[7070 I can't figure out how to take it apart / whats wrong?

[denalae]

Does anyone have step by step instructions on taking apart a 7070? I got the frontmost panel off, but the main metal panel is giving me trouble.

I'm trying to get to the knob pots so I can clean them. My sound keeps cutting out in the left channel, unless I use MONO. That kind of narrows it down a little bit, if I could find a schematic. Other than that I was just going to clean out the MONO/STEREO selector, and all the other pots. I had this thing cleaned/serviced about 2.5 years ago.

So..does anyone know how to take it apart, or more specifically what could cause my problem?

Thanks!

 

[so_ein_pech]

http://www.hifiengine.com/manual_library/sansui/7070.shtml

I don't remember having any specific trouble getting the faceplate off it that's what you mean. Make sure you have all the hex bolts around potentiometer shafts unscrewed.

Deoxit is the first thing I would try, just as you plan to do. If that doesn't fix it, look for a broken solder joint somewhere in the signal path. You can sometimes find them visually.

 

[denalae]

This is how far I've gotten (see pictures). I tried pulling out the bass/high/mid board from the bottom, but the wires are too short.

I looked at those manuals already and it doesn't have disassemble instructions.

Do I need to take apart the board more than this, or can I just squeeze the Deoxit tube in there and spray n' pray?

 

[so_ein_pech]

I don't have my 7070 in front of me (its not even in the same state) so I can't say for sure. I seem to remember being able to get the light assembly detached to get at the pots underneath it.

Just be careful if you loosen anything connected to the tuner's dial string. You don't want to have to restring that.

Is that lower panel on the front independent or connected to the main chassis?

 

[denalae]

haha yeah I am trying to avoid that tuner string. It looks like a bitch to work on.

The front panel is screwed to the chassis I think, but I'm not totally sure.

I'm going to squirt some deoxit up there while I work the knobs. Hopefully that fixes it. Does the deoxit work on switches? The STEREO/MONO switch alters the problem so that might be the culprit.

 

[larryderouin]

Go from the bottom. Follow the wire bundles back a bit and remove/loosen the wire ties to get SLACK in the wiring. Then slide the board back until the ends of the shafts just clear the holes. Tilt the back of the board up as you bring it out and clear the shafts. Then tilt up the end with the shafts and you have access to the pots.

Bend the straw 90* about 1/4" and warm it up with a hair dryer. Stick a piece of wire inside so the lumen doesn't close when heating up. Let it cool once you get the bend to stay. Remove the wire. The end with the bend will react violently (Newton's 3rd law of Motion) if the nozzle is set for M or H.

Stick the bend in the slot where the leads go in to the pot and spray lightly. Don't take much. Then turn it 3-5 times to spread it around and then do all of them. Once you get them all, go back to the 1st one and exercise it 30-40 time vigorously. repeat for all.

Reassemble, and check for loose wires (sometimes one or two will come off if you didn't get enough slack). Reattach any that came off.

If it goes up and down, in and out, or Round and Round (except for the tuner cap) it gets DeOxit.

 

[Zekeman]

Larry - do you really spray deoxit on the variable tuning cap?

 

[LBPete]

It's been awhile since I've been in a 7070 but it's a pretty basic chassis. It may not be necessary to take the front rail of the chassis off to get to the pots. Turn the chassis on it's side, transformer side down and remove the bottom panel. You may be able to access the pots from there. you may also be able to pull out the whole tone board through the bottom by taking the retaining nuts off the controls.

Fair warning though, if this basic disassembly is causing you trouble, consider bringing it to a pro before you get even further over your head.

- Pete

 

[larryderouin]

Larry - do you really spray deoxit on the variable tuning cap?

If you go back and READ my post you'll see I specifically EXCEPTED the Tuner Variable Cap!

 

[denalae]

Thanks guys! I ended up being able to spray the pots and switches from the bottom. It's working now, except for some reason the two FM meters on the top left aren't lit up anymore

 

[LBPete]

If the rest of the dial lights are lit, check the meter bulbs.

- Pete

 

[avionic]

If the rest of the dial lights are lit, check the meter bulbs.

- Pete

Or cold solder connections on the lamp leads/connections.