I'm wondering if anyone can help identifying the transistor in the pics, these are from a Fluke 5200A.
On one side I can clearly see they are Motorola transistors and they are marked SPS 7278 but googling that number didn't help, so it got me thinking that the 7278 could possibly be a date code?
So on the back side they are painted with the color code of Yellow, Blue and White or Grey so I though they are possibly identifying the transistor number by color code as I have seen this done with some diodes from the 70's so I also Googled 2N468, 2N469, 2N864 and 2N964 and while some of those numbers brought up transistors there where none that looked right as the package types where metal cans.
So any idea what transistor this is? Also what is the package type number, I thought TO-220 or TO-202 but the plastic part is wider that the tab whereas the TO-220 and 202 types shows the plastic encapsulation being the same width as the tab?
IIf the color code's are not the transistor number then does anyone know what the meaning of the code is? HFE matching possibly ?
I show it as Motorola Case 152, rated about 10W max. compare with TO-220 15-100W in the same databook.
Example part numbers are NPN MPS-U05 or U07 and PNP MPS-U55 or U57 (100V annular ring). MPS-U10 300V 0.5A.
Nothing starting with SPS in 1978, 1980 Power Device Data and no mentioned about the three stripes, I see that on many parts from the same era.
Fluke may have matched or used select hFE groups, like Tektronix.
Yes, I just found a 1975 Motorola Databook online and it is definitely Case 152 which is also called Uniwatt in the 1975 Databook the vintage of the Databook does seem to tally with 7278 possibly being a date code.
What board is it from ? The 3042 number should be found in the service manual, no ?
When I Googled Motorola SPS it seems to stand for Semiconductor Products Sector so I don't believe it's a special.
I'm still the the 7278 is a date code and am leaning on the side of the color codes, initially I was Googling 2N and then 468, 469, 864 and 869 as all the combinations of the color code but now I believe it may belong to either BC, BD or BF families of transistors as they all have 3 digit numbers.
This board is all PNP transistors, there is another board with NPN transistors and the colors for either 762 or 267
The service manual I have only list an internal Fluke part number
The board is the Power Amplifier board but there is no mention of what transistor is used only a Fluke internal part number and Googling that doesn't help much.
The "FLUKE 5200A Instruction.pdf" I found has a full list of parts. For power amplifier assembly there is this strange Q20 and Q23 "XISTOR" 'Adapter'..
Also the Power-Amplifier board should have number 5200A-1040 according to schematic and be a big board. Maby this 3042 is just an option or a daughter board ? Where is it plugged ? Any silk screen print hinting toward it´s function ?
Did you try the Fluke part number at NTE?
Could the stripes be the date code?
The "FLUKE 5200A Instruction.pdf" I found has a full list of parts. For power amplifier assembly there is this strange Q20 and Q23 "XISTOR" 'Adapter'..
Yes, that is the board, it is 4 transistors in parallel on one board with 4 PNP transistors and another board with 4 NPN transistors but they don't tell you what the individual transistors are in the manual as they use an internal fluke number.
From the size it could be one of the MPS-Uxx parts from the "Motorola Bipolar Power Transistor Data Book".
Maby MPS-U10 with 300V Uce ?
I found this statement on
https://talonelectronics.com/shop/item.aspx?itemid=7385 "EF Johnson Uniwatt Transistor marked 2027, equivalent to MPSU01. Alternate part number 576-2-27"
Just saw a video on Youtube where a member of the forum Defpom was fixing up one of these calibrators and on his the board with 4 transistors was replaced by a single 2N6214 so will try that first once I can get hold of one. Hopefully that will work.
I don't know other power transistors with EBC pinout. Is this Q21/Q23 you are looking for? Just to know the VCE etc. if you want modern substitutes to avoid sourcing antique parts.
Search 5200a on the forum and lots of other posts, schematics: https://www.eevblog.com/forum/repair/fluke-5200a-ac-voltage-calibrator-teardown-and-repair/msg382207/#msg382207
This is Q23 which is actually a small adapter board with 4 matched transistors on it, the board fits a TO66 outline and pinout so could be replaced with a TO66 transistor. Actually Q20 which on the schematics is a single NPN transistor is also a 4 transistor board on my unit but the unit in the video in the posts above has a single TO66.
Looking at the circuit the VCE for Q20 and Q23 looks as though it could get as high as 350 VDC, the 2N6214 has a VCE of 400V but might look to see if I can find something with a higher VCE to increase the safety margin.
Dropping in a higher voltage tranny also means lower current rating, lower hFE, weaker SOA so I would not do it.
The part should not see over 190V despite bias taken from the 300V rails.
I would consider
MJE15034 NPN TO-220 350V 4A, and PNP MJE15035.
Dropping in a higher voltage tranny also means lower current rating, lower hFE, weaker SOA so I would not do it.
The part should not see over 190V despite bias taken from the 300V rails.
I would consider MJE15034 NPN TO-220 350V 4A, and PNP MJE15035.
I got the 350V estimate from seeing that the base and emitters of Q20 and Q23 are bootstrapped to the amp output via L10, R85 and then a 10V Zener to each of Q20 and Q23. So at maximum amp output of 120V RMS the peak of each half cycle would be at 120V x 1.414 or around 170V, this is reduced by 10V by the 10V Zeners so that would give 160V at the base and emitter of Q20 or Q23 depending whether positive or negative half cycle of the amp output.
So with 160V at Base and Emitter plus the 190V on the Collector that is where I estimated that a VCE of 350 minimum is required. I could be reading the circuit wrong though
