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 Post subject: Realtone TR-970 --
PostPosted: Apr Sun 21, 2019 8:23 pm 
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Joined: Mar Wed 27, 2019 1:55 am
Posts: 8
Hello,

I've been troubleshooting a Realtone TR-970 and the MW oscillator is dead.

Fortunately, I have the excellent schematic and parts list.

The oscillator transistor tests as damage -- it's a 2SA153 PNP , according to the parts list, which matches the spec printed on the transistor.

According to the Radio Museum website this is a germanium diffused high-frequency transistor.

Question: Can I replace this PNP with a silicon 2N3906 PNP transistor intended for general purpose low-power amplifying, or do I need a replacement more specifically matched?

Thanks ...


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 Post subject: Re: Realtone TR-970 --
PostPosted: Apr Sun 21, 2019 11:38 pm 
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Joined: Aug Sat 16, 2014 2:19 am
Posts: 1317
Location: Palos Verdes, CA
I believe that the replacement transistor for a 2SA153 would be a NTE 126 transistor. - Mark


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 Post subject: Re: Realtone TR-970 --
PostPosted: Apr Mon 22, 2019 1:12 am 
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Joined: Mar Wed 27, 2019 1:55 am
Posts: 8
Thank you.


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 Post subject: Re: Realtone TR-970 --
PostPosted: Jun Sun 09, 2019 5:54 pm 
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Joined: Mar Wed 27, 2019 1:55 am
Posts: 8
Still working on the same radio.

I needed to replace the audio driver transistor, an NEC 2SB113 -- PNP germanium.

Can I replace with a general purpose silicon PNP 2N3906?

Thank you.

Richard


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 Post subject: Re: Realtone TR-970 --
PostPosted: Jun Sun 09, 2019 7:32 pm 
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Joined: Aug Sat 16, 2014 2:19 am
Posts: 1317
Location: Palos Verdes, CA
Richard - I checked the NTE website for a 2SB113 transistor, a NTE102A was a replacement. When I looked up a 2N3906 transistor, an equivalent NTE transistor could not be found, although it was listed as a general purpose transistor. Perhaps someone else will comment. Below is the NTE website:

https://www.nteinc.com/quickcross/


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 Post subject: Re: Realtone TR-970 --
PostPosted: Jun Sun 09, 2019 9:57 pm 
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Joined: Mar Wed 27, 2019 1:55 am
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Thank you.


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 Post subject: Re: Realtone TR-970 --
PostPosted: Jun Mon 10, 2019 12:55 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 32041
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The 2N3906 doesn't look like a good choice for an audio driver;

Quote:
The 2N3906 is a commonly used PNP transistor. It very much similar to the bc557 transistor except for that it has high collector to emitter voltage and hence high voltage loads can be toggled. This transistor has only a gain value of 300, hence not suitable for amplifier circuits.

https://components101.com/2n3906-pinout ... -datasheet

I looked in my 1980's ECG master replacement guide, and the sub they recommend for the 2SB113 is an ECG 102A, which would be the same part number as the NTE device.

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 Post subject: Re: Realtone TR-970 --
PostPosted: Jun Mon 10, 2019 4:31 am 
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Joined: Mar Wed 27, 2019 1:55 am
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Thank you.


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 Post subject: Re: Realtone TR-970 --
PostPosted: Jun Mon 10, 2019 6:20 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6418
Location: Black Hills, SD 57745
Cool radio! Three bands LW, MW, SW. Must be cramped inside. Lots of pics of it online, such as the one below I found, but I didn't get a peek inside one. Sounds like you've got a handle on getting it going, just a matter of subbing modern versions of the old Germaniums.
-Ed


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Realtone. -970jpg.jpg
Realtone. -970jpg.jpg [ 267.93 KiB | Viewed 247 times ]

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 Post subject: Re: Realtone TR-970 --
PostPosted: Jun Tue 11, 2019 8:43 pm 
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Joined: Mar Tue 12, 2019 6:09 am
Posts: 97
That pic is of one beat up Voyager! (TR-970)
This thing has been kicking around ebay for months now, don't know if it has been sold yet.
If you notice, a previous owner adapted a line cord to it.
The battery bay is stuffed with power supply bits, like a step down trafo, rectifier and filter capacitor.
I attached another pic from the auction.


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tr970a.png
tr970a.png [ 1.28 MiB | Viewed 210 times ]
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 Post subject: Re: Realtone TR-970 --
PostPosted: Jun Sat 15, 2019 1:02 am 
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Joined: May Sun 26, 2019 4:25 pm
Posts: 17
Here is what the gutz look like in an unmolested set.


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