Replacing the relays in the Yaesu FT-480R (FT-280)

tl:dr:

Figure 1:
The front panel of my "FT-280R" all-mode 2 meter
transceiver including paper labels showing the "new"
modes.
Click on the image for a larger version.

If you have a Yaesu FT-480R that doesn't work, it's probably the relay(s)!

* * * * *

Back in 1994 I picked up an FT-280R at a local swap meet for a good price - particularly for an all-mode 2 meter transceiver.

Except, of course, there was never such a thing as an "FT-280R":  This radio had clearly been modified, a previous owner attaching pieces of self-adhesive paper with "R" written on it after the model number, and similar "+" and "-" labels added to the MODE switch.

A look under the hood shed some light on this mystery:  It had likely been sent back to Yaesu at some point as an FT-280 - an uncommon radio (perhaps sold only in the Japanese domestic market?) that did not have repeater offsets - and modified to the otherwise-identical FT-480R which did "know" about repeater offsets.

At some point I acquired the manual for the FT-480R (I don't recall if I got it from Yaesu, or if it came with the radio) which the elements of a service manual - including schematics, locations of semiconductors and adjustment/test point and alignment procedures - but it was clear that this radio wasn't exactly like an FT-480R, either, as it contained an additional board with a pair of relays on it that the manual didn't show.

Figure 2:
The "unobtanium" 221D012 relays used in the FT-480.
These relays use a different from factor from modern/
available relays requiring a bit of "adaptation".
Click on the image for a larger version.

It quit working!

As this radio was probably made in 1980 or 1981, it's long in the tooth and about a dozen years ago, it gradually became too unreliable to be useful, requiring more frequent "percussive repairs" to make it transmit or receive and the problem was traced to three relays used to steer important things like the transmit and receive voltages to their respective circuits.  A bit of "cleaning" (piece of paper between contacts, contact enhancer, etc.) would help initially, but even that stopped working.

These relays were Fujitsu 221D012 - low-current, DIP-style DPDT units, but a quick check revealed that their form factor (pin-out, pin spacing, etc.) was not in common with anything else that was in current production.  I did find new-old stock units that some were available - some on EvilBay (who knows what they really are?) and others from RF Parts - but they were quite expensive, on the order of $20 each from RF Parts.

Figure 3:
One of the control boards with two of these relays.  This
board seems unique to the "upgraded" FT-280 as it doesn't
match what is in the FT-480 manual.
Click on the image for a larger version.

Since there were three relays that had gone intermittent, I didn't relish spending $60 (plus shipping) for relays that were likely 40+ years old - and since these were un-sealed, they would likely have (or soon have) the same oxidation issues that made the original relays so unreliable.

"Substitute" relays

As no drop-in relays were available, I found some similar-sized, 12 volt DPDT relays - using a now-common pin-out (I used Hui Ke HK19F-DC12V-SHG relays - but many others share the same pin-out and could have been used) - and set about making a "carrier" board to accommodate them.  While I could have made a PC board to adapt their pin-outs to those of the original Fujitsu, I decided that with just three relays in question, doing so wouldn't be worth the effort.

Figure 4:
Carrier board with relay mounted to it.  The clearance on the
board shown in Figure 3 allowed the relay's position to be
slightly shifted, simplifying construction as the new relay's
pins offset from the original relays'.
Click on the image for a larger version.

Instead, I used a small piece of phenolic prototype board.  For the undocumented board with the two relays, I had a bit of extra space available on either side which allowed them to be offset from the original pins:  Short pieces of wire (26 AWG) were soldered to the proto-board in the locations of the original relays' pins and short wire jumpers were run from there to the locations of the corresponding pins on the new relays.

To "ruggedize" this assembly, the jumper wires were covered with UV-cured resin before the new relays were soldered into place and then each relay assembly was soldered into place on the board.

The third relay - next to the carrier oscillator, on the main RF board - was a different matter:  It was surrounded by components which meant that there wasn't enough room to offset it from the homebrew carrier board, so the new relay had to be placed directly atop the original pins.

