Restoration of FT-480R - Page 1
Forum section: electronics / rf-microwave

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: March 29, 2016, 06:24:59 pm
content: Hi,Today I've found on the dumpster an FT-480R missing some front panel parts.When I got home plug it and the radio is put in RX mode, but (there is always a but) no display.With one portable radio I press the PTT and track the signal with the FT-480R, all was good on RX, click the PTT of the FT-480R and the radio is TXing.First job will be replace all the electrolytic caps, the see what is going wrong with the display.Will upload the manual and pictures.

author: 4cx10000
author_rank: Regular Contributor
timestamp: March 29, 2016, 07:19:39 pm
content: I had an FT-480R many years back, I do not even remember whenAnyhow, I also had trouble with the display which I fixed. Think it was a cold solder joint or the DC/DC converter which feeds the display with a minus-voltage-something. Could have mixed up that with the IC-211E because that one was really full of cold solder joints.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: March 29, 2016, 07:29:27 pm
content: Nice findAll mode VHF is rare as hens teeth.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: March 29, 2016, 08:06:27 pm
content: Well on the second time that I turn it on, the display came alive, but not for long the digits start to disappear on after the other, and then no dispay.The sirvice manual is here <http://www.radiomanual.info/schemi/FT480R_serv.pdf>, will upload some photos tomorrow.The display is on page 190 and 191 of the PDF.That show the 7805 (Q28) feeding the 16x 2SA733 (Q03 - Q18), also shows the signal leaving the UPD 1511-011 (Q01), also +13V from T01 after Q30 that feed the display, the middle of the display show -24V that comes back to the T01 (DC-DC converter).Will have to check all this.I hope that this is better not be display LD8231/F1P9C5, that is rare, they use to be install in some calculators in the 80's.

author: 4cx10000
author_rank: Regular Contributor
timestamp: March 29, 2016, 08:09:42 pm
content: I will have a look att the schematic, and yes, I remember now that it was the -24 volts I hade problem with./Sm2GXN

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: March 29, 2016, 08:10:40 pm
content: Quote from: Radio Tech on March 29, 2016, 07:29:27 pmRadio Tech, thanks, yes this is a nice finding, if I can make it work on the display.The V/UHF all mode is very rare, only one is the TS-2000, IC-9100 (but they've HF), in production, don't know why the tree big one doesn't come up with one of this, like the famous TS-790, IC-910.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: March 29, 2016, 08:12:31 pm
content: Quote from: 4cx10000 on March 29, 2016, 08:09:42 pmI'll look at the -24V rail, also at the 7805.

author: 4cx10000
author_rank: Regular Contributor
timestamp: March 29, 2016, 08:17:17 pm
content: QuoteDo so, interesting to see what you come up with.As you see this converter has a winding for the filament.

author: borjam
author_rank: Unknown
timestamp: March 30, 2016, 07:44:07 am
content: Quote from: Nuno_pt on March 29, 2016, 08:10:40 pmDon't forget the FT-817

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: March 30, 2016, 12:06:07 pm
content: Today I've disassemble the front panel of the radio, to take a look inside.Missing top right side panel and some buttons.Nothing obvious at first look, no measurements where taken, and no power to the radio, will have to make the power cable first.Yesterday it was plug with two alligator clips from the power supply.Clean the PCB with IPA to remove the old flux that was on the board.Will try in the next few days to make some measurements starting by the Q28, T01 and also the -24VDC rail.Some photos here <https://onedrive.live.com/redir?resid=A26220D7C8CFDD26!10982&authkey=!APT-FVNkjrxKb-g&ithint=folder%2cJPG>.I don't think that the resolution is great since the cam is HP 7.2MP, will've to buy one good but cheap cam to take good photos, or maybe one Andonstar microscope, Any opinions about this?

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: March 31, 2016, 09:19:49 am
content: New update this morning.Powering the radio the display came to live but only partial, looks like the case of many HP34401a DMM with the VFD problem, half numbers, when the main dial is turn, the half numbers stay the same, so can't read the frequency.Toggling the radio on and off, the display pass from showing half numbers to only showing the dots, separating the decimal places.I've take some measurements, the +5V are on the VFD entrance, also the -24V all steady, but I take the measurement on the display pins, like on the page 191 of the manual (PDF), half right of the display show +5V on all the pins, but the left side show all negative voltages on almost every pin.I've check RB03 and RB04 block of resistors, they all show 100K ~5%, the manual doesn't say the value of this.My best bet for now is the VFD is bad.But will dig some more.