Technics SA-8500X

[Geotex]

Got a question maybe someone can answer. I have an SA-8000X under the bench with a bad right channel. This was one of my first forays into quad, and a departure from old tube-type shortwave radios to mid-70's audio. So. stripped down way too much stuff from the r-r amp and left it set for another day. In between this and now, some fairly good restores on Sansui stuff.

Anyway, just got a SA-8500X off the bay. Starting out with the same problem on this one. All channels except right rear work fine.

Is this a known problem with the technics quad, or am I just "lucky"?

 

[ryuuoh]

Is it just no sound, or is it making bad noises?

 

[AK 47]

I stick to my Technics by preference, but never had a 70's unit that didn't need a few squirts of cleaner/lube in the electro mechanics.....sw's and pots. Chuck

 

[lha1992]

Is the channel making any scratchy noises or is in just dead quite?

The technics may just need to have the controls cleaned with deoxit.

 

[Geotex]

Early testing shows just dead quiet. I need to do more testing to verify if it is the amp or preamp sections. I do not get any right rear sound from the fm band and when run in 2-channel strapped mode, the right channel drops to about 10% output.

Overall, the controls and switches seem to be clean. No static or scratchy from any controls or switches heard on the 3 working channels.

note: It obviously has not be re-capped, but sounds pretty clean in stereo mode after getting about 2 hours run-in today. I have it hooked up to a couple of Jensen Digital 135 watt speaker sets normally used as front channel speakers on a Sansui QR6500.

 

[ryuuoh]

Any visible damage on the right rear board? Bad solder joints, signs of previous work?

 

[Geotex]

Any visible damage on the right rear board? Bad solder joints, signs of previous work?

Damage report after the weekend. I really won't have done more than open and clean before. We closed my wife's retail store about a year ago and lost my bench space, so have to set everything up and take it down until I get my home office reworked to accommodate all my test equipment. Hopefully can get a signal gen and scope set up this weekend to get some definitive input.

 

[ryuuoh]

Good luck~
The 8500 is pretty nice, I remember drooling over that receiver when I was a kid.

 

[Geotex]

Good luck~
The 8500 is pretty nice, I remember drooling over that receiver when I was a kid.

Thanks! The good luck wish paid off --

I opened the box, looking for the worst. Saw nothing, so started with the obvious. After checking for broken wires, found a perfectly good looking fuse that wasn't. Looked great, but failed a ohm meter test, and when replaced in came the RR channel.

I let it run for most of a day, sounds good, so will just do some minor clean up, Other things, no light bulbs, could be another fuse, and AM doesn't work.

 

[ryuuoh]

Sweet~

 

[Geotex]

Well, dug into the unit today to see what I would find. Top side looks gook, probably because the unit came from Arizona. When I started looking for a bad connection to see why no panel or meter lights, found a problem area only after pulling the bottom panel. See the close-up of one of the power supply boards. No work now until a service manual shows up.

 

[ryuuoh]

That one cap is surely cooked.

 

[Geotex]

That one cap is surely cooked.

Probably a couple resistors and a diode or 2 also. They will be easy enough to test, but I want to see some schematics before I go tearing into the set. Could be caused by a shorted/burned wire, or was done by careless work. Won't know until I get into it.

I am waiting for a download to be posted on the service manual I ordered today, hopefully real soon as I really don't want to wait a couple of weeks just for a pdf.

 

[lizzieweth05]

Hi there I was wondering what you found out about this unit after this last post because I just got the same unit in with the same cooked cap and resistors. Almost identical damage on mine so I’m VERY curious to see what you ended up doing. I’m just hoping it’s not been too long to find out! Lol

 

[zman173rd]

Got a question maybe someone can answer. I have an SA-8000X under the bench with a bad right channel. This was one of my first forays into quad, and a departure from old tube-type shortwave radios to mid-70's audio. So. stripped down way too much stuff from the r-r amp and left it set for another day. In between this and now, some fairly good restores on Sansui stuff.

Anyway, just got a SA-8500X off the bay. Starting out with the same problem on this one. All channels except right rear work fine.

Is this a known problem with the technics quad, or am I just "lucky"?

I've had mine since new in the 70's. Just this past year did they start going out. I have to two bad channels. Also looking for replacements. If you have a lead to some partis, please let me know.