Transistor Equivalents - UK Vintage Radio Repair and Restoration Discussion Forum

EdGizzard · 19th Sep 2023, 2:28 pm

Hi All,

Can't find any info on this Transistor. See attached. 109A

Any thoughts of equivalents or where buy?

Thanks Guys

paulsherwin · 19th Sep 2023, 2:35 pm

That looks like a house code. Are the other transistors on the board the same? If so, remove another one and do some basic checks on it. You should be able to decide between NPN/PNP and the gain band that way.

If it's NPN, one of the standard jellybeans will probably be OK - 2N2222, 2N3904, BC547, whatever you have handy.

Jez1234 · 19th Sep 2023, 2:46 pm

There is a J109 FET but I don't think there is a version with an A suffix. It could well be a house code.

EdGizzard · 19th Sep 2023, 2:49 pm

Thanks so much Paul,

Looking at CD they all (4 of this type) appear to be PNP. Unfortunately it doesn't give the transistor type. Just a symbol.

paulsherwin · 19th Sep 2023, 2:49 pm

The leads are marked EBC which strongly suggests bipolar, though it's not a guarantee of course.

If it's PNP then just try an appropriate jellybean - 2N3906, BC557, BC327 etc. It's unlikely to be critical.

What is the PCB doing?

Station X · 19th Sep 2023, 2:50 pm

What's it installed in?

G6Tanuki · 19th Sep 2023, 3:00 pm

109A could be BC109A??

Not sure about the manufacturer but in the past it was not unusual for manufacturers to use their initials in place of parts of the type numbers, I have a number of 2N3055 here marked RCA3055 for example.

EdGizzard · 19th Sep 2023, 3:16 pm

Thanks All,

Its generates the bass in an electric organ. This PCB does Vibrato also but that's a different part on the board. I'm Feeling NPN the more I look at it. There are a few variations of these organs. My CD is for another variation so can only be used as a guide really. Thanks Guys

paulsherwin · 19th Sep 2023, 3:26 pm

It's very unusual for designers to use predominantly PNP transistors as these used to cost more - not sure if that's still the case.

I guess it could be a BC109A in a TO92 package, though that would also be unusual.

Aub · 19th Sep 2023, 3:29 pm

That M looks a bit like a smudged Motorola symbol?

Aub

paulsherwin · 19th Sep 2023, 3:32 pm

Motorola did use house codes a lot at one time.

Jez1234 · 19th Sep 2023, 4:59 pm

Quote:

Originally Posted by paulsherwin

The leads are marked EBC which strongly suggests bipolar, though it's not a guarantee of course.

If it's PNP then just try an appropriate jellybean - 2N3906, BC557, BC327 etc. It's unlikely to be critical.

What is the PCB doing?

Ah yes well spotted!

Maarten · 19th Sep 2023, 7:02 pm

Often the most important clue is, the brand and type of the equipment (organ).

Motorola, might be a BC109A equivalent seems the best that can be done without context.

Sideband · 19th Sep 2023, 7:36 pm

Quote:

Originally Posted by Aub

That M looks a bit like a smudged Motorola symbol?

Aub

I was going to suggest the same....certainly looks Motorola-ish.

llama · 22nd Sep 2023, 10:17 am

Is the equipment faulty (in that area)?
If working, or a similar board is working, it could be worth noting its voltages for future reference, to help identify the part, or to fault-find if/when it stops working.
Graham

Maarten · 23rd Sep 2023, 10:26 am

Besides the brand and type of the organ, other context that might contain clues, are the country it was made in (Italy? UK?) and numbers on other transistors (Motorola but also other brands if used) to establish if there's a system to it.

Richardgr · 23rd Sep 2023, 3:43 pm

I was looking fr some equivalents recently and found this useful old dcument from 1981 ...
Bernards bp85-international-transistor-equivalents-guide.pdf

There was one hit containing 109a, a National Semiconductor device.

Oldmadham · 26th Sep 2023, 1:38 am

Manufacturers like to reduce their inventories and often use the same transistor in critical & non-critical positions.
If one of the same type is doing some "grunt" work like turning on an indicator LED, steal that one for the critical spot, & replace the "LED driver" with a "jelly bean" component.

19th Sep 2023, 2:28 pm	#1
EdGizzard Tetrode Join Date: Mar 2022 Location: London, UK. Posts: 59	Transistor Equivalents Hi All, Can't find any info on this Transistor. See attached. 109A Any thoughts of equivalents or where buy? Thanks Guys Attached Thumbnails

19th Sep 2023, 2:35 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,160	Re: Transistor Equivalents That looks like a house code. Are the other transistors on the board the same? If so, remove another one and do some basic checks on it. You should be able to decide between NPN/PNP and the gain band that way. If it's NPN, one of the standard jellybeans will probably be OK - 2N2222, 2N3904, BC547, whatever you have handy.

