| steenoe |
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:cool: |
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| steenoe |
Thanks a lot Adam, but I have a persisting problem; File does not excist. Can you download the tif file?? I can not.
Steen. |
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| GRollins |
It comes up for me.
Grey |
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| acaudio |
| quote: | Originally posted by steenoe
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 |
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| steenoe |
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.:cool: |
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| steenoe |
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:cool:
Steen:) |
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| apassgear |
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: :smash: |
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| apassgear |
Steen,
Could you post a pic of the inside? |
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| Duo |
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. |
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| steenoe |
| quote: | | 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:D ) 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:cool: |
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| steenoe |
| quote: | | Could you post a pic of the inside? |
Yes, I can. Tomorrow, propably! You are gonna drewl:D 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:)
| quote: | | 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:cool: |
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| apassgear |
| quote: | Originally posted by steenoe
You are gonna drewl:D It smells like NP had his hands in there!!
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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. |
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| steenoe |
| quote: | | 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:D What a set of output devices:D :D 24 per channel! I dont know if you noticed, but I fell in love:D :D
Steen:cool: |
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| apassgear |
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 :D
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? |
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| steenoe |
| quote: | | 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:cool: |
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| steenoe |
| quote: | | 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:cool: |
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| apassgear |
| Ok, so the T 1V is a thermistor. |
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| steenoe |
| quote: | | 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:cool:
I do see T1v now, have no idea what it is!! |
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| docjoe |
Hi Stinoe
here are threads where this has been dicussed allready...
http://www.diyaudio.com/forums/show...t=&pagenumber=2
http://www.diyaudio.com/forums/show...&threadid=34275
http://www.diyaudio.com/forums/show...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 |
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| Nelson Pass |
I notice that the amplifier has been modified at one time
or another. |
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| docjoe |
Hi, Nelson!
I bought this amp about 20years ago, second hand and I have no idea on what was done before...
I noticed some discrepencies with the plans I found on Diyaudio but the amp was fine sounding for all these years, until it showed some oscillation problems...
As for visible modifications, i had to put some new binding posts at the speakers and ground solder lugs, as too much soldering had burned the tracks...
added some local decoupling caps on the power boards, you can see and some caps on the underneath of the pcb.
of cource main caps were changed to 22.000/100v BC with bypass polypropylene...
the VBE transistor in now under the PCB
some bleeders resistors to discharge the reservoir caps in the test process but will be removed when the amps are OK
but otherwise the circuit was not changed!
Well it's been a while since I had these oscillation problems,
BTW I' looking for a couple of replacement PCB, because, you know, desoldering and soldering dont leave the tracks undamaged...
best regards |
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| steenoe |
Thanks a lot for all the information, docjoe:) I will read through the threads you listed, and try to follow your advice. I did find out one thing though. The peak meter lighting up on one channel, is a fault in the display circuit itself. There is a switch on the rear that can turn the leds on/off. Even in the off pos. they keep lighting in left channel and turns off nicely in the right channel. Somebody obviously got tired of looking at the lights, once. So he mounted a switch. It was not the current owner.
Anyway, here are a few pics.
Steen:) |
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| docjoe |
HI,
I do not have this switch on my amp!
can you put me a diagram of the switch wiring assembly?
have ou a dc offset on the faulty side? and how much? |
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| steenoe |
Hi doc. The switch is not on the original amp. The guy who made it, took the two peak-sensing leads on the outputs and soldered them to the switch and soldered two other leads from the switch to the outputs. In that way it is possible to break the signal that goes to the front peak display. I can post a close-up picture tomorrow. I just assembled the amp so I could take a good listening to it on my own system tomorrow.
Steen. |
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| steenoe |
I have been busy:mad: Just took a good listening session with this amp. It is louder on the left channel for sure. Also the right channel gets hotter on the heatsink, so I recon its the oscillation thing, allright. It measures like 10 deg. C more than the left cannel. As for DC offset, it is not a lot; left channel is 0,020v right channel 0,034v's. So the bad channel has more offset, no surprise. Otherwise the listening session was fabulous:D Except for the lower output of the right channel, it sounds really good:) I could drive my ProAc clones to high volumes, with really good control. The offset is measured with music playing, right at the speaker binding post's.
As a sidenote, I have to mention this odd thing; On the rearplate the right side says left, looking aft from the front and the left channel says right:xeye: I think someone screwed up:D If the silkscreen is correct, you have to cross the speaker cables:D :D
Steen:cool: |
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| jacco vermeulen |
Unless the owner is cross-eyed !
