Re: Technics SU-9070

[MazdaBoi]

Re: Technics SU-9070

Hello all,

I am in a bit of a pinch and was looking for some advice... I have a rack of beloved Technics equipment from the late 70's and early 80's... One of the pieces is an SU-9070 stereo preamplifier.

The volume and balance pots are trashed... Scratchy, breaking contact, etc. I've tried my best to clean them and breathe some new life into them... Unfortunately, they seem to be too far gone to actually be salvaged.

The pots are actually a gang of about 6 or so all linked together.

I'm looking for two things:

1) Does anyone have any advice on what route I should
go in order to repair this preamp?

2) Does anyone have a schematic of this piece of equipment?
I am ordering the service manual, but I'd like to start ASAP.

Thanks,
Brad

 

[Netlist]

A few weeks ago I had an old Pioneer amp with very scratchy pots.
Spraying them wasn’t too satisfying and the amp was very dirty inside.
I decided to give it a thorough cleaning and as our member Janneman ones suggested I put the amp (top and bottom plate off) in the dishwasher and let the machine do it’s job.
After keeping it warm on the radiator for two days to make sure it was completely dry, I repaired the one broken channel and had a listen.
No scratchy pots anymore and a nice looking amp, inside and outside.
How’s that for a Diy solution while waiting for the schematic?

/Hugo

 

[MazdaBoi]

Lol that sounds like more than I am willing to do. Haha. Then again, I have tossed electronics into the bathtub and scrubbed em... Guess there isn't much of a difference between the two.

Thanks,
Brad

 

[dimitri]

I put the amp (top and bottom plate off) in the dishwasher and let the machine do it’s job.

What kind of detergent did you use?

 

[Netlist]

Sun 3 in 1.
Good for the sound as well.

On a more serious note, I wouldn't do that trick with cd players or gear with displays or monitors and the like.
But these old robust amps can take it with amazing results.
It's the second one I washed, the first one is playing every day for more than a year and the second one for a few weeks now.
Keep in mind that it should be completely dry before plugging in the mains, hence why I left it standing on the radiator for two days.

/Hugo

 

[anatech]

Hi Hugo,
You always did like your amps to sound clean. Arrrrgh Sorry.

This treatment would end the life of a CD unless you got very, very lucky. How was the front end alignment after you were done?

-Chris

 

[Netlist]

The first was a power amp and the second one an integrated.
No receiver. But I bet the old gear front ends don't care.
I'll report next time I'll 'threat' a receiver.

/Hugo

 

[anatech]

Hi Hugo,
I was woried about the ......................... trimmer caps. You know, the water seeps in and never leaves. Then there are the IF coils on older sets. The wire is so thin it might go away by itself.

-Chris

 

[Netlist]

You could be right. Unfortunately I don't have an old tuner at hand to try....wait, an old Rotel is collecting dust on one of the shelves.
But it's clean. One of these days, I'll give it a try, I like the challenge.

/Hugo

 

[anatech]

Hi Hugo,
Should be interesting. I am not going to try that one. An amp, maybe.

Cheers!