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post #23656 of 24765
Quote:
Originally Posted by DefQon View Post

Quote:
Originally Posted by miceblue View Post

Wow so all of this "you can't use it with American voltages" stuff actually hasn't been tested by people here and you're just blindly suggesting things? o.0

 

What do y'all use then?

I'm still sticking by my recommendation as a single poster made a thread regarding running there 100v Stax on the mains and half the amp ended up popping fuses due to the state they were in the States the mains fluctuated more then the 125v rated fuse can handle. KG and Spritzer has already chimed in and said it's best to stick to the right voltage step down trafo or replacing the wallwart completely. Don't say you weren't warned.

Will this work?

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_203036_-1

 

Does an "unregulated" linear wall mount work? Or will that lead to my amp exploding too?

post #23657 of 24765

It looks fine but I'm not familiar with that particular unit.

post #23658 of 24765
Quote:
Originally Posted by DefQon View Post

It looks fine but I'm not familiar with that particular unit.

Mmk. Maybe I'll go ahead and get it and report back here. I'd like a second opinion on it though in terms of the supplied specifications to make sure everything is accounted for.

 

Last time I was going to buy a switchmode wall wart before someone said otherwise...

post #23659 of 24765

It depends. If you have a volt meter, check the voltage of the mains socket and see whether it's at 220 or 230 volt. If it's really at 230 volt, it's best to set up the amp for 240 volt to be on the safe side. It is common however that in countries that used to have 220 volt mains, 220 volt is still what comes out of the wall. In that case, you can set up the amp for 220 volt.

 

Quote:
Originally Posted by davidsh View Post

Voltage in my country is 230 volts. So, would 220 or 240 be best for amp and headphones?
post #23660 of 24765

What diode replacement would be for markings: 

 

309 . ct ?

post #23661 of 24765

voltage is in Denmark same as in Switzerland (specs) : 230V.

Earlier days it was 220V, but with a high toelrance of 220V -10V, +20V

 

I actually measured 237V on the outlet in Switzerland.

 

I set up my STAX SRM-717 for 240V.

post #23662 of 24765

Not sure about the ". ct ?"

 

Any other markings, colored bands?

 

A 1N309 appears to be a germanium diode, 50V.  I would think you could find a Schottky to replace it if you know what parameters you're trying to meet in the circuit.

 

I'm sure one of the guys with these amp memorized will chime in any minute! bigsmile_face.gif

Quote:
Originally Posted by DefQon View Post

What diode replacement would be for markings: 

 

309 . ct ?

post #23663 of 24765

  Nearest I can find to "CT" is "color television" [for the use of] Germanium usually have a much higher frequency band width and speed than standard silicon diodes other than the ones like Shipsupt has said --Shottky  Diodes. So its possible that was what it was indicated for [very early use].  

post #23664 of 24765
Quote:
Originally Posted by K_19 View Post

 

If anyone with the knowledge of the inner parts of the Amp and the power supply of the 252s can confirm this then that would be great.  

 

I see that Elusive Disc's description of the 2170 specifically warn of doing this though, saying it can damage the amp and the headphones...

 

Let's not assume all the PSU's Stax uses are identical as they just aren't.  That said I just measured my 100V SRS-2170 PSU and it gives 18.47V unloaded off a 100VAC source and 21.86V off a 117VAC source.  Utterly unregulated and only people who want to buy new amps regularly would use the 100V transformer at anything other than 100V. 

 

Quote:
Originally Posted by DefQon View Post

That's exactly what I'm going to do today. Since my DMM is borked and a replacement on it's way early next week. I'm going to do two things to identify damage and rule out whatever components is borked.

 

Originally I said the two ELNA 350v caps I measured (assuming one for each channel) one of the cap's measured 315vdc on the neg pole and 620 on the positive pole while the other ELNA cap measure 315vdc and 0vdc respectively, thanks to spritzers "replace/measure diodes in the output stage" idea, I looked at the PCB more carefully following the tracings from the R/L-input to the trafo ps and what looks like (assuming) is the output stage 4 diodes with bypassed ceramic film caps and 2 ELNA caps, the white bias 600v B+ wire connects to the 4 transistors and copper bridge comes from this section.

 

Now I'm going to first de-solder the 4 diodes in that output stage (?) and record the values down and see if I can get replacements if required. Next I'm going to resolder the pairs of the diodes and swap positions with the other two. This way, if the right channel is dead but the left channel is ok, this should give me 315/620vdc on the neg/pos poles of the ELNA caps respectively. And the right channel should read 0vdc on the pos pole with no sound.