Even today those Threshold boards look awesome. |
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| steenoe |
| quote: | | Unless the owner is cross-eyed ! |
:D :D
Hi Jaccoboy! You are right, it is really an amplifier!! If it was my own, I would propably restore it;) Now, I dont think I will use all those ours, to replace everything, like the doc did:bawling: I dont know, maybe this winter, if I need something to work on;)
A Threshold Stasis isn't just any amp;) Still, the damping factor must be brilliant, as it really controls the speakers:)
Steen:cool: |
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| docjoe |
hi steenoe and jacco
now i've completed a first 12 hours run.
the temp is about 40 ° C. and bias set 0.75 amp on both channel; offset is 10 mv on one chanel and 60mv on the other...
have to trim those 47R and 33R resistors in the diff pair, as I changed these to BC550c.
yes you have to cross the speaker wires, unless you display the back of the amp in your setup. |
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| steenoe |
Thats a pretty sight, doc;) I really do not get this right/left thing on the rear panel:D Hmmm, I guess my old friend has to wait a bit, before his amp is getting fixed! I simply do not have the time at this point, to make a larger restoring:xeye: Doc, do you have a specific opinion about what is causing the oscilation?? Maybe the Tantal's as you mentioned, or the trimpots?? If I had something specific, I might give it a shot;) Thanks in advance:)
Steen:cool:
BTW I measured 40 deg C on the healthy channel and 50 deg C on the other. |
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| apassgear |
| quote: | Originally posted by docjoe
yes you have to cross the speaker wires, unless you display the back of the amp in your setup. |
Hey guys, your not serious, are you???
To read them correct you must end those comments with a :clown: |
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| steenoe |
| quote: | | Hey guys, your not serious, are you??? |
As a matter of fact, this is actually correct:clown: At first I did take several readings on the rear panel, and had to conclude the facts: they actually swapped right/left on the silkscreening:clown:
Well, the guy doing this could be somehow excused, I guess:o Looking at the rearpanel from aft, would imply that the right channel is at the left and "vica verca":clown: :clown:
Steen:) |
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| docjoe |
yes that' correct, but I presume that for maintenance point of vue, if you work on it, the PCB, are on the back as are the bias pots, its seems easier to .
anyway even if they crossed sides, the diode bargrap display is ok!:clown: |
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| steenoe |
Just to let you guy's know, I decided to deliver the amplifier back to the (unhappy:bawling: ) owner at this point:xeye: It was quite a hard decision, but I simple do not have the time for a major workover at this point. Besides, it is way too hot in Denmark, to do big soldering jobs right now:hot: Thanks a lot for your inputs, anyway:) I will keep you posted if (probably when!)
I take it it on again:)
Steen:dead: |
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| docjoe |
What, you guys in Denmark dont have air conditioning?
well in Paris it is about 20°c now
Well I think I've finished my rebuilt, I hope it will last another 25 years...
I'll be pleased to hear about you... |
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| steenoe |
| quote: | | well in Paris it is about 20°c now |
I am sure we have like 30C now, I feel for a swim right now! Lucky enough
to have Denmarks nicest beach, 500 meters away:D Well, the guy actually took the hole thing in a cool way. He would look for a ML! He has a pair of big Apogee clones, and they really demand some power. Those darn speakers, which are very well build indeed, are the size of a door:D But the impedance is hopeless;)
Otherwise, I would have made an Aleph for him, of course:D
The chassis with heatsinks could house an Aleph 5;)
Steen:cool: |
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| apassgear |
| When he gets those ML buy his Stasis :clown: :clown: |
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| Nelson Pass |
| Assuming that he still wants to sell it. :cool: |
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| docjoe |
yes, I would not sell mine...if I had apogees..
I've bought a dead 400...
I'm gonna breethe some life into it again:angel: |
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| jacco vermeulen |
| quote: | Originally posted by steenoe
[B]But the impedance is hopeless[B] |
So is the sound.
If i wished to clone an Apogee, i'd jank a cat by the tail, gives me the same kind of shivers.
Tell the owner he is hopeless, the amplifier is hopeless, buy it and revamp it.
The exterior looked brandnew on the pics you posted, Bruce SunburnSteen. |
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| steenoe |
| quote: | | The exterior looked brandnew on the pics you posted, Bruce SunburnSteen. |
I am not sure I can convince him to sell it to me, at least not cheap:D I figure he will get suspicious;) I have to go gently on that one:) But you are right Jacco, the amp is in perfect condition on the outside.
Steen, still overheated:hot: |
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| steenoe |
| quote: | | If i wished to clone an Apogee, i'd jank a cat by the tail, gives me the same kind of shivers. |
Here is your "cat", Jaccoman:D I couldnt resist, taking a few pic's of those "room-dividers". Quite impressive work:)
Steen:cool: |
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| steenoe |
I choose to reopen this thread since the amp is playing music again. The information might turn out useful for somebody else.
Well the owner of the Stasis brought it to a guy with some experience in repairing amp's. You wont beleive it, but the cause of all the problems was simply the 3 electrolytics on each pc board!
