When I lost my Mastr-II continuous duty PA going into winter, I swapped the board for a 110W mobile from an Executive-II with the TO-220 power regulation transistor, I just gobbed on some heat sink grease and bent the transistor slightly so I could use one of the original TO-3s mounting holes.
Also, Taking a note from the computer overclocking community I recommend using a product called "Arctic Silver 5" for the heat sink compound. This has a +8 to +12 degree centegrade increase of heat transfer over standard silicon compound and is made from real silver particals. A little pricey at $7-$13 for about enough for a MASTR-2 heat sink, but well worth it. Just bust out the denatured alchol and clean off the white crap from the heat sink and transistors before hand. There are alot of phoney "silver" compounds that are about 95% aluminum so don't but the cheap stuff. After the meltdown and rebuild, I pegged a Bird 100watt slug (45.7uA into a current meter from the detector module Birds normal full scale = 30uA) and another meter says 157W. I don't know if I beleive it, but it is deffentanly an improvement as the last PA would do 100 and throttle back to 60watts after 15 minutes of talking. The new PA with some 120mm fans on the heatsink won't budge. On Wed, 2 Mar 2005 18:31:18 -0500, Jeff DePolo <[EMAIL PROTECTED]> wrote: > > > On Wed, 02 Mar 2005 22:45:48 -0000, Laryn Lohman wrote > > --- In [email protected], "Gary LaForce" > > <[EMAIL PROTECTED]> wrote: > > > > > > What transisor is used to replace the to-92 intermittent duty > > > transistor on the mastr 2 mobile pa. I have a UHF PA that i have > > > mount in a cont. duty heatsink and would like to change out the > > > transistor. > > > > > > > > > Thanks Gary N0PBM > > > > Is the transistor different between the two? > > > > Laryn K8TVZ > > Maybe I'm confused as to what the original question was, but if you're > talking about the pass transistor in the power control circuit, it's a TO-220 > case part on an intermittant duty PA, and a TO-3 mounted to the side of > the "frame" on the heatsink. Is that what we're talking about? > > Probably any run of the mill NPN power transistor would work like a 2N3055, > 2N3771, 2N3772, etc. Check the parts list in the LBI - it probably > says "Sim. to 2Nxxxx" for the part in question. > > > Yahoo! Groups Links > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