Figure 5:
Carrier board and relay used near the FM oscillator on the
main board.  Unlike that in figures 3/4, this relay couldn't
be offset so the pins were folded over and wires used to
connect the relay to the carrier board so that it could sit
directly atop the original location.
Click on the image for a larger version

To accommodate this, wires were soldered through the homebrew carrier board like before, but the pins on the new relay were laid onto their sides and short pieces of 30 AWG wire-wrap wire were used to connect to the proper locations.  Again, this was flooded with some UV-cured resin for both mechanical stability and to prevent the relay's pins from touching the wires on the carrier.  A bit more resin was then used to adhere the new relay to the carrier board, making a solid unit.

With the leads protruding from the bottom of the carrier board straightened,  they were carefully aligned and pushed through the main PCB and soldered into place.  As it turns out, although the "new" relay sits slightly higher than the original, it just clears the bracket for the switches on the bottom panel of the radio.

Testing the radio

With radios of this vintage - with individual wires going everywhere - the bane of the service technician is wires breaking off their soldered connections on switches and/or PC board.  If caught early, the "bend" of the wire will keep the broken-off end very close to where it should be attached - but too often, one spends a lot of time reverse-engineering:  While the schematic is (mostly?) complete, neither it or the parts layout diagrams detail where every wire and connection go - particularly on the front-panel switches.

Figure 6:
A look on the main RF board on the underside
of the radio's chassis.  The two "new" relays are
along the top edge while other relay below and
to the left of center, just above the metal box
with the black label (the FM modulator).
Click on the image for a larger version

The broken wires fixed, the radio worked the first time it was powered up - more or less:  Going through the (somewhat incomplete and ambiguous) alignment procedure in the manual brought the radio back to usable condition - but one "semi-major" problem remains:  None of the top-row buttons (the yellow-brown) work reliably.  A bit of testing revealed that shorting the terminals on the back of the board resulted in their functions working, but a check with an Ohmmeter showed that they had all gone to high resistance despite having been injected with several flavors of "DeOxit":  The button switches themselves will have to be replaced, but I'll have to get with a friend with a 3D printer to come up with a means of mechanically coupling the front-panel buttons with the "new" switches.  Fortunately, the radio is perfectly usable - particularly when using SSB - even if none of these buttons work.

* * * * * *

This page stolen from ka7oei.blogspot.com

[END]

Repair of a (lightning struck?) Yaesu FT-1000 MP Mark V

The background - and initial assessment:

A month or so ago an acquaintance of mine in the local amateur community asked me to take a look at his radio - a Yaesu FT-1000 MP Mark V.  While I don't routinely repair other people's radios, I decided to make an exception, as I've known this gentleman for decades.

The complaint was "The receiver is dead" - which is a very broad assessment, but it was an obvious starting point and upon putting this rather large, ponderous piece of equipment on my workbench - which itself proved to be a challenge - I noted that it took about a 0dBm signal to attain an "S-9" reading:  Yes, the radio was deaf, to the tune of around 70dB!  Knowing that the antenna A/B relay and/or antenna tuner could be a problem with this particular radio, I tried different configurations - even the (differently-routed) rear "RX Antenna" jack - but no difference.

Figure 1:  A blast mark!

Getting it apart:

This radio's technology and construction is what I would refer to as "transitional" -  mostly reminiscent of 80s Japanese radios in that there is a mix of through-hole and surface mount, and the boards are mostly interconnected with a myriad of white wires with unmarked plugs on them that go everywhere in the case - with the occasional gray coaxial cable that use the odd board-mounted plug-in cables.  Fortunately - unlike some of those older radios - the boards are mostly double-sided epoxy rather than single-sided paper phenolic.

Of course, the main receive RF board was buried under the very large heat-sinked power amplifier assembly, so I first did a test on the "sub" receiver board, which was accessible:  That receiver seemed to be reasonably sensitive when I injected a signal directly into it, but there was no sign of RF getting to that receiver via the radio's rear coaxial cable connector.

The next, obvious step was to remove the PA board - which, like many things about working on this radio,  was a real pain:  Only four screws, but two of them were buried under a mass of white wires -  I pulled the amplifier module out from the radio with trepidation, knowing that I'd eventually have to get it back together.

