Threshold SA-3 problem (or not?)

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gullaz

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Joined 2010
I recently got this amplifier which seems in original condition. Serial# 36, so probably quite old and appears to have been well used.
It plays very silent but there are a couple of small issues: a "thud" at startup
not so loud to worry for the speakers though; I wonder if this is normal?
Second issue is that after shutting down it continues to deliver distorted
sound for some 10/15 seconds.
Bias seems ok at approx. 55 celsius on both heat sinks (average temperature of 26 in the room).
Maybe time to change main caps and/or check anything else?
 
G

gullaz

Member
Joined 2010
Here are some pictures. I can't make out the manufacturing date of the capacitors but if they are the originals might well be 30+ years old.

pBqRqT.jpg

9grlpa.jpg

yLoD8N.jpg
 
N

nec3

Member
Joined 2005
gullaz said:
I recently got this amplifier which seems in original condition. Serial# 36, so probably quite old and appears to have been well used.
It plays very silent but there are a couple of small issues: a "thud" at startup
not so loud to worry for the speakers though; I wonder if this is normal?
Second issue is that after shutting down it continues to deliver distorted
sound for some 10/15 seconds.
Bias seems ok at approx. 55 celsius on both heat sinks (average temperature of 26 in the room).
Maybe time to change main caps and/or check anything else?
Click to expand...

"It plays very silent" "deliver distorted
sound for some 10/15 seconds."

So i think there is no need to change power supply caps since they can accumulate energy long enough indicating their capacitances keeps enough if not original value.

For heat sink, i would check the temperature of power transistor case and compare with heatsink to know if thermal grease is ok.

I would keep its originality unless i have to not.
 
G

gullaz

Member
Joined 2010
nec3 said:
"It plays very silent" "deliver distorted
sound for some 10/15 seconds."


For heat sink, i would check the temperature of power transistor case and compare with heatsink to know if thermal grease is ok.

I would keep its originality unless i have to not.
Click to expand...

I'll have to loan a laser thermometer to check thermal behaviour.
I also tend not to mess with something working ok but this amplifier is expensive (to me at least), runs quite hot and it's not young so to prevent expensive failures...
 
L

llwhtt

Member
Joined 2008
Since the first band (brown) is wider than the rest it usually means wire wound, been thru this on Audio Research and Phase Linear. If there was a blue band on the end that would mean flameproof. These are IRC brand color codes, I don't if it's an industry standard.

Craig
 
R

ricoh

Member
Joined 2007
jacco vermeulen said:
Bradley, as in the same color band code, an Allen Bradley color chart is easy to find on the web.

The one in the picture has rounded ends, plus lines/edges along the length of the body, most likely a TRW.

(the ones by e.g. IRC, AB, Ohmite, Speer are smoother, flatter ends)
Click to expand...

Can you help me? Got recently SA4e; change the big can capacitor with exact values 31-K mF and been working for a month. Last night, after 45-mins of playing, the amp shut down.
check the fuses all is OK, turn on several time on power (no power light).
Can anybody comments where to check?

Ricoh
 
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