HP 3582A Repair help - Page 1
Forum section: electronics / repair

author: bsgd
author_rank: Regular Contributor
timestamp: March 12, 2021, 12:44:12 pm
content: Hi guys!I need some help from the experts in here.I have spent a few days trying to find many issues Im having with a HP 3582A spectrum analyzer. It powers on but all I get on screen is garbage. ALL front panel LEDS are on, no Data Loading blinking, so I know the processor is not running. I have narrowed the problem down to the A7 Processor board, since I have managed to get another board borrowed from a friend whose 3582A works fine and my unit does power up with this board installed.I have tried my best to find the source of the problem on my board, but nothing helped so far. Here's what I've done on the processor board:- Tested and replaced all electolytics (the originals were fine but I replaced them anyway since I had already desoldered them).- Dessoldered all ICs on the board, except for U19, U20, U22, U6 and U1 (the processor itself). I have tested every IC using the TTL/CMOS test function of a universal programmer and all of them pass the test, even though Im not sure how realiable these tests are. U19, U20, U22, U6 are all HP part numbers so I wouldnt be able to test them with my programmer, and Im not sure how often these fail to test them on a breadboard, and even if such test would give useful results since I wouldnt be able to replicate the speed and conditions these usually work on.- Tested all transistors (there are only 3 of them on the board)- Tested -5V regulator U24- Clock signal seems fine at TP1 and TP2I dont know what else to try or to look for as I have been banging my head on this for a week nowwith absolutely zero progress so far...

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 12, 2021, 01:11:11 pm
content: Are the 4 supply voltages correct?Does the processor get the reset (POP?) pulse?Is there any activity on the address/data lines?Did you inspect the pcb thoroughly?

author: bsgd
author_rank: Regular Contributor
timestamp: March 12, 2021, 03:30:24 pm
content: Quote from: PA0PBZ on March 12, 2021, 01:11:11 pmYes, +5, -5, +12 and +7V are spot on.Processor does get the POP voltage. When device is turned on voltage is 0V and after a second or so goes to +5V and stays at +5V. Pressing the reset button makes voltage go to 0V and back to +5V when released.I did inspect the PCB a thousando times and saw nothing wrong. It was in 100% original condition, no leaky caps and nothing out of ordinary. I will take another look today with a magnifier.Regarding the activity on data lines, I wouldnt know what to look for so I havent checked. What pins should I look and what should I expect to see?

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 12, 2021, 04:08:11 pm
content: Looks like they call it the IDA bus (Instruction Data and Address), there's a nice connector on the top of the PCB with all the signals.You do have a scope I hope?

author: bsgd
author_rank: Regular Contributor
timestamp: March 12, 2021, 06:00:30 pm
content: Yes, I do have a scopeI have made some measurements on the IDA connector, the one on top of the Processor board. There is activity, but my impression is that the waveforms make no sense for a communication bus.I do not know which pin is 1 on the IDA connector, so I called pin 1 the first pin on the left, staring ate the component side of the board. I only probed the pins on this side, even thoug the connector is double sided.PIN 1 reads +5VPIN 3 reads 0VPIN 7 reads +5VPIN 10 reads +5VPIN 11 reads 0VAll pins after pin 11 are interconnected to pin 11.The other pins do have some waveform present, and I have attached all print screens for each of these pins. Sorry for the very small images, not sure why my scope is doing this. I have also attached a picture of my 3582 screen so you get the idea of whats going on here.NewFile1.png(5.47 kB. 320x234 - viewed 376 times.)

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 12, 2021, 07:47:33 pm
content: Do you have the service manual? What kind of processor is this anyway?Pin 5 doesn't look too healthy, and I can't even explain what seems to be a sine wave on pin 9.According to the service manual pin 0-15 are IDA0- IDA15 which should all have the same levels, by the looks of what you are showing 0-5 volts.

author: bsgd
author_rank: Regular Contributor
timestamp: March 12, 2021, 08:32:21 pm
content: Yes, have the service manual here.I dont know whats pin 9, but I decided to put in the working board I borrowed and compare. Here is a screen shot of what pin 9 should look like.To me it looks like some kind of clock signal that is pulled high from time to time. Not sure what this is, but I do know that on the not working unit this signal never get pulled high.I also probed the other pins on the working board and signals are square waves from 0 to 5V with varying 'bits' going through the communication bus, as expected. On the defective board, most comunications is just not happening as far as I can tell, although some signals are present.

author: sparkfun
author_rank: Newbie
timestamp: November 29, 2023, 10:20:52 pm
content: I just repaired the processor board in my device. The analyzer was not operated for about 8 years and then it was broken.Screen looked correct in test mode but otherwise it shows just weird/ no characters and lines. (Actually it is the same screen you get when holding the reset button pressed on a working set. There were all lights on at the front panel and no reaction to any controls.I found no signals at all at the connector above the processor. It was not getting warm despite all voltages and clocks were present, Reset pin was also working.I pulled the board and found that the -7V line that goes only into to the processor had no contact (There was no diode to be measured to GND).So I removed the die cast with the processor below. It is contacted with a golden thick thread. The processor is bonded on a ceramic substrate with golden pins but the looked grey and corroded.Hence I cleanded the contacts on the ceramic with an eraser that they looked shiny again.I mounted the processor and everthing worked immediately again as expected.