utahluge
join:2004-10-14
Draper, UT
 ·Comcast
1 edit | Yaesu FT-2800M = Broken via 24 Volts
Radio:
»www.yaesu.com/indexVS.cfm?cmd=Di···chived=0
Ok, to make a long story short and get to the point, after a freak problem my Yeasu FT-2800M got supplied with 24 volts.  Now, somewhere in the radio it is letting the current from one wire (+/-) through to the other wire, blowing the fuse as it should.
I'm at a loss for what to do... The radio was relatively cheap (under $200). I don't want to spend to much in repairs cuz I would rather have a parts radio sitting around just in case something happened to the new one. If the repairs are only a fraction of the cost, thats ok with me.
How much do you think it would cost to repair? How long to repair (local hamfest coming up)? Better to have a spare parts radio? Thoughts?
Thanks!
Edit: Title |
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alphapointe
Premium,MVM
join:2002-02-10
Columbia, MO
clubs: | Re: Yeasu FT-2800M = Broken via 24 Volts
I would check the voltage regulator. I'd bet it shorted to ground. If that's what it is, it's a $2 part.
Can a sighted person confirm this and help with part location and testing? |
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drjim
Premium,MVM
join:2000-06-13
Long Beach, CA
clubs:
| reply to utahluge
Re: Yaesu FT-2800M = Broken via 24 Volts
They usually have a reverse polarity protection diode in the radio where the power leads come in. I'm not sure wht the specs are on the diode, but look for a big diode where the power leads solder to the board, and check it.
--
One man's Magic is another man's Engineering. |
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Axilla
Finger, Finger
Premium,Mod
join:2001-03-26
Schofield, WI
clubs:
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| said by drjim  :They usually have a reverse polarity protection diode in the radio where the power leads come in. I'm not sure wht the specs are on the diode, but look for a big diode where the power leads solder to the board, and check it. That was my thought as well, I had to replace one in that same radio once. Unfortunately it had other issues as well after I fixed it. . .
*cough* be real careful to make sure you solder the S0-239 back to the board properly. |
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utahluge
join:2004-10-14
Draper, UT
·Comcast
| reply to drjim
Thanks. I opened it up tonight and took some pics. I uploaded them to my blogger account so they could be full-size w/ file-size limit. 
»4.bp.blogspot.com/_J3BJClp5cnQ/S···+090.jpg
»2.bp.blogspot.com/_J3BJClp5cnQ/S···+091.jpg
»2.bp.blogspot.com/_J3BJClp5cnQ/S···+093.jpg
»4.bp.blogspot.com/_J3BJClp5cnQ/S···+094.jpg
»1.bp.blogspot.com/_J3BJClp5cnQ/S···+095.jpg
»2.bp.blogspot.com/_J3BJClp5cnQ/S···+096.jpg
»3.bp.blogspot.com/_J3BJClp5cnQ/S···+100.jpg
»2.bp.blogspot.com/_J3BJClp5cnQ/S···+101.jpg
»2.bp.blogspot.com/_J3BJClp5cnQ/S···+102.jpg |
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alphapointe
Premium,MVM
join:2002-02-10
Columbia, MO
clubs: | Aaron says that in picture 100, the 7808A looks like it has burnt terminals. That is a voltage regulator if I'm not mistaken (Google is not cooperating with me right now)
You might test to see if it's bad. |
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utahluge
join:2004-10-14
Draper, UT
·Comcast
| »www.alldatasheet.com/datasheet-p···API.html
I took another look (not the pic, but at the radio) at it looks like its the angle of the photo. Plus:
»2.bp.blogspot.com/_J3BJClp5cnQ/S···+091.jpg
Would I be able put my multimeter on it and should any of the leads let through the ohm test (or not let through)? |
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UHF
All static, all day, Forever
Premium,MVM
join:2002-05-24
clubs: | reply to utahluge
Check D301. If it reads shorted in both directions, it's bad.
