We calibrated the TS-505, Simpson 303, HP-412 and other VTVM models. They were all replaced with newer technology or deemed too expensive to repair. We had a quonset hut full of obsolete test equipment Tektronix, HP, Radio Labs, don't even remember all the brands anymore. All the operator and service manuals were with them. The U.S. government had a limit on costs spent to repair each piece of equipment. I was an ET during the Golden Age of electrinics. Nice item here and well preserved. Boeing probably had very high standards for maintaining their test equipment. Our standards equipment was traceable to the National Bureau of Standards in Boulder Colorado.
I acquired one of these for $10. Used to be in the inventory at Boeing. Similar condition, operational, but in need of electrical re-fresh. Very timely content and should prove helpful for the process. Thanks for the great content!
Hi this is a beautiful piece, I have restored a HP427A and am currently working on restoring an HP3400A there a Nuvistor tube is used in the input amp - it was also faulty in my meter, luckily I was able to buy a brand new one. The photo chopper in this meter is also solved using neon lamps - I hope it will work, but with your meter, the bulbs with the motor are completely luxurious. For the HP 3400, I checked all the Sprague electrolytic capacitors and was amazed because some of them had better parameters than the new ones I bought for replacement. So I hope it serves you well and measures accurately. Nice day 🙂 Tom
What year is your 412a? I restored a 1962 and the gain pot is on the top of the off that lower section where yours is on the side. Also the meter cal is accessed from the right side just above the chopper. Thanks for the video. It helped me! The .47’s, the 20uf’s and that 1500uf were all bad! The 1500uf showed as a resistor, like 2 milliohms. Yeah, it was bad. But changing that allowed for the bias adjust to work, before it would just peg the meter. I also replaced any resistors that were out of spec. Nothing on the selector rotary switch got changed as those are super high quality. Edit. That 1500uf cap on mine was only a 10v. Are you sure that’s a 100v on yours? If so I may try to find something with a higher voltage!!!
I bought one at a good price. I am thinking of using banana plugs so I can use different cables, however, I see on lines are grounded. Not sure how that will work out. I might test before committing.
@@ZenwizardStudios I am assuming to reduce outside noise at the lower voltages. Pretty much my thought. A BNC connector and cable with a alligator on the end might work but that has it's down side too.
For these cables it is also important to connect the shield ONLY on one end not both. It will throw things off if there is current flowing in the shield. Ground loops can be hair pulling to track down.
The burden voltage is the voltage developed across the current shunt. In this case I was using one of the exotic pieces of gear in the lab a Keithley 2450 SMU. This gives me a direct read out of the burden voltage. I will need to do a video on how to measure it with out the SMU but I can add that to the video list if there is interest.
@@ZenwizardStudios SMU is a completely luxurious matter, once you get used to it, it is difficult without it, it can make a lot of measurements easier.
We calibrated the TS-505, Simpson 303, HP-412 and other VTVM models. They were all replaced with newer technology or deemed too expensive to repair. We had a quonset hut full of obsolete test equipment Tektronix, HP, Radio Labs, don't even remember all the brands anymore. All the operator and service manuals were with them. The U.S. government had a limit on costs spent to repair each piece of equipment. I was an ET during the Golden Age of electrinics. Nice item here and well preserved. Boeing probably had very high standards for maintaining their test equipment. Our standards equipment was traceable to the National Bureau of Standards in Boulder Colorado.
I acquired one of these for $10. Used to be in the inventory at Boeing. Similar condition, operational, but in need of electrical re-fresh. Very timely content and should prove helpful for the process. Thanks for the great content!
I hope the restoration goes well it is a fantastic meter with quite good accuracy for the time.
Hi this is a beautiful piece, I have restored a HP427A and am currently working on restoring an HP3400A there a Nuvistor tube is used in the input amp - it was also faulty in my meter, luckily I was able to buy a brand new one. The photo chopper in this meter is also solved using neon lamps - I hope it will work, but with your meter, the bulbs with the motor are completely luxurious. For the HP 3400, I checked all the Sprague electrolytic capacitors and was amazed because some of them had better parameters than the new ones I bought for replacement.
So I hope it serves you well and measures accurately.
Nice day 🙂 Tom
I like that repurposed ashtray. I haven't seen one of those in a long time.
Nice meter.
Believe it or not it came with the building. Nice heavy glass dish for bad parts.
What year is your 412a? I restored a 1962 and the gain pot is on the top of the off that lower section where yours is on the side. Also the meter cal is accessed from the right side just above the chopper. Thanks for the video. It helped me! The .47’s, the 20uf’s and that 1500uf were all bad! The 1500uf showed as a resistor, like 2 milliohms. Yeah, it was bad. But changing that allowed for the bias adjust to work, before it would just peg the meter. I also replaced any resistors that were out of spec. Nothing on the selector rotary switch got changed as those are super high quality.
Edit. That 1500uf cap on mine was only a 10v. Are you sure that’s a 100v on yours? If so I may try to find something with a higher voltage!!!
I bought one at a good price. I am thinking of using banana plugs so I can use different cables, however, I see on lines are grounded. Not sure how that will work out. I might test before committing.
The cables are shielded for the lowest ranges.
@@ZenwizardStudios I am assuming to reduce outside noise at the lower voltages. Pretty much my thought. A BNC connector and cable with a alligator on the end might work but that has it's down side too.
For these cables it is also important to connect the shield ONLY on one end not both. It will throw things off if there is current flowing in the shield. Ground loops can be hair pulling to track down.
My brain is not working well today (medication). How does one figure out the burden voltage with a meter? Thanks Rick
The burden voltage is the voltage developed across the current shunt. In this case I was using one of the exotic pieces of gear in the lab a Keithley 2450 SMU. This gives me a direct read out of the burden voltage. I will need to do a video on how to measure it with out the SMU but I can add that to the video list if there is interest.
@@ZenwizardStudios SMU is a completely luxurious matter, once you get used to it, it is difficult without it, it can make a lot of measurements easier.
@@ZenwizardStudios I would love to see a video about calculating burden voltage. Sorry for the delay, life got in the way.