Threshold Stasis 2.

steenoe · 2005-07-02 8:05 pm

I have a Threshold Stasis 2 comming in for repair! Could any of you post a schematic for that one? I did search, but the links didnt seem to work anymore:-( Now, I never claimed that I actually could repair this thing, only promissed that I would take a look! But man, I would love to bring this baby to sing again. I remember those Stasis amp's back then!! I had never heard anything like it

They really rocked the place

I really hope to make it sing again. As I understood, the trouble is, that one of the channels is louder than the other! Also he said that one of the VU meters in front was lighting up all the time. Now this guy is not whatever, kind of guy. We go back all the way to school!!
Hope some of you guys are prepared to help out? I will post the excact problems on monday, when I get my hands on the amplifier!!

Steen

acaudio · 2005-07-02 9:03 pm

http://www.passlabs.com/np/stasis2-3schem.tif

???
Adam

steenoe · 2005-07-02 9:11 pm

Thanks a lot Adam, but I have a persisting problem; File does not excist. Can you download the tif file?? I can not.

Steen.

GRollins · 2005-07-02 9:51 pm

It comes up for me.

Grey

acaudio · 2005-07-02 10:03 pm

steenoe said:
Thanks a lot Adam, but I have a persisting problem; File does not excist. Can you download the tif file?? I can not.

Steen.

Yes, no problem, check your settings (virus scan or protection ???)

I have saved it as *.gif see here:

Adam

steenoe · 2005-07-02 10:09 pm

Thanks a lot, guys. I just uninstalled DAP, and then I could download the document

Well, from my first posting, any ideas how to get this running again?? This Monday I will try to do some measuring.

Steen.

steenoe · 2005-07-05 9:11 am

Does any of you have a service manual for this amp? A link to it would also be fine. The amp itself actually sound pretty good, only one channel is a bit louder than the other and from the Peak meter on the front, it seems like one channel is putting out some more signal than the other. Even without a signal, the leds lights up. (the first 4-5 leds). Any thoughts on that problem? I would really appreciate a little help on this.
This elderly amp, is very finely build

Steen

apassgear · 2005-07-05 4:41 pm

I don't know anything about Stasis, not even seen one. But I would start checking bias and comparing it to the "good" Channel. Next I would check voltages at different nodes.

You have beside a seeminly good channel so it should not be that dificult :clown:

apassgear · 2005-07-05 4:45 pm

Steen,

Could you post a pic of the inside?

Duo · 2005-07-05 4:49 pm

This is highly interesting. I draw two conclusions.

1: Perhaps the channel with the constant VU indication is oscillating. I have had this happen while only causing a reduce in audible gain and causing the amplifier to run a little warm.

2: I doubt the possibility of this idea, but DC offset?? (You'd have probably noticed that by now.) All VU meters I've seen are AC coupled so far. So I doubt offset is doing it, it's not as if it'd reduce the gain any.

Hope that at least gave a bit of input to the subject.

steenoe · 2005-07-05 4:53 pm

You have beside a seeminly good channel so it should not be that dificult

Yep, you are right, Tony. Uhhh, this amp is fairly packed and not easy to make some measurements on. I hardly dare to stick in the testprobes. The q's are sitting darn close on the driver board, they are also quite longlegged (wich is nice on girls, not on q's

) I guess I just have to give it a shot. I really like this amp, as I said, it's built like a tank, and is really a beauty.

Steen

steenoe · 2005-07-05 5:18 pm

Could you post a pic of the inside?

Yes, I can. Tomorrow, propably! You are gonna drewl

It smells like NP had his hands in there!! I did read the manual, and it says that all components are matched! The amp runs with no NFB too. I guess it would be a bit reckless to just replace one component,then.
I will post a nice set of pic's of this amp

Hope that at least gave a bit of input to the subject.

Thanks a lot, DUO.

I am happy you guy's are with me, on this one

Steen

apassgear · 2005-07-05 6:22 pm

steenoe said:
You are gonna drewl It smells like NP had his hands in there!!

Gonna love seeing those pics!!!

That's what I also thought that it might be packed inside. It won’t be a good idea to take readings then. Start disassembling
:clown:

DUO might have the clue, it may be oscillating. Cleen the input jacks with cramolin or something similar. Or change input jacks...resolder.... Check those signal cables/wire. Seems a good way to start.

steenoe · 2005-07-05 6:37 pm

DUO might have the clue, it may be oscillating. Cleen the input jacks with cramolin or something similar. Or change input jacks...resolder.... Check those signal cables/wire. Seems a good way to start.

Very good, Tony

I will do just that! Yeah, oscillating might be it! I have just arranged that I will pick up the amp tomorrow

I sure will post some pic's of this amp

I saw it yesterday, with no lid on, I was amazed

Didnt dare to bring it home though, but if you guy's back me up, I am confident

Man, that amp looks good

What a set of output devices

24 per channel! I dont know if you noticed, but I fell in love

Steen

apassgear · 2005-07-05 6:43 pm

Does it work with and w/o FB?

If so, look for the switch and change it.

The 5K bias pot might also be a source for oscillations, me think so. Moving it just a bit to both sides could kleen it, if you dare

I would also look at the thermal breaker. Check bypassing it.

Near the bias pot is a circle marked T 1V, any clue to what it is?

steenoe · 2005-07-05 6:50 pm

If so, look for the switch and change it.

I dont think there is any switch! The hole topology is NFB! At least that is what I gathered from the manual. Also, I did notice that there was a Thermistor :bawling:

That doesnt excactly make it easier on measuring?? You just cant keep turning this thing on and off??

Steen

steenoe · 2005-07-05 6:53 pm

The 5K bias pot might also be a source for oscillations, me think so. Moving it just a bit to both sides could cleen it, if you dare

Yep, I do dare! That was my first thought!! Give it some massage

Steen

apassgear · 2005-07-05 6:56 pm

Ok, so the T 1V is a thermistor.

steenoe · 2005-07-05 7:17 pm

Ok, so the T 1V is a thermistor.

I have studied the schematic posted earlier on, cant see T 1V!! I did spot the thermistor in the amp, though! It was sitting right there at the power inlet!

Steen

I do see T1v now, have no idea what it is!!

docjoe · 2005-07-06 6:36 pm

Hi Stinoe

here are threads where this has been dicussed allready...
http://www.diyaudio.com/forums/showthread.php?threadid=5396&perpage=15&highlight=&pagenumber=2

http://www.diyaudio.com/forums/showthread.php?s=&threadid=34275

http://www.diyaudio.com/forums/showthread.php?threadid=4153&highlight=

I have a Stasis 2 sitting on my bench, with same oscillation problems:

Change the bias adjust pot for a multiturn one
I changed the drivers for MJE 15030/15031
Changed all the TO3s for MJ 15024/15025
the thermistor is 1K

Change ALL the capacitors, especially the tantalum 0.1 and 4.7 Uf they often cause problems, anyway in such a warm environment they get Roasted after some 20+years....

Open the sides and you'll get plenty of place to work

For testing, do not unsolder the input wires from the back panel, and do not unsolder the tiny grey wires that come from the star earth under the square ground plane and attaches to the negative cinch pin. if not you loose the ground return for the input section and you'll light all the leds

check for output offset and set bias at about 0.7 to 0.8 A

Threshold Stasis 2.

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