MX-1000, how bad did I mess it up?

RayN

Active Member
I recently purchased an AS-IS MX-1000 from the bay for a project. Other than being very dirty and bent, along with some loose connections on the speaker outputs, it worked! I spent some time cleaning it and bending it back into shape, the last thing I needed to do was replace some of the bulbs for the meter. Unfortunately when I was putting the front meter assembly back on I temporarily removed the main power leads coming from the transformers for access to the connectors for the front panel. When I replaced them I accidentally installed one of them offset by one pin. Now the system won't power on, however, I saw no smoke and smelled nothing burning. I hear a relay kick when I press the power button but both the power and protection lamps are dark. Help! I feel like a complete idiot.

The fuses seem fine so I suspect the power supply. I'm comfortable replacing parts and I have the schematic, just hoping someone can help me jumpstart the process.

Thanks
 
I recently purchased an AS-IS MX-1000 from the bay for a project. Other than being very dirty and bent, along with some loose connections on the speaker outputs, it worked! I spent some time cleaning it and bending it back into shape, the last thing I needed to do was replace some of the bulbs for the meter. Unfortunately when I was putting the front meter assembly back on I temporarily removed the main power leads coming from the transformers for access to the connectors for the front panel. When I replaced them I accidentally installed one of them offset by one pin. Now the system won't power on, however, I saw no smoke and smelled nothing burning. I hear a relay kick when I press the power button but both the power and protection lamps are dark. Help! I feel like a complete idiot.

The fuses seem fine so I suspect the power supply. I'm comfortable replacing parts and I have the schematic, just hoping someone can help me jumpstart the process.

Thanks
Make sure you have all wires correctly connected
Check all fuses once more
Find a DBT and use it to power up the unit
Report back with the results
 
Thanks, I discovered my mistake when it didn't power up and it's connected correctly now. I'll build a DBT tonight and definitely use it in the future. I'm just surprised that if it was a dead short that I didn't let any smoke out.
 
if you post the schematic and what pins were shifted (left or right) we suggest avenues of
investigation.
 
OK, pull the connector, and it seems the left side are the bridge rectifiers, I'd check them for shorts.

then the right side are the transformer taps, again, check for shorts.

put a dbt on the thing, measure the voltages on the right side - make sure they are AC active
then try without the DBT, and no connector, the left side transformer taps are correctly
supplying voltage.

then with an enlarged copy draw the mistaken connections made and see what got across
from the left side to right.

then if you are absolutely certain that nothing is shorted, the measure the voltages at the
bridge rectifier outputs. should be what the schematics call for to drive the various circuits.

this is not a step by step but more of a process.
 
OK, pull the connector, and it seems the left side are the bridge rectifiers, I'd check them for shorts.

then the right side are the transformer taps, again, check for shorts.

put a dbt on the thing, measure the voltages on the right side - make sure they are AC active
then try without the DBT, and no connector, the left side transformer taps are correctly
supplying voltage.

then with an enlarged copy draw the mistaken connections made and see what got across
from the left side to right.

then if you are absolutely certain that nothing is shorted, the measure the voltages at the
bridge rectifier outputs. should be what the schematics call for to drive the various circuits.

this is not a step by step but more of a process.

Thank you, this is what I plan to do. My guess is I fried some or all of the diodes in the bridge rectifier which is why I'm not getting DC voltage to the power lamp. Ugh.
 
Thank you, this is what I plan to do. My guess is I fried some or all of the diodes in the bridge rectifier which is why I'm not getting DC voltage to the power lamp. Ugh.
If no blip of a hearth beat, look for open traces as well.
 
check all fuses everywhere you see them.

bridges are easily replaced, and even if you have the requisite power diodes, you can
sub them in.

I have found 'bridge" rectifiers to be sensitive in spite of their dragster specs. so having
one blowup is OK since it will prevent cascading failures into the circuits they power.
 
I missed this when I read yout post. If F301 is OK, use a DBT to power up the amp and report back.

Ha! It was F301! Strangely there's continuity between the posts on that fuse so I had originally tested it as good when it was installed. I'm back up and running, thank you all so much!!
 
I've noticed this amp goes into protection mode at medium to high volumes. It doesn't seem to be with one channel or the other. Any thoughts? I'm looking into a recap of at least the power supply area.
 
I've noticed this amp goes into protection mode at medium to high volumes. It doesn't seem to be with one channel or the other. Any thoughts? I'm looking into a recap of at least the power supply area.
yep, you need a recap ASAP
Had one that did the same thing. After recap and a few cold solder joints repairs, it sang like a canary
 
I did not see a list but it does seem reasonable and a legit place.
you will most likely not receive the correct 110V 820uf caps on the main board.

you will also need the relays. Check your mail box for a list of parts you would need...give it a few mins
 
Last edited:
I did not see a list but it does seem reasonable and a legit place.
you will most likely will not receive the correct 110V 820uf caps on the main board.

you will also need the relays. Check your mail box for a list of parts you would need...give it a few mins

Could you share your list with me please? Thank you!
 
Back
Top Bottom