L'Amp: A simple SIT Amp

[DIYspaceW]

I just came upon this page: ƒjƒtƒeƒB�[”­Œ¾�W
As you can see the Tj is 120 C.
I assume but cant measure, only put my hand on the heatsink, that my SITs are running at 50-60 C whit 50W disipation at
ambient temperatures around 30 C...
I assume thats still in green zone.

 

[Michael Rothacher]

Can I send you $10 via paypal so I don't have to wait?
Seriously.

Send me your email so I can keep you posted.

 

[Michael Rothacher]

I just came upon this page: ƒjƒtƒeƒB�[”*Œ¾�W
As you can see the Tj is 120 C.
I assume but cant measure, only put my hand on the heatsink, that my SITs are running at 50-60 C whit 50W disipation at
ambient temperatures around 30 C...
I assume thats still in green zone.

Do you have a temperature probe?

 

[DIYspaceW]

Do you have a temperature probe?

No. Need to get one.
Did you measure yours?

 

[Michael Rothacher]

For TO-3, I measured the case temperature and used .8C/W for the case to junction thermal resistance.

 

[DIYspaceW]

For TO-3, I measured the case temperature and used .8C/W for the case to junction thermal resistance.

I got the probe and measured the temperature of the transistor case (drain),
it is 60-61 C and the heatsink has around 53 C...

 

[DIYspaceW]

I got the probe and measured the temperature of the transistor case (drain),
it is 60-61 C and the heatsink has around 53 C...

Need to make correction.
The Case temperature of the transistor after 2 hours of operation by
ambient temeprature 29 C is 75-80 C. The disipation is 52.7W.
I assume the Tj is even more!

I think I will have to lower the disipation to 40-45W.

 

[Michael Rothacher]

52.7W? Which version did you build? What's your Vds/Id?

Also, using the thermal resistance from case to junction may result in a higher than expected estimate, so there's a little bit of room in there.

 

[DIYspaceW]

52.7W? Which version did you build? What's your Vds/Id?

Also, using the thermal resistance from case to junction may result in a higher than expected estimate, so there's a little bit of room in there.

The Vds is 74V and the Id is 0.85A, the gate has -12V.
I build my own version whit parafeed topology and output transformer.

For insulation I use aluminum oxid, I bought here: Link

 

[juanitox]

1 amp output transfo !!! schema pleaaaase

 

[DIYspaceW]

1 amp output transfo !!! schema pleaaaase

I am still working on the circuit, its an hybrid...Will post the schema
as I am finished.
This is a parafeed, so there is no current i primary.
I read something about an SIT SET in Linear Audio vol.4,
they used PASS SIT-1 and had an special made output transformer that
could take the current but didnt have enough inductance for low end.

 

[juanitox]

can't wait , sounds good to replace the 10OOOuf output electrolyte with a parafeed film one

 

[OllBoll]

can't wait , sounds good to replace the 10OOOuf output electrolyte with a parafeed film one

One thing Nelson has started doing is to just parallel the electrolytic with a 1 uF, say MKP or similar. Much cheaper than buying a large expensive non electrolytic cap =)

 

[Zen Mod]

or , as already written oomphteen times - send boom to woof via elko (still bypassed with nice cap) and send shhhh to squawker via adequately sized small solid cap

that demands two pairs of terminals per channel ....

in case of feeding just FR , proceed simple as usual

 

[juanitox]

One thing Nelson has started doing is to just parallel the electrolytic with a 1 uF, say MKP or similar. Much cheaper than buying a large expensive non electrolytic cap =)

that's what i'm doing with a 10UF ones and it's really better ( say faster) than with the electrolyte alone .. i must deal with a full range speaker

 

[Michael Rothacher]

The Vds is 74V and the Id is 0.85A

I forgot you're doing that. Just lower that dissipation (as you mentioned) and I'm sure you'll be just fine.

 

[Nelson Pass]

For TO-3, I measured the case temperature and used .8C/W for the case to junction thermal resistance.

If those are the 4mm chips, then the figure is more like 2+

 

[DIYspaceW]

Whit 45W disipation the heatsink has 52-55 C and the case of 2sk82
has 52 C.
So its looks no more then 50W disipation whit this heatsink. I can live
whit that perfectly.

 

[Michael Rothacher]

Thanks, Nelson. I hope the whale watching's good.

This just in: I'm informed the 2SK60 is 1.5 Max. Is it fair to assume the 2SK82 is a little bigger?

 

[Nelson Pass]

This just in: I'm informed the 2SK60 is 1.5 Max. Is it fair to assume the 2SK82 is a little bigger?

I don't assume that. I have seen a 4mm spec on the chip, and all the mfr
numbers point toward 2.5 deg/w - 150 deg C junction max, and a 63 watt
rating at 25 deg case temp.

I have seen photos of dual chips in a TO-3 case, but from the curves I get I
don't think that's what Acronman is selling. I guess I'll cut one open if I get
bored.