The guy soldered in 3 new caps per channel and the amp sounds just great again:) I just went and visited my old friend and I was just surprised that the solution was that simple. It just goes to show that when you have trouble with an old amp, swap out the caps;) The diode bar had a bad solder somewhere so thats working again too:) Thats what you get for trying too hard to find some failure. No need to change all the output devices and everything else with them. The repair costed the owner something like 50 bucks.
Happy ending indeed.
Steen.:cool: |
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| Nelson Pass |
| quote: | Originally posted by steenoe
It just goes to show that when you have trouble with an old amp, swap out the caps;) The diode bar had a bad solder somewhere so thats working again too:) |
Good advice on both counts. |
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| apassgear |
| quote: | Originally posted by steenoe
You wont beleive it, but the cause of all the problems was simply the 3 electrolytics on each pc board!
The guy soldered in 3 new caps per channel and the amp sounds just great again:)
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That's true also of many PC board failures. Lytics are the week components on any electronic circuitry.
My son gives away many fine PC boards including motherboards and video cards, I just replace the caps and they have a second life on one of my computers. No matter how much you pay for those components they are dead in 3 or 4 years for that reason.
One interesting fact on my son’s last video card acquisition, all caps were rated at 125V never saw that before and it also sported some OsCon caps - which might not be that uncommon this days. |
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| VintageAmp |
The outputs will give you the most trouble. You need to use Motorola output devices or risk lots of oscillation. Replace the small caps on the driver cards with some nichicon 470 u, 16V
47uF 63 or 100V
The main caps are probably worn out too, but you should be able to at least make it work. Lift the emitter resistors and measure with a diode checker to determine which output devices are bad.
JOn |
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| Forrestc |
Jon, Nelson, or anyone, I have a pair of Stasis 2s that I will be using to power my bi-amped Apogee Duetta Signatures (directly coupled to each driver, electronic crossover only).
Both amps have a little more DC offset than they should:
Amp #1: R= 0.215 Vdc L= 0.140 Vdc biased to 42-43 degrees C.
Amp #2: R= 0.095 Vdc L= 0.070 Vdc biased to 47-48 degrees C.
Also, I replaced all the electrolytics both big (4 x 22000uF) and small (Blackgates) on both amps.
Both of these amps sound great especially now that the electrolytics have replaced, but even when using amp #2 to drive the tweeter sections, that small amount of DC offset causes the tweeter ribbon to move out of it "home" position. Previously, I used a Threshold S-150 Series II that has a DC offset low enough(L=0.050Vdc R=0.045Vdc) not to adversely effect the tweeter ribbons.
Question: How can I lower the DC offset of my two Stasis 2 amps? Is this a sign of other aged components that are in need of replacement? If so where should I start?
Thanks
Forrest |
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| Nelson Pass |
You will find a schematic at www.passlabs.com/np
On it you will find at the negative rail a 300 ohm resistor
between the negative rail and the emitter of an A42 transistor.
Adjusting this value slightly will alter the offset.
:cool: |
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| VintageAmp |
It is also possible to match up the differential pair of transistors. The available parts are A 18. A pair of 6571 was often used during the manufacture of these units. If one of these devices is damaged, the offset will go out of spec. I always look for less then +/-50 mV
JonS |
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| Forrestc |
Jon, I think that I just may ship you one of my Stasis 2s and let you get it back in shape for me.
Thank you Nelson and Jon! |
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| kfarrand |
Jon,
Listening to Stan Getz and Astrud and Astrud Gilberto via iTunes (MacBook Pro) through a 400A (picked up a couple months ago) with Hafler 101 and a pair of Dynaco A-25s. Vintage system sounds quite nice with the 400A on AR-3as and Klipsch Forte IIs. Have not hooked the 400A to the "The AR turntable" or the small Maggies or the Infinity Primus 360s on the other end of the living room yet.
Question re powering up the 400A: I did not realize that I should have (or should I have not)cycled the power switch on the front panel on the 400A a number of times with the power off before firing it up for the first time (I don't have a variac). The first couple of times I powered the 400A up I heard (and saw) sparks from the front panel switch. The amp now is left with the front panel power switch in the "on" position and I power it up through a Discwasher 'Spikemaster' and all sounds OK to me. Should I continue with this set-up or am I asking for a disaster?
I'm also running a small (Honeywell) fan just at the edge of the 400A for cooling and am wondering if the differential in cooling between the edge with the fan vs the other side could create pproblems over time? The temp without the fan does not seem excessive (using the fingers on the cooling fins for ten seconds test)
I'm located on St Simons Island, Georgia but used to teach occasionally in Citrus Heights at the University of New haven (Connecticut) when they had a campus in Citrus Heights.
Sorry if this post is in the wrong 'pew' but was hoping to get your take on this, Jon. Thanks . . .
Pre- Threshold 400A - Klipsch vintage system is at:
http://forum.stereophile.com/photop.../cat/all/page/1 |
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