IFR 7550 - dead keyboard - Page 1
Forum section: electronics / testgear

author: KD9CJX
author_rank: Contributor
timestamp: March 17, 2020, 12:54:11 am
content: Hi! I'm working on some projects I haven't had a chance to work on. I have an IFR 7550 spectrum analyzer with a dead keyboard. Boots up fine but will not respond to any input from the front. Previous owner suspected it might be a dead 3v lithium and I tracked it down to the digital motherboard that the keyboard is connected to by a ribbon cable (remember those!)Fortunately I have a working 7550 and I'd just like to swap the boards to see if that is in fact the issue before I break out the soldering iron. I did check the battery and she's stone cold dead, but again...before I start undoing something that "professionals" soldered during the cold war, I'd like to make sure.If they were the same firmware/revision, I'd just go right ahead, but the unit in question has PCB REV C and firmware version 3.7. Donor board is REV A and running firmware 2.80. Don't want to go creating two parts units if you know what I mean. Magic smoke is hard to come by right now with Coronavirus provisions.73JoeKD9CJX

author: korlatos
author_rank: Regular Contributor
timestamp: March 17, 2020, 11:23:07 pm
content: Hi Joe, you will need to replace the dead battery. I would recommend installing a 23mm coin cell holder. Once you install the holder and a fresh battery, follow the instructions from the last page of the service manual (attached) to reset the unit.

author: KD9CJX
author_rank: Contributor
timestamp: March 17, 2020, 11:55:39 pm
content: A little update - I was feeling saucy after a day of wondering if I'll be unemployed to all this virus stuff, so I figured what the heck. Put the other digital motherboard in and it fired right up and the keyboard works!I'll replace the battery next time I'm out and will go from there. After that, I have an IFR 1200S that needs the power supply looked at.Will post another update once it's done.73

author: jimmc
author_rank: Frequent Contributor
timestamp: March 18, 2020, 11:35:10 am
content: Thanks for the information, my A7550 has the same unresponsive keyboard so I shall take a look.In a similar vein does anyone have images of the EPROMs, I've not seen them for the A7550 (and the EPROMs are getting pretty old).At the risk of hijacking the thread does anyone have a service manual for my other analyser the IFR A8000.Jim

author: korlatos
author_rank: Regular Contributor
timestamp: March 18, 2020, 03:48:23 pm
content: My plan is to create EPROM images fairly soon - maybe this weekend. I believe there are three of them - two on the CPU board and one on the Video board. My A-7750 unit has the 3.70 firmware. Unfortunately, I don't have the A-8000 service manual.

author: KD9CJX
author_rank: Contributor
timestamp: March 20, 2020, 12:10:31 am
content: Sorry jimmc - I only have the A7550 manuals.73

author: jimmc
author_rank: Frequent Contributor
timestamp: March 20, 2020, 07:34:40 pm
content: I've now replaced the battery on the Control Processor board and I'm pleased to say that the analyser is working again.As korlatos suggested I used a 2032 battery holder which fitted the original holes although the positive pin had to be bent a little so that the holder cleared the adjacent resistor network.While the instrument was apart I imaged the EPROMs in spite of the warnings from this strange threadhttps://www.eevblog.com/forum/repair/ifr-8000a-repair-(manuals-welcome)/msg428733/#msg428733.My Control board is rev B and the firmware ver 3.60, the Video board is rev A with no version marked on the EPROMs.The checksums all matched, I confess that I was worried that after 30+ years the EPROMS might have started to become forgetful.Jim

author: KD9CJX
author_rank: Contributor
timestamp: March 21, 2020, 01:58:35 am
content: Man...those Z80 processors are sexy beasts. I had a TRS-80 model 4 when I was a kid. Blazing 4 MHz clock speed.

author: boelem_b
author_rank: Newbie
timestamp: August 09, 2023, 08:19:46 pm
content: Hi Korlatos, did you ever make an image of the 3.7 firmware on the Control PCB? Or can you share the checksums? My unit also has ver 3.7 and I would like to verify that the firmware is (still) OK. My checksums are 6B33 for U11 and 5CCE for U9. I can replace with the 3.6 firmware that is elsewhere in this thread, but I'm not sure if that is compatible with my unit. Background: My A7550 has no horizontal sweep. I traced it back to the CTC CE line staying high always. This originates from the video processor module, chip U20, which is a decoder chip, driven from the video CPU, U19 (also a Z80). I need to check inputs to U20 tomorrow and trace back some more. I don't have a logic analyser, so it is rather challenging working on a system with two CPU's. I suspect that the Sweep must be activated quite early in bootup sequence, as not even the IFR logo can be displayed without a sweep.