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Zenith MC 7040 repair questions

M

MaxO933

New Member
I'm fairly new to audio equipment, but I recently put together a system in a small room with an old (late 70's I think) Zenith MC 7040, and a pair of PSB 500i's. It sounds quite good to my ear, but I noticed quite a lot of dust inside of the Zenith when I looked through the vents. I was thinking of opening it up and blowing off the dust and cleaning the volume pot. Is there anything else that I should do while I'm in there that might inhance the sound? Preferably something that's not too difficult; I'm fairly handy but inexperienced with the insides of a receiver.

Thanks in advance for any suggestions.
 
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Here are a couple of pictures of the Zenith: image.jpegimage.jpeg
I'll update once I've cleaned it. Any advice would be much appreciated. Thanks.
 
Nice receiver.

If the controls are noisy, then you can clean them with contact cleaner, otherwise nothing to be gained.
Search the forum for tips.

Some folks like to blow the dust out with compressed air.
I have no air compressor, so I poke around the circuit board with a soft paint brush and vacuum the dust out.

Clean up any corrosion you see.
Check any ground connections you see are tight.

Look at both sides of the power supply and main amp boards and for signs of heat damage, crusty solder joints, etc.

Post some nice pictures of the inside (top and bottom) and knowledgeable folks here may provide some feedback.

Don't touch the fins on the tuning capacitor with anything other than a clean bush.
 
One of my standard "new project once overs" is to remove inspect/clean and reinstall all the connectors. An amazing amount of problems come from dirty contacts etc. Some are resonably self cleaning so just reseating them can help. Just be aware of brittle plastic. I have fixed more than one repair project by reseating a connection.
 
Very nice receiver! I didn't know Zenith was in the SS game this late.

+1 on cleaning controls as a first step. This will clear up most issues. Lots of documentation here - use Google to search the forum, and look for 'DeOxit' threads.

If you use an air compressor to blow this out, be VERY gentle with the nozzle. Keep it a long way from the PCBs at first - you can cause havoc with too much pressure.

Mike
 
Thanks so much for the pointers everyone! I think that I'll have at it on Wednesday, so I'll make sure to update you all with pictures and descriptions.
 
The only things you need at this point are some contact spray (i use crc QD, other folks prefer caig, YMMV) to clean the pots and a screwdriver to remove the cover. Dirty old post can do more than sound bad, they should be cleaned. lubing after is a good idea, will prolong the life of the pots, but isn't required (like waxing a car). Just be aware that the cleaning sprays REALLY clean some things and leave them more vulnerable to corrosion. $11 at home depot gets you the CRC QD cleaner and the CRC 2-26 lube. With those two sprays you can "fix" much of what causes people to abandon stuff in the first place - dirty pots.

It's a weak yardstick, but I've yet to come across an old receiver with all it's lights working. To me that's a good sign this wasn't used or moved much.

Clean the pots and enjoy. IF you notice a degradation in sound, stop using it and then start digging. Some folks like me take perfectly good gear and rip it apart, but unless you enjoy that sort of thing, my advice is if it ain't broke, don't fix it.
 
Here are a couple of pictures from after and before cleaning the dust:image.jpeg image.jpegI cleaned the dust off, and cleaned the pots. Next I'm doing some soldering. Then hopefully I'll manage to replace the two right bulbs and glue in the cracked clear plastic around the bulbs seen in the pictures.
 
Nice!! How do you like it now that you've had some time?? I just purchased one, hopefully it'll be in next week.
 
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