MFJ-266 Analyzer help

[kd2goe]

I have/had a working MFJ-266 I need the schematic or need to know what "D3" is on the RF board
it is a SOT-23 device with the markings "AH" mighty be a HV but I am 90% sure it is AH

the unit powers up and tunes I can here it on my radio but there is no SWR or impedance readings the device D3 was smoked I can only guess some one plugged it in to the radio and keyed off in to it "dam friends I am never lending out my testing gear" any way I think it is a 5.1v zener diode..


http://www.s-manuals.com/pdf/datasheet/m/m/mmbz5221b-mmbz5261b_semtech.pdf

I have removed D3 all the other zeners test good

 

[k3cfc]

Ages ago i was warned about loaning equipment out so i do not. i just say MFJ sell's them everyday.
If i were you i would put the part back put a note in with the 266 telling them what you did and what you suspect happened to it in the first place and send it in for repairs. there may be more damage then you know. I have a 259 and i was told to always short the pl 259 to ground because there is a diode that will fail with a static charge. i even go so far as to short out a pl259 and screw it on when not in use.

Good luck.

 

[jonwienke]

A dummy load would work just as well for static protection.

 

[k3cfc]

A dummy load would work just as well for static protection.

There's always one!!!!!

 

[kd2goe]

well looking deeper in to it... they look to be Schottky diode not Zener... I though it was odd that the code on the part came back 5.1v zener when it is in an RF circuit.... so I whent and ordered the Schottky diode 's and 20 IRF520's to have on hand

I called MFJ guy there told me to call back Monday

I found this info on the MFJ-269
MFJ-269 Repair

 

[k3cfc]

well looking deeper in to it... they look to be Schottky diode not Zener... I though it was odd that the code on the part came back 5.1v zener when it is in an RF circuit.... so I whent and ordered the Schottky diode 's and 20 IRF520's to have on hand

I called MFJ guy there told me to call back Monday

I found this info on the MFJ-269
MFJ-269 Repair

I think you are on the right track talking to a factory tech. I don't remember what the touchy diode is only that it won't any static that's why i use a shorted pl 259 to protect it.

 

[kd2goe]

MFJ-266 antenna analyzer "R1" help

if any one has an MFJ-266 antenna analyzer can you look inside on the RF board next to the N-connector and tell me what value of Resister "R1" is or the print in it... there was an accident with mine I got it working by replacing the detector diodes but R1 was damaged. I have a 47 ohm test resister in there in there now it seems to be working fine now but I would like to get the right value in there.


I did call MFJ and because it is an import I am waiting on a phone call back don't even know if there going to be able to help..

 

[kd2goe]

well it looks like MFJ cant help me. they cant even give me a schematic. I know 2 diodes D1 and D3 and R1 where cooked I replaced R1 I got the SWR reading back.
I used the info from MFJ-269 Repair to give me a guess at what there diodes where so I ordered 6 and was going to swop out D1, D2, D3, D4
at first I just did the 2 that where shot... ok seemed to help I did D4 and lost the SWR readings put the old one back and got the SWR meter back... so there leaves me to guess the diodes are not right at all...

I can't believe MFJ cant give me any info on a product they still sell!

ill have to Call them up Monday and press them some more.. I am trying not to get pissed at them...

 

[k3cfc]

well it looks like MFJ cant help me. they cant even give me a schematic. I know 2 diodes D1 and D3 and R1 where cooked I replaced R1 I got the SWR reading back.
I used the info from MFJ-269 Repair to give me a guess at what there diodes where so I ordered 6 and was going to swop out D1, D2, D3, D4
at first I just did the 2 that where shot... ok seemed to help I did D4 and lost the SWR readings put the old one back and got the SWR meter back... so there leaves me to guess the diodes are not right at all...

I can't believe MFJ cant give me any info on a product they still sell!

ill have to Call them up Monday and press them some more.. I am trying not to get pissed at them...

Well if you can't fix it you'll probably just have to buy another. every lesson in life has a price this is what it cost you. NEVER EVER LOAN YOUR EQUIPMENT!! I have B&K precision CB service master and a signal generator that i have had sense 1980 and it is in pristine condition because i never load my equipment. I feel the pain.

 

[kd2goe]

Well if you can't fix it you'll probably just have to buy another. every lesson in life has a price this is what it cost you. NEVER EVER LOAN YOUR EQUIPMENT!! I have B&K precision CB service master and a signal generator that i have had sense 1980 and it is in pristine condition because i never load my equipment. I feel the pain.

getting a new one is not going to happen my wife is laid off and I am working 2 jobs to just keep us afloat...

 

[kd2goe]

I have to do some more testing but I think I have it working 90% +

I tested some old schottky diode I snagged out of an old radio..

 

[k3cfc]

I have to do some more testing but I think I have it working 90% +

I tested some old schottky diode I snagged out of an old radio..

Keep plugging away you'll get it. just make notes to the part numbers and what you did to fix it.

Good Luck
K3CFC

 

[k3cfc]

What is the number of R1

 

[k3cfc]

if any one has an MFJ-266 antenna analyzer can you look inside on the RF board next to the N-connector and tell me what value of Resister "R1" is or the print in it... there was an accident with mine I got it working by replacing the detector diodes but R1 was damaged. I have a 47 ohm test resister in there in there now it seems to be working fine now but I would like to get the right value in there.


I did call MFJ and because it is an import I am waiting on a phone call back don't even know if there going to be able to help..

I looked around and found R1 is a 100k

Hope this helps.