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The ultimate DIY? A Stax SRM-T2!


spritzer

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Hi,

Does anyone know if there has been issues with amp pertaining to the heat. From all accounts reading thru the threads

that some for example GeorgeP was a bit concerned. Now that the amp has been in use for a good while has anything

emerged. As I am about to start on mine. Anything that needs to be upgraded now is the time to do it.

Les

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Me too. Though my Sumr transformers have been reliable with about 1000 hrs on them (with one of the HV transformers developing a light buzz early on). Design temp rise is 33C for filament and 26.4C for HV - but that is with 16 inches of air clearance while the KG chassis has roughly one inch of clearance. If I recall, the surface temps were into the >50C range. Though wouldn't mind having a beefier set as a back-up. 

 

And vertical fins would add a lot more surface area than the horizontal fins (but don't look nearly as bad ass). What sort of temps are you getting with vertical fins?

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I don't have fin temps, but I do have a few device temps. I have them somewhere I can post them once I shake the flu :( When measuring toroids it seems that the highest temp rise is between the potting compound and the side opposite from the wire leads. I finally gave up on my IR thermometers and bought a pyrometer that I can touch directly to the device I want to measure. This seems to help getting accurate measurements.

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GeorgeP I am making up my own chassis, heat sink fins will be vertical and the height will be 4". That's 1" taller than

Kevin's Chassis. If you said his chassis height leaves 1" spare the that will give me 2" and I was thinking I might mount

a heat sink to the top of each transformer. Hopefully give me some insurance as I never like really hot things in electronics.

Thanks for the reply guys and would be interested in temps.

Les

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So, my filament transformer is spec'ed at 33C temperature rise (relative) and the other two are 31C temperature rise. At maximum current, where the load on each supply is equivalent to the current limit and similarly the heaters are loaded, I measured max temperature at 52C (absolute) after 1 hour of operation all cased up. There is 1.5" of clearance above the toroids, with lots of venting above. For what it's worth, that resulted in a max temperature of one of my loads to be around 178C, which was bolted to the same case (!). The maximum device temperature in the PSU, as measured at the bolt of the device was 78C. Again, this is definitely "worst" case. In this configuration, the noise seems to go up slightly, I think my highest rail noise was .76mV (!). 

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Rather than asking for larger cores, I would ask for less temperature rise. Be the customer with requirements, not the engineer. Also you might ask someone for measurements who is using SumR so the comparison is somewhat sane. (Notice the temp rise spec in GeorgeP's post and compare to my post. Hint: I went down this road already and still wouldn't mind cooler transformers)

Edited by luvdunhill
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Marc, are you on your original transformers or did you make a change after time for temp reasons? And did you end up going with SumR? I corresponded with Richard a while back about getting second set as a back-up and specifically addressed the temp rise issue - he suggested he could make some changes to the flux (going by memory, would have to dig up his email) to get the temps down - he seemed reluctant to change the size of the transformers for some reason (or could have just been my interpretation).

 

Les, if you look around the first quarter or so of this thread, you will see some transformer design considerations (I believe made by Craig Sawyers). Those posts may (or may not) be useful. I believe Craig got his transformers locally (ie. England).

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I know a few guys were asking about Tran/Lil Knight and chassis progress.  He just got back to me with an update...  Tran will come through!  

 

Hi Chris,

The fact is, my CNC machine man messed up with the plan and he couldn't catch up with it. The Chinese New Year is coming very soon and they also are having a break for 2 weeks. I know this is very hard for you guys because I expected to have everything last December. Please understand for my situation because I am only the middle man, been trying to push them hard... I am way more than worried you guys, all of the money was transferred to them. I have their promise that they will get things back on track after the CNY, which I really hope so. If possible, please let the others know about this. I am still here and will definitely deliver the chassis, just a bit longer than expected.

Cheers
Tran

Edited by shipsupt
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  • 4 weeks later...

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