HP 3314A Function Generator--No Display - Page 1
Forum section: electronics / repair

author: N2IXK
author_rank: Frequent Contributor
timestamp: July 21, 2024, 09:16:31 pm
content: Have a 3314A on the bench that I am trying to bring back to life. Powers up, fan runs, but none of the displays or annunciators light up. Not even a brief blink at startup.A quick check of the power supply rails found +/15V OK, +5V was around 1.6V. The 470 uF output filter cap (C105) on the +5V rail was found to be open (read 8 nF). Replacing it restored the +5V, so now the power supply is apparently functioning OK. All 3 rails at proper voltages and free from ripple. Because of the 1 bad electrolytic, I will plan to completely replace all the electrolytics in the unit. The lithium CMOS battery was also stone dead, and beginning to leak. Clipped it out.But restoring the power supply rail has failed to bring back any display or other sign of operation. A few quick checks with a scope show that the 2 1MHz clocks are running OK, and probing random pinsof the CPU and memory shows bus activity. The LED on the controller board comes on at power up, blinks a couple times as I hear a few reed relays somewhere clicking, then then goes out. It would seemthe the CPU is booting and executing code, at least up to a point. Tack soldered in a 3V coin cell in place of the dead CMOS battery, no difference. The power supply rails are making it to the frontpanel/display board. No chips seem to be getting excessively hot on any of the boards.This is apparently a later production unit (1987/1988 date codes on most parts, with only 2 ROMS on it, rather than 6.) The 2 ROMS (U206 and 207) look like they have been replaced, as the sockets appear to have been soldered in by hand, and the chips (27256 EPROMS) do not have HP labels/part numbers on them, just handwritten ones saying U206 and U207. The service manual troubleshooting charts and the various self tests you can initiate using the DIP switch all presume that you have a signature analyzer available, which I do not.Does anyone have any suggestions how to proceed from here? Any place I can get the files for the ROMs, so I can compare to what is on mine? Only seem to find the files for the 6 chip mask ROM version of the board.Thanks, and appreciate the input...

author: wn1fju
author_rank: Frequent Contributor
timestamp: July 22, 2024, 11:37:53 am
content: Go to K6JCA site:https://k6jca.blogspot.com/Select the two posts concerning HP3314A. Lots of repair ideas there. Also links to the ROM images on KO4BB's site.

author: Doug@APQ109
author_rank: Newbie
timestamp: March 26, 2025, 03:17:31 pm
content: I have an HP3314A with this same issue. Prior to no display it had the error, ERR30. It now has no display and the 3V battery is dead. I don't have the skill to fix it. I have little experience troubleshooting digital circuits. But when these devices are working they can be sold for a good amount as I have seen online. I was wondering if you would be interested in taking this one off my hands. I do not like seeing equipment like this being thrown away. I am not selling it. I just don't need it and will give it to anyone that would like to take a stab at fixing it, Or, selling it for part. It doesn't matter to me. I just don't want to throw it away. It is physically in fair shape: missing the power button extension and one foot is also missing.