Need help with MX-2000

tea_hous

Member
Hey everyone,

I recently found and purchased an MX-2000 after reading tons of AK posts and researching.

Unfortunately, it has been a bit abused... the wood panels are chipped on the side, and the glass broken on the front. It looks as though it were dropped on its face. However, everything looks great internally as far as I can see. It sounds and functions perfectly as well... even the meters and lights behind the broken glass still work.

My first question is, is there anything internally that might be easily broken from such a drop (or whatever bumps and bruises this poor thing has sustained) that I should check over? Or, rather, are the circuit boards and capacitors fairly 'bulletproof' and able to sustain shocks?

My next question is regarding general restoration... Besides obviously replacing the side panels and the glass, is there anything else that should be replaced? It seems controversial whether the capacitors should be replaced or not...

Lastly, I have a request that may be a tall order, but hopefully someone will be interested in helping... It sounds like a bias check and adjustment is a good idea... I have experience working with computers and simple circuits, but have never done this and wouldn't know where to begin. I'm hoping someone who has done this on an MX-2000 or similar could help walk me through the process... I would gladly provide pictures of my progress to aid in communication which, in turn, may help others in the future as well.

Many thanks-

IMG_7134_zps50609f64.jpg
 
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Yes. The power supply board on the under side and the Meter board right behind the meters are rather thin boards that don't flex and crack easily. Look for cracks around all the mounting screws.
 
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The only adjustments are idle (bias) adjustment and meter calibration adjustment. No DC offset adjustment provisions.
 
Thanks Avionic... that service manual is invaluable. I looked for a while for one some time ago, but didn't find anything.

I'll open it up and take a look at the boards... Do the test point for the mV check use something friendly to the prongs of a typical multimeter?

Also, what does '60mV +- 590mV' mean? That must be a typo, right? I saw this mentioned somewhere else on an AK thread before as well... not sure if it was resolved though. That is too much of a variance, yes? Could they mean 5.9mV?
 
Thanks Avionic... that service manual is invaluable. I looked for a while for one some time ago, but didn't find anything.

I'll open it up and take a look at the boards... Do the test point for the mV check use something friendly to the prongs of a typical multimeter?

Also, what does '60mV +- 590mV' mean? That must be a typo, right? I saw this mentioned somewhere else on an AK thread before as well... not sure if it was resolved though. That is too much of a variance, yes? Could they mean 5.9mV?

I'd say a major typo. Most likely its suppose to be 60mv +/- 5.90mv
 
Thanks Avionic... that service manual is invaluable. I looked for a while for one some time ago, but didn't find anything.

I'll open it up and take a look at the boards... Do the test point for the mV check use something friendly to the prongs of a typical multimeter?

Also, what does '60mV +- 590mV' mean? That must be a typo, right? I saw this mentioned somewhere else on an AK thread before as well... not sure if it was resolved though. That is too much of a variance, yes? Could they mean 5.9mV?

Would highly suggest using mini-grabbers like the ones in the photo.
 

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I'll try to pick up some grabbers tomorrow... looks like a good tool to have.

I'll post some pics of the boards too when I check for any damage.

What's your opinion on replacing the capacitors?
 
Ok -- I'll add that to the list. What should I look for in the replacements? The same size and specs, of course... but, any particular makes?

Is there anything else that should be serviced besides this?
 
Lots of audiograde caps it there. Blackgates,tonerex,duorex,Nichicon "Muse".

Blackgates are no longer available.:sigh: I'd use Elna "RFS" series to replace'm.:thmbsp:


BTW theres and outfit on EBAY that has the right stuff for the front clear acrylic with the green edging. I sent you a link.
 
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Nice find with the glass -- with free cutting too, that's a bargain. Hopefully the original one comes out easy and clean, where I can take the needed measurements with dial calipers.

About the caps... for some reason I was under the impression that it was only the two large electrical capacitors that may need replacing... but it's every cap in the entire amplifier!? Yikes... there must be about 50 to be replaced then, yes?
 
Nice find with the glass -- with free cutting too, that's a bargain. Hopefully the original one comes out easy and clean, where I can take the needed measurements with dial calipers.

About the caps... for some reason I was under the impression that it was only the two large electrical capacitors that may need replacing... but it's every cap in the entire amplifier!? Yikes... there must be about 50 to be replaced then, yes?

Usually the big caps are least prone to failure.Its the smaller ones that usually go south.Yep theres a shit load.
 
Its going to be real tough to find replacements for the two large smoothing caps due to there physical size and OEM mounting hardware.
 
Do you think I should just leave em' as is?

I'm actually currently taking this thing apart to take a look at the underside -- will post pics soon.

I just read that it's only the electrolytic caps that need to be replaced... is this true? If so, that would drop the amount that I had initially estimated considerably...
 
I just read that it's only the electrolytic caps that need to be replaced... is this true?
Thats about all.. Film,ceramic and mica caps age very well. Electrolytics don't.
 
Well, I just took the top, bottom, and front off... everything looks good with the exception of the meter board... as you predicted, it is cracked on both the bottom left and bottom right corner... I tried to grab a pic of both, but only one came out, but the same thing happened on both sides. The PCB cracked where the post coming from the meter display meets the board, at which point there is another screw just adjacent to it that attached the meter board to the chassis behind.

I'm not sure if they built it with the two mounting points being so off from eachother that the board had to bend right at the corner, or if somehow the meter board was pushed in internally along it's bottom edge... which would be weird because the glass in front of it didn't actually deform and shatter, but just cracked... I don't know.

Here is a pic of the damage, with a few pics of the other boards as well, then the backside of the glass at the end...

IMG_7158_zpsd1eb2240.jpg


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So, this all leads me to a couple key questions... Any suggestions about what I should do with the broken PCB? It functions fine, amazingly enough... should I just reinforce the back side behind where the post of the meter display hits it, and maybe super glue the board together?

Also, any ideas on how to remove this ridiculously strong adhesive glue that holds the glass in place?
 
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I've a MX-2000 here with the same issue on the meter board,only it cracked/broke all 4 corners. Have to wait until I can get back to my shop to look over my board. (I'm at work right now)Does the crack appear to have cracked any copper traces on the circuit board ? Super glue works great to reattach this PCB material ,followed up with a coating of 2-part epoxy.
 
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any ideas on how to remove this ridiculously strong adhesive glue that holds the glass in place?

On the interior side . you can try to score it around the perimeter with a razor blade. Or maybe use a heatgun around the perimeter to soften the adhesive.
 
The way it shattered it looks like acrylic rather than glass.
 
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