dx-10

AM Radio discussion. Directional arrays are FUN!
Post Reply
Abebe Ashenafi
Posts: 5
Joined: Sun May 31, 2015 1:48 am

dx-10

Post by Abebe Ashenafi » Thu Nov 05, 2015 5:04 am

Hi there , I have a problem with the dx-10 transmitter ,that indicates 'band pass filter vswr' due to the change in the operating frequency .When i diagnose the oscillator board ( the led board on the led board indicates that the oscillator is ok) the out put frequency has completely changed ,even though i replace the ic U1,U2,U3 and U5 the out put still not correct and unstable .additionally when i open the jumper p2, the frequency divider ICs (U1 and U2) delivers the correct out put but when i connect p2-1 and p2-3 the operating frequency would double , please any help
Abebe

COMMENG
Posts: 106
Joined: Wed Dec 18, 2013 4:30 pm
Location: Midwest

Re: dx-10

Post by COMMENG » Thu Nov 05, 2015 10:17 am

Did you do a recent retune of the transmitter?


I would consult sections 6.3 and Q.11-Q.13 and check waveforms with a scope and Frequency counter.

DX-10 Tech Manual.pdf
(3.71 MiB) Downloaded 681 times
Commeng

RodeoJack
Posts: 164
Joined: Fri May 29, 2015 12:54 pm
Location: Port Orchard, WA
Contact:

Re: dx-10

Post by RodeoJack » Fri Nov 06, 2015 12:10 am

A bandpass VSWR error wouldn't cause a frequency change, but would likely show up because of it. I would expect the error to disappear, once you figure out why you changed frequency in the first place.

The bandpass null is very sharp, but is adjustable (see C-101). However, it's part of the transmitter's output network, which probably isn't all that happy right now, either. Sounds like you'll find your problem in the middle cabinet. The rest of the transmitter is probably OK.

Abebe Ashenafi
Posts: 5
Joined: Sun May 31, 2015 1:48 am

Re: dx-10

Post by Abebe Ashenafi » Fri Nov 06, 2015 5:54 am

Hi guys , appreciate your kind response , first I want to say sorry for my poor English, I think I have to make you clear that the whole problems that had happened . The first problem was " band pass filter VSWR " .This indicates after the transmitters starts normally and when I pressed the 'RAISE' button. After a long period of diagnosis ( i tried by replacing the filter capacitors in low voltage power supply by finding any loose contact at the back of PA modules but no change even i tool a frquency measurement ) one day i got the the fuse F1 on the oscillator has burnt (+22V) immediately after i replace the the fuse ,again the R29 has burnt ,i got U4 pin 4 and pin 14 has a short , i replace with the normal one ,the problem is still persisted .I tried to list what I did during troubleshooting the failed Oscillator board ,please refer schematic diagram of oscillator (888-2247-097-E))
. By disconnecting the Jumper P2 when I measure the output frequency at P2-3 it is the right frequency(1233khz),but when I connect P2-3 and P2-1 the frequency at U5-7 or at P3-1 will be doubled (2466khz)
. The frequency at Q2 collector at any condition is 9864khz ( jumper P2-3 and P2-1 connected or not ) never changed
. The frequency at R31 is more than 5000khz and not constant
. The jumpers all connected correctly according to the instruction on the manual
. I replaced ic U1,U2,U5 ,U4 and U3 but the problem still persist I cannot get the right frequency.

Post Reply