I'm downloading a schematic now, I'll take a look and let you what else to check. |
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UHF
All static, all day, Forever
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join:2002-05-24
clubs:
 ·Dish Network
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| reply to utahluge
Also check Q301, Q302, and the 8V regulator as mentioned by another poster. 13.8V normally is fed to Q116, and directly to the microprocessor, and the output PA module, so those could be fried.
My bet is on the PA module, first thing I would do is unsolder and lift pin 5 to that and see what happens. I would put a small fuse in at that point, 1/4A if you have one, if it still blows your problem is somewhere else.
Let us know how it goes, and good luck. |
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Eat Me
join:2002-09-25
Sussex, NJ | The PA module would definitely be one of the first areas to check. They're fed directly from the DC supply. |
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Axilla
Finger, Finger
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join:2001-03-26
Schofield, WI
clubs:
Host:
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1 edit | reply to utahluge
D301 looks like its bad, its an input diode that protects the radio itself. it normally should only show no continuity in only one direction but I would bet it reads as an open circuit both ways right now. Whether or not you fryed something else I cant tell for sure right now.
Getting the board out to replace a component requires you to desolder the SO-239 from the baord on this radio. Be very careful not to bridge the connections when you fire it back up, Yeasu has a VERY healthy solder pool laid down from the factory here, thorough separation between the two solder pools is very important, I would recommend a lot of work with a desoldering braid on reassembly. But also make sure your connections are good, no cold joints!
edited for clarity.
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INFLOW-WI |
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utahluge
join:2004-10-14
Draper, UT
·Comcast
| Ok. Rather than re-do my notes, I just scanned them in. |
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alphapointe
Premium,MVM
join:2002-02-10
Columbia, MO
clubs:
·Mediacom
| If Russ is explaining your drawings accurately, D201 is shorted. You can try cutting it out of the circuit, but know that if that diode is not the only problem, doing that could blow something else up. It sounds, however, that blowing it up more isn't much of a concern based on what the radio is worth.
If you decide to cut that diode out of the circuit and the radio works after that, replace the diode. Don't leave it without reverse-polarity protection.
My 2 cents, take it for what its' worth.
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»boone.mo.scanamerica.us/
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utahluge
join:2004-10-14
Draper, UT
·Comcast
| Ok. I have cut D301 and when I applied power, the radio does turn on. So, now I guess I just need a replacement.
Thank you very very much for your help! I hope one day I will be able to help you too! |
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Hank
Its all relative
Premium
join:2002-05-21
Burlington, WV | Can you tell the forum if it transmits and receives ok? |
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utahluge
join:2004-10-14
Draper, UT
·Comcast
| Ya. Sorry. I tested with my brother about 25 yards away and I could TX & RX no problem. Note: I was transmitting 65 Watts and forgot to make sure the low-end (5 Watts) was working well too. I should be able to test again later this evening for the low-end. Thanks. |
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Hank
Its all relative
Premium
join:2002-05-21
Burlington, WV | Thanks for the response. If HI power working the low should be good. Very happy to hear you resolved the problem. Good going. |
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drjim
Premium,MVM
join:2000-06-13
Long Beach, CA
clubs: | reply to utahluge
Nice to hear you found the problem! |
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Splitpair
Premium
join:2000-07-29
Cow Towne
 ·T-Mobile US
| reply to utahluge
In image 101 that slightly out of focus D301 looks heat damaged and cracked close to the + end.
Just for la la's try nudging the center of that diode with an orange stick or some non conductive probe it is easily pop's open you didn’t break, it's already broke!
Leave the diode open re-fuse the unit with a fuse rated for the RECEIVE amperage, grab a fire extinguisher, power up and see what other damage awaits you.
Wayne
--
If you cannot fix it with a buttset and some beanies you ain't a technician |
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drjim
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join:2000-06-13
Long Beach, CA
clubs:
1 edit | Good catch! i didn't look at all the images, but I agree with Wayne...it definitely has a crack on one end.
I seem to remember diodes with a "KE" in their part number to be more than just a "diode". IIRC, they're a surge supressor type similar to a Zener. I have some big diodes at home like that. *IF* I remember, I'll look for them when I get back home tomorrow afternoon.
--
One man's Magic is another man's Engineering. |
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