A visual and an olfactory inspection of the receive board - before removing it - was done, and nothing was obviously amiss, so I removed a bunch more screws and cables - marking them as appropriate (you will hate life if you don't mark where they went as you remove them!) I was able to pull the board away and immediately saw the first indications of the problem:  A very obvious black mark on the aluminum chassis under the board and a corresponding area of char on the board itself (see Figure 1, above and Figure 2, below).

What might have happened:

Figure 2:  Carbonized crater in the RF board.

While it is difficult to determine what, exactly, happened to this radio, I suspect that it was likely a nearby lightning strike that did the initial damage, with peripheral damage occurring later.  In inspecting the radio and referring to the service manual, which I found online, I saw that capacitor C1278 on the "RF unit" - and its related circuit board trace, and a portion of the board itself - had been wholly transformed into the black mark on the aluminum chassis.  The fix for this was pretty simple:  Scrape away all of the now-conductive PC board carbonized residue and replace the vaporized surface mount 0.1uF capacitor with an axial-leaded unit to both replace both the component itself and the trace as seen in Figure 3.

Knowing that this was not likely to be the only problem, I half-installed the board again and checked the receiver:  Very slightly less terrible - but still deaf as a post, but with access to the board, I cranked up the signal generator to 0 dBm and started poking around with the oscilloscope to see where RF disappeared.

Figure 3:  New cap, carbon excised!

Fortunately, I was seeing RF at the input to the RF board - and even though many of the key probing points were on the (inaccessible!) bottom side, I found a few places where I could test on the top and discovered that the RF signal stopped at D1056, a PIN diode found at a low-pass filter stage in the RF path.  Pulling the board again I started probing with the multi-meter and discovered that not only was this PIN diode completely open, but R1157 and L1086 - both part of the DC path of this and (the still-working D1055) were open:  I had a suitable SMD replacement for R1157, but used a small, molded 1mH inductor for L1086 to accommodate the damage due to a blown-off pad and trace that hadn't been immediately obvious and I used a much more rugged PIN diode than the original to replace D1056.  While I was at it I did more probing around and found that R1150 - part of what appears to be a DC drain on the antenna circuit - was also burned open:  Because this resistor can only be "reached" via the 1 mH inductor in series with it, this meant that it was not likely RF that blew it up, but rather a transient with a strong DC component - or at least a low-frequency AC component - maybe lightning?

Initial re-testing:

Putting the board back in, temporarily, I re-checked the receiver sensitivity and found that it was "OK", in that I could touch a screwdriver and put it in the rear-panel RF connector and hear signals, but a quick check with the signal generator indicated that something was still amiss as it seemed to be off by about 15dB based on the specs in the alignment procedure.

At this point I decided to check the transmitter and to my gratification, I was able to get about 90 watts out of it.  My initial satisfaction was short-lived, as I soon realized two three things:

• I should have been able to get at least 150 watts out of the transmitter.
• The SWR indicator on the radio was showing a mismatch, with the tuner bypassed, into a known-good load.
• I smelled epoxy smoke from the "RF Unit".

Figure 4:  Original TX isolation relay - welded!

At this point a felt a bit silly:  I should have checked to see that the unit had a functional TX/RX isolation relay - and a quick check with a signal generator and probing with the oscilloscope told me that it did not, the apparent culprit being  RL6414, a reed relay on the "Tuner-Main" unit that was clearly welded - a fact soon verified by multimeter.  The radio's power amplifier had dutifully cut back its power because it was seeing a mismatch caused by the receiver being connected at the same time as the dummy load.

At this point I again removed the RF unit and replaced D1056 (again!) - the apparent source of the smoke that I'd smelled and - without transmitting - restored the operation of the receiver.  In reviewing the service manual and online forums, I discovered that the failure of RL6414 was semi-common, and also that this particular relay - seen in Figure 4 - was difficult to source.  Nevertheless, I sent an email off to Yaesu Parts to find out.

A few days later I'd heard back from Yaesu:  This relay was available - but it would take 6-8 weeks.  In the meantime I'd tried to find an exact replacement elsewhere, but to no avail:  The original relay had a non-standard pin-out and was a brand that was simply not carried by U.S. parts suppliers - and I couldn't be sure if this particularly relay was still made!  In speaking with the owner of the radio I gave him two options:  Order the part and wait 6-8 weeks, or get a more common part and adapt it to fit:  He opted for the latter, so I placed an order with DigiKey, set the radio aside and waited.

