Technics SA-R210 Receiver

I have one of those and an SA-160. The 160 had a problem with cracked
solder joints on voltage regulator transistors on the main heatsink.
The 160 is a little odd to disassmble and I think the 210 is similar.
Got a digital camera?

take lots of pics as you open it up so you can
get it back.

You _might_ have a thermally intermittent power regulator
but bad (metal fatigue) solder is far more common.

I've got an old Technics SA-R210 stereo receiver from the 80's which I've relied
on for ages.

Woke up this morn and it played for a while, then <silence>. Powered down,
let it sit 10 min., powered up and it worked again for 15 min.,
then <silence>.

Receiver is in a cabinet with little ventilation. Obviously likely
to be a
heat related problem.

Does this suggest a particular component? I can bench-test, solder
a little.
How difficult to repair DIY??

  Thx,
  P

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."

Receiver is in a cabinet with little ventilation. Obviously likely to be a
heat related problem.

On Tue, 17 Aug 2010 18:49:18 -0700 (PDT), stratus46_at_yahoo.com wrote:

I have one of those and an SA-160. The 160 had a problem with cracked
solder joints on voltage regulator transistors on the main heatsink.
The 160 is a little odd to disassmble and I think the 210 is similar.
Got a digital camera?

Yup.

take lots of pics as you open it up so you can
get it back.

Will do.

You _might_ have a thermally intermittent power regulator
but bad (metal fatigue) solder is far more common.

Not sure when I'll be able to get to it. Too many irons
in the fire ...

So ... find the big heatsink. Voltage regulator is on
this unit? Remove regulator cover to find transistors and
possibly cracked joints??

Much Thanks,
P

Hi!

Receiver is in a cabinet with little ventilation. Obviously
likely to be a
heat related problem.

You should move it to a place where it can get better ventilation.
Some of
these run quite hot.

Is this receiver losing power totally, or do some functions (like
the
display and tuning buttons) continue to work? If it does, I'd bet
that it's
going into protection to save your speakers from a disaster. Most--
if not
all--of these units used Sanyo hybrid audio amplifier ICs (a large
many-legged black thing) and I think it's safe to say those were
the weakest
point of them. They don't like heat and it seems like Technics
skimped on
the heatsink in many of these units.

William

Hi!

Receiver is in a cabinet with little ventilation. Obviously likely to be a
heat related problem.

You should move it to a place where it can get better ventilation. Some of
these run quite hot.

Is this receiver losing power totally, or do some functions (like the
display and tuning buttons) continue to work?

If it does, I'd bet that it's
going into protection to save your speakers from a disaster. Most--if not
all--of these units used Sanyo hybrid audio amplifier ICs (a large
many-legged black thing) and I think it's safe to say those were the weakest
point of them. They don't like heat and it seems like Technics skimped on
the heatsink in many of these units.

point of them. They don't like heat and it seems like Technics
skimped on
the heatsink in many of these units.

William

A properly operating SA-R210 idles at a very modest temperature.
Obviously it warms up if delivering serious power but by and large the
heat output is pretty modest - certainly not above average.

I just checked the service manual for the 210 and it does mount the
regulator transistors on the main heatsink flanking the main audio
power IC. Q705 reduces the -48 to -19.7. Q701 and 702 are in parallel
to drop the +48 to +15.6. Note that there are regulators following
these to achieve -13.9, +15.5 (capacitor multiplier) and +5.7 for the
microprocessor (using another diode to get to +5V).

On the similar SA-160 which has 2 regulator transistors on the main
heat sink, all 6 terminals were cracked loose. After re-soldering
those I unsoldered the main power IC and resoldered it too since it is
mounted the same way as the transistors. Surprisingly, none of the
foil pads were damaged.

On my R210 the solder connections under the volume raise / lower
buttons cracked making the buttons flaky. Re-soldering them left it
working perfectly again. No bad pads on this unit either.

