Uploaded January 2021 | Updated September 2026, 2 weeks ago
Note! I comment on the headband magnifier in the video and I say it is a LUXOR magnifier BUT when I looked at it after making the video I see it has printed in it OPTI-VISOR the Luxor company makes lamps I use when working on the work bench I got the two companies mixed up ...Senior Moment ...Designed in the 1970's the Heathkit IT-121 is a good instrument for testing bipolar transistors, Fet's and dual gate Mosfet transistors this one because of the brown case was produced probably in the early 1980's at Heathkit . I bought this one cheap as is because it did not work . This turned into quite a long project as many electronic repair items do. My total time working on it I estimate to be over 20 hours and was done over a three week period working evenings .I strived to do the job with what was on hand and did accomplish that . I found the main problem only after receiving the assembly manual and following the assembly instructions step by step if you buy a Heathkit manual on the internet and you are repairing a Heathkit you may want the assembly instructions too some people who copy manuals and sell them do not copy the assembly instructions they only copy the operating instructions there are copies of the IT-121 sold on the Internet that have lines and circles on the front cover these copies do not have the assembly instructions which I find helpful I bought this manual from the Radio Attic website the price was reasonable and it has all the assembly instructions in it . The short circuit I found was not visable at all it was under a coating of brown colored solder flux on top of a very crowded multi switch assembly.
I did not use Alcohol to clean the flux off of the many multi contact switches because I did not want the flux getting into the switches where it could cause more problems . Following the assembly instructions eventually led me to the hidden short circuit and then the successful repair of this nice instrument . It is obvious that this IT-121 never did work properly if at all. due to the shorted switch contacts and it set unused for probably over 40 years . 73 and have a happy 2021 everyone Bob
Bob
Note! I comment on the headband magnifier in the video and I say it is a LUXOR magnifier BUT when I looked at it after making the video I see it has printed in it OPTI-VISOR the Luxor company makes lamps I use when working on the work bench I got the two companies mixed up ...Senior Moment ...Designed in the 1970's the Heathkit IT-121 is a good instrument for testing bipolar transistors, Fet's and dual gate Mosfet transistors this one because of the brown case was produced probably in the early 1980's at Heathkit . I bought this one cheap as is because it did not work . This turned into quite a long project as many electronic repair items do. My total time working on it I estimate to be over 20 hours and was done over a three week period working evenings .I strived to do the job with what was on hand and did accomplish that . I found the main problem only after receiving the assembly manual and following the assembly instructions step by step if you buy a Heathkit manual on the internet and you are repairing a Heathkit you may want the assembly instructions too some people who copy manuals and sell them do not copy the assembly instructions they only copy the operating instructions there are copies of the IT-121 sold on the Internet that have lines and circles on the front cover these copies do not have the assembly instructions which I find helpful I bought this manual from the Radio Attic website the price was reasonable and it has all the assembly instructions in it . The short circuit I found was not visable at all it was under a coating of brown colored solder flux on top of a very crowded multi switch assembly.
I did not use Alcohol to clean the flux off of the many multi contact switches because I did not want the flux getting into the switches where it could cause more problems . Following the assembly instructions eventually led me to the hidden short circuit and then the successful repair of this nice instrument . It is obvious that this IT-121 never did work properly if at all. due to the shorted switch contacts and it set unused for probably over 40 years . 73 and have a happy 2021 everyone Bob
Bob
