The ultimate DIY? A Stax SRM-T2!

[Craig Sawyers]

If it is white grease it is basically thermally conductive oxides in silicone grease. Providing it is still paste-like and not really thick and goopy you should be OK.

[wink]

As long as it doesn't have any Beryllium Oxide it's safe.

https://en.wikipedia.org/wiki/Beryllium_oxide

[jose]

I have always believed that this grease contains in most cases aluminum oxide. So it can be conductive.

[JoaMat]

https://en.wikipedia.org/wiki/Aluminium_oxide

[jose]

Thanks Joachin !

[kevin gilmore]

thermal grease lasts forever. I have a jar with original Newark part number on it, and its 50 years old. Still good.

the stuff contains aluminum oxide or silicon oxide, or various other compounds in silicone and for voltages less than about 2.5kv its an insulator. Although it can have more capacitance than you might think.

[nopants]

Thanks for the input, seems to have done the trick for replacement but still tracking down the issue/s in one channel.

also I smelled something funny while troubleshooting and it turns out the 100k feedback burned up somehow

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[nopants]

Getting some weird behavior under load, the rails measure fine until I hook them up to a channel, then everything sags...also the led "diagnostics" seem to have spread to the both sides which makes me think the power supply might be acting up in general.

PS Anyone have a set of original boards for the T2? Trying to build up some insurance in case I fuck something up reworking the amp.

[GeorgeP]

Sounds like current limiting in the power supply if only one side is powered up at a time and it powers up normally - 30r resistor to 25r or 20r will fix that. What happened though to cause you to start replacing parts in the amp section first - there may be something else afoot?

[nopants]

I guess it's easier to recount the trail of events:

• Swirling/Static in left channel, left channel goes out mid-use (happened before in a channel years ago, ended up having to replace a k216 somewhere after checking some of the behavior near the power rails). At this point I was able to power up both channels and only the left one wasn't functioning properly. 
  • Right channel was fine throughout this time - rails weren't acting up etc.
  • While powering on (only) the faulty left channel afterward I saw something spark near the output CCS and take out the stacked LED's
• Left it alone for a few days, tried out the right channel just to verify that it was still working so I could compare voltages etc. Problem as stated in the previous post - rails all measured like the limiting kicked in

I do think I've messed with the current limiting at one point, but my recollection is kind of fuzzy - I was actually going to search through this thread because I feel like I've encountered it before

 

[GeorgeP]

So you only have one properly working side then?

[nopants]

neither channel works atm

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[GeorgeP]

Ooof - then it sounds like you have some work ahead of you...

[Kerry]

Start with the right channel and check all of the test point voltages.  Also, what are the voltages for each rail.

Edited May 6, 2019 by Kerry

[nopants]

Yeah I started doing that, but I got spooked when I saw one of the tubes start red plating and flashing. I switched to a cheaper tube and the heater/cathode was still flashing similarly in the same spot.

I'll tackle it when I have some more free time this week.

Thanks for the help guys

[Laowei]

16 hours ago, nopants said:

Yeah I started doing that, but I got spooked when I saw one of the tubes start red plating and flashing. I switched to a cheaper tube and the heater/cathode was still flashing similarly in the same spot.

I'll tackle it when I have some more free time this week.

Thanks for the help guys

What tubes?

JJ 6CA7 and KT77 tubes have problems in the DIY T2 circuit.

[nopants]

XF2s and EH's. Was only one tube socket but I panicked pretty hard haha

[Hugo]

Santa came much earlier this year!!!

Thank you so much, Kerr.. I mean, Santa! ?

Edited May 17, 2019 by Hugo

[JoaMat]

Wow magnificent! Nascent Audio?

[nopants]

looks like Kerry's build

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[Kerry]

Yeah, Nascent Audio is me.  Thanks Hugo!

[TMoney]

Wow. That is one damn good looking chassis!

[chinsettawong]

So beautiful!

[johnwmclean]

So Epic! 

[Helium]

Beautiful!

Kerry, how did you treat the chassis to achieve polished surface?

Seems to be steel, not aluminum?

Is is mechanically polished or galvanized?