Products > Test Equipment
History of Tachikawa (TMK)
fanOfeeDIY:
--- Quote from: joeqsmith on November 07, 2017, 01:31:13 pm ---Thank you for taking the time to check. I would have bet on it protecting the current input. It's strange how they would change how it was wired but maintain the same functionality. I wonder if this change was a labor savings.
--- End quote ---
Was or is your meter behaving differently when it does not have the fuse?
I am not completely understanding how the rotary switch work on the schematic (model AMK-200, you have posted on this thread), however the fuse seems to work for voltage and current but not for resistance.
https://www.eevblog.com/forum/testgear/history-of-tachikawa-(tmk)/msg1318383/#msg1318383
I just would like to know about this meter and your knowledge of surge protection knowledge on your youtube videos. :)
mzacharias:
I constantly peruse eBay for mutimeters. I have seen many variations on the theme of this IBM model. Lafayette had quite a few, Radio Shack even had one or two, maybe even Eico / TruVom (spelling?) I believe the OEM companies like TMK and Kamoden had agreements with Lafayette, Radio Shack, et al prohibiting them from directly competing in the U.S. market. This I believe is why you rarely see Kamoden or TMK branded VOM's in the U.S. but see many of their products from Radio Shack, Mura, and others.
coppice:
--- Quote from: mzacharias on November 08, 2017, 01:46:53 pm ---I constantly peruse eBay for mutimeters. I have seen many variations on the theme of this IBM model. Lafayette had quite a few, Radio Shack even had one or two, maybe even Eico / TruVom (spelling?) I believe the OEM companies like TMK and Kamoden had agreements with Lafayette, Radio Shack, et al prohibiting them from directly competing in the U.S. market. This I believe is why you rarely see Kamoden or TMK branded VOM's in the U.S. but see many of their products from Radio Shack, Mura, and others.
--- End quote ---
Was Lafayette a brand name of Radio Shack/Tandy? I remember seeing some TMK meters in the UK branded as Lafayette after Tandy starting opening shops there.
joeqsmith:
--- Quote from: fanOfeeDIY on November 08, 2017, 11:32:26 am ---Was or is your meter behaving differently when it does not have the fuse?
--- End quote ---
Mine originally worked like your dad's. The fuse only protected the resistance measurement. I changed the design to protect both the resistance and current measurements. The voltage still works without the fuse. The only reason I made this change was if I decide to use the meter in some future video for current, I wanted the added protection.
--- Quote from: fanOfeeDIY on November 08, 2017, 11:32:26 am ---I am not completely understanding how the rotary switch work on the schematic (model AMK-200, you have posted on this thread), however the fuse seems to work for voltage and current but not for resistance.
--- End quote ---
In that schematic, the fuse is in-line with everything. I am not sure how much protection it would really provide (for the meter) but it's better than nothing. I don't like meters that will not display the voltage with a blown fuse.
In the attached, I have marked the path for the 250mA setting.
--- Quote from: fanOfeeDIY on November 08, 2017, 11:32:26 am ---I just would like to know about this meter and your knowledge of surge protection knowledge on your youtube videos. :)
--- End quote ---
Those few videos where I modified the Kasuntest ZT102 and the UNI-T UT61E were my attempts at explaining it. From what I have seen most of the meters, well the ones that actually survive to some decent levels anyway, basically take the same approach to hardening the front end.
fanOfeeDIY:
--- Quote from: joeqsmith on November 08, 2017, 02:10:24 pm ---
--- Quote from: fanOfeeDIY on November 08, 2017, 11:32:26 am ---Was or is your meter behaving differently when it does not have the fuse?
--- End quote ---
Mine originally worked like your dad's. The fuse only protected the resistance measurement. I changed the design to protect both the resistance and current measurements. The voltage still works without the fuse. The only reason I made this change was if I decide to use the meter in some future video for current, I wanted the added protection.
--- End quote ---
I see, even I did not change the internal wiring, and it was different from yours, the fuse on my meter (or dad's :) ) was only for resistant and the fuse was not protecting the voltage and current.
I have an other analog meter made by Sanwa, and when I removed the fuse, all voltage, current and resistance stopped working.
Different analog meters seem to have different approach.
Looking forward for your future video. :)
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