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Yaesu FRG-7700 receives AM, not SW
"saki" wrote in message ... I have a Yaesu FRG-7700 shortwave receiver, bought new in 1981, with a problem. I haven't used it in about a year. It's been stored on a shelf indoors. Turning it on again I find that alignment is fine, digital readout is fine, AM reception is fine but the radio won't hear anything above 1650 MHz except white noise. Antenna length affects volume of white noise but there are no discernible signals, nothing that causes the s-meter to move. I've checked the attenuator in the back (DX/Local), which works normally in the AM frequency range. The front panel ATT, gain and mode are all working well. I just can't get shortwave out of it. My Icom R75 and Drake SW4-A hear signals on the same antenna used by the FRG-7700. Try using some spray tuner cleaner on the backside of the bandswitch.. Looks like it may not be functioning. |
Yaesu FRG-7700 receives AM, not SW
Jon Doe wrote:
Try using some spray tuner cleaner on the backside of the bandswitch.. Looks like it may not be functioning. I'll do that, though it appears that the bandswitch is working okay. At least when I change bands the frequency readout changes too and I hear different levels of white noise. Thanks for the suggestion! ---- |
Yaesu FRG-7700 receives AM, not SW
It sounds like either your synthesizer is out of lock or the bandswitching
diodes in the front end aren't being switched by the microcontroller. You probably have some sort of current booster chip such as a ULNXXXX or some switching transistors that switch the receiver above the 1.6MHz range. Since you are hearing different levels of white noise, I believe that your synthesizer is ok. You can determine that by connecting a frequency counter to your 1st LO injection point. If everything in this section of the circuit is ok, you will see a frequency that is above your actual displayed frequency by whatever the 1st intermediate frequency is. The key is that when you change your tuning frequency by 1MHz for instance, your 1st LO frequency will change by that amount. I don't know if that receiver uses relay or diode switching to switch different ranges of the preselector when you tune the shortwave bands. You could actually bypass the preselector and connect an antenna wire directly to the low-pass filter that is ahead of your 1st mixer. On a final note.............................is there a switch on the back panel of the 7700 that selects between long wire and 50 Ohm inputs? If so, that could be the cause. Either that switch is set to the wrong position or it is dirty. Good luck! Pete "saki" wrote in message ... Jon Doe wrote: Try using some spray tuner cleaner on the backside of the bandswitch.. Looks like it may not be functioning. I'll do that, though it appears that the bandswitch is working okay. At least when I change bands the frequency readout changes too and I hear different levels of white noise. Thanks for the suggestion! ---- |
Yaesu FRG-7700 receives AM, not SW
I just downloaded the service manual from mods.dk. Your receiver does use
switching diodes for the preselector, along with an MC14555 chip that drives them. The 50 Ohm input has a 4700pF coupling cap. The long wire input had a different path. If you have a high speed internet connection you can register at www.mods.dk and download the manual. This will give you a good starting point. Pete "saki" wrote in message ... Jon Doe wrote: Try using some spray tuner cleaner on the backside of the bandswitch.. Looks like it may not be functioning. I'll do that, though it appears that the bandswitch is working okay. At least when I change bands the frequency readout changes too and I hear different levels of white noise. Thanks for the suggestion! ---- |
Yaesu FRG-7700 receives AM, not SW
Forget what I said in the last post..............I was looking at another
schematic. The 7700 schematic itself it blurry, but you will need to take a look at that to get an idea of what is going on. "saki" wrote in message ... Jon Doe wrote: Try using some spray tuner cleaner on the backside of the bandswitch.. Looks like it may not be functioning. I'll do that, though it appears that the bandswitch is working okay. At least when I change bands the frequency readout changes too and I hear different levels of white noise. Thanks for the suggestion! ---- |
Yaesu FRG-7700 receives AM, not SW
On Feb 4, 5:25 pm, saki wrote:
