HP 6428B power supply ammeter mount repair advice - Page 1
Forum section: electronics / repair

author: hagbard
author_rank: Newbie
timestamp: November 01, 2022, 01:49:24 am
content: Ladies, Gentlemen, I humbly beg you for sage wisdom. My father gave me a 1970s vintage HP 6428B power supply that appears to be fully functional but has suffered a mild, unfortunate accident where the ammeter on the front panel was pushed inwards enough to break the little plastic tabs that held it in place. The meter still works marvelously.I am hoping that someone here may know a clever way to retain the meter in place on the front panel or recognize the plastic clip as a generic part that I can source from somewhere. According to the service manual, the ammeter is HP part number 1120-1180 but I can't find anything on the internet using that number. A part number visible on the meter itself, 525-536C appears to be common to many different HP analog meters and google searches for that PN have found some sellers offering used meters, but I've only found one that appears to also have the plastic clip for $30 here:https://teamequip.com/hp-hewlett-packard-5060-4961-sk-525-536c-volt-meter-t96521/I believe the part I want is listed in the service manual as, "Bezel, Meter, <unreadable> MOD," and has the part number 4040-0296. Googling that I find it listed on a few websites with an NSN, 6695-01-094-1575. This appears to be a unified DOD/NATO identifier of some sort and despite many websites listing it, none appear to actually have it for sale.The face of the meter appears to be 3.5" wide and 1.75" tall.My first idea was to just epoxy the meter to what remains of the plastic retaining clip and, while crude, I may resort to just that. Another idea was to replace the meter with something digital as it appears to just sit across a 0.01Ω shunt. There is a small, second transformer with a full bridge rectifier presumably as a logic supply voltage I can probably tap off of to power a digital panel meter. This also seems non-ideal.Here are some images of the patient and wound.First, the plastic clip I'm babbling on about:The meter. Note, the four small springs that sit in pockets around the meter face aren't shown as I'd already put them in a small envelope for safe keeping.A side view of the identically-sized voltmeter showing how it's held in place:Lastly, in removing the front panel, the plastic housing with the "power on" neon indicator lamp came apart. Replacing neon indicators with LEDs seems to be sufficiently common that I think I can handle this on my own, but I welcome any suggestions.Thank you for your thoughts.

author: enut11
author_rank: Super Contributor
timestamp: December 03, 2022, 08:51:48 am
content: I would glue the meter in place. If you want to make it less permanent, what about silicone sealant?enut11

author: factory
author_rank: Super Contributor
timestamp: December 03, 2022, 02:16:37 pm
content: From the 3DP thread, there is a meter frame, only trouble it gives no sizes and these panel meters were made in a couple of sizes.Quote from: beanflying on March 09, 2019, 06:32:38 amNeon panel lamps are still made, 2150A4 with diffused lens is the similar to the original (check the diameter is correct) expect the resistor is inside the lamp (according to the datasheet), unfortunately nil stock ATM, but others are in stock:https://www.mouser.com/c/optoelectronics/lamps-holders/panel-mount-indicator-lamps/?mounting%20hole%20size=5%2F16%20in&operating%20supply%20voltage=105%20VAC%20to%20125%20VACDavid