FT857 Query

Does anyone know what’s hidden in the large ugly plastic boot on the FT857D’s power lead… Neither Yaesu’s service manual nor google seem to be able to help on this one, but surely someone out there’s had one apart!

Many thanks in anticipation

73 de Paul G4MD

If you mean the black unit in this picture -


It’s the in-line fuses.

73 Ed.

It will be a choke / capacitor filter block I guess. I think there is some similar in my IC706 power lead.


It’s a large ugly plastic plug SOTA operators cut away.

That’s the one! Seemed just too big and feels too “lumpy” to be nothing more than a ridiculously large plug. Why couldn’t they just fit powerpoles as standard and save me the job…

Thanks to all for their input :slight_smile:

73 de Paul G4MD

and save me the job…

… and me. :wink:

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I wonder if it’s a Europe-only required filter - The iCOM IC-7300 comes with a metal box with a power filter in it, that apparently isn’t supplied with units in the US. This is the 13.8v DC supply, so I don’t see how this will be different on each side of the pond so I’m guessing it’s some EU regulation - perhaps this is the case with the “boot” in the FT857 lead as well - which isn’t in the offocial replacement lead that I gave the picture of, from a US retailer.

73 Ed.

Hi Ed,

The boot is actually on the power lead emerging from the radio, rather than the “extension” lead with the in-line fuseholders. Not sure whether non-EU rigs are the same, but it’s pictured and identified in the official Yaesu Service Manual as “T9207026 WIRE ASSY” so I’m assuming it’s universal.

I’m going to take a scalpel to mine and explore within but might first check with the vendor that it won’t void the warranty :roll_eyes:

73 de Paul G4MD

Edit… just had a look at the pic of the assembly in the Service manual, it is different to the one fitted to my radio - much less bulbous and ungainly so maybe it is some kind of regional variation. Obvious really but I guess I could always ask the nice man who sold me the radio!

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AHA - so is it the white Molex connector that is inside the black bulge! That makes sense as there’s no space on the rear panel to fit a Molex socket! Hence the suggestion to add Anderson power poles instead.

You should be able to slide the rubber off without cutting it I would have thought ?? Perhaps not.

73 Ed.

Coincidentally this is exactly what I did Pom last month on my 15 years old (June 2004) battered FT-857, that has done quite a few activations. I don’t use the radio in my shack.

The power leads where they go into the grommet at the back of the radio were chafed and the conductors on both cores were starting to be exposed. The rig is unsaleable anyway due to its external condition and I wouldn’t want to sell it on anyway. I decided therefore to do away with the twin lead, booted connector and fuses completely! I’ll take the chance.

Now there is less to go wrong. I found some substantial enough red and black power lead, drilled out the grommet - the orginal wires are moulded into it with heat I believe, so they wouldn’t just pull out. And I then resoldered the new wires on to the board inside and put some heat shrink sleeving either side of the grommet which should stop any strain on the power cable connections on the circuit board. The plug is now an RC5 radio control modellers plug which fits all the batteries that I use for /P work.

Only used the radio once since on G/DC-008 about 10 days ago. I ran 60 watts and made 34 QSOs with the radio on CW / SSB with no adverse reports. 73 de Phil G4OBK


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Spot on Ed :slight_smile:

Sadly too tight to slide back and have a look. However judicious palpation now leads me to suspect there’s actually one or two toroids in there with one or two turns of the power leads wrapped through them. Maybe that bulge does have a purpose after all :frowning:

73 de Paul

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Sadly mine’s new out of the box. Maybe keep that one for the shack and pick up an old knacker to butcher for SOTA purposes :wink:

73 de Paul G4MD

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OK Paul. The bulging plug and fuses went a few years ago after I got dodgy conenctions, cannot recall any ferrite within, just that white moulded plug protected by a boot. Wasn’t sure why Yaesu fit a twin lead - 2 reds and 2 blacks. There was also a thin brown wire, which went to ground on the circuit board. It didn’t connect to anything on the moulded plug, just went to a dead pin, so I removed that completely at the same time. Radio has had a hard life and doesn’t like it if the DC voltage from the battery drops much below 12 Volts, but it still works.

Congratulations on getting the new radio!

73 Phil

Thanks Phil :slight_smile: Got my first LiFePO4 battery to go with it too but not used either in anger yet…

A bit more careful prising has confirmed my initial diagnosis - definitely at least one ferrite toroid in there so I’m guessing amputation might be frowned upon by Yaesu’s warranty department… Anyone got a superannuated but functional '857 going for a song :wink:

I think they double up the power wires to keep within the current rating of the plug contacts. The thin brown wire when grounded limits the output power to 20W (10W on 70cm).

73 de Paul G4MD

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On eBay that’s a good condition radio, probably someone would ask £50 less than the new price for such a 15 year old set!

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Mainly because it is supposed to be hidden behind the dashboard of a car! All you need to know is in the diagrams on page 8 of the manual. Two 25 amp fuses which are useless but probably required by law in a vehicle installation.

Sadly not Brian :frowning: No mention of RF choking toroids built into the power lead in any resource I’ve been able to access. Even the picture of the plug (or is it actually the socket?) on P8 of my manual looks nothing like the large gobby item fitted.

Whilst the fuses might not do much to protect the radio, I’d imagine that their main purpose is to protect the leads - in the event of chafing of the insulation causing a short, for instance which could cause your car to do a realistic impression of a severely abused LiPo :wink:

73 de Paul G4MD

There’s no toroid in mine, Paul, perhaps its a recent innovation, my rig is about ten years old.

It used to be Ford Pintos that were always on fire. Looks more like Vauxhall/Opels Zafiras with dicky heater/fan controls that spontaneously burst into flames.

Yes. The negative lead fuse is important to protect in the event of a failure in the earth (negative) bonding in the car metal work when the radio is connected to both the positive and negative battery terminals.

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Thanks for that Brian - ties in with Phil’s observation so probably right. May well be a regional modification to comply with some recent euro-directive or other :roll_eyes:

73 de Paul G4MD