:34 pm »
Look also for defective trimpots...It happen often.
Are they the open skeletal type oldway?
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Offline German_EE

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #6 on: October 13, 2015, 07:46:14 pm »
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.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline felixd

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #7 on: October 13, 2015, 08:07:16 pm »
This looks like a crack joint for me R813 next to cap that I touched.
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Online tautech

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #8 on: October 13, 2015, 08:15:47 pm »
This looks like a crack joint for me R813 next to cap that I touched.
That wouldn't worry me, look more, especially around power connections and inter-connects.
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Offline felixd

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #9 on: October 13, 2015, 09:44:19 pm »
This looks like a crack joint for me R813 next to cap that I touched.
That wouldn't worry me, look more, especially around power connections and inter-connects.

Well 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 ;)
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Pawel 'felixd' Wojciechowski
 

Offline g3

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #10 on: February 01, 2018, 06:32:40 pm »
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.
 

Offline TonyLangley

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #11 on: March 30, 2018, 07:55:30 pm »
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 you

Tony
 

Offline Moonbase

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Re: [Video] Hitachi Oscilloscope V-1085 100MHz problem
« Reply #12 on: October 27, 2018, 02:47:43 pm »
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?
 


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