Rockland 5840 FFT revival - Step 1- Rechargeable Power Supply board - Page 1
Forum section: electronics / repair

author: guswin95
author_rank: Contributor
timestamp: January 29, 2023, 10:44:36 pm
content: Hello all,A short while ago I got a Rockland in somewhat working condition, from eBay. Have never seen any of these before and there is very little info on the net. Always like the idea of a spectrum analyzer for audio. And of course, no manuals nor much info is available anywhere. If anyone has info and can share it, it would be appreciated.Although it powers up and somewhat works it complains about the NVRAM, and smells hot very quickly.After a good outside cleaning, I took it apart and it is very unique equipment. It has a back cover with a universal PS and a secondary board that charges a large Panasonic 6V 10-amp battery. Probably used for field operation.Of course, the Panasonic 6V battery is dead, and shows as a complete open circuit. When initially testing the unit I smelled a bit of overheated components, therefore the need to open up.In this back cover is the universal supply as mentioned, and a secondary supply that is the board I will concentrate on. There is a big resistor that gets very hot very quickly. It appears a classic design with an LM723 and a 2N3055, but extra parts are unclear the purpose.BTW, the 3.25V button type battery on the main board was dead, and a rechargeable battery of 3.6V was also dead. Parts are coming for that as the battery was not as common. It's a CR2325, large disk.I will post pictures and will continue with the secondary board's problems.

author: bidrohini
author_rank: Regular Contributor
timestamp: January 30, 2023, 01:02:55 am
content: Did you ask the seller for a manual? Without that, the task will be very difficult.

author: EEVblog
author_rank: Unknown
timestamp: January 30, 2023, 01:04:29 am
content: I had a Rockland FFT once, sold it on ebay. Brings back memories.

author: edpalmer42
author_rank: Super Contributor
timestamp: January 30, 2023, 01:42:04 am
content: Really? First hit on google.sphere.bc.ca/test/stuff/parts10/rockland_5840a_users_manual.pdfNo schematics, unfortunately.Sounds like a company with a sense of humor.Quote

author: guswin95
author_rank: Contributor
timestamp: January 31, 2023, 08:17:21 pm
content: Hello all,Sorry for the slow progress as work and weather have delayed things.I appreciate the manual, as I did look in Google and not much appeared so far in my search. I knew some colleagues here have a lot better skills finding documents.I will post pictures now and do a recap.

author: guswin95
author_rank: Contributor
timestamp: January 31, 2023, 08:18:32 pm
content: Pictures

author: guswin95
author_rank: Contributor
timestamp: January 31, 2023, 08:33:26 pm
content: So far the issue is R14 gets hot very quickly. And LED D15 will not iluminate.But this is with a dead battery that appears to be open. The red and black cable going to the battery provide a steady 7.2V if I remember correctly.Connector J2 has the following notes:1- Red - 14.6 VDC from switching PS2- Black - 0 VDC Ground3- Blue - 7.04 VDC4 - NC5 - Yellow - 6 VDC6 - NCQuestion is the battery necessary to complete the circuit and that is why R14 is so hot? Per the manual it appears it is not necessarily so. In that case suggestion on where to start looking to troubleshoot this board. Passive measurements show all components to be ok, and the output voltage appears steady and constant.Suggestions are welcomed.

author: varjag
author_rank: Contributor
timestamp: October 04, 2024, 08:02:09 pm
content: Hi,I recently obtained the same model unit by basically saving it from a dumpster. Operational but with dead backlight.What's the value on your R14, can't quite make it from the picture? Mine came with a baked and cracked carbon resistor that I replaced with a 5W 100Ohm to my best guess.The display is a Panasonic unit with electroluminiscent backlight sheet. Trying to figure out if it's the backlight sheet or its supply that is dead…

author: guswin95
author_rank: Contributor
timestamp: October 18, 2024, 03:24:03 pm
content: Hello,Before mine fully discolored, it appeared to be a 15-ohm 3 W resistor. Still measures that. I have not done much progress as other easier projects are popping up and taking my time.Keep us posted if you can, and good luck.

author: varjag
author_rank: Contributor
timestamp: October 21, 2024, 08:10:56 pm
content: Quote from: guswin95 on October 18, 2024, 03:24:03 pmThank you! Hope you don't mind me hijacking your thread a bit.My unit came without a battery and not sure it ever was installed. Either way the charger circuit is there.Right now the unit is a pile of boards on the bench. It's not quite HP tier mfg quality. The OEM Japanese display controller looks like it was made a decade after the rest of the unit.

author: varjag
author_rank: Contributor
timestamp: October 23, 2024, 06:55:44 pm
content: So this is how the unit looks inside. EL panel supply is on the middle board.

author: varjag
author_rank: Contributor
timestamp: October 23, 2024, 07:00:18 pm
content: The panel in question. Completely alien tech to me. What kind of supply it expects, some AC I figure? What's the proper way to test it?The size is 242x110mm under lamination, nothing like this p/n on eBay. 3.6M across terminals. Only two of the terminals are connected to the traces and one of those doesn't look good.

author: varjag
author_rank: Contributor
timestamp: April 28, 2025, 07:20:28 pm
content: Finally got some time to look into this again. It looked like the backlight inverter had troubles starting up. Sometimes however it would kick in producing 1.5KHz at 110V which as I understand is within expected for electrofluorescent backlight. It however would immediately die under load.So I checked the transformer subassy. The electrolytic cap was reading erratic; 56nF high voltage film cap was shot. I replaced these and for the good measure pulled other electrolytic and tantalum caps from the controller board. Two 3300 nF ones were reading 30% over capacity which I figure isn't a good sign. The two tantalums were OK but I also replaced those just in case.Lo and behold, the display is now alive and clearly readable, although it feels that the EL panel is on its last legs anyway. Now I think to recap display controller board and the PSU and to finally put the instrument together: it was in pieces for soon a year.

author: varjag
author_rank: Contributor
timestamp: June 21, 2025, 06:23:05 pm
content: OK I finally got it working after re-capping. The culprits were both film and electrolytic caps on the inverter subassy. I put it together in two videos here:https://youtube.com/playlist?list=PLPBMw-cHVHfzy-Ma3bCcVkNh9jZoOiIUd&si=hXPnvgTf6E6nRJGD