Realistic STA 2290 Mystery

i have a realistic sta 2290 that is acting up a bit.....i am running 2 sets of speakers and when i get to about 50 watts the speaker relay kicks out the speakers and within a few seconds they come back on and does it all over again.....if i run just 1 set at a time it doesnt happen ...i can hear it click back on (when it cuts off the sound i turn down volume so i can hear where the clicking is coming from) but as soon as i push it to about 50 again it starts all over again....the speakers are a set of mach 1,s and a cheap set of technics SA-A52,s that fill the bill for my needs...any idea what might be causing this?......i can run these speakers on other receivers without this happening

I think the power meter on that receiver is based on 8 ohm. Since you're running closer to a 4 ohm load (or lower) the 50 watts you read is actually 100.

The behavior you describe doesn't surprise me but I never tried pushing one of those as hard as you are. Does it get very warm when this happens?

It's probably a normal behavior. Some amp designers tend to make the protection circuits overly aggressive, in an effort to cut down on warranty service cost. If I had a schematic, then I could probably tell you how to reconfigure it, but I'm not taking any of the blame if you blow it up!

yes it gets hot....i was wondering about the ohm load.....i ran this setup of speakers on a sony str v6 and a sta 2000d and didnt have this happen...since i dont have an owners manual for it i dont know for sure if it can do the 2 sets of speakers at 8 ohms each....but it says on the back that it can do 2 sets at 8 ohms

i am just trying to figure out if it may be bad relays or like you say normal for this receiver....like i said this speaker setup hasnt done that on other receivers or amps i tried them on before

I doubt it's a bad relay, the coil is what will de-energize and that's fed from a separate source.

My guess is it's tripping on thermal overload. My best guess is possibly BIAS. I had to adjust the BIAS on my STA-2000 and afterward, it didn't run as hot when I pushed it or even at idle. Best guess is a service manual for it. I have one for the 2270, but the 2290 and the 2270 are quite different. My 2270 is not configurable, it's preset I believe.

ok thanks live wire......i will see if i can find a service manual....i know the 2290,s run hot from what i have read but i have not run into anyone saying the relays would cut out and then back on even if the volume isnt turned down

Actually, have you checked the DC offset on it yet? If it's higher than it should be (150mV +) it could be tripping on DC protection.

There's a really good sticky on how to check it in the vintage forum.

no i havnt checked it....never thought about it......will check it tomorrow and post the numbers

Ok, sounds good

i decided to stay up and check ....the numbers i get are not steady...right side goes between -10 and +8....left reads between -10 and +15....even just sitting idle for the 20 mins or so while i checked the top gets very warm but from what i have read its normal for this model

The readings sound normal, they will flutter a little bit. Does seem a little out of the ordinary to flutter about 20 mV, but probably not horrible.

The only thing I can figure, is it is spiking every once in a while.

DC offset pots?

Hi, I'm trying to revive this very old thread because I've just brought home a STA-2290 that runs (as I've heard they will) VERY hot. So, while I'm cleaning and de-oxit-ing, I'd like to adjust idle current and dc offset.

I found a .pdf on the akdatabase.org site (http://akdatabase.org/AKview/albums/userpics/10007/Realistic%20STA-2290%20Scans.pdf )
that has a few pages of the service manual, including the part about adjusting idle current, but I'm damned if I can find anything (even for ready money) that'll tell me where the pots are for adjusting DC offset. It's measuring pretty close to zero at the moment, but I'm told that if I start messing with bias current I'll also need to adjust DC offset.

Does anyone have a service manual for the STA-2290? If so, can you help me locate the DC offset trim pots, if any? I see only two VRs on the power amp circuit board, VR501 and VR502 for bias.

Oh, and anyone who know an easy way to get at the front controls for the de-oxit routine is more than welcome to chime in... I'm a little daunted by all the circuit boards up front.

THANKS!