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Thanks, all! I forgot about the Auto Null function.

What a mess and unfortunately it happens. In addition to the various cleaning hints at least with nicad batteries I have found they do leave conductive stuff. Even though the boards been cleaned. In

excuse my mistake, I have done restoration 427A and 204B side by side on the table. The 22.5V Battery is correct. Can be swapped by 2 pcs of 9V Blocks lithium for backup light , they deliver 10.2V

Yes!!! You are a truffle pig! Tam With best regards Tam HANNA Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at https://www.instagram.com/tam.hanna/

Is it the video on the HP 419 meter? "https://youtu.be/vrmwql2msbU"

You are right, there are 3 CdS cells, and two lamps that are used to operate a Wein bridge that performs the auto null function. The last 334 that was in my shop had one bad CdS cell, and the bridge

Well to be fair, yours was a pretty general question that certainly applies here too. -Dave

Jeremy, Auto null. The neons and light sensitive resistors are used in a Wien bridge to automatically balance the null. Page 4.2 onwards describes the circuit in detail. Loss of a neon and its back to

Original battery is 22.5V. They are available but expensive. I made a battery pack using two 8 cell battery holders for AA cells and left one cell out putting a wire in place of the battery. probably

Jeremy, Auto null. ------ Best regards, Goran Finnberg The Mastering Room AB Goteborg Sweden E-mail: mastering@... Learn from the mistakes of others, you can never live long enough to make them

Unless my memory is failing, it's not strictly a chopper, but it's part of the automatic tuning system. The choppers are digitally-controlled switches, but I believe the LDR-based subsystem in the 33x

Purely out of curiosity, what is the purpose of a chopper in a 334 distortion analyzer? HP used choppers in a lot of their DC voltmeters to convert the DC to AC. They’d run the AC through some

hello Dave, yes, specials: The Power Line Supply is a Option and not always inside. 427A have a Set of 4 obsolete 6.75V mercury batterys, if they are tired and there is no PSU, build it self. The

Hello, a dude named CarlsonLabs has had a 2h video on replacing these neons. Never sat through it all the way to the fartingsound, don?t have a link handy but wanted to mention it. If there is

Certainly it could, but a bit of engineering time would be required to make sure that none of the specifications were compromised... -Chuck Harris n4buq wrote:

Tim, The other device was made by ADTECH as you noted, later ECI, which was bought by Alpha Microwave (when Control Data owned them) and became the basis for their MMW mixer line. My first boss at

Same problem with neon-choppers as found in the 410C. HP replaced that with a fully solid-state board towards the end of production. I wonder if something similar could be done for the 334A? Thanks,

Tim, Demornai-Bonardi 633 devices were directional couplers that coupled to a crystal detector on one coupled side and a flange on the other.? They were generally used with a reflecting cavity

Thanks everyone for the great suggestions. I will try them all. Starting with the simpler ones then moving up. The RF board is just a simple D/C to DC power supply. I shall report back. Thanks Dave

Thanks Nigel, I have found the IFR group. I should have looked first. Thanks Dave