#37 Hewlett Packard 410A VTVM tear down  - Page 1
Forum section: electronics / general

author: Radio Tech
author_rank: Frequent Contributor
timestamp: March 15, 2016, 12:11:38 am
content: In this video we tear down the HP 410A vtvm.Inside the bottom of the unit we find a board that appears to be an add on that is not listed in the B.O.M. or schematic.Will be a lot of work to get this old unit back operation but I think it is doable.2-01c tubehttps://frank.pocnet.net/sheets/140/2...Hewlett Packard manual archivehttp://www.hparchive.com/hp_equipment...Will add some pics to my websitehttp://gokarters.com/smf/index.php?to...

author: German_EE
author_rank: Super Contributor
timestamp: March 15, 2016, 09:19:22 pm
content: If you have the schematic (and you are used to tracing tube circuits) could you not add the extra module to the schematic and find out what it does that way? I once did a similar exercise in a digital clock and found out that it was an addition to convert it from 60Hz to 50 Hz operation.Glad the Icom parts have arrived, I'm looking forward to seeing that one fixed.

author: AF6LJ
author_rank: Unknown
timestamp: March 15, 2016, 09:43:00 pm
content: Looks like a ballast tube they are used for voltage regulation usually in filament circuits and on rare occasions in some solid state gear.From the Wild Ass Guess department.I wonder if the filament winding on the main transformer is bad and someone added that transformer and ballast tube to keep the 410A going...

author: Radio Tech
author_rank: Frequent Contributor
timestamp: March 15, 2016, 10:32:35 pm
content: Quote from: German_EE on March 15, 2016, 09:19:22 pmYep already did a makeshift diagram of it. I do a little more explanation on Sues reply below.And yes, was glad to see those parts arrive. Although Icom charged me for all the parts but shorted me 2 12 pf caps. After a quick email to Carl he kindly shipped the missing parts. Part two of the Icom IC 745 series coming tonight.Quote from: AF6LJ on March 15, 2016, 09:43:00 pmYour first part is correct. Paul and Mike both had information on the mysterious circuit.It was actually a add on from HP and is a current regulation circuit for the 2-01C tube. The tube on board is a 6-4 and does the current regulation. It is very similar to the 410B vtvm and that one has it built into the main transformer.So Sue, pretty darn good guess there.

author: RobertoLG
author_rank: Frequent Contributor
timestamp: March 15, 2016, 10:40:45 pm
content: interesting this probe inside, never saw something like that, before you opened it, I was thinking why a so big probe, kinda funny looking lol

author: Radio Tech
author_rank: Frequent Contributor
timestamp: March 15, 2016, 10:46:42 pm
content: Quote from: RobertoLG on March 15, 2016, 10:40:45 pmI have heard of them, although never seen one. The 2-01C is just a diode in tube form. Very interesting.

author: RobertoLG
author_rank: Frequent Contributor
timestamp: March 15, 2016, 10:59:12 pm
content: I know it doesn't have anything to do with the HP, but just for the sake of it lolan ancient transistor

author: Radio Tech
author_rank: Frequent Contributor
timestamp: March 15, 2016, 11:02:05 pm
content: I think I have some like that in the shop. Will have to look

author: RobertoLG
author_rank: Frequent Contributor
timestamp: March 15, 2016, 11:19:23 pm
content: a mechanical filter, you probably will have one of these too

author: Andy Watson
author_rank: Super Contributor
timestamp: March 15, 2016, 11:30:26 pm
content: HP journal (1950, Vol 2, 3) mentions an upgrade kit to incorporate some of the 410B improvements into the 410.http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1950-11.pdf

author: Radio Tech
author_rank: Frequent Contributor
timestamp: March 15, 2016, 11:39:14 pm
content: Quote from: RobertoLG on March 15, 2016, 11:19:23 pmOne or two laying around here. most of what I have is vintage Collins filters.You seem to have a few also.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: March 16, 2016, 12:05:49 am
content: Quote from: Andy Watson on March 15, 2016, 11:30:26 pmVery nice, Thanks Andy.

author: RobertoLG
author_rank: Frequent Contributor
timestamp: March 16, 2016, 02:04:11 am
content: Quote from: Radio Tech on March 15, 2016, 11:39:14 pmyes, just a few parts, random stuff from old boards and stuff I did take apaaarrrtt!

author: AF6LJ
author_rank: Unknown
timestamp: March 16, 2016, 03:04:01 pm
content: Quote from: Radio Tech on March 15, 2016, 10:32:35 pmThat is exactly what I thought it was for.