 

This is one theory I have of what has happened.

 

The next option is to desolder the 4 big transistors and again swap a pair in for the other pairs position so just swapping places. I'll do it in in steps so if one thing goes kaputz once I turn it on I can narrow this down as a suspect and confirm my findings once I get the DMM in by measuring the points.

 

So it's pretty much a pair of transistors for each channel, pair of offset/balance trimpot adjustment for each channel, output stage has a pair of diodes (used to rectify AC to DC) bypassed by some ceramic film caps running in parallel with two ELNA 350 47uf caps (1 each channel). 

 

If one component was half damaged then I would at least get some static out of the left side through L+/- pins. But the fact that it means there is no sound at all, could only mean dead transistor or diode. Upon close-up inspection nothing looks blown, all solder pads that look half-arsed has been reflowed. If a resistor was blown, my early measurements would've been out of line and physical burnt marks could've been seen. 

 

One small flaw to all of this... there is only one PSU for both channels.  Two caps stacked on top of the other, or one cap gives 315VDC and the other one on top of it also gives that too but since it's "ground" is 315V the output voltage is 630V. 

 

No chance that there are Germanium diodes in this amp.  The one I restored had bog standard Si from Toshiba which I replaced with something similar.  Even the Stax amps from the late 60's has Si everything. 

 

The problem is clearly in the amp section so look there.  Measure between the channels but a simple test of the output voltages will confirm that it at play here. 

post #23665 of 24765
Quote:
Originally Posted by spritzer View Post

Quote:
Originally Posted by K_19 View Post

 

If anyone with the knowledge of the inner parts of the Amp and the power supply of the 252s can confirm this then that would be great.  

 

I see that Elusive Disc's description of the 2170 specifically warn of doing this though, saying it can damage the amp and the headphones...

 

Let's not assume all the PSU's Stax uses are identical as they just aren't.  That said I just measured my 100V SRS-2170 PSU and it gives 18.47V unloaded off a 100VAC source and 21.86V off a 117VAC source.  Utterly unregulated and only people who want to buy new amps regularly would use the 100V transformer at anything other than 100V.

So...now you're saying to use a transformer instead of a wall wart? -_-''

 

Since no one answered it:

Quote:
Originally Posted by EveTan View Post

So this would be all I need to change the voltage? 

 

http://www.voltage-converter-transformers.com/product_info.php?category_id=10016468&products_id=10061420

post #23666 of 24765

I rechecked the 1N309 and its definitely a very early germanium diode universal- 30V-100MA When I said for early use I was meaning used in early TV design as the CT ending could be color TV. Just answering DefQons comment . Maybe he can elucidate  the question.--Like to add looked at the transformers in EveTans comment and just last week bought a 2KV A example of the 3000W unit in the advert . from an American girl at a boot[trunk] sale for £5/about $8 will fit both 2 pin and 3pin USA- The unregulated power supply worry about over voltage is mostly unfounded as although you measure over voltage that voltage is mainly the stored energy in the  output smoothing cap.and amounts to very little current not enough to blow fuses or destroy an amp. Having said that I only use fully regulated supplies for "peace of mind" and a MUCH LOWER ripple current-thats where regulation[by a quality supply] beats unregulated.


Edited by duncan1 - 7/19/13 at 3:08pm
post #23667 of 24765

Unsolder the transistor and test them. There is method on the net for this.

post #23668 of 24765

What's with the wires on the last picture of the unit? Why are there bare wires showing without any sort of connector? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=121143067271

post #23669 of 24765
Quote:
Originally Posted by EveTan View Post

What's with the wires on the last picture of the unit? Why are there bare wires showing without any sort of connector? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=121143067271

 

SRD-7SB is just a transformer box -- you need to connect it to a speaker amp with a fair amount of power (or a very strong headphone amp with high gain). The bare wires are for connection to the speaker amp. 


Edited by mudihan - 7/19/13 at 10:02pm
post #23670 of 24765
Quote:
Originally Posted by mudihan View Post

SRD-7SB is just a transformer box -- you need to connect it to a speaker amp with a fair amount of power (or a very strong headphone amp with high gain). The bare wires are for connection to the speaker amp. 

does it.... requires soldering wires together? How does it connect? (I probably should take a look at the back of my speaker amp for the answer... but... it's a pain to take out)

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