Re: Technics SU-9070

MazdaBoi · 10th February 2006, 07:42 PM

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 · 10th February 2006, 07:57 PM

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 · 14th February 2006, 08:10 PM

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 · 14th February 2006, 08:20 PM

Quote:

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 · 14th February 2006, 08:46 PM

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 · 14th February 2006, 08:52 PM

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 · 14th February 2006, 09:00 PM

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 · 14th February 2006, 09:05 PM

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 · 14th February 2006, 09:13 PM

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 · 14th February 2006, 10:58 PM

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

Cheers!

10th February 2006, 07:42 PM	#1
MazdaBoi diyAudio Member Join Date: Sep 2005	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

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10th February 2006, 07:57 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	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

14th February 2006, 08:10 PM	#3
MazdaBoi diyAudio Member Join Date: Sep 2005	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

14th February 2006, 08:46 PM	#5
Netlist diyAudio Moderator Join Date: Jan 2003	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

14th February 2006, 08:52 PM	#6
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	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

14th February 2006, 09:00 PM	#7
Netlist diyAudio Moderator Join Date: Jan 2003	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

14th February 2006, 09:05 PM	#8
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	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

14th February 2006, 09:13 PM	#9
Netlist diyAudio Moderator Join Date: Jan 2003	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

14th February 2006, 10:58 PM	#10
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Hugo, Should be interesting. I am not going to try that one. An amp, maybe. Cheers!

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