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My KA-7100 Restoration

jheu02

jheu02

AK Subscriber
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Recapping and upgrading a trusty 7100 I got. Most likely going to give it to my daughter who's into vintage stuff. So far just the main board/power supply is done (though I may still put in some new resistors). For the trimmers I used 500 ohm Murata multi-turns. Pulled, cleaned, greased and reinstalled the power Qs and then checked and adjusted the Offset and Bias. Main filter caps are Panasonic TS-HA's bypassed with 1uF film caps underneath. The other caps are also mainly Panasonic FM/FCs except for the LL which is Nichicon UKL.

Before and After Pics
 

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Control Board

Forgot to take a pre-recap photo. Went thru with new Nichicon UKL, FG, and FR caps, and replaced the tantalums with film. I think I'll order a couple Elna RFS caps for this panel. C7,8 (IIRC) are directly in the audio path, though the stock caps were low-leakage 10uF/16V which I've replaced with UKL 10uF/25V.

All switches/pots cleaned/lubed with D5 and F5 as appropriate. I also had to clean some sticky residue from some of the knob shafts. I'm guessing the prior owner thought WD-40 or some other oil was a good idea. :nono:

Tomorrow will be the preamp section and then time to button up everything. in the meantime...
 

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Finished!

Recapped the preamp today and finished buttoning things up. Also did a bit of cleaning: switches, pots, faceplate, covers... Sounding nice! :music::music:

Here's today's work plus a couple others:
 

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jheu02 said:
Recapped the preamp today and finished buttoning things up. Also did a bit of cleaning: switches, pots, faceplate, covers... Sounding nice! :music::music:

Here's today's work plus a couple others:
Click to expand...

Tell us more about the details in improvements resulting from recap, cleaning
 
jheu02 said:
I'm guessing the prior owner thought WD-40 or some other oil was a good idea.
Click to expand...

On the shafts that go to the speaker, input and record switches, it IS a good idea. The old grease gets all gummy, and most of the effort when turning the knobs is used to overcome this friction, rather than turn the switch.

Lee.
 
leesonic said:
On the shafts that go to the speaker, input and record switches, it IS a good idea. The old grease gets all gummy, and most of the effort when turning the knobs is used to overcome this friction, rather than turn the switch.

Lee.
Click to expand...

Then I guess the prior owner hadn't done anything and it was gummy from age, because it was just as you described. At any rate, it's all cleaned now and they move properly and noise free. :yes:
 
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