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Old 29th Sep 2023, 3:01 am   #81
steve ss
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Default Re: NAD 3020A No sound after changing capacitors.

Ok all good but perhaps a different approach!

Sooner or later as a tech you learn to deal with these problems.

In the early days copper track lifted from the bakelized (phenolic) "cardboard" circuit boards just by looking at it the wrong way!

The fix was to super glue the track back to the board and heating the track (watch out for the fumes) and solder bridging any cracks.

This technique worked very well and still does but requires a certain skill level and care.

When working on troublesome boards today there are number of tools that work well.
The two that are most helpful are:

A product called "Quick Chip" which is a low temp solder that alloys with existing
solder on the cct board so little heat is required to melt the component joint.

And the use of hand operated solder suckers (damped plunger/spring type) that allow the operator to control the vacuum "release rate" manually while observing the desoldering process.

This process works very well with little likely hood of board/track damage.

The only down side is the whole process is a little slow but worth it!
Also use a quality temperature adjustable\controlled soldering iron.

Now DO's and DON'Ts.

Since the NAD 3020 is the current topic.

In 2019 I came across a NAD 3020 for sale a first generation one with silver aluminum front panel and board Rev .0.00.
After a clean up and internal vac I brought it up on a variac (since it appeared not to have been run for some time) and all was well.
The sound was pretty much as I remembered nice, warm and a bit slow.
If anything a bit slower and less dynamic than my original impressions.
However the longer it ran the sound steadily improved!
That said I felt it could do better.

A quick scout around the board revealed a plentiful supply of ubiquitous green caps
and middle aged japanese electros.

At this point I decided to recap the amp to see what improvement could be made
using modern hi quality polyester caps no green or brown caps and new quality electro's.


Technique:

Do not attempt this when tired or distracted!
One component at a time is good fishing.
Take your time there is NO rush!
If you have to break off for any reason re orientate your self before resuming
the build.
Observe the polarity of electrolytic's do not reverse them!
Have all the replacement parts to hand before you start.
Photograph cct board\s as a memory back up.
Patience pays off, saves fault finding in most cases!

So!
Well it did take a little time but the result was quite surprising with a better than expected improvement in all areas without the loss/change in overall house sound.
Very nice indeed
Er! dare I say an unqualified success!

So the take away from all this is "find out" what mods work for any particular amplifier the components that were used for the mods and be careful and thorougher
and success is likely to be yours.
One other perhaps not so obvious aspect, is this can be beneficial in removing an existing fault and\or avoiding one down the track however this is not a recommended fault finding technique.

enjoy!

Steve ss.
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Old 29th Sep 2023, 10:07 am   #82
Radio Wrangler
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Default Re: NAD 3020A No sound after changing capacitors.

Quote:
Originally Posted by knobtwiddler View Post
If you can nip the legs off, remove them quickly with tweezers - and then suck the hole clean - that would be my tip for fragile boards.
Agreed. In removing a part you have to have asked yourself which do you want to be able to re-use, the part or the board? Being prepared to destroy one can be a big help in preserving the other.

David
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Old 29th Sep 2023, 1:18 pm   #83
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Default Re: NAD 3020A No sound after changing capacitors.

Anyway, this thread has evolved and got stuck in the eternal recap/don't recap discussion that we've had several times and seems bottomless, so the mods have decided that it's time to close.

David
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