The way I remember it and I think Bob Pease discussed this in his book
is that the oldest 2N3055 transistor was fabricated using a mesa
process which resulted in basically no secondary breakdown but low Ft
which is consistent with the list just posted showing an Ft of 0.3
MHz. Later replacements uses diffusion processes which both raised
the Ft into the 2 to 3 MHz range, sometimes causing oscillation
problems in older circuits, and lowered the secondary breakdown limits
significantly.
Considering the wide range of Ft specifications shown in the list, I
would not hesitate at all to use a any modern low Ft replacement and
would worry more about power handling capability and breakdown limits.
As far as the pinout problem goes, add some short lead wires and bolt
the transistor down in a more convenient location as is done with the
high power compartment TO-3 pass transistors.
On Sat, 15 Dec 2012 14:04:08 -0800 (PST), Jim Reese <nfeinc@...>
wrote:
Hello to all,
?
The MJFxxxx package is the isolated case?version of the TO-220 MJExxxxT metal power tab TO-220 version with much less thermal?conductance and power capability. The original MJE TO-127 versions are typically good for 90 watt max dissipation. The TO-220(T) is good for 60-75W dissipation, and the MJF package good for 30-50W max.
?
FYI, the 2N3055 TO-3 version also went though a change in the die/mount/connection structure/design a couplel decades ago. It seems the new versions can't handle the same instant overload, etc. that the old ones can.
?
We at where I work have also found the same issue on LEDs. The old Monsanto MV5752A generic red LED could handle a lot of short pulses at?high current, up to the maximum power dissipation rating. The new ones?fail in about 3 flashes of the LED under the same conditions.
?
My input for today.
?
Regards,
?
Jim
--- On Sat, 12/15/12, Ed Breya <edbreya@...> wrote:
From: Ed Breya <edbreya@...>
Subject: [TekScopes] Re: Complete List of TM500/5000 Mainframe Pass Transistors
To: TekScopes@...
Date: Saturday, December 15, 2012, 12:57 PM
I believe the MJF 2955 and 3055 are the exact same die as in the original 2N2955 and 3055, in TO-220 rather than TO-3. The specs except for power dissipation should be the same - I hope that helps fill in the spec table.
I think any of these should be good subs for each other as long as the type (NPN/PNP) is right, the correct pinout is attainable, and the size is right - the high power hole needs bigger devices.
Since these are almost always used as power supply pass regulators for the plug-ins, what matters most is the DC-SOA ratings. The transistors in this size and rating class should be similar in that respect, but when in doubt, always consider the SOA graphs when comparing possible substitutes, versus the original designed-in parts. With the wide variety of plug-ins, it will be nearly impossible to predict tha actual DC operating condition limits, so use the original part SOA curve as the benchmark to be met or exceeded.
Ed
--- In TekScopes@..., "Dennis Tillman" <dennis@...> wrote:
TEKTRONIX TM500/5000 MAINFRAME PASS TRANSISTORS
Compiled by Jerry Scheltgen and Dennis Tillman
?
Tek used at least 12 different pass transistor part numbers during
the time the TM500/5000 mainframes were in production. In some
cases different parts were used over certain serial number ranges.
The high power compartment (when present) used the higher current
transistors. Tek changed to different semiconductor families and/
or manufacturers (MFR####) over time.
?
Tek specified these parameters for the various part numbers used.
?
TEK PART TYPE? MFR####? Ic???BVceo? PWR? hFE@Ic? VSat FtMIN CASE
-------- ----? -------? ---? ----- ----? ------? ---- ----- ------
151-0140 NPN???2N3055H? 15A? 60V???115W? 20@4A???1.1V .3MHz TO-3
151-0258 PNP???2N4905???15A? 60V? ? 87W? 20@4A???3.V? 4.MHz TO-3
151-0349 NPN???MJE2801? 10A? 60V? ? 90W? 25@3A? ? ? ? 2.MHz TO-127
151-0373 PNP???MJE2901? 10A? 60V? ? 90W? 25@3A? ? ? ? 2.MHz TO-127
151-0413 NPN???2N6258???30A? 80V???250W? 20@15A? 3.V? .8MHz TO-3
151-0436 NPN???MJE2801? 10A? 85V? ? 90W? 25@3A? ? ? ? 2.MHz TO-127
151-0651 PNP???TIP36C???25A? 100V? 125W? 10@15A? 4.V? 3.MHZ TO-218
151-0652 NPN???TIP35C???25A? 100V? 125W? 10@15A? 4.V? 3.MHZ TO-218
151-0917 NPN? ? ? ? ? ? ? ? ? NO DATA
151-0918 PNP? ? ? ? ? ? ? ? ? NO DATA
151-0937 NPN???MJF3055? ? ? ? NO DATA? ? ? ? ? ? ? ? ? ? ???TO-220
151-0938 PNP???MJF2955? ? ? ? NO DATA? ? ? ? ? ? ? ? ? ? ???TO-220
?
**
TM501
NPN 151-0349 (Select from MJE2801, MFR####: SJE924)
PNP 151-0373 (MFR####: SJE925)
**
TM501A
NPN 151-0349 (Select from MJE2801, MFR####: SJE924)
PNP 151-0373 (MFR####: SJE925)
**
TM502A
NPN 151-0436 (MFR####: SJE966, MJF3055), 151-0937 (MFR###: MJF3055)?
PNP 151-0373 (SJE925 SEL VER), 151-0938 (MFG####: MJF2955)
**
TM503
NPN 151-0349 (SEL FROM MJE2801)
PNP 151-0373 (SJE925 SEL VER)???
**
TM503A
NPN 151-0436 SJE966 SEL VER
PNP 151-0373 SJE925 SEL VER, MJF2955, 151-0938
**
TM503B
NPN 151-0937 MJF3055
PNP 151-0938 MJF2955
**
TM504 verify on later versions
NPN 151-0436, 151-0413 (OPTION 2 ONLY, 2N6258 HI PWR COMP)
? ???151-0140 (STANDARD ONLY)
PNP 151-0373, SJ7028, 151-0258 (OLDER VER HI PWR COMP MJ2955)
**
TM504A
NPN NO DATA
PNP NO DATA
**
TM515
NPN 151-0436 TO-127 (Select from SJE966)
PNP 151-0373 TO-127 (SJE925)
**
TM506
NPN 151-0436, 151-0140
PNP 151-0373, 151-0258 (MFG####: MJ2955)
**
TM506A
NPN 151-0917, 151-0652 (MFG####: TIP35C)
PNP 151-0918, 151-0651 (MFG####: TIP36C)
**
TM5003
NPN 151-0436 (Select from SJE966), 151-0937 (MFG####: MJF3055)
PNP 151-0938 (MFG####: MJF2955), 151-0373 (MFG####: SJE925)
**
TM5006
NPN 151-0436 (Select from SJE966), 151-0140 (MFG####:SJ7020)
PNP 151-0373 (MFG####: SJE925), 151-0258
**
TM5006A
NPN 151-0937 (MFG####: MJF3055), 151-0652 (MFG####: TIP35C)
PNP 151-0938 (MFG####: MJF2955), 151-0651 (MFG####: TIP36C)
**
?
-30-
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