Vintage Twins: Beckman DM78 and Hioki 3217

Today we have two tiny multimeters to take apart and see what we can learn from how their designs progressed:

On the left is Hioki 3217 and on the right – Beckman DM78

VintageTwins

Vintage twins next to the EEVBlog uRuller

The things are very tiny (108mmx54mmx10.2mm), true pocket meters with basic VDC, VAC, Resistance, Diode and Continuity buzzer. The latter even specs a 1mS response time! As I’ve discovered from the discussion on the EEVBlog forum, these are just two out of very many brand names that offered related meters over the year. Some of the other names included Micronta, Universum DM-6511.

Beckman Industrial DM78

Beckman

Beckman

No datecode I could decipher but one telltale is "made in Japan"

No datecode I could decipher but one telltale is “made in Japan”.

The user manual does mention 1990, so we have to assume the meter is at least that old. There is no removable battery compartment, instead a “Hinge” is made from the plastic of the back cover:

Bendy plastic- feels cheap

Bendy plastic- feels cheap

With one screw removed, the cover pops out pretty easily:

Not much here.

Not much here.

Good attention to details on test leads strain relief

Good attention to details on test leads strain relief

In-board components

In-board component-I am guessing a MOV

The board is held by a few case tabs and by the knob's locking washer

The board is held by a few case tabs and by the knob’s locking washer

And now we get to the “money shot”: a fairly clean and well though out design 

Some type of oscillator?

Some type of oscillator?

Conductive rubber contacts for the buzzer

Conductive rubber contacts for the buzzer

Front cover

Front cover-LCD with a zebra strip, Buzzer and range switch. Note the adjustment hole above the buzzer, aligning with the pot on the board

Guides for the buzzer conductive posts

Guides for the buzzer conductive posts

 Hioki 3217

And now let’s compare and contrast Beckman to Hioki, which most likely was the OEM for both:

An actual battery compartment. Back cover held by screws

An actual battery compartment. Back cover held by screws

Hioki is traditionally pretty transparent as far as the date of production- this one was made in 1986

No bent plastic here but a much less impressive buzzer connection

No bent plastic here but a much less impressive buzzer connection. Display is attached to the board with tabs

Batteries left in for quite a while

Batteries left in for quite a while

Similar trimming access hole on the front, some shielding foil around an oscillator

Similar trimming access hole on the front, some shielding foil around an oscillator

And now on to the main board:

Main board-

Main board-the SOIC looks very much identical to the one used on Beckman, wired buzzer.

Almost looks like a hack

Almost looks like a hack

Buzzer wiring and LCD

Buzzer wiring and LCD

Range switch pads

Range switch pads

 

Less convenient strain relief

Less convenient strain relief

Brief testing and conclusion:

Using my trusty DMM Check plus, we can check how well both meters operate 25+ years after manufacturing. Pretty impressive- isn’t it?

DMM Check Plus Beckman Hioki
100Ohm 100.2 100
1k 0.999k 1.002k
10k 9.99k 10k
100k 100k 100.1k
5V Dc 4.99V 4.99V
5V AC 5.45V 5.45V

It is interesting to see how related these two meters are- it is undeniable that they originated from the same design, with Beckman version mostly optimizing manufacturability and cutting a few corners in the case design.

Resources:

 

3 thoughts on “Vintage Twins: Beckman DM78 and Hioki 3217

  1. Mine is a hybrid. It is like the DM78 on the front but the back and battery compartment is like the Hioki. The internals are the same as the Hioki with wired buzzer and display attached to the board. My first meter, bought new in the 90s for very little. I need a new display for it.

  2. Thanks for this post. Because of it, I was able to disassemble my Beckman, clean the contact slides on the dial, and make it work like new! It’s now good for another 25 years of trustworthy service.

    One think you might mention is that one has to be very careful with the small black rubber? conductive cylinders that make contact with the piezo buzzer mounted on the front of the case. They are very small and are easy to lose. When removing the circuit board, one should be careful to look for the cylinders. In my case, one remained in the plastic housing on the front cover with the buzzer, but the other came off with the board. When I examined the board, I wondered what the strange component was that made only one contact with the board. Later, I heard something fall to the floor. Sure enough, the strange component was gone, and the buzzer didn’t work when I reassembled the unit. I did manage to find the missing piece, but it would have been nice to have been warned.

    Thanks, again, for this post. I am grateful that you have returned my beloved meter to service.

    Regards,
    K.

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