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PostPosted: Mon Jun 12, 2017 8:56 am 
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Posts: 291
Location: Toronto, ON, CA
Teo Audio wrote:
Frank Wang wrote:
How bad an old relay can be...


(regarding cleaning relay contacts and leaving a smooth clean 'still plated!' surface behind)

Canadian tire now has a regular line of 4x 11"x8.5" sheets of 2000 grit sandpaper, in the automotive painting section. Decent quality 3m product, best price around, available in 500 locations, or thereabouts. FYI for all interested, kinda thing. Probably in their automotive 'Parts Source' stores as well.

(Ultra fine grit is best for relay and switch contact jobs. Critical, actually)

-- 12 Jun 2017 12:50 --

alexander_x wrote:
Nice work Frank. Inspiring.
Now when you say "resoldered"...does that just mean "reflowed"?
For example...your 'Speaker board' pic.
I ask because I am contemplating tackling my Kenwood KA9100 this summer



I tend to reflow with new solder, then use a solder pump to clean it out, then get to the re-soldering. I've almost exclusively used a solder pump for 30 plus years, and I even have two desoldering stations. I don't use either one of them, as they clog up and need maintenance. I just reach for the solder pump and it works every time. The solder pump needs cleaning but it is ultimately more reliable and less time consuming, IMO.

The desoldering stations are more there for some critical stuff that might come along, where things are a bit more stubborn than what a soldering pump can deal with.


Sand paper for non air-tight relay? It does polish the contact point, but also destructive more or less. Good luck with oxidation and humid.


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 Post subject: Marantz 1152DC Restore
PostPosted: Sun Oct 08, 2017 7:31 am 
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Location: Toronto, ON, CA
A friend has a Marantz 1152 int. amp made in Japan around 1980...needs a bit restore ....

The transformer is heavy, bit of tricky how to disassemble this amp...
-Remove the top cover;
-Turn the amp upside down;
-Remove bottom panel ...

voilà...
-Two main power filter caps are huge, diameter around 41mm...18,000uf/55V;
-The PCBs look "dirty" due to at that time the protection paint was not as shinny ...the machine actually is pretty clean ...
-As usual, put screws from different areas separately into their own bags...this could save a lot of trouble when putting the machine back ...


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PostPosted: Sun Oct 08, 2017 8:22 am 
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Joined: Fri Feb 11, 2011 9:30 pm
Posts: 271
Location: Regina, SK, CA
Frank Wang wrote:
How bad an old relay can be...


a tired relay is 90% of the issue with old amps. it is not just the contact surface, it is the spring strength.
The relay is at rest off, and under stress on, so the more it was used, the more long term stress on the spring fingers to stay in place. The more they loose their effectiveness to stay in place. Add the corrosion and pitting. Your pic is a good example. the outside ones are more damaged, likely they are the ones making the least contact. so cleaning them is actually useless.
A lot of people who start hearing one channel not engaging jump to clean the volume control, and then while that might have been a second condition fixed, the root cause is still the relay.
just replace any relay that is 20-30-40 years old. and yes, they circuit board types, and today it is hard to find. You can buy a new socket to place the new relay that solders in the pcb, or there are ways to extend the pins on a new relay to go back into the circuit board. just takes a little time and effort.
The bigger the wattage amp, you sometimes have not just the power protect board, but speaker switching relays. do them all.

_________________
Vintage has a place.....mostly in my basement.


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PostPosted: Sun Oct 08, 2017 9:21 am 
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Location: Toronto, ON, CA
Use solderwick remove fader from PCB...
Clean it, lubricant it with DeoxIT F...
“seal" it with piece of tape...move on


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PostPosted: Mon Oct 09, 2017 3:32 am 
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Location: Toronto, ON, CA
Relay...the part in music gears which is moving and has contacts...even though no heat...as time goes, trouble emerges...mostly the contact surface gets carbonized and left some black residuals...bad contact ...

Best way to deal with relay is to replace it with a new one, problem is relay comes in various models and layouts, especially vintage gears, those models might be hard to find...

--------
There is only 1 relay in 1152, resides on a small board which will delay couple of seconds and then engage speaker..i.e. this relay is signal connection, no big current surge...and the situation is not that bad, just a bit "dirty"...cleaning & protecting it could do the trick...


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PostPosted: Tue Oct 10, 2017 4:52 am 
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Location: Toronto, ON, CA
The 2 big caps are in pretty bad status, after all 30 yrs passed...

Replaced original 18,000uf caps with 22,000uf caps, same brand and size...


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File comment: Cleaned...
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File comment: New caps in place...the smaller cap for comparison is Elna LAO 10000uf/63V
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PostPosted: Tue Oct 10, 2017 9:15 am 
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fully recapped...


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