I picked up an MFJ 868B and have an issue

[Crambone]

so the guy gave me a 120v to 12Vac supply rather than the 12Vdc supply required. I didn't notice till after it was hooked up for a while and nothing was working properly. I opened it and was checking complements for power when I realized it was showing AC power.
My question is as this has never happened to me before is how much damage can this have caused?

 

[Unit 75]

Check D3 it's a 1n4007 protection diode

 

[Crambone]

Ok thank you I just seen that on the schematic I did t realize it was In the manual.

 

[Unit 75]

I have had a few of those. Check all the soldering of wires etc. while you have it open. 3 units I came across had absolutely no solder on some wires. The wires were pushed in through the holes but they forgot to solder them. NO KIDDING.

 

[Crambone]

Funny you say that because when I looked at the underside of the board it looked like a novice soldered it! If that is factory solder joints shame on them! I’ve owned a number of tuners from MFJ and never had an issue but this meter, uh!

 

[midnight special]

mfj uses college kids from miss state as assemblers,,,,,

 

[Road Squawker]

mfj uses college kids from miss state as assemblers,,,,,

Actually, they don't.
Most of the employees are long time

 

[Rwb]

MFJ= more Fine Junk

 

[Crambone]

Checked the dummy diode last night in circuit and tested good. I’m going to check some voltages I know sometimes things test good in circuit and bad out but it’s SMD and didn’t have the time (1am).Tuesday I’m going to check some voltages especially the op-amp.

 

[Crambone]

MFJ= more Fine Junk

Agree!

 

[Unit 75]

Did you get a proper DC wall adaptor for the meter?

 

[Crambone]

Did you get a proper DC wall adaptor for the meter?

Yes I have a bunch laying around.

 

[Crambone]

So I tried a 9v battery in it last night and nothing at all no movement of any kind. With 12Vdc I get half of what I should be getting so that’s leading me to check incoming voltage to the Op-amp. As I’m new to this does that sound like the correct route?

 

[Unit 75]

Let me find a schematic and take a looksi

 

[Unit 75]

Ok... with your 9v battery installed and the red on/off button on, I want you to take some voltage measurements for me. I installed a 9v in one here and took some measurements for you. See if you get something close as battery voltage will differ some. Let me know how you make out.

Q1 (2n3904) collector voltage should be around .672v
Q4 (2n3906) emitter= 14.7v base= 15.4v collector= .7v
Q5 (mpsa13) collector= 15.3v