Sansui CP 7

[boomboxbilly]

Hi Guys, I noticed this site recently when looking for some parts for a Sansui CP 7, and found a bunch of people who are really into their boomboxes!
Well I have had my Sansui (UK) for decades and have used it for monitoring, bringing me back to tape when I got sick of digital, split up as a portable, put back together as a home unit, borrowed the speakers as a test for other amps and then put back as a complete unit. Yes it is flexible and sounds great.
Over the years though, certain things have gone wrong with it.

First, is, one channel is now out, both speakers work in the left channel (as a test), but I guess the right channel needs a new cap(s) or resistors or whatever. I could get this done by a local competent engineer.
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Next, the cassette deck has now freaked out, used to function, then started that slow rewind business, now the play, pause light comes on, but the logic doesn't kick in to play a cassette any more.
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The tuner works and scans, but the lcd has a screwy look to it.
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And finally, I have lost the door to the battery cover (house moves over the years, or it might be in a bag somewhere lol) and there is a ding to the aerial on the base telescope, so it only retracts ALMOST fully and doesn't sit back into its holder when transporting. And one slider on cassette record is missing, Mildly annoying.
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Needless to say, it still sounds good even with one channel going and I will occasionally monitor mixes on that one speaker to get different perspectives.
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So would you think it worth restoring, or would it be best as a parts donation for machines that are cosmetically better?
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It might be a bit beyond me to fit a logic board or whatever might be required, but then it is quite a cool machine and I am less tempted to just use it as a (stereo if I get it fixed) amp and speakers.
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Thoughts from boombox afficionados much appreciated!
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[baddboybill]

Welcome 👍. Anyway most of issues sound like a good cleaning with new belts. As for the lcd screen we had a member here purchase and replace with new one. I think he got screen from eBay. Finding used parts for these are hard since they are rare. Hopefully Skippy1969 will ring in since he restored one 😉. Good luck!!!


Bad Boy Bill

 

[boomboxbilly]

Thanks for the welcome Bad Boy Bill.
A good cleaning with new belts sounds about right. Found out that the Lcd problem might just be the ribbon becoming a little loose over time. I think they built this thing with quality in mind. Cheers for the tips!

 

[JustCruisin]

Very nice unit! Welcome!

 

[boomboxbilly]

Thanks mate I am enjoying looking round this site at some crraaazy boomboxes like the Delmon!
Bet the designers enjoyed their jobs! And probably had to put up with some **** from management when they went out on a limb.
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[oldskool69]

I would say restore it but I am a Sansui homer. Getting the parts for the LCD won't be as easy as others but the amp section should be workable. I have the service manuals.

I also own a sh!tload of Sansui boxes, the load being relative to the amount in existence.

 

[boomboxbilly]

Hi oldskool, just a little question about the "squidgy" buttons on the CP7.
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Would you say that the "bounce" is due to little rubber pieces ​inside the hollow button face?
Shoulda taken some pics when I had it apart, but was just looking at the tasks generally.
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I Wasn't quite sure if there are carbon contacts within those squidgy buttons or whether there was some slightly perished rubber. Anyways, if they are rubber I thought about fabricating some little inserts. Just an idea? I seem to recall reading that forum member Skippy was having a bit of trouble with the squidgers

 

[Superduper]

Those are cheap quality tactile switches. Basically a conductive mylar plastic "bubble". When you depress it, the dome collapses causing a snap feel to it, and which also closes the contact below. When there's no more give to it, the switch is toast since the entire "tactile" mechanism is gone. You'll need to try to source new tactile switches that are similar size. BTW if you ever get tired of it, I'd like to buy it from you!

 

[boomboxbilly]

Oh right, I think I've come across those type of switches before somewhere. Presumably the dome and contacts are hidden in the little tin boxes of the switch on the board. I was looking at the wrong end for the "bounce".
Funny though, because I've never been frantically pressing those things, which is why I thought there might be some perished rubber or something, because inside the hollow buttons it looked like decomposed rubber, with a magnifying glass.
I have got some other projects on Superduper, so if you would like to pm me with a figure, I might be interested in parting with 'ol faithful!
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[oldskool69]

Norm is absolutely correct. Skippy (Scott) had the same problem with his CP-7. I actually sent him a sketch of how the switch works. If I can find it I'll post it here.

 

[boomboxbilly]

Cool, if you get the chance I would like to see the sketch.

I didn't get down to the amp board yet before I put it back together, but I did pick up a chip that could be the problem with the right channel (or so an engineer told me, I was amazed that he nodded at it and said he has a schematic for it in his vintage repair collection).


I'm not an expert on this stuff lol, but apparently there is such a thing as conductive glue which is used to seal lcds when they are done at the factory.
And over time this seal comes apart.

So sometimes a tbar on a soldering iron can be used (maybe over a silicon pad) on the cabling or area directly preceeding the lcd. And this can get it functioning correctly.
Now whether this is a potential solution or not I don't know. Just read about it.

Engineer said that the "sandwiches" or liquid crystal stuff in it dry out.
He also said it is a labour of love lol. But he will do the (amp) board work if required.
I've only assembled mic pres and not really good at fault finding.
And I need a new soldering iron to replace the iron baseball bat I usually use.
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[Superduper]

Forget about restoring the switches, it's a lost cause. It's like trying to restore the 40 year old tires on your car which are now square, dry-rotted and cracking on the sidewalls, all because new exact replacements are no longer available. Simply get new replacements of the correct size. The style and look might be a little bit different and maybe size is a tad off, but you can drive with them and it will have a new feel to it.

Just open up the box and measure the switchs overall dimensions. If I recall, they are square shaped. Measure that and the height as well. Then go to either Mouser.com or Digikey.com and look up tactile switches. You will get like 10,000 results so it will take some time to weed through them to find ones that will work comparing specs but you should be able to find some to replace the whole set.

As for PM, I will do that when I get a chance. Looks like you are still having fun with it so, I guess no hurry then hmm?

 

[boomboxbilly]

Yes that makes sense, thanks. No particular hurry.

 

[boomboxbilly]

I am back into vintage Lilliput land. Had a look at these switches. Would you say that the b3w-1050 might be a candidate or am I way off here? https://www.omron.com/ecb/products/pdf/en-b3w.pdf

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[redbenjoe]

this is a very cool and interesting thread -
great box --gorgeous sound -
well worth these effots

 

[boomboxbilly]

Well all I've managed to do is get a new aerial for it! Not sure if 6mm switches will do and whether I would have to bend the pins and wiggle and crap and end up with wobbly buttons, so I've left that to have another think about it.
I traced the 1230's to the speakers and they both beeped (one channel out issue), got a genuine NOS 1230, along with one that was wrong,(a newer version H2 not H!) but not attempted that yet.
Could be a dry joint, the chip or a wobbly wire, who knows..
Plus, the lovely Weller station I borrowed that I used on another project had to go back and I have a 25w thing (15w had to go back to shop, not hot enough).
After looking at what you guys are doing and have done with boomers I am out of my depth lol. I might need a periscope and oscilloscope.
The aerial refit went well lol
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