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Did I destroy my power amp?
Did I destroy my power amp?
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Old 18th August 2019, 04:09 PM   #21
wiseoldtech is online now wiseoldtech  United States
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In the Technics line of amps and receivers made in the late 1980s up to the 1990's, they had a DC fan on the rear panel to draw hot air out from the SVI's heatsink inside.
While I adore Technics products, the design of this cooling system was crappy.
That fan was only triggered to run at higher volumes from a 2 transistor circuit that sensed speaker level audio, plus the fan motor was a cheap DC motor similar to toy race car motors.
And it was noisy and unreliable once the bearings got dry after a while.
Plus, the airflow over the heatsink was poor due to the layout.



In my own receiver, I converted the system to a better quality 12V PC-style fan, added aluminum shrouding to the heatsink to increase coupling to the fan and airflow through the fins, and re-designed the transistor circuit by using a thermistor right on the heatsink.
So now, at "turn on" the fan idles silently, and as the heatsink warms up, the fan speed will increase up to a point - still quietly, and pulling a substantially more amount of air through the heatsink than the original did.
It works quite well, and Technics should have done this to maintain reliability, because those SVI chip amps are now almost impossible to replace.
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Old 18th August 2019, 04:40 PM   #22
turk 182 is offline turk 182  Canada
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Quote:
Originally Posted by wiseoldtech View Post
Technics should have done this to maintain reliability, because those SVI chip amps are now almost impossible to replace.

we live in an economy that only interested in the next fiscal quarter...longevity and reliability are pipe dreams from an era long ago...far far away...i've often seen stuff with seemingly simple shortcoming and wondered is this planned obsolescence or some bean counters great way to save the company money.
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Old 18th August 2019, 05:18 PM   #23
wiseoldtech is online now wiseoldtech  United States
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Quote:
Originally Posted by turk 182 View Post
we live in an economy that only interested in the next fiscal quarter...longevity and reliability are pipe dreams from an era long ago...far far away...i've often seen stuff with seemingly simple shortcoming and wondered is this planned obsolescence or some bean counters great way to save the company money.

I agree with you.
I've had to "re-engineer" plenty of things to increase the reliability and overall quality of them.
Basically, I like to buy something ONCE, be satisfied with it......... and keep it for a long time.
I don't like to keep putting money out for lackluster performance and compromised quality.
Because that's BS in my opinion.
Being a long-time professional service technician, I've got the know-how to eliminate the "flaws" that I see in products, and address some of them right after purchase, to hell with the warranty, I don't want to deal with that crap.
I've had my share of warranty headaches with manufacturers over the years when dealing with with those idiots for warranty service for customers.
Samsung tops my list of idiots working in Customer Service.
And you'll find plenty of class action lawsuits filed for their crappy flat screen tvs if you poke around the internet.


And the recent products we're forced to deal with from "far away lands" - well, lets just say I've had to "de-chinese" lots of things in order to improve them.


And I'll go on to mention that purchasing "high-end" products is also a lousy lie - without mentioning names, they're built to impress the customer with superficial glitter, while the "guts" in many cases are something the consumer never sees, yet pays dearly for, and in reality are overpriced.
You're buying a "name" - hyped up through advertising and praised by reviewers that have been compensated handsomely by the manufacturers.


I don't mean to sound bitter, trust me, I just want to let others know about this increasing scam to the consumer.

Last edited by wiseoldtech; 18th August 2019 at 05:21 PM.
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Old 20th August 2019, 05:59 PM   #24
JaneyBleep is offline JaneyBleep  United States
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Guys,guys (and girls..? ),

Relax,the power amp will be restored with it's original components (resistor-$1.45,AC-Cooling fan- $15.00 ) No big deal,I just wanted to know if I fried it like an egg.Apparently not since it still produces great sound!
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Old 21st August 2019, 03:44 AM   #25
turk 182 is offline turk 182  Canada
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yea!!!! (i knew girls liked this stuff too! SoundGirls.org – Empowering the Next Generation of Women in Audio)
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Old 23rd September 2019, 05:49 PM   #26
JaneyBleep is offline JaneyBleep  United States
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Old 25th September 2019, 06:27 PM   #27
Mark Tillotson is offline Mark Tillotson
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Note that substituing non-mains fan for a mains fan is asking for fires to start. Your insurance company will not pay out on a fire thus caused. Never connect non-mains rated devices to the mains.


I suspect that the resistor saved you from catastrophy by burning out before the relay clicked in and blew up the fan...
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Old 25th September 2019, 07:03 PM   #28
wiseoldtech is online now wiseoldtech  United States
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Quote:
Originally Posted by Mark Tillotson View Post
Note that substituing non-mains fan for a mains fan is asking for fires to start. Your insurance company will not pay out on a fire thus caused. Never connect non-mains rated devices to the mains.


I suspect that the resistor saved you from catastrophy by burning out before the relay clicked in and blew up the fan...

Being a service center technician, I agree.
Our shop must, not an option, must ahere to electrical building and design codes, particularly centered on Liability Issues.
This way, should a customer ever attempt to implicate us in a lawsuit due to fire, death, or harm, we'd be safe and in the clear.

Most of these diy'ers don't take that into account of course, and for good reason... they're not enlightened to liability issues, since being a hobby doesn't provide you with that important information.


I've seen things come across our counter with fuses wrapped in tinfoil!
And this is from a so-called self-professed electronics genious!
Naturally, the article is now beyond reasonable repair.


I've had another one insist on "just bringing the amp in", which I was wary of..
This was out of a console stereo too heavy for them to bring in.
I did the needed restoration of the amp, but warned the customer that careful and proper re-installation is mandatory, and should something happen, it's their fault.
Guess what?
He shorted out the wires for the filament supply, fried the whole chassis wiring.
And it cost him yet AGAIN another restoration.
But this time he called me to the home to replace it........ properly.
I've seen it all by now.
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Last edited by wiseoldtech; 25th September 2019 at 07:11 PM.
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Old 1st November 2019, 06:57 PM   #29
JaneyBleep is offline JaneyBleep  United States
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Peavey 1.3k Power Amplifier has been fully restored to it's original state .
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Old 1st November 2019, 07:17 PM   #30
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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