Yaesu FT-100D repair [1], Something is Screwed up



 I just purchased a "for Parts or repair" FT-100D, from the estate of a silent key. There are some things immediately identifiable as problems. 

1. The Microphone cord rubber has completely disintegrated. This is super common, it seems pretty much all of them do this. All that should be needed is a replacement cord.

2. The fans are tied together and connected to a 12V cigarette light plug. So the radio has either no fan or full power fan all the time. It's quite loud.
3. On power on, the unit draws 8 amps all the time.
4. There does not seem to be any transmit capability on any band.

The most concerning thing at the moment is the 8 amps on power on. I don't want to further damage the unit. I need to find the source of the short soon.

While opening the unit to inspect it one of the screws stripped and I could not remove it. Come in the reverse direction drill bits. They are very useful and have helped me remove a few very stripped out screws. I first drill a small hole in the head with small diameter bit. The hole makes space for a large bit to bite into the sidewalls of the new hole, then the screw will turn and can be removed without any damage to the casing. If you don’t have a set of reverse drill bits, I suggest you get some, you might now need them all the time but they are a really good tool when you need them. 
Above: Reverse Twist Drill Bit


Above: Removed Stripped out Screw

  

Once I was able to open up the case I started looking for any obvious issues. I quickly found one. There has been a temperature sensor,  a Kemet OHD3-40M which has one terminal soldered onto the Power Amplifier (PA) board of the FT-100D. The other terminal is floating in the case. Normally the FT-100D has 2 thermistors, TH3001, and TH3002 which measure the temperature of the PA Board. I have not yet measured the output to see if these are still working. Generally I believe the temperature sensor controls the fans for cooling as needed. Perhaps an issue happened when the previous owner was using the radio.

The power draw of 8 amps is will above the 1.2-1.6 amp typical value that the service manual states for receive only current draw. I am thinking there may be a pad output transistor which has shorted. This seems like the most reasonable thing as they are directly tied to ground and 13.8 v and 8 amps would mean a 6.8 amp abnormality. Which is a 2 ohm current path somewhere. 

I hope to figure out the issues with the obvious problems soon and then I can get working on the more tricky issues like the transmit capabilities. 


 



Comments

Post a Comment

Popular posts from this blog

Yaesu FT-100 YSK-100 Separation Kit

Image
If you are looking for the YSK-100 or other separation kit. This is the right place. Yaesu no longer makes their CT-5L cable. There are a few options: 1. Buy used. They sometimes come up on Ebay, or other resale methods. but they are usually expensive or connected to a radio purchase. 2. Buy third party. There are a few options for this. I provide one of these. I have a FT-100, a FT-8100, and a FT-8500. They all use the same cable the CT-5L. I made an set of adapters that lets you use your own Ethernet cable to connect the head to the body. The adapters screw on to the head and body of the radio using the original interface. There is no modification needed on the radio.   There is a bracket which is now discontinued, Yaesu part number MMB-72. The MMB-72 is quick disconnectable. The head unit slides on and snaps in place. If you cannot get a MMB-72 bracket I also have made some 3D printed brackets to fit the adapters I also have a 3D Printed Bracket that fits the small adapters, sho...
Read more

Yaesu FT-90 Separation kit /YSK-90

Image
 I have been working on a separation kit for the Yaesu FT-90. It’s very small and has been a challenge. The biggest issue it really the size. Finding four conductor cables with a sufficiently small diameter has been hard. I have been trying to make it fit the original form factor. I think I am pretty close to having one complete. I have had a few functional prototypes but the wire size remains an issue.  I have tried using the wire from a TRRS extension cable and that seems to work but the conductors which are really just headphone cables seem pretty delicate.  I may make a version that abandons the size and uses a 4P4C RJ type jack. It would not need to be too much larger. And all my other kits use them, I think it might work by adding a little depth to the head bracket to be able to use a RJ-12 or similar size jack. If you are interested in getting one of these once I have finished creating them. Send me an email to contact@radiorework.com to get on the mailing list of ...
Read more

Yaesu FT-900 YSK-900 Alternative Separation Kit

Image
 My newest project has been a separation kit for the Yaesu FT-900. This kit is a little different, it uses 8 contacts, I was able to use the same basic design as the other Yaesu separation kits and the same Ethernet connectors. I was able to modify the FT-100 head bracket model so I did not have to start from nothing. The brackets are compatible with the AMPS standard holes, ie, the hole pattern that is  on a 38mm x 30mm rectangle. Theses are common for attaching a LIDO mount, or RAM ball.  If you would like your own, please email to Contact@radiorework.com
Read more