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Old 10th Aug 2019, 10:58 am   #1
jubilado
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Default Armstrong 626 transistor equivalents

Hi, as an absolute newbie I have been trying to improve (gain) some knowledge by "refurbishing" a couple of Armstrong 626 receivers.
I am currently looking to replace some components on the Z20 board and seeking guidance about replacing the transistors on there.

1. I have 2 circuit diagrams, (an early model and a late model) but both show a BC267 as one of the transistors. Is there a modern equivalent of this as I can't see this model on Farnell or RS sites or am I safe to buy from eBay?

2. The other transistor is shown as a 2N5294 on the early model and 16351 on the later. One of the two receivers I have is fitted with a 16351 and the other with TIP122 - are these equivalents?
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Old 10th Aug 2019, 12:56 pm   #2
Herald1360
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Default Re: Armstrong 626 transistor equivalents

BC267 is a run of the mill 50V 375mW NPN silicon transistor and can probably be replaced by anything similar.

Can't find 16351, it sounds like an RCA code but may be an in-house special. The plot then thickens- 2N5194 and TIP122 are very different- one's a NPN power transistor, the other a NPN power darlington (two cascaded transistors inside).

Have you got circuit information that might help pin things down? Are the circuit symbols the same or different?
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Old 10th Aug 2019, 1:30 pm   #3
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Default Re: Armstrong 626 transistor equivalents

Also, why do you want to replace these transistors? Are they faulty? If so, how have you determined that?
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Old 10th Aug 2019, 2:24 pm   #4
Maarten
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Default Re: Armstrong 626 transistor equivalents

Quote:
Originally Posted by Herald1360 View Post
BC267 is a run of the mill 50V 375mW NPN silicon transistor and can probably be replaced by anything similar.
375mW doesn't sound like much but the maximum current is 1A which is high for a small signal transistor.
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Old 10th Aug 2019, 5:26 pm   #5
jubilado
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Default Re: Armstrong 626 transistor equivalents

I have attached a circuit diagram for the area in which I am interested.

Why replace?
Well,
In one of the sets the 2N5294/16351 is replaced by the TIP122 which I was unsure about and the BC267 was a small black plastic transistor and the only BC267 I had seen were metal TO18 packages. Also the area of the board around this second transistor looks a bit "cooked"

In the other set, I was advised there was a problem with the power board and was looking to replace just about every component in a "Hope for the best" shotgun approach. (I did say I was a newbie at this). Also the BC267 on this board is a metal cam but marked what looks like BC77-7. This set has an RCA 16351 fitted.

I've just realised this thread is perhaps a bit specific for this topic - apologies to all.
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Old 10th Aug 2019, 5:47 pm   #6
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Default Re: Armstrong 626 transistor equivalents

Quote:
Originally Posted by jubilado View Post

In the other set, I was advised there was a problem with the power board and was looking to replace just about every component in a "Hope for the best" shotgun approach. (I did say I was a newbie at this). Also the BC267 on this board is a metal cam but marked what looks like BC77-7. This set has an RCA 16351 fitted.

l.



Seriously, please don't do that. You could easily introduce more faults.
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Old 10th Aug 2019, 5:52 pm   #7
jubilado
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Default Re: Armstrong 626 transistor equivalents

Quote:
Originally Posted by evingar View Post
Quote:
Originally Posted by jubilado View Post

In the other set, I was advised there was a problem with the power board and was looking to replace just about every component in a "Hope for the best" shotgun approach. (I did say I was a newbie at this). Also the BC267 on this board is a metal cam but marked what looks like BC77-7. This set has an RCA 16351 fitted.

l.



Seriously, please don't do that. You could easily introduce more faults.
Thanks for that advice. The brakes are now well and truly on!
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Old 10th Aug 2019, 6:49 pm   #8
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Default Re: Armstrong 626 transistor equivalents

The circuit helps.... it shows the 16351 as a simple transistor, though quite possibly a TIP122 darlington would work. There might be more likelihood of it oscillating perhaps.

The BC267 needs its voltage and dissipation ratings but can't pull more than 40mA in the circuit so the 1A current rating is less important. 2N5294 looks fine though other NPN power devices of similar ratings like TIP41B would also be fine.
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