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technics sa-800 safety shut off mode

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Palmal_rodeo

New Member
hello..
I have a technics sa-800 that I traded for a nice old TT.
there was a buzzing sound on the right channel when I toggled the acoustic controls. it was rather curious so I opened it up and wiggled the monster caps. the buzzing changed tones. so I took the caps out and checked around. no one could give me a definite answer if they were good or bad. but because they worked and sound pretty sweet with no tonal control I soldered them back in. the only change I made was putting a good bead of solder on both side of the bridge between the caps. I noticed when I pulled them out only one side was soldered, the other was folded like a brad on an envelope. I'm not sure why.. but when I soldered it all back in place I fired it up. no buzzing, all the acoustic controls worked. it really sounds super nice. but I noticed when I turned the volume up to about two the lights started dimming..man this thing has some power..and heat! so I decided the power transistors on the heat sink block maybe were not transferring heat like they used to. I pulled off all the transistors cleaned everything including the mica insalators. then bought some arctic silver to dress the resistor then the mica against the heat sink. it gets very loud after ive done this. thereis still heat but it sounds really good.
now then.. this is the issue..
at two and a notch on the dial it starts waivering..the lights start to flicker and the leds are registering in the 200 watt range. granted this is loud. but is it some thing in the amp that is saying stop save me! or the speakers saying save me and telling the amp to stop. because the power never turns off. just the speakers.. then after abit I can pop them back on..
my speakers I have on this unit are a set of AR94Si and a set of kenwood jl-630W..

any feed back to this behavior?
thank you..
matt king
 
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The AR94 series appear to have an impedance dip of about 3 ohms. You are likely tripping the protection by running the amp too hard with that load.
 
Using Arctic Silver for heat sink compound is asking for trouble, it's electrically conductive.

Craig
 
llwhtt said:
Using Arctic Silver for heat sink compound is asking for trouble, it's electrically conductive.

Craig
Click to expand...

I second that!, I too thought that it would be a good conductor of heat and it is, until time passed, then it became conductive and shorted out the output stages!
My first experiment with applying high Voltage to a spot of Arctic Silver looked OK, but I didn't account for what time does for electrical conductibility.
This is NOT an issue on COMPUTER heat sinks, there is NO Voltage between the computer processor and the heat sink, that is, there is nothing to "short".

DO NOT USE ARCTIC SILVER ON ENERGIZED OUTPUT DEVICES AND GROUNDED HEAT SINKS!! :no: :eek:

Mark T. :music:
 
Thanks for all good feedback!
:)
Ive tried both sets of speakers now..
it seems the AR's are the only speakers that will push past two comfortably..the kenwoods dont like the amp..maybe the amp has too much power for the kenwoods? So im running just the set of AR's..
..
i dont REALLY want to clean off the all the silver paste! everything sounds good on the one set of speakers! I will make a video to show you...later after work..
the AR's really have a nice punch!
Thank you again for all the replies!
Old radios are ALOT of fun..
 
wmgwizard said:
How many speakers are you using ?

Are they connected Left / Right or A/B ?
Click to expand...
they are on separate channels..
I was using the AR's as the main and the Kenwoods as the remote..
but I think the kenwoods just don't like the amp..maybe the amp is too much for the speakers?
its rather crazy..but fun..
 
markn2wae said:
I second that!, I too thought that it would be a good conductor of heat and it is, until time passed, then it became conductive and shorted out the output stages!
My first experiment with applying high Voltage to a spot of Arctic Silver looked OK, but I didn't account for what time does for electrical conductibility.
This is NOT an issue on COMPUTER heat sinks, there is NO Voltage between the computer processor and the heat sink, that is, there is nothing to "short".

DO NOT USE ARCTIC SILVER ON ENERGIZED OUTPUT DEVICES AND GROUNDED HEAT SINKS!! :no: :eek:

Mark T. :music:
Click to expand...
Is it super important to take off the silver and redo the heat sinks with white grease? if so I will do it..
 
ryuuoh said:
The AR94 series appear to have an impedance dip of about 3 ohms. You are likely tripping the protection by running the amp too hard with that load.
Click to expand...
I'm amazed with these AR speakers.. I traded a sound bar for them..i couldn't listen to the soundbar one more day..and it was only a week old!
but iended up having to refoam them and I think I used a klipch surround because the dudes that hold the AR foams wanted an astronomical amount for them.. so I got my measurements and matched them nearly identical to the AR foams.. they sound very nice and are VERY heavy!
 
Punker X said:
Moving to solid state, doe not seem like your have a radio (tuner) issue with your unjit.
Click to expand...
I do think you are right..i believe it is either the speakers not agreeing with the amp..the kenwoods..
or its the speaker wire not being right..
I did adjust the gain on the output side..so maybe I improved it alittle..
 
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