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 Post subject: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 14, 2018 4:46 am 
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Joined: Dec Tue 08, 2015 12:53 am
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Location: shirley NY...Long Island
Hello...is there a good replacement for the 2SA70 transistor???

I know I can buy them, or it online, I was curious about it..

I have a Sony..a TR-911 that once in a while the volume gets lower, and I either lightly tap on the trans....or take a lighter and warm a screwdriver and touch it on the case of the trans..I believe it is the Mixer trans X2...not sure.

I could show a location pic if someone needs it


Thanks All ........Kenny KE4HVE


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 14, 2018 5:42 am 
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Location: Rayleigh, BC, CANADA
That's one of those TO-7 packages where the fourth lead is tied to the case for shielding.

read somewhere they were often prone to failure.

I used to have some AF117 that were good subs for that application.

you can still get them: https://www.ebay.com/itm/2SA70-Original ... 2218222960


Attachments:
2sa70.jpg
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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 14, 2018 5:50 am 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 3261
Location: The Old Dominion VA 23518
Follow Sony's recommendation: Use a 2SA341.

https://www.ued.net/ued/viewItemAction. ... e=SNY2SA70 But, NLA from Union (who list ALL Sony parts, regardless of age!)

2Sa341's:

http://talonelectronics.com/shop/item.aspx?itemid=1269

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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 14, 2018 11:55 am 
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Posts: 20
Another good replacement is the OC170. It's easy to obtain, and has the same pin-out and case style to maintain appearance (if that's important to you).


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 14, 2018 6:54 pm 
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Joined: Dec Tue 08, 2015 12:53 am
Posts: 391
Location: shirley NY...Long Island
$17 plus shipping...I dont think that is right...I can see maybe 8-10$

Does anyone think the 2SA455, 456 will work???

Yea yea I know, if I want to get it fixed it doesn't matter the cost..

KNY


Last edited by Kennynva on Sep Fri 14, 2018 7:21 pm, edited 1 time in total.

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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 14, 2018 7:18 pm 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 3261
Location: The Old Dominion VA 23518
Kennynva wrote:
$17 plus shipping...I dont think that is right...I can see maybe 8-10$

Yea yea I know, if I want to get it fixed it doesn't matter the cost..

KNY


Not sure what you are referring to with the $17 (I posted the one where they are 2 bucks, not sure on shipping.....)

And I thought I'd share some more Sony suggested replacements for the 2SA germanium types:
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Sony2.jpg
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Sony.jpg
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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Sun 16, 2018 4:27 am 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 4171
Location: Sunnyvale CA
Kennynva wrote:
Hello...is there a good replacement for the 2SA70 transistor???

I know I can buy them, or it online, I was curious about it..

I have a Sony..a TR-911 that once in a while the volume gets lower, and I either lightly tap on the trans....or take a lighter and warm a screwdriver and touch it on the case of the trans..I believe it is the Mixer trans X2...not sure.

I could show a location pic if someone needs it


Thanks All ........Kenny KE4HVE



A Russian NP416a should work, or an NTE160. This application is particularly undemanding. I am at least a little skeptical that the transistor is the issue, I would look at intermittent soldering or cracked traces, but you could be right. Usually, when they short out from tin whiskers, they just don't work at all.

Brett


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Thu 27, 2018 6:14 pm 
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Joined: Dec Tue 08, 2015 12:53 am
Posts: 391
Location: shirley NY...Long Island
I was refering to Findm-Keepm who linked me to this..

https://www.ued.net/ued/viewItemAction. ... e=SNY2SA70





Thanks to all that helped...I did not see or answer this thread until today..and sorry it took so long..

Kenny KE4HVE


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 28, 2018 5:13 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 10357
Location: Powell River BC Canada
Sansui recommends forward substitution for 2SA70 as 2SA440 A

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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 28, 2018 4:14 pm 
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Joined: Mar Tue 03, 2009 11:12 pm
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Location: Hutchinson KS
I know I'm going to catch flak for this but often times a silicon transistor with similar specs will work with out any other changes being made. In low power devices such as transistor radios, what can it hurt?


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 28, 2018 5:51 pm 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 10357
Location: Powell River BC Canada
From what I remember radios using the 2SA70 often had resistors that had
starred values, that needed tweaking after transistors were replaced.

You could make the radio deaf as a post, or squealy in the extreme.
See R25 below. ~~ 50 years ago

Attachment:
8TP902SUPER8.jpg
8TP902SUPER8.jpg [ 211.12 KiB | Viewed 522 times ]
.

