Author Topic: Hioki 7020 - looking for service manual  (Read 1305 times)

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Offline DavidKoTopic starter

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Hioki 7020 - looking for service manual
« on: October 25, 2021, 08:50:47 pm »
Hello,
I'm searching for service manual for Hioki 7020. Hioki official statement is that it is long time unsupported device. Some frequencies are out of the range. There is lot of trimpots and test points inside, but the marking does not give a hint.

At least I have dumped the FW 1.20 if someone can have a use for it
 

Offline DavidKoTopic starter

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Re: Hioki 7020 - looking for service manual
« Reply #1 on: November 17, 2021, 11:05:27 pm »
To my surprise the device uses universal transformer. After some measurements I have changed the "jumper" to from 100V to 240V one (one cable is not necessary, but I do not waste him, so I have only doubled the connection that is already there).

I have also replaced the input filter before doing this. I have bad experience with X2 caps in old devices
 

Offline DavidKoTopic starter

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Re: Hioki 7020 - looking for service manual
« Reply #2 on: November 17, 2021, 11:17:54 pm »
Some pictures

The picture of the first board is missing. During the first repair I have dumped the FW, but I forgot to make a picture  :(. It cannot be removed without removing the front panel.
 

Offline DavidKoTopic starter

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Re: Hioki 7020 - looking for service manual
« Reply #3 on: November 18, 2021, 10:14:16 am »
It looks that service manual is unobtainium. I have tried to ask for it, but the reply is that they will not calibrate it and it is unsupported device.

At least the user manual is still available online on their site https://www.hioki.com/download/29153
 

Offline alex-kv

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Re: Hioki 7020 - looking for service manual
« Reply #4 on: September 22, 2024, 02:10:34 pm »
The low current output stage had failed on my 7021, so I reverse-engineered to better understand what I was doing during repair.
Here is the partial schematic of the motherboard
 

Offline alex-kv

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Re: Hioki 7020 - looking for service manual
« Reply #5 on: September 22, 2024, 02:15:48 pm »
Also, my 7021 needed readjustment, so I made again a bit of reverse-engineering of the REF/DAC board. The schematic is not complete, the whole part around the AC-to-RMS AD536A and the Voltage-to-Frequency Converter AD654 is absent.
 

Offline alex-kv

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Re: Hioki 7020 - looking for service manual
« Reply #6 on: September 22, 2024, 02:25:59 pm »
... and now the main analog board part, still partial. The digital part and most of the stuff around the relays and the power resistors is missing.
I have made some notes next to resistors leads, which was THT radial mounted: C means "short lead" and L means long lead. There is also some notes B and H for Bottom and Top respectively.
The Excel file shows what can be adjusted by turning most of the pots.
« Last Edit: September 22, 2024, 02:30:27 pm by alex-kv »
 

Offline alex-kv

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Re: Hioki 7020 - looking for service manual
« Reply #7 on: September 22, 2024, 02:27:45 pm »
And to finish, here is the EPROM V1.20 of the 7021 (7020 without the AC option)
 


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