| Author |
Message |
    
Rogerbeep
| | Posted on Tuesday, June 24, 2003 - 2:53 am: | 
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my 2980 was working great till I turned it on one day and it was stuck on 29.685. Doesnt matter if you put it on a, b, c, or d, or am, fm, lsb, usb, fm, or even change the channel knob, its still stuck on 29.865. It even transmitts on that on that freq. What could have happend, and what part and number do I replace to fix it. |
Kc0gxz
| | Posted on Tuesday, June 24, 2003 - 5:47 pm: |
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Rogerbeep
Try disconnecting the power and hold in the CPU reset button for a couple of seconds. Any memory that you had stored in memory will be lost but it should restore the CPU.
Possibly someone else can help with your problem.
Jeff, kc0gxz. |
2600
| | Posted on Wednesday, June 25, 2003 - 11:56 pm: |
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Uhh, for starters, the 2980 is NOT a computerized radio that will reset like that. It's jut a big, overgrown 40-channel radio with a big PLL chip and a band switch. That "10-meter" thing is all about getting around the FCC's import and resale restrictions.
First likely cause for a radio that was working great, then quit is the 10.24 MHz crystal. When it quits, The PLL will "lock" the frequency either as high as it can go, or as low as it can go. Resoldering the pins on that crystal will sometimes "shock" it back to working, but usually only for a while.
73 |
Tech808
| | Posted on Thursday, June 26, 2003 - 10:42 pm: |
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Rogerbeep,
I did get your e-mail but I believe 2600 answered your question in the above post on what to check.
I apologize for the delay in getting back to you.
Lon
Tech808 |
Rogerbeep
| | Posted on Friday, June 27, 2003 - 12:05 am: |
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Thanks for the tip. When I read 2600 and 808's post I was eager to try your suggestion. I did as you both instructed, but, no luck. Do you believe replacing the 10.24 is the trick or do you have another rabbit in your hat? I am really looking forward to your comments. Its kinda like water in the well, you dont miss it until it runs dry. LOL
Thanks, awaiting your reply. |
Crappie
| | Posted on Friday, June 27, 2003 - 2:43 am: |
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Rogerbeep
I would check the VCO control voltage at TP2 (adjustment of L17 may have been changed in a peak & tune attempt). The voltage here should be set as specified in the PLL alignment instructions. |
Adshar64
| | Posted on Friday, June 27, 2003 - 4:19 am: |
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Id be checking for vco tune coil first - adj to see if lock available |
2600
| | Posted on Sunday, June 29, 2003 - 2:26 am: |
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You really need a 'scope to tell if the 10.24 is running. Best way for sure is to observe pin 4 of the 145106 PLL chip. If the 10.24 oscillator and crystal is not driving the PLL chip, you won't have the nice, 8 Volt peak-to-peak square wave. The radio doesn't use this pin, so hooking a 'scope probe onto it won't disturb anything sensitive. Looking at a crystal with a 'scope probe can cause the crystal to shut down, in some cases.
It's hard to tell much about a dead PLL without a scope. Meter readings on a PLL are only useful when it is properly in "lock". A meter is not much help with a broken one. Since the VCO in that radio has such a wide range to start, tweaking that slug is not the first place to look, unless you suspect a "golden screwdriver" was applied to it already. If the problem is JUST that VCO slug, some bands will lock up okay and some bands will not. The bands that DO lock in okay will all be at one end of the bandswitch, either the top one, two or three will work, or the bottom one or three. L17 will NOT drift enough on its own to kill ALL the bands. Somebody would have to spin the slug to cause that.
73 |
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