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Amateur Radio Literacy Club. May we help you read better.
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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Fri 28, 2018 11:48 pm 
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Joined: Aug Mon 03, 2015 2:54 am
Posts: 321
Location: Knoxville, Tennessee, USA
Findm-Keepm: Would you be so kind as to post that Sony Semiconductor Replacement Manual to a drop box site - or post the url to download it? I'd appreciate a copy :)


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Sat 29, 2018 12:25 am 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 3261
Location: The Old Dominion VA 23518
KnobDial wrote:
Findm-Keepm: Would you be so kind as to post that Sony Semiconductor Replacement Manual to a drop box site - or post the url to download it? I'd appreciate a copy :)


With 370 pages to scan, no way it's possible for me. They show up on eBay occasionally - 1981 and 1986 are the two publication years. '81 and 86 both have a supplement - the last version I saw on eBay was the '81 supplement. As to my copy, I got from Sony for $32 in 1992 when their CXA-series VCR chips were popular (and had generic replacements :wink: ). It came with a 1990-issued thin supplement that I can't find - lost in a mid-summer move years ago.

If you ever need a suggested replacement, just ask - I'm happy to provide that info piecemeal, free. It only includes the Sony-suggested replacements, like the A341 for the A70, above. There are broader, Japan-published transistor sub manuals -I have those too, the whole series, Diode, Fet, Transistor Data, and Transistor Sub. MCM sold them for about 29 dollars or so as a set, or 9 dollars separately. They too have multiple publication years - 83, 87, 91, 92, and 94. I have the '87 and 92 versions, supplied in the same purchased set. Here's the '92 Transistor spec manual:

https://www.ebay.com/itm/1992-CQ-Transi ... SwstxU2Tjr

Not mine, no affiliation, yada, yada, yada.

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"Capacitor Cosmetologist since 1979"
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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Sat 29, 2018 12:40 am 
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I've found intermittent/noisy germanimium osc transistors can be sensitive to supply voltage. Couple months back I had one that played fine on slightly weak batteries, but dropped out with fresh ones.

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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Sat 29, 2018 12:50 am 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 3261
Location: The Old Dominion VA 23518
As an oh-by-the-way, Union Electronics Distributors also lists the Sony-Suggested replacements - my sampling suggests all the transistors listed in the guide are also on their website:

UED.net - under "parts lookup"

The 2SA70 page: https://www.ued.net/ued/viewItemAction. ... e=SNY2SA70

The 2SA163 page: https://www.ued.net/ued/viewItemAction. ... =SNY2SA163

Works for other brands too - the ubiquitous 2SC564 Panasonic transistor (FAILS miserably, lists PNP subs.... :shock: :
https://www.ued.net/ued/viewItemAction. ... =MSC2SC564

They used to have tons of transistors, bias diodes and the like, but one or two posts over on RepairWorld caused a run on their parts back in the early 2000s.

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"Capacitor Cosmetologist since 1979"
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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Sat 29, 2018 2:55 am 
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Joined: Aug Mon 03, 2015 2:54 am
Posts: 321
Location: Knoxville, Tennessee, USA
Findm-Keepm wrote:
With 370 pages to scan, no way it's possible for me.

My misunderstanding, sorry, somehow I thought you had a digital copy.

Book scanning is a market niche just waiting for someone to exploit: it'd be nice to slide a closed book into a slot, a jump drive into another slot, press a button and walk away with a scanned book. Jus' wishin'.


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Sat 29, 2018 4:34 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 10357
Location: Powell River BC Canada
I have a page reading machine. It is the size of a washing machine.
It has a track with 4 small spotlights that scan the page. I think it uses
an 8080 processor. It outputted ascii . Seems like a large number of
dip chips.
Junk now. Junk when I got it.

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Steve Dow
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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Sun 30, 2018 4:42 pm 
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Joined: Dec Tue 08, 2015 12:53 am
Posts: 391
Location: shirley NY...Long Island
Well...it was, is, a good thread, and as many times that I have worked on radio's, all types, the problem with this radio, seems to be.....................A SOLDER JOINT...

The prize, or the star goes to.......Brett_Buck
He was right so far....thanks Brett...

I checked these joints before, and it would stop working when the transistor was pushed, and the solder joint is right under the transistor, BUT, so far it was a solder joint on a part right next to the transistor..but it was fun, and I learned alot from all the post.

Now it is on to the BUSH radio, when it comes in...gotta go thru the entire radio...

Kenny KE4HVE


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Sep Sun 30, 2018 10:24 pm 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 4171
Location: Sunnyvale CA
Kennynva wrote:
Well...it was, is, a good thread, and as many times that I have worked on radio's, all types, the problem with this radio, seems to be.....................A SOLDER JOINT...

The prize, or the star goes to.......Brett_Buck
He was right so far....thanks Brett...


I will PM my address to send the giant novelty check!

Brett


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 Post subject: Re: A replacement for a 2SA70 germanium transistor..PNP
PostPosted: Oct Mon 01, 2018 5:17 am 
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Posts: 12703
Location: Omak,wa,usa
Hello guys,
yep I also had some issues


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