[Nanoframe]

Hi everyone!
 
I'm not sure if this the right place to post, but here goes!
 
I have been using the SR-507/SRM-600 Limited combination for about a year now. The thing is, recent usage has seen the right channel sounding crackled and distorted until it eventually died. Thinking that is was the phones, I brought it down to the dealer where he plugged it into an SRM-323 and was found to be working perfectly fine.
 
I now think the amp is faulty. Here's what I have done so far;
 
1) Tried a different source. (iPhone 5 to amp, didnt work, right channel still dead, the original setup was an Audio-Gd Reference 5 fed by an Anedio U2 from the PC)
 
2) Tried different interconnects, both SE and balanced, didnt work, right channel still dead.
 
3) Tried swapping positions on the interconnects (left to right etc), right channel still dead.
 
4) Tried swapping position of the tubes, right channel still dead, but the left channel started giving the same symptoms like the right before it died. (I did not re-bias the amp when I swapped positions, could that be why?)
 
Could I have done anything that could have killed the amp? Did I miss anything out when troubleshooting?
 
Any help would be greatly appreciated.
 
Thank you!

 

[n3rdling]

Do you have a multimeter?

 

[wink]

 
 
Quote:

The down side staying in a oil sand work camp. I need a bigger night stand.
 

 
 
 
 
Quote:

Yeah that looks pretty awful.

 
 
 
Stack needs to be at least 250% higher to get the "air".

 

[wuwhere]

Quote:

Hi everyone!
 
I'm not sure if this the right place to post, but here goes!
 
I have been using the SR-507/SRM-600 Limited combination for about a year now. The thing is, recent usage has seen the right channel sounding crackled and distorted until it eventually died. Thinking that is was the phones, I brought it down to the dealer where he plugged it into an SRM-323 and was found to be working perfectly fine.
 
I now think the amp is faulty. Here's what I have done so far;
 
1) Tried a different source. (iPhone 5 to amp, didnt work, right channel still dead, the original setup was an Audio-Gd Reference 5 fed by an Anedio U2 from the PC)
 
2) Tried different interconnects, both SE and balanced, didnt work, right channel still dead.
 
3) Tried swapping positions on the interconnects (left to right etc), right channel still dead.
 
4) Tried swapping position of the tubes, right channel still dead, but the left channel started giving the same symptoms like the right before it died. (I did not re-bias the amp when I swapped positions, could that be why?)
 
Could I have done anything that could have killed the amp? Did I miss anything out when troubleshooting?
 
Any help would be greatly appreciated.
 
Thank you!

 
Do you have the schematic?

 

[Nanoframe]

Thanks for the quick replies guys!
Quote:

Do you have a multimeter?

 
Yup, I actually measured the amp by following this thread and got very similar readings, in fact the only difference was pin 3 for both sockets, where the readings differed by 1 or 2. I hope I'm not doing this wrong... 
Quote:

 
Do you have the schematic?

 
Unfortunately I dont. I'll try searching around to see if I can find it.
 
 
EDIT: Got it! I didn't realise it was in the manual. My bad!

 

[spritzer]

That's not the schematic but you can find the near alternative by searching for the SRM-T1 schematic.  First thing to check with these amps are the LED's in the circuit and if they are all lit.  It also wouldn't hurt to get new tubes as if the right one had a short you probably killed the left channel swapping them. 

 

[Nanoframe]

Thanks for the input spritzer! You can tell I'm not electronics savvy!

I'll try looking for the schematics and try getting a replacement set of tubes.

If I accidentally killed both channels, I'll have to replace the whole amp?

Thanks again for all the help!

 

[spritzer]

The amp should be repairable but it really depends on what happened. 

 

[Nanoframe]

Quote:

The amp should be repairable but it really depends on what happened. 

 
Ok, thanks a lot for the help! Fingers crossed while I find the exact cause.

 

[livewire]

Spritzer, I have a SRM-252S that blew the right channel.
I tracked it down to one of the little red LEDs, all of the transistors seemed to check out ok.
Before I solder in a replacement, could you tell me what the forward voltage rating of the LED should be?

 

[wuwhere]

Quote:

Spritzer, I have a SRM-252S that blew the right channel.
I tracked it down to one of the little red LEDs, all of the transistors seemed to check out ok.
Before I solder in a replacement, could you tell me what the forward voltage rating of the LED should be?

 
Can't you just measure the left channel?

 

[livewire]

Quote:

 
Can't you just measure the left channel?

I could but it would require that I de-solder the left channel LED to find it's "turn on" voltage.
Dont want to check the live circuit for this characteristic because the voltage drop shown on the DMM
may be influenced by other components in the circuit. Stax typically uses LEDs in the various stages of their amps
to act as a voltage reference for the rest of the circuit. To maintain correct functionality, the LED's Vf rating is crucial.
These LEDs are tiny, I am afraid by de-soldering the left channel, I could do damage to it.
 
Besides, it is easier to ask an expert who has torn into many of the same amp for their knowledge! 

 

[justin w.]

Quote:

Spritzer, I have a SRM-252S that blew the right channel.
I tracked it down to one of the little red LEDs, all of the transistors seemed to check out ok.
Before I solder in a replacement, could you tell me what the forward voltage rating of the LED should be?

 
did you check to see if the LED is actually bad?  its probably an indicator that something else in the circuit is wrong.  but if you want to try to replace it 1.7V is a pretty typical value.

 

[livewire]

Thanks Justin, I knew that 1.7V is a common value for this type of circuit,
although I've seen KG use LEDs up to 2.2V in some of his designs.
I just wanted to be sure what Stax specs for this part in the SRM-252 so as to avoid any channel balance issues.
 
Yes the LED is bad, it's open. All the others were lit.
I desoldered it and checked it with the DMM outside of the circuit.
I got the dreaded "OL" when reading it both ways.
Suspecting something else in the neighborhood might be borked as well,
I checked all the transistors and resistors in that part of the circuit and compared
the readings to the working left channel. All else seems A-OK.

 

[spritzer]

I've never seen a Stax schematic where the LED's are marked with a part number, just "red led" so 1.7V would be the best bet.