It's worth noting that RL6414 is an SPDT relay with the RX signal path connected in the "Normally Open" position with the "Normally Closed" position grounded - that is, the relay must be energized for the receiver to be connected to the antenna.  If the radio is turned off, there is no direct path, so whatever "killed" the receive, must have either happened with the radio turned on, while it was receiving, or it was sufficiently energetic enough to weld the relay and, apparently, blow away the ground "N.C." contact:  Yet more evidence of a "high energy discharge" from lightning.

Resuming work:

Figure 5:  New relay on homebrew carrier board.

About a week later I again had some time to work on the radio and the relay from Digi-Key had arrived.  This relay - a Comus BFH-1C-12C (Digi-Key P/N:  1835-BFH-1C-12C-ND) was an actual RF reed relay with decent voltage and current ratings - but the pin-out was different from the original, requiring me to construct a simple "carrier board" to reroute some of the connections of the relay footprint to match the tuner board:  With plenty of headroom, the extra height of the combination was not an issue.

At this point, I will note again how difficult it is to work on this radio - highlighting, in this case, the antenna tuner.  This module consists of two boards, face-to-face, meaning that no components are accessible unless they are separated.  Unfortunately, there are several wires that appear to have been pulled through from the "lower" board (with the tuning capacitors) and then cut short - and none of the other wires were any longer than they absolutely needed to be.  Disassembly was pretty easy (especially with proper desoldering equipment) but re-soldering the short wires was an exercise of patience and the careful manipulation of small tweezers and screwdrivers to try to align all of the wires simultaneously without causing one or more of them to pop out of place!

Figure 6:  New TX isolation relay - looks right at home!

With the TX isolation relay (RL6414) once again functioning I found that the transmitter's output now exceeded 150 watts with no reflected power on the radio's meter - and no smoke!

Alignment - and more problems:

Not having part of the transmitter signal path in parallel with the receiver input helped the sensitivity a bit, but it still wasn't right so I did a bit more checking with the signal generator and scope, finding no-where that things were obviously amiss on the RF Unit - but I did notice that the secondary receiver was more sensitive than the main:  Since they share the same signal path that more or less ruled out an obvious problem with the RF unit when operated in the normal fashion so I decided to perform a realignment.

To my surprise, the I.F. stages in both receivers were quite far out of alignment - particularly on the main receiver - and after finishing this, the receivers "woke up" and met specifications:  I was surprised to see this on a modern receiver and am at a loss to explain it.  It seems unlikely that it detuned itself with age, so it was either not properly aligned at the factory, or someone else tried to "improve" it - but I'm suspecting the former.

In performing the alignment steps, I then "discovered" that the "VRF" circuit - an electronically-tuned preselector - was inoperative, about 25 dB of excess attenuation:  This problem was traced back to being caused by RL1005 having welded contacts, not allowing this preselector circuit to be fully switched into the signal path.  This not unexpected as this is in the same signal path as the vaporized trace and capacitor.  Fortunately, these exact relays were readily available from Digi-Key as well.

All's well that ends well:

The replacement of RL1005 turned out to be the last problem that was found and the radio easily met its specs when the job was done.  The reassembly of the radio was, as expected a bit of a challenge:  The inboard mounting flange of the PA unit shares the same channel as dozens of thin, white wires and there is practically no visibility as one tries to maneuver the screws into place while trying to avoid them getting knocked off the magnetic driver while, at the same time, trying to make sure that none of the dozens of small, white wires get pinched in the process - all the while trying to align to invisible holes!

In the end, the radio was handed off to the owner, with the recommendation of added lightning protection or, at least, disconnecting things when not in use - good advice for anyone!

This page stolen from ka7oei.blogspot.com

[End]

A quick fix for a Yaesu FT-757GXII blank display

A couple weeks ago I was contacted by an old friend of mine, having obtained his amateur license in mid-2017, who has a Yaesu FT-775GXII - a synthesized, all-mode HF transceiver from the the mid-late 1980s which had been working well until, one day, there was no display.  Clearly the main processor was fine as the front panel buttons would work, he could transmit and receive and he could even "see" and control the radio's frequency and mode on his computer via the serial CAT interface.

