is a TO3 case better? - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th March 2008, 01:41 AM   #1
diyAudio Member
 
Jonny Hotnuts's Avatar
 
Join Date: Dec 2007
Default is a TO3 case better?

This may seem like a tard quesion but wondering if the TO3 was a better trans.

So few amps run them.....but the amps that do are usually VERY expenisve. Just wondering.....
  Reply With Quote
Old 15th March 2008, 01:51 AM   #2
TheMG is offline TheMG  Canada
diyAudio Member
 
Join Date: Jan 2008
To assume a TO-3 transistor is higher quality than a TO-2XX equivalent would be an incorrect assumption.

I can see one advantage being better mechanical ruggedness and better thermal dissipation, but they also have their disadvantages such as more difficult mounting, more complex heat sink design, and higher cost.

As for the quality of the magic stuff (what's inside, where it really counts), there's nothing to be said about that. Just like any other transistor, there are fakes and knockoffs, and many varied specifications, no different than any other type.
  Reply With Quote
Old 15th March 2008, 03:55 AM   #3
djQUAN is offline djQUAN  Philippines
diyAudio Member
 
Join Date: May 2004
Location: manila
Send a message via MSN to djQUAN Send a message via Yahoo to djQUAN
in my own opinion, due to the rarity of TO-3 transistors in car amps, manufacturers are taking advantage of this and making people think "TO-3 is rare, it must be expensive, so it must be good!"

not sure if my assumption is right though.

but I do agree with TheMG's comments.
  Reply With Quote
Old 15th March 2008, 05:23 AM   #4
diyAudio Member
 
Join Date: Feb 2008
I don't know if I would say better. Alot of the earlier TO3 amps are still in use. I have about 20 different old amps with them, and they all work but one.
TO3's are in alot of the vintage amps. later Linear Power (the first few models didn't have TO3's that I know of, early 80's Majestic, , early 80's Coustic , ect.
One thing that I remember about the older Linear powers with the TO-3's is the scream they made when doing a db test. The amps squealed loudly under a heavy note. Only heard this on Linear Power amps. Could have been the TO3's, not sure. Haven't strained one like that in 20yrs. Anyone else remember the earlier TO3 LP's screaming?
  Reply With Quote
Old 15th March 2008, 06:13 AM   #5
diyAudio Member
 
Join Date: Dec 2005
Location: Northern California
The "screaming" was most likely the loosely wound toroids that LP was famous for. I remember it well also, and on many other brands over the years.

TO-3's have a following mostly based on ten year lifespan testing where they seem to have the advantage. This along with thermal characteristics that seem to have some better advantages in some cases.
Manufacturers have come out with much better packages since then, and the margins between the packages has narrowed greatly over the years. With estimated MTBF being equal if not better with todays newer package designs.

There are a whole host of spec's to be considered, even the differences between a Aluminum case or a steel case TO-3 seem to hint at different quality standards, and lifespans. But there are so many variables to be considered, one would also remember that all these tech spec's are also in the hands of Sales Engineers also before we get them as end users.

Do I like them ? There OK, They pose different service related issues, mostly time consuming
  Reply With Quote
Old 15th March 2008, 06:20 AM   #6
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
TO-3 case offers THERMAL AND MECHANICAL advantages.

Ease of heat transfer/dissipation from the transistor to heatsink
I have seen plastic devices going into smoke at 90degC, but never seen a metal case device failure even at 120degC. Metal case offers much more thermal stability than plastic case devices.

If the ambient temperature is more than normal, TO-3 case devices always offer an edge over plastic devices.

Click the image to open in full size.
  Reply With Quote
Old 15th March 2008, 06:33 AM   #7
diyAudio Member
 
Join Date: Nov 2004
Location: Florida
It's way easier to mount a big TO-264 and you get nearly the same performance and power handling.

TO-3 may be a bit rated higher, but with all the BS you go through mounting them, it's not much of a gain. Now if you have a GOOD TO-3 heatsink, that's different.

BUT IMO, TO-3 is still the toughest transistor. I've killed very few of them. I used to collect any high powered ones I'd find.

If you have a large heatsink with a THICK base, TO-264 is the way to go. Also, it's EASY to parallel TO-264, which works even better with the heatsink.

You can't mount a typical TO-3 with a thick base heatsink because of the B-E leads. Thermal flow in the heatsink is also way better when the base is thick, so the sink isn't just hot around the transistor. With a few flat pack TO264 devices, and a good thick heatsink, I can get better performance than with TO-3s. I can also fit more transistors on to one heatsink with the flat pack devices.

I just use my TO-3's as overkill transistors in low power stuff, so I don't have to use heatsinking. And running only 1A or so in a 20A device won't hurt
  Reply With Quote
Old 15th March 2008, 06:37 AM   #8
diyAudio Member
 
Join Date: Feb 2001
Location: Mars
Ease of heat transfer/dissipation from the transistor to heatsink

Transistor -> goo/insulator-> heatsink

This is good


Car amps may do this.

Transistor -> goo/insulator -> thin metal bracket -> goo -> heatsink

not very good.

When the design is not executed well, the transistor case
is not the problem area.

Then you have a second variable. The amplifier design as a whole.
  Reply With Quote
Old 15th March 2008, 06:44 AM   #9
diyAudio Member
 
Join Date: Nov 2004
Location: Florida
Brackets really hurt thermal conduction. Heat doesn't go through the thin metal good enough. I've seen that done so many times with mostly TO-3, but others too. The bracket and transistors get hot first, before the sink gets warm

I agree with you, mounting directly to a thick metal heatsink is the best way.

Why don't they just make a flat-metal transistor with 3 leads coming out the top??? Like TO-3, but rectangle, and the leads in a much better place.
  Reply With Quote
Old 15th March 2008, 07:27 AM   #10
TheMG is offline TheMG  Canada
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally posted by EWorkshop1708
Why don't they just make a flat-metal transistor with 3 leads coming out the top??? Like TO-3, but rectangle, and the leads in a much better place.

$$$
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
B&C Sub, ATI case ShinOBIWAN Swap Meet 2 15th October 2006 09:34 PM
What to use for a case ???? la9 Chip Amps 3 22nd August 2004 03:34 AM
DIY Case dhole Pass Labs 9 15th August 2004 02:47 PM
case theChris Parts 2 8th February 2003 08:08 PM


New To Site? Need Help?

All times are GMT. The time now is 02:38 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2