[NamelessPFG]

And to think that, in the past, I saw those SRM-1/Mk2 Pros sell for around $300-325 by themselves, or even $400 with an SR-Lambda Pro...
 
I'm honestly starting to think that the headphones themselves are the cheap part of electrostatic systems, and the amps are the real wallet slayers. It would be a lot easier if I just wanted Pro bias, given the cheaper SRM-212s and SRM-252s floating around, but I'd really hate to give up support for the original SR-Lambda.

 

[livewire]

Quote:

 
I'm going to start a cap list for the recap tonight.  I'll look at the panasonics or nichicons.  I haven't looked yet, but what make caps should I use for this application?  film, aluminum, etc??

 
Panas or Nichis are good.
You want to source aluminum electrolytic capacitors. Not aluminum organic polymer caps.
The electrolytic caps look like small aluminum beer cans with a plastic label wrapped around the outside.
The guts of the electrolytics dry out over time. They are the caps that need to be replaced.
Make sure the capacitance and voltage ratings are the same or slightly higher than the old ones.
For a given capacitance value, modern caps tend to be physically smaller than the old ones.
Check the data sheets for actual dimensions as compared to the old ones.
An important aspect is the radial lead spacing. It should be close or the same so they will fit into the circuit board holes.
Also avoid buying anything with an outside diameter that is larger than what the old parts have,
If you do go wider on the diameter - check for fit around the periphery of the existing component. (not crowded with nearby parts)
Most electrolytics are marked on the outside to indicate polarity. (+ / -)
Do not insert them into the board backwards. They will explode and possibly ruin your amplifier.
If your board is not marked as to the cap's polarity, draw a map indicating polarity orientation before removing the old caps.
Good luck!  Replacing these parts usually makes a big positive difference in the way things sound.

 

[Keithpgdrb]

Quote:

 
Panas or Nichis are good.
You want to source aluminum electrolytic capacitors. Not aluminum organic polymer caps.
The electrolytic caps look like small aluminum beer cans with a plastic label wrapped around the outside.
The guts of the electrolytics dry out over time. They are the caps that need to be replaced.
Make sure the capacitance and voltage ratings are the same or slightly higher than the old ones.
For a given capacitance value, modern caps tend to be physically smaller than the old ones.
Check the data sheets for actual dimensions as compared to the old ones.
An important aspect is the radial lead spacing. It should be close or the same so they will fit into the circuit board holes.
Also avoid buying anything with an outside diameter that is larger than what the old parts have,
If you do go wider on the diameter - check for fit around the periphery of the existing component. (not crowded with nearby parts)
Most electrolytics are marked on the outside to indicate polarity. (+ / -)
Do not insert them into the board backwards. They will explode and possibly ruin your amplifier.
If your board is not marked as to the cap's polarity, draw a map indicating polarity orientation before removing the old caps.
Good luck!  Replacing these parts usually makes a big positive difference in the way things sound.

couldnt have asked for better instruction.  A huge thank you.  Spritzer suggested a diode swap out as well.  diode suggestion?  When I did my Fisher 500c, I was totally cool with doing the work, but I needed the kit to make sure I had the right parts.  I learned a lot, but clearly not enough.  plus, you guys are the stax experts.  I cant wait to hear this amp all tuned up.  I may actually be done with my mid-fi stax setup for a while.

 

[spritzer]

UF4007's work for the power supply diodes and remember that you have to adjust the DC offset and balance of the amp once the work is done.  I have a SRM-1 Mk2 PP incoming soon that I will completely rebuild and I can list part numbers when all is said and done. 

 

[pkshan]

Hello
I rewired a SRM600 from 100v to 220v today,
 
No smoke came out,I can hear the music,sound pretty good
& the +/- bias voltage is under 1v.
 
BUT when i measure +/GND,the voltage is -200v??
 
I did the same conversion on 007ta before & got no problem
any ideas?

 

[kevin gilmore]

You need to adjust the offset pot to get it back to zero.
 
But first measure the power supply rails.
 
Don't leave it this way for long, the plate resistors will burn up.

 

[pkshan]

You need to adjust the offset pot to get it back to zero.
 
But first measure the power supply rails.
 
Don't leave it this way for long, the plate resistors will burn up.
 

 
I just rolled back to 100v, and using a  220v to100 transformer now.
but the +/GND voltage is still -200v....
 
I tried to adjust the TVR2 offset pot, the lowest I could get is about -170v
 
Seems the amp was already damaged when I received it.
 
is there something burned ?

 

[kevin gilmore]

don't have a picture of the srm600 handy.
 
make sure the volume control is at zero.
 
The + power supply can be measured easily at the top end of
the plate resistors.  Should be +320 (version 1)  should be +350 (version 2)
 
The - supply i don't remember the easiest place to measure.
Should be -350 (version 1) or -375 (version 2)
 
Since you have a minus offset, i would measure the + supply first.
 
Same for both channels??

 

[schorsch]

Has one of you ever tried this amps?
 
http://www.high-amp.de/html/frame.html
 
Scroll down -< there is an English version of that homepage....
 
 
Regards Georg
 

 

[pkshan]

Quote:

don't have a picture of the srm600 handy.
 
make sure the volume control is at zero.
 
The + power supply can be measured easily at the top end of
the plate resistors.  Should be +320 (version 1)  should be +350 (version 2)
 
The - supply i don't remember the easiest place to measure.
Should be -350 (version 1) or -375 (version 2)
 
Since you have a minus offset, i would measure the + supply first.
 
Same for both channels??

 
  
 
I measure from the 220uf large capacitors , the value is +400v & -397v,
 
yes both channels are same....

 

[kevin gilmore]

Your power supply voltages are 50 volts high resulting in the circuit not being able to balance
correctly. You are also running very close to the maximum voltages on the electrolytics.
According to my schematic, the voltage between orange and brown as AC should be 270v
and the voltage on red and white should also be 270v
 
blue to blue should be 12.6v ac
 
If you want to continue to run at these voltages you are going to need to increase the value of R20
which is 1.5k.  Make it 2.5K  This is the resistor in series with tvr2 and might be labeled differently.
 
If you are actually 240v instead of 220v, then you might be wiring the transformer incorrectly.
And your 220v to 120v transformer might also be 15% high
 
Measure the +15 and -15 voltages, because a bad +15 voltage could also cause this.

 

[pkshan]

I did more measurement,
seems there are some issues in the tube voltage(pin3?)
please help

 

[kevin gilmore]

-400 volts on the center of the filament consistent with everything else.
 
cathode and grid voltage the same is a bad thing.
 
check values of plate resistors with the power off.
 
could be the tubes are trashed.

 

[pkshan]

Sorry, noob question
you meant this one? i measured it, it's 1kohm
 

 

[pkshan]

I unplug the tubes, measured again
pin1:+80v
pin2:-390v
pin3:-415v
pin4:-415v....

...
 
update: I replace the tubes with new one, still no luck..