19th Sep 2023, 2:46 pm	#3
Jez1234 Banned Join Date: Mar 2021 Location: Morpeth, Northumberland, UK. Posts: 936	Re: Transistor Equivalents There is a J109 FET but I don't think there is a version with an A suffix. It could well be a house code.

19th Sep 2023, 2:49 pm	#4
EdGizzard Tetrode Join Date: Mar 2022 Location: London, UK. Posts: 59	Re: Transistor Equivalents Thanks so much Paul, Looking at CD they all (4 of this type) appear to be PNP. Unfortunately it doesn't give the transistor type. Just a symbol.

19th Sep 2023, 2:49 pm	#5
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,160	Re: Transistor Equivalents The leads are marked EBC which strongly suggests bipolar, though it's not a guarantee of course. If it's PNP then just try an appropriate jellybean - 2N3906, BC557, BC327 etc. It's unlikely to be critical. What is the PCB doing?

19th Sep 2023, 2:50 pm	#6
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 20,660	Re: Transistor Equivalents What's it installed in? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

19th Sep 2023, 3:00 pm	#7
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,461	Re: Transistor Equivalents 109A could be BC109A?? Not sure about the manufacturer but in the past it was not unusual for manufacturers to use their initials in place of parts of the type numbers, I have a number of 2N3055 here marked RCA3055 for example. __________________ I played a blank tape at full volume. The mime-artiste who lives next door complained.

19th Sep 2023, 3:16 pm	#8
EdGizzard Tetrode Join Date: Mar 2022 Location: London, UK. Posts: 59	Re: Transistor Equivalents Thanks All, Its generates the bass in an electric organ. This PCB does Vibrato also but that's a different part on the board. I'm Feeling NPN the more I look at it. There are a few variations of these organs. My CD is for another variation so can only be used as a guide really. Thanks Guys

19th Sep 2023, 3:26 pm	#9
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,160	Re: Transistor Equivalents It's very unusual for designers to use predominantly PNP transistors as these used to cost more - not sure if that's still the case. I guess it could be a BC109A in a TO92 package, though that would also be unusual.

19th Sep 2023, 3:29 pm	#10
Aub Octode Join Date: Mar 2005 Location: Nuneaton, Warwickshire, UK. Posts: 1,971	Re: Transistor Equivalents That M looks a bit like a smudged Motorola symbol? Aub __________________ Life's a long song, but the tune ends too soon for us all.

19th Sep 2023, 3:32 pm	#11
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,160	Re: Transistor Equivalents Motorola did use house codes a lot at one time.

19th Sep 2023, 7:02 pm	#13
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,062	Re: Transistor Equivalents Often the most important clue is, the brand and type of the equipment (organ). Motorola, might be a BC109A equivalent seems the best that can be done without context.

22nd Sep 2023, 10:17 am	#15
llama Octode Join Date: Jun 2006 Location: St Osyth, Nr Clacton, Essex, UK. Posts: 1,476	Re: Transistor Equivalents Is the equipment faulty (in that area)? If working, or a similar board is working, it could be worth noting its voltages for future reference, to help identify the part, or to fault-find if/when it stops working. Graham __________________ Half my stuff is junk - trouble is, I don't know which half!

23rd Sep 2023, 10:26 am	#16
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,062	Re: Transistor Equivalents Besides the brand and type of the organ, other context that might contain clues, are the country it was made in (Italy? UK?) and numbers on other transistors (Motorola but also other brands if used) to establish if there's a system to it.

23rd Sep 2023, 3:43 pm	#17
Richardgr Heptode Join Date: Oct 2019 Location: Täby, Sweden Posts: 541	Re: Transistor Equivalents I was looking fr some equivalents recently and found this useful old dcument from 1981 ... Bernards bp85-international-transistor-equivalents-guide.pdf There was one hit containing 109a, a National Semiconductor device.

26th Sep 2023, 1:38 am	#18
Oldmadham Pentode Join Date: Sep 2019 Location: Perth, Western Australia, Australia. Posts: 171	Re: Transistor Equivalents Manufacturers like to reduce their inventories and often use the same transistor in critical & non-critical positions. If one of the same type is doing some "grunt" work like turning on an indicator LED, steal that one for the critical spot, & replace the "LED driver" with a "jelly bean" component.