Figure 1:
The front panel of an FT-757GXII with a working display!

One clue was that when power cycled, the display would occasionally flash very briefly, a possible indication that something was almost doing what it was supposed to.  Via email (he lives across the country from me) I had him do some preliminary troubleshooting such as the checking of voltages - but based on the rather sparse information available in the service manual and the difficulty in accessing some of the test points:  Even a couple key capacitors in circuits that often cause problems with displays in some radios - namely the switching supplies that provide the odd voltages for the vacuum fluorescent display - were swapped out, but the display remained blank.

I offered to look at it, so he packaged it up and sent it to me.  When I put it on my workbench I started probing the various lines on the display processor with an oscilloscope:  I could see many of the signals that I was expecting - namely the 500 kHz signal from the display processor's clock, the data coming from the radio's main processor that changed as I pushed buttons and turned the main tuning knob and another signal that appeared to be an acknowledgment pulse from the display processor to the main processor.  What I seemed to be missing were half of the multiplexing signals that drove the display:  It appeared that I was seeing the "common" signal lines for the display, but the signals on the pins that appeared to carry information as to which display segment was to be illuminated were missing as if the display was supposed to be blank.  Without both sets of signals activated appropriately, a multiplexed display will remain forever dark.

I'd already consulted the internet and determined, based on postings in various forums, that at least for its predecessor, the 757GX, the failure of the display processor wasn't terribly uncommon - but not surprisingly this part was long gone from the spare parts inventories of Yaesu and other means of repair/replacement such as getting displays from scrapped radios or even the construction of an "alternate" display unit using a different processor and driver transistors was discussed.  What was interesting was that the "important" signals - namely those for data, acknowledgement, scanning and synchronization - seemed to be present, so the display processor clearly wasn't completely dead.

Figure 2:
Annotated picture showing the two buttons that, when both are set to their
"in" position will disconnect the radio's internal memory back-up battery.
If both buttons are in when the radio is turned off the processor will
be reset to its "factory" state.
Click on the image for a larger version.

At about that point the old adage drilled into me from the early days of computers and Windows came back to me - although it probably should have been one of the first steps to be taken when the display went blank:  "When in doubt, reboot!"  Perusing the user's manual I determined that a complete "memory reset" was done on the FT-757GXII by setting both the "Linear" and "Marker" switches on the back panel (see Figure 2) to the "in" position at the same time and turning off the radio for 30 seconds - and then turning it back on and restoring the two rear switches to their normal position:  It would appear that these two switches have a second, "non-intuitive" function that when used together, disconnects the internal battery.

The result?  The display came back to life!

What had apparently happened was that somehow, the data stream between the display and main processor wasn't what it should be and the main processor was apparently sending some sort of garbage that the display processor didn't understand - probably due to something in the main processor's static RAM.  It would appear that in the absence of sensible data, the display processor remains blank, relying on the main processor to send the various bits and bytes that display frequency, mode, etc. rather than reverting to some sort of static display.  Clearing the battery-backed RAM of the main processor and resetting it apparently cleared whatever junk had gotten into the memory that had caused it to work improperly.

I checked the back-up battery - an innocuous-looking 2-cell NiCd pack that was near the rear of the main synthesizer board - and it read 2.8 volts with the radio having been disconnected from power for over 24 hours indicating about 1.4 volts/cell, which was appropriate for a properly-charged NiCd.  Visually, this small battery pack looked OK in that there were no signs of corrosion, so it is probably OK, despite its age - longevity being one of the virtues of a properly cared-for, high-quality NiCd cell.

How did the main processor's memory get scrambled?  Who knows - it could have been an entirely random event, due to static from a finger touching the front panel, the back-up battery's voltage having sagged below the point of memory retention while the radio was turned off or the results of some sort of spike - perhaps lightning - intercepted by the antenna that found its way into other circuits.  This sort of "display failure" - apparently caused by the processor's memory being scrambled - doesn't seem to be too common, so my friend considers himself very lucky!

After restoring the radio's operation I did a few tests and found that everything seemed to be working as it should, so it will be packed up and returned to its (very fortunate!) owner very soon.

[End]

This page stolen from ka7oei.blogspot.com