obsolete transistor replacement

I'd think that any PNP power xistor with an adequate voltage rating would do - this is just a pass xistor wired as an EF isn't it?

David

Xref:

I know very little of transistors other than their basic function, so I don't know the answer to your question above.

As I noted, it's being used to (down)-regulate negative DC voltage. What might the reason have been to opt for this transistor over a regulator? There is a +5VDC regulator right next door in the same circuit.

Can I use the regulator in place of the transistor?

2SB527 PS TO125 110 v 90v 5v 2A 10WT 50minHFE Froms Towers Transistor Selector No freq. given.

There is also some crosses at

Also my page.

Maybe, maybe not. The 2V difference probably isn't critical, but we don't know how much current is being drawn. The 7815 is only good for around an amp with a big heatsink, (some variants 1.5 A), the 2SB527 is good for 2A. You could try one and measure the current, I doubt the current draw will be anywhere near 2A. You'll probably want a decent heatsink though, and to get closer to 13V you could bung 3 series diodes in the output of the regulator output to give 15-2.1=12.9V. Take care to use diodes rated higher than the current though, 1n400x might not be adequate. Again, they're only good for 1 Amp.

As for a replacement transistor, just about any power transistor of similar (or better) rating and similar physical size will do, it isn't critical in this application. You could use something in a TO220 package like a TIP42c which is a popular transistor here in the UK.

Dave

If the base is being driven by a 13.6V zener and the collector has 26V, then I'd expect a 13V output on the emitter.

---.--------.---------------------. -26V | | | | x | | x 5k6 | | x | | | |/ = 100uF .-----.--xxxx--------| | | | 470R |> do - this is just a pass xistor wired as an EF isn't it?

I forgot to list the USA/Euro equivalant, also in the Towers book.

2n5180 and Euro BD140

Type in BD140 in findchips.com

Most people would just use the NTEreplacement. I found a distributor who claims to sell this Towers International Transistor Selector from 1977 ??

greg

That's odd... I am finding all over the place on the net:

2SB527 TO220 110V 100V 0A8 10W 50minHFE 300maxHFE

That's 800mA rated, not 2A. Where did you get 2A rating?

Towers International Transistor Selector book.

2A max, 500ma hfe test.

I read again with magnifiers, thats TO126 package. Perhaps the orginator can identify which case?? TO220 or TO126 ??

Jordan"

The more I read the responses, the more confused I get. There appears to be literally hundreds of thousands of different transistors. They have various ratings including, but not limited to:

ECO EBO BCO Ic Ib hFE (min AND max) Pd in Watts

Which ones need I concern myself with? The various "cross-reference" pages all give different results when presented with search keywords. The most confusing term I see is hFE... I consulted a catalog (digikey) to try to get a handle on how these ratings correspond to each other, the various packages, etc. The "hFE" rating may jump from 25 to 1000 between a "40V,

1A" and a "60V, 2A" transistor. ???

What I mean is, without getting into the meat of transistor theory and operation (yeah, I know, I've got to go there sometime), is there a simple way for me to pick an "equal or greater value" transistor to replace my bad one? For example another poster suggested TIP42C as a replacement.

Here's how they stack up

Parameter 2SB527 TIP42C V(CBO) 100 100 V(CEO) 110 100 Ic 0.8A 6A Pd 10 10

I was all happy until I saw the hFE rating. This is a measure of transistor's gain. There was no absolute maximum gain given for the TIP42C, the value is "30" at 0.3A, so I'd imagine that might approach the value of "55" given as the absolute max on the 2SB527 as Ic approaches zero on the TIP42C.

Thanks a lot for your assistance so far, I think I'll rummage around a bit and see if I can scare up ANY PNP power transformer rated at >100V and >1A.

It's a TO-220 looking at it...

I'm still showing BD140 as a replacement for a 2SC527 TO126

Raising max current usually lowers HFE, so keep it near. As long as the voltages are above, don't worry too much unless your driving max current which stresses max voltage limits. Keep HFE rating near. Changing parameters too much may cause circuit opperation changes.Generally, higher voltage transistors have less current gain. Darlington's have a magnitude greater HFE's

greg

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AHHHH, I am seeking replacement of 2S_B_527, not 2S_C_527 as you note, above.

By "near", what do you mean. I looked at the hFE vs. DC amps for the TIP42C and it appears to range from about 20 to 100, whereas the 2SB527 is spec'ed at 55 to 300. Close enough? I can't find a curve for the 2SB527. The NTE292 looks pretty good too with hfe of 15 to 150.

Howdy Dave......I like your simple solution to use a 7915 from your junk box and in the process, simplifying your circuitry a little! Of course my first choice would have been something like a 7912 with a single gen purpose diode (1N4001 etc) inserted in the leg to ground to bump the reg voltage output up nearer to 13. With your 7915 you could likewise add a couple of similar diodes in series with the output to lower the voltage to your load.

Keep on tinkering.

Gord

I'd like to go the diode route as they are more readily available than any particular transistor. How would I wire them up as relates to my 7915 to drop (actually raise) the voltage by 2V to -13VDC?

Each diode has a voltage drop and I just string 'em together to add up to

2VDC and tie them from the output of the 7915 to ground? I always figured a diode was like a one-way resistor. Could I just use a resistor to ground to get rid of some of my voltage? And, if so, how do I size it if I don't know my current through the circuit? (I can't measure it, the transistor is dead). Trial and error is a laborious process.

How can a diode RAISE the voltage of a 7912 (I'll dig around, might have one somewhere)? Thanks a lot and pardon my ignorance.

Dave

Dave you wouldn't put the diodes from the 7915 output to ground but from the output to your load in series......being a negative polarity output you'd put the cathode towards the 7915 (and any additional diodes as well).

The trick to bumping up the voltage of a 3 terminal fixed regulator is to insert a diode between the ground pin and ground (keep in mind to insulate the tab if you do this!). The regulated voltage will now be pushed up by the junction voltage of the diode or diodes (Diodes placed as such in a 7912 would have their cathode face the ground pin.....anode to ground).

clear as mud?

You mentioned not knowing the load current Dave.....(with the limits that you could look up the max collector current and device dissipation for the old device and deduce a ballpark figure). The beauty of using the diodes is that they behave (when forward biased...within their normal operating range) as a somewhat-constant voltage drop despite current.....thus no big math for some quick trials.

Gord

We used to sub a 2sb633 which cost about a U.S. dollar. Chuck

If its a TO220 then its a TO220. I found my Japanese cross reference book. Here goes. Still a TO126

2SB527 SAN 2SB631 TOS 2SA815 NEC 2SA985 MAT 2SA1110 ROHM 2SB1085

A trouble may reside in you transistor manufacturer. You would have to look at the manufacturers spec sheet to get exact figures.

If you make a regulator with diodes, put some capacitance across the diodes.

greg