I have a Yaesu FRG-7700 shortwave receiver, bought new in 1981, with a problem. I haven't used it in about a year. It's been stored on a shelf indoors. Turning it on again I find that alignment is fine, digital readout is fine, AM reception is fine but the radio won't hear anything above 1650 MHz except white noise. Antenna length affects volume of white noise but there are no discernible signals, nothing that causes the s-meter to move. I've checked the attenuator in the back (DX/Local), which works normally in the AM frequency range. The front panel ATT, gain and mode are all working well. I just can't get shortwave out of it. My Icom R75 and Drake SW4-A hear signals on the same antenna used by the FRG-7700. Is there something I should be focusing on to troubleshoot, or is this something I should have a Yaesu/ham gear repair person examine? Any help would be much appreciated. ---- SAKI, Yaesu FRG-7700 Information WebPage http://www.crocuta.com/FRG7700/index.html http://wiki.radioreference.com/index.php/Yaesu_FRG-7700 The "Yaesu FRG-7700 Shortwave Receiver - Survival Guide http://foxtango.org/frg7700/FRoG-7700.htm Fox Tango International -by- Wim Penders [PA0PGA] Modern Shortwave Receiver Survey @ DXing.Com http://www.dxing.com/rx/frg7000.htm Yaesu FRG-7000 General Coverage Communications Receiver "Recently Sold" Radio Equipment @ Universal-Radio.Com http://www.universal-radio.com/CATAL...r/frg7700.html Yaesu FRG-7700 Shortwave Receiver http://www.universal-radio.com/used/sold099.html Notes: The Yaesu FRG-7700 covers 150 kHz to 29.9 MHz which is tunable in 1 MHz bands. This multi-mode radio has a digital and analog display. It also has a built in 12 hour clock-timer and S-Meter. There is a carry handle on the right side. This radio has the optional MU7700 memory unit installed which can be fine tuned. * The Rear Panel has Dual Antenna Inputs http://www.universal-radio.com/used/ub53rear.jpg http://www.universal-radio.com/used/u865ant.jpg and timer relay contacts. The Yaesu FRG-7700 Receiver Users Group @ Yahoo! http://groups.yahoo.com/group/FRG-7700/ hope this helps - iane ~ RHF |
Yaesu FRG-7700 receives AM, not SW
Clean ALL your switches, and pots, mode, band, squelch, etc
I have one of these and that seems to be a common problem corrosion on the controls ( or dirt, smoke, etc ) My Mode switch still requires a couple clicks in both directions to work right, probably from wear. "saki" wrote in message ... I have a Yaesu FRG-7700 shortwave receiver, bought new in 1981, with a problem. I haven't used it in about a year. It's been stored on a shelf indoors. Turning it on again I find that alignment is fine, digital readout is fine, AM reception is fine but the radio won't hear anything above 1650 MHz except white noise. Antenna length affects volume of white noise but there are no discernible signals, nothing that causes the s-meter to move. I've checked the attenuator in the back (DX/Local), which works normally in the AM frequency range. The front panel ATT, gain and mode are all working well. I just can't get shortwave out of it. My Icom R75 and Drake SW4-A hear signals on the same antenna used by the FRG-7700. Is there something I should be focusing on to troubleshoot, or is this something I should have a Yaesu/ham gear repair person examine? Any help would be much appreciated. ---- |
Yaesu FRG-7700 receives AM, not SW
"labtech1" wrote in
: Clean ALL your switches, and pots, mode, band, squelch, etc I have one of these and that seems to be a common problem corrosion on the controls ( or dirt, smoke, etc ) My Mode switch still requires a couple clicks in both directions to work right, probably from wear. Good advice. I've cleaned some but not all. Certainly won't hurt, in any case, even if the switch appears to be working. Thanks! ---- |
Yaesu FRG-7700 receives AM, not SW
On Feb 5, 12:13 pm, saki wrote:
"labtech1" wrote : Clean ALL your switches, and pots, mode, band, squelch, etc I have one of these and that seems to be a common problem corrosion on the controls ( or dirt, smoke, etc ) My Mode switch still requires a couple clicks in both directions to work right, probably from wear. Good advice. I've cleaned some but not all. Certainly won't hurt, in any case, even if the switch appears to be working. Thanks! ---- SAKI, Caution - Keep the Contact Cleaner "OFF" the Face Plate of the Receiver - Sometimes Sh*t Happens to the Markings when the Liquid {Solvent} gets on them. ~ RHF |
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