The ultimate DIY? A Stax SRM-T2!

[iwik]

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

[GeorgeP]

No concerns - heat seems to be consistent with others and temp of traffos within range of expected heat rise (especially considering there is no clearance).

 

What are you using for a chassis?

[luvdunhill]

Moving to vertical finned heat sinks is enough to make the thing run a lot cooler. I worry most about my transformers, they run hotter than I would like.

[GeorgeP]

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?

[luvdunhill]

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.

[iwik]

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

[luvdunhill]

I have been considering how to heatsink toroids but havent found a strategy that works well. Be careful to avoid creating a shorted turn as well.

[iwik]

Yes a must not to provide a shorted turn. Have a we look at this link, may help don't know. How is the Toroid mounted in

the T2?.Wonder how much help to beef up the transformer by say 25-50%?.

Here is the link.

http://www.pa-international.com.au/index.php?option=com_easyblog&view=entry&id=6&Itemid=177

[luvdunhill]

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 (!). 

[iwik]

Thanks for the temps, Sumr will supply transformers with the next sized cores for an extra $10. They are 110mm in

diameter, not a problem for me as I will make the ps a little bigger.

[luvdunhill]

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 January 27, 2014 by luvdunhill

[GeorgeP]

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).

[luvdunhill]

I Don't want to step in a minefield here The facts are in the thread if you want to do something other than follow the previous builders. I didn't.

[GeorgeP]

Agreed.

[luvdunhill]

The obvious solution: build two PSUs and go dual mono. Then it's a all a moot point.

[iwik]

Thanks Guys,

I agree to, think I will go with the status quo until something untoward happens. Don't like

to change anything unless needed to. Dual Mono power supplies as a backup plan.

[kevin gilmore]

always wanted to see someone do the dual mono power supply stack. but you are going to need another power supply

board to do that. It was designed that way from the start for Mikhail class pure insanity.

[luvdunhill]

Total weight would have to be a record. We should have had Andy compare when he had two

[justin]

so which PSU do you reference the bias voltage to?

[luvdunhill]

Shouldn't matter. The reference is earth.

[blubliss]

Total weight would have to be a record. We should have had Andy compare when he had two

hmmm, I do have an extra set of transformers, a box, and a board......

[spritzer]

Get cracking!!!  We expect results by next week!! 

[shipsupt]

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 January 31, 2014 by shipsupt

[niner]

Please PM me if anyone has an extra set of T2 boards (amp+ps).

 

EDIT: I love to take the chassis set off your hand too, if you have them.

 

Thanks

[blubliss]

where are you located?