Repair of a Yaesu FT100 HF/VHF/UHF Transceiver

[mrz80]

I realy dont know why people buy yaesu stuff,in my opinion its underbuilt over rated junk!!,every thing designed by bean counters not engineers,ive had a few yaesu radios before i knew any better!!.

My FT-100's been giving stalwart service for many years, most of 'em mobile and portable, getting banged around and overheated. I will concede it's a right pain in the rear to work on, with everything jammed in cheek-to-jowl in such a tiny case. So long as you baby that unobtanium VHF final (I don't run 2m or 440 at more than half output just to keep it running cool) it's a fine rig.  My big like is the 6m and VHF receivers are worlds ahead of the newer 857/897, and the Icom 706-of-whatever-generation.

A few bad apples.. just like any other brand  I have a FT-450AT; and modified it with a RX out for SDR purposes (HupRF high impedance buffer). Built like a tank. I can run 100W CW with a brick on the key for hours. Built like a tank.

Just remember to use a dummy load instead of an antenna for that torture test, or you might get a nastygram from th' FCC! 

[gi4ohh]

x-runner can you pm me please

[xrunner]

x-runner can you pm me please

I have PMed gi4ohh and he asked me to point to the resistors on the board. I told him to go back to this thread so I can post the pics here so that it may help other people in the future.

I will make the post in a bit ... 

[gi4ohh]

thanks

[xrunner]

Check the schematic and the annotated circuit board, that will show you the resistors to be replaced.

Good Luck!

[gi4ohh]

the 5.6k resisters
my readings are as follows
5.6k
5.4k
4.28k
4.36k

the6.8k resisters
my readings are as follows
4.18k
5.16k

[xrunner]

Remember that measuring resistors in-circuit might not give the value on the resistor because it might be in parallel with other resistances. For example R3040 is essentially in parallel with R3035 & R3033 (and perhaps other things in other places not shown) as far as measuring it's resistance in-circuit. If you are concerned that the radio has the same problem as the one I repaired, I would just replace all of these resistors because it's not hard and the cost is so little.

[Velund]

I have a FT-450AT; and modified it with a RX out for SDR purposes (HupRF high impedance buffer). Built like a tank. I can run 100W CW with a brick on the key for hours.

Cannot say anything bad about cooling of FT-450, but once tried to use my 450AT in a contest (RDXC, IIRC). After hearing for the first CW pileup replaced them with my old good FT-900CAT, without that buggy DSP, that cannot handle more than 2-3 CW signals in a passband.  What was a nice pileup on FT-900 appear to be a meaningless chaotic beeping on 450... BTW - no such problems on Elecraft K3.

[gi4ohh]

replaced resisters now full 100 watts on  hf
but on vhf uhf 1.5 watts only

[gi4ohh]

SUPPOSE THE CHANCES OF GETTING A MOTOROLA SRF 7043 MOSSFET ARE  SLIM
HAS ANYONE TRIED A REPLACEMENT OR EQUIVALENT WOULD LIKE TO GET THIS RADIO GOING ALSO ON 2 METERS AND 70CMS

[keystone]

Hi xrunner.  I am putting together a test bench and looking for attenuators.  Was wondering where you got that one.  I'm working on an old kenwood tr-7800 fm 2 meter radio that has a problem with the squelch circuit, no squelch.  I've looked at your post of the tr-740o repair.  Thanks for posting that and this one too.  Have you ever run into a no squelch problem with a radio like this before?  Keep up the good work.

[xrunner]

Hi xrunner.  I am putting together a test bench and looking for attenuators.  Was wondering where you got that one. 

The 40 dB? Oh I got it from a Chinese supplier on Ebay. You can find others used too that came out of commercial equipment.

I'm working on an old kenwood tr-7800 fm 2 meter radio that has a problem with the squelch circuit, no squelch.  I've looked at your post of the tr-740o repair.  Thanks for posting that and this one too.  Have you ever run into a no squelch problem with a radio like this before?  Keep up the good work.

Well I don't have the radio anymore because I repaired it for a friend, and have never touched one either before or since. You'll just have to do the troubleshooting on the bench and follow the schematic. I'm sure you can fix that.

As far as what you asked me in the PM, concerning what test equipment to get, let's talk about it here since there are other members that can input suggestions too. You said you got a DS1045Z. That's great. Some of the items on my bench include -

HP RF signal generator 100 kHz to 1 GHz
100W dummy load
Rigol DS1045Z
Rigol 30 MHz function generator
Rigol Bench DMM
Rigol DS815 Spec. Analyzer w/tracking generator
13.8V 30A power supply for testing ham gear
Two hp power supplies for low current applications
Other selections of various inline attenuators with both SMA and N connectors
Also a whole lot of other test equipment on the side but the above will do a lot of good for you.

[N4wy]

Hello Xrunner,  I have been searching for a replacement control board for the FT-100 for two years now.  Either Ebay has a board listed for the price of a used FT-100 $300+ or nobody has one.  This surprises me as many FT-100's are sitting around with problems.  You'd think someone would be piecing them out for parts.  Have you run across another source other than ebay for FT-100 parts or FT-100 for sale - not working for parts?  Thanks.  N4WY

[xrunner]

You'd think someone would be piecing them out for parts.  Have you run across another source other than ebay for FT-100 parts or FT-100 for sale - not working for parts?  Thanks.  N4WY

Hello.

No, I'm afraid I don't know of other sources for parts. Keep looking on Ebay they're bound to turn up over time. 

[F4IUJ]

Hello,

I have exactly the same issue, so I am going to replace the SMD resistors. So, do you know what size they are so that I can order them before dismantling the transceiver ?

73,

Yannig

[xrunner]

Hello,

I have exactly the same issue, so I am going to replace the SMD resistors. So, do you know what size they are so that I can order them before dismantling the transceiver ?

73,

Yannig

One of my posts earlier noted that they were 0805 size.

[F4IUJ]

Ooops,

Sorry, I need some better glasses!!!

Anyway, thank you for making this info public, I don't think that I would have diagnose the issue alone.