I recently acquired a Sansui T-80 am/fm tuner. The sound was pretty good,
but I had some flaky performance issues: The tuner would periodicaly lose
its' quartz-lock and the "tuned" inducator would drift badly. Also, the
entire digital display would periodically dim and lose some or all
functionality.

I opened up the case and first off noted that the main filter caps on the
power supply were leaky. Well, I figured, might as well bite the bullet and
replace all of the electrolytics given that this tuner was built in 1981.
So last night I replaced all 44 caps. I had trouble finding one of the spec
caps, a 0.15uF 100V electrolytic, and so ordered and installed two film caps
of this rating instead. All replacement caps matched the ratings of the
originals EXCEPT those 0.15uF caps... I think a previous owner had run into
the same problem with availability of this cap in an electrolytic and had
substituted a 0.22uF 100V.

I cleaned up the boards, put the whole unit back together and powered it up.
Well, first thing I noticed was the sound... low volume, tinny, no base at
all. Whereas before I started 25% volume on my amp would shake the house,
now I can easily go past 50% and still can't feel any thump in the floor.
The tuner drift issue has gone away, I suspect a cap labelled "AFC bias" was
the culprit there. However, I still have the dimming issue with the digital
display; perhaps the +5VDC regulator that powers the display board is flaky?
It's in a tough spot to blast with heat or cold without affecting a whole
whack of other components.

I left the tuner on all night thinking maybe there is some sort of initial
"burn-in" period and I THINK it sounded a bit better than at midnight last
night, but who knows...

Can anyone tell me where I might start to diagnose the tinny sound problem?
There are but a handful of coupling caps in the FM signal path, some in the
IF amp section, some adjacent to the MPX decoder. I am inclined to toss
back in the 0.22uF electrolytics that I replaced with film caps; they are
output coupling caps just to see what happens.

Any assistance greatly appreciated.

Dave

If you actually replaced 44 caps, you deserve to get this working!

Look for free-standing TO-220 voltage regulators. Freeze 'em or heat
them up, see if any effect, or just replace them (heck, you've already
replaced most of the PS). Might be worth a shot...

Good luck.

"Mr. Land" wrote in message
oups.com...
If you actually replaced 44 caps, you deserve to get this working!

Look for free-standing TO-220 voltage regulators. Freeze 'em or heat
them up, see if any effect, or just replace them (heck, you've already
replaced most of the PS). Might be worth a shot...

Good luck.

I replaced the single +5VDC regulator last night. We'll see if the problem
goes away.

Dave