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Message |
    
Airplane1
Advanced Member
Username: Airplane1
Post Number: 759
Registered: 5-2004
| | Posted on Thursday, May 04, 2006 - 12:22 pm: | 
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Can someone tell me what bias current is?
I sent my 2985dx back to ranger cause the display started dimming very low after a month of use and the sent it back explaining it was fixed. I pluged it in and it is dimming just as before I sent it in.
I thought for sure it was the internal power supply but the tech note says that they adjusted transitor driver bias was set to high.
What ever that is it did not fix it and I cant believe they sent it out to me like this.I emailed them to see what I need to do next.
I waited 4 weeks for this radio cause they were backed up and hate to wait again + out 45 bucks shipping for nothing.
AP |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1515
Registered: 9-2004
| | Posted on Thursday, May 04, 2006 - 11:24 pm: |
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In electronics, current bias is a steady-state current that is forced through an electronic device like a transistor, coil or other source of load. This is accomplished by varying the voltage across the device in order to fulfill the equation
V=I(R)
which relates the voltage (V) with the current (I) passing through a device and its resistance (R). Current bias can be "broken" if the load induces a voltage that cannot be maintained.
for our purposes, the bias setting has to do with the efficiency of the final and driver transistors.
some people will turn these up in an attempt to get more power, but they just end up hurting the radio.
so, does your display dim while transmitting?
modulating?
all the time?
flickering?
do all the lights dim at the same time, or is it just the display?
channel or freq. display?
matt |
Airplane1
Advanced Member
Username: Airplane1
Post Number: 761
Registered: 5-2004
| | Posted on Friday, May 05, 2006 - 11:26 am: |
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Well when it was new 2 months ago it did not dim at all, now I never touched the inside so nothing was changed but at a month old it started. what it started doing is both meter lights and green backlight display would dim on am when just keying the mic and even worse when modulating, SSB only when modulating. This happens with rf power turned all the way down but gets very bad when rf power is turned all the way up. It is all lights, meter and display. Now what could have happened? like I said it worked perfect for a month and then ranger did the bias transistor adjust and said it was fixed but it came back doing the same. I emailed them with no followup from them.
I have a little more info for you that might help you help me. There is a humming from my power supply, I was told this is not normal but it is just slight hum not real loud but enough to here when sitting in front of radio with volume tuned down.
Thanks,
AP |
Akbowtie
Member
Username: Akbowtie
Post Number: 53
Registered: 5-2005
| | Posted on Friday, May 05, 2006 - 8:37 pm: |
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Goofy Rangers! 
My lights on my 2990 kept going out. I replaced the resistors and the ummm...3 legged surface mounted transistor? i guess. I'd get nasty loud static on my recieve when this happened. I re powered the lights and grounded to a diff. source, put in a variable control to turn the lights up and down. I have never had a problem since.
Dunno if this really help you, but my two cents worth. |
Airplane1
Advanced Member
Username: Airplane1
Post Number: 762
Registered: 5-2004
| | Posted on Saturday, May 06, 2006 - 3:40 pm: |
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Kid_vicious
would a bad power supply be causing this? I just thoght that because it is humming a little maybe the power supply is going bad after the month I had it and that is why the display and meter lights just all of a sudden started dimming.
AP |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1524
Registered: 9-2004
| | Posted on Saturday, May 06, 2006 - 10:23 pm: |
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yep, oh yeah,
you got yerself a power supply problem.
i know at this point it doesnt seem like good news to hear, but actually it is!
you see, the fact that the problem is in the power supply means that all the complicated electronics are probably fine.
i cant believe the techs there at ranger couldnt correctly diagnose this problem!!!
as a matter of fact; I dont believe it.
this is a very common complaint and any tech worth his salt should have seen it right away.
wanna know why they tried what they did to fix it?
because they didnt have to buy or replace any parts!
their repair was fast and cheap. for them!!!
i feel for you; you think you can at least trust the manufacturer!
ok, lets try to troubleshoot this thing a bit.
even if you dont feel comfortable doing the repair yourself.
if you can find someone who is comfortable with soldering inside electronics, you can show them exactly what to replace.
you can do this!
does this radio have an amp built in?
dual or single final?
do you have an external power supply handy that you can test the radio with?
we are going to make sure the problem is in the power supply first. (it most likely is)
if the radio has a built in amp, then you need a 30amp continuous supply. if not, 10 amp continuous.
dont bother with anything less currentwise. you just may see the same symptoms.
ok, checked radio on external supply of sufficient current rating?
lights still dimming? problem lies elsewhere. not power supply.
no dimming? now we can start to locate the source of the trouble.
no power supply?
no prob!
go out to the car with some wire, hook the ext. supply input on the radio to the car battery. (directly!)
start the car, raise the idle up a bit, and key the radio.
no antenna?
just stick a 102" length of wire into the antenna socket, and keep your key ups under three seconds long, and space them out.
you should be able to tell pretty quickly whether or not the problem is still there.
if its determined that the problem is in the power supply, you can choose to send it out for repair again; armed with the knowledge that you know what the repair will entail, or you can do it yourself.
poking around the power supply can be dangerous, so keep the set unplugged, turn the power switch on, and leave it on for a good half hour.
this will discharge the caps.
now its time to look inside the radio for obvious culprits.
the big three are the main filter cap(s),
the regulator transistor/IC,
and the power switch itself.
i would just buy replacements for the filter caps and regulator, hopefully with higher rated parts.
and to see if the switch is the problem.
go buy a spst heavy duty switch from rad shak that is rated at 10 amps or more.
sub this switch for the old one, and see if problem goes away.
now if this is it, you may have to change the look of your power switch or hunt down something of quality that will look the same.
ok, enough for now. i'll look for some info on this radio and post again.
tell me what you discover.
use all your senses.
matt |
Airplane1
Advanced Member
Username: Airplane1
Post Number: 763
Registered: 5-2004
| | Posted on Sunday, May 07, 2006 - 11:32 am: |
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Thanks you Kid_vicious,
I tend to think it is power supply related just because I had the problem with a mobile unit I hooked up to a to small of a power supply and it did the same, put it on a higher amp supply and it worked great.
Ranger got in touch with me by phone and they are going to eat the cost for shipping both ways and look at it again + they said it will be priority this time so I dont need to wait 4 weeks again. I will give them one more chance to get it right because people do make mistakes and I believe in second chances.
I am not a tech but I am includeing a note that I think it seems like the power supply transformer might be the problem and just went bad after the month I hade it.
I dont want to give up this 2985dx because when it was working I was alsome and I like it very much.
If it comes back still in disrepair I will fix it my self or send it to another tech.
Thanks Kid_vicious, I might still need your help so post all the info you get for me and I will post if it gets straightened out or not.
AP |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1528
Registered: 9-2004
| | Posted on Sunday, May 07, 2006 - 4:03 pm: |
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you got it!
well, thats a pretty good outcome. if they will eat the shipping cost, then you're home free.
if you want you can include some of my guesses as to what the problem was.
anyway, good luck, if i find anything interesting, i'll post it, and be sure to bring this thread back to the top when you get the radio back.
any chance they will do an alignment while its there?
couldnt hurt!
matt |
Airplane1
Advanced Member
Username: Airplane1
Post Number: 764
Registered: 5-2004
| | Posted on Monday, May 08, 2006 - 8:38 am: |
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I asked if they will align it and they said it should not need it but if I want they will for like 70.00. To much so I said no.
AP |
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