On Wed, 18 Aug 2010 22:21:21 -0700 (PDT), stratu...@yahoo.com wrote:

 ...

point of them. They don't like heat and it seems like Technics
skimped on
the heatsink in many of these units.

William

A properly operating SA-R210 idles at a very modest temperature.
Obviously it warms up if delivering serious power but by and large the
heat output is pretty modest - certainly not above average.

This is consistent with my experience with them. I've been running
mine 15-16 hours/day for about the last 10 years.

I just checked the service manual for the 210 and it does mount the
regulator transistors on the main heatsink flanking the main audio
power IC. Q705 reduces the -48 to -19.7. Q701 and 702 are in parallel
to drop the +48 to +15.6. Note that there are regulators following
these to achieve -13.9, +15.5 (capacitor multiplier) and +5.7 for the
microprocessor (using another diode to get to +5V).

I am finding Q705, Q701 and 702 markings and the regulator transistors
etc on the main board/heatsink, no problem.

On the similar SA-160 which has 2 regulator transistors on the main
heat sink, all 6 terminals were cracked loose. After re-soldering
those I unsoldered the main power IC and resoldered it too since it is
mounted the same way as the transistors. Surprisingly, none of the
foil pads were damaged.

If you could render just a rough break-down of what was involved
in resoldering the regulator transistors, it might well enable
me to repair this unit.

On my R210 the solder connections under the volume raise / lower
buttons cracked making the buttons flaky. Re-soldering them left it
working perfectly again. No bad pads on this unit either.

I am:

a.) A relative bonehead re detailed electronic repairs.
b.) Willing to learn. Retired, with a house-full of electronic stuff.
    Much of it can't be replaced, something breaks most every day.

I can post pics if it would be helpful.

  Thx,
  P

"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."

A simple voltmeter can give a lot of information particularly while
it's in 'failed' mode. While power devices (transistors and the main
audio power IC) can go 'thermal, I haven't seen a thermally sensitive
transistor in many years. The most common way back when was the TO-220
case devices - just like Q 701,702 and 705 but I would put money on
bad solder joints.

On the similar SA-160 which has 2 regulator transistors on the main
heat sink, all 6 terminals were cracked loose. After re-soldering
those I unsoldered the main power IC and resoldered it too since it is
mounted the same way as the transistors. Surprisingly, none of the
foil pads were damaged.

On Thu, 19 Aug 2010 19:51:55 -0700 (PDT), stratus46_at_yahoo.com wrote:


A simple voltmeter can give a lot of information particularly while
it's in 'failed' mode. While power devices (transistors and the main
audio power IC) can go 'thermal, I haven't seen a thermally sensitive
transistor in many years. The most common way back when was the TO-220
case devices - just like Q 701,702 and 705 but I would put money on
bad solder joints.

On the similar SA-160 which has 2 regulator transistors on the main
heat sink, all 6 terminals were cracked loose. After re-soldering
those I unsoldered the main power IC and resoldered it too since it is
mounted the same way as the transistors. Surprisingly, none of the
foil pads were damaged.

If you could render just a rough break-down of what was involved
in resoldering the 6 terminals, it would be very much appreciated.

Thx,
P

Reworking cracked joints on a practical level involves no more than applying
a nice hot iron to the side of the joint, then when the existing solder
melts, running a small amount - no more than 2 or 3 mm - of new flux-cored
solder into the molten joint. Hold the iron on the joint for a further 1 to
2 seconds, then slide it quickly away. This should leave a nice shiny joint
(assuming this is standard leaded solder) with no signs of a crack,
dullness, or crystalline appearance. If you want to be really pedantic about
the job, you can remove the existing solder first, before making a new joint
with fresh solder, but in order to do that, you would need at the very least
some solder wick, and if you lack the soldering experience to be able to go
for this repair without checking on the best way to go about it first, I
guess that it's going to be unlikely that you have any, or the experience to
use it to clean the joint.