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 Post subject: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Feb Tue 25, 2020 3:08 am 
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A few years ago, I bought a Raytheon 8TP-2 transistor radio that was for sale on eBay that the seller said it did not work. I could see that one of the transistors was missing and the rest had been replaced, with the exception of one Raytheon transistor. When I got the radio and removed the chassis from the case, I found out that someone had replaced all of the transistor sockets! The new transistors were the correct type, so I had a NTE100 transistor to replace the missing Raytheon CK760 and was disappointed when all I got was static. I tried replacing all the transistors with other transistors that I had collected over the years, but could not get the Raytheon 8TP to work. I was looking for parts for another radio today and found that I had a Lafayette 6 transistor radio in poor condition, but it had GE plug-in transistors. I tried the GE transistors that could replace the CK760, but all I still got was static. There were also 2 GE 2N188A transistors in the Lafayette, but these were equivalent to a NTE102 transistor. Figuring that I had nothing to lose, I plugged-in the 2N188A transistor and to my surprise, the Raytheon 8TP-2 worked great! Since the radio now works, it would be nice if I could find all the original type blue Raytheon transistors, but they would probably cost more than what I paid for the radio originally!


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Raytheon 8TP-2 transistor radio.JPG
Raytheon 8TP-2 transistor radio.JPG [ 98.58 KiB | Viewed 3792 times ]
Raytheon 8TP-2 transistor radio 2.JPG
Raytheon 8TP-2 transistor radio 2.JPG [ 112.64 KiB | Viewed 3792 times ]
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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Feb Tue 25, 2020 6:02 am 
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Congrats on getting it working again, and interesting that it does so with the original paper caps, of which there seem many!

You can probably eventually get the blue Raytheon's by keeping an eye on eBay, and acquiring them one by one over time. The only trouble is, Germanium Transistors can eventually start giving up the ghost as they age.

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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Feb Tue 25, 2020 11:45 pm 
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I checked the serial number of the Raytheon 8TP-2 with the replaced transistor sockets and it probably had the black Raytheon CK718 transistors that I believe were soldered into the sockets as I have another 8TP-2 with a later serial number that also has the black transistors. The previous owner could have tried to replace some of the transistors and ended up damaging the sockets and then decided to replace them.


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Feb Wed 26, 2020 12:23 am 
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fifties wrote:
Congrats on getting it working again, and interesting that it does so with the original paper caps, of which there seem many!

You can probably eventually get the blue Raytheon's by keeping an eye on eBay, and acquiring them one by one over time. The only trouble is, Germanium Transistors can eventually start giving up the ghost as they age.



No they don't. Under poor storage conditions, maybe, but so will a tube or silicon transistor for that matter. Corrosion will start on the leads.


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Feb Wed 26, 2020 4:30 am 
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n3uvt wrote:
fifties wrote:
Congrats on getting it working again, and interesting that it does so with the original paper caps, of which there seem many!

You can probably eventually get the blue Raytheon's by keeping an eye on eBay, and acquiring them one by one over time. The only trouble is, Germanium Transistors can eventually start giving up the ghost as they age.



No they don't. Under poor storage conditions, maybe, but so will a tube or silicon transistor for that matter. Corrosion will start on the leads.

Yes they will. It happened to more than one Transistor I've had since the '50's. I've heard that they grow tin whiskers inside.

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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Feb Wed 26, 2020 5:09 am 
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Hey Mark,

Glad you got it working ! Am surprised that the 2N188A audio transistor worked well as the converter/mixer as that stage is often finicky in some sets... May have to try one in mine out of curiousity !

John


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Feb Wed 26, 2020 8:05 pm 
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John - I looked at my notes when I purchased the Raytheon 8TP-2 and found that it was missing the CK-759 (converter transistor) and the CK-760 (IF amp transistor). I originally used NTE-100 transistors as replacements, but only got static. The transistor sockets that the previous owner used had 5-pin sockets, except for the converter and oscillator transistors, which only had 3 pins. Having sockets made it easier to replace the transistors, but I did break-off one of the leads off a spare Raytheon CK-760 transistor, which made me decide not to remove Raytheon transistors from other radios I own in an attempt to get the 8TP-2 working. - Mark


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Feb Wed 26, 2020 9:00 pm 
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Glad you got it working.


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Mar Mon 23, 2020 1:34 am 
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I have another Raytheon 8TP-2 7 transistor radio and although the label says that the radio uses CK721 transistors, the 1st audio amp was changed to a Raytheon 2N133, with the 2nd audio amp using a 2N130, with both audio output transistors using 2N138 transistors, all which are the smaller blue Raytheon transistors. This Raytheon 8TP-2 does perform better than the radio using the CK721 transistors. - Mark


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Mar Mon 23, 2020 2:37 am 
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Only a few type grew tin whiskers, none were US made as far as i know. I do have some bad ones i saved but i forget what the failure was. I very much doubt tin whiskers was the major failure mode. Most likely a poor seal or corroded leads going into the case.
https://nepp.nasa.gov/whisker/anecdote/ ... index.html

As i said, storage conditions are probably the main factor in them not working.


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Aug Mon 10, 2020 5:39 pm 
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I've been looking on eBay for transistors so I could get my Raytheon 8TP back to original configuration and saw a seller with a number of old transistors:

https://www.ebay.com/itm/Very-old-Rayth ... Swx~FfJs39

As there was a CK-716 in the collection for sale, I figured the winning bid would be high, but was surprised at the outcome!


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Aug Tue 11, 2020 1:04 am 
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WOW..... I never would have thought they would go for that much.

Al

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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: Oct Tue 06, 2020 8:09 pm 
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After installing 2 Raytheon CK718 transistors into the 8TP-2, performance increased significantly during the day, but found that reception at night is poor. I have another Raytheon 8TP that has all blue transistors and it doesn't have a problem tuning in stations in the evening and probably why Raytheon replaced the black CK721 transistors used previously. - Mark


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: May Thu 12, 2022 2:10 am 
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I was able to purchase some Raytheon CK721 transistors and found that my Raytheon 8TP now works quite well. I even put back the Raytheon CK718 transistors and now only need a CK759 and CK760 to have all the transistors be made by Raytheon.


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Raytheon 8TP with Raytheon transistors.JPG
Raytheon 8TP with Raytheon transistors.JPG [ 588.6 KiB | Viewed 322 times ]
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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: May Thu 12, 2022 1:26 pm 
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n3uvt wrote:
fifties wrote:
The only trouble is, Germanium Transistors can eventually start giving up the ghost as they age.



No they don't. Under poor storage conditions, maybe, but so will a tube or silicon transistor for that matter. Corrosion will start on the leads.

Yes they fail, especially Sylvania ovals of the 50s. Been my experience after setting unused 50+ years, even the good ones will become leaky or open in just a few hours usage.

Norm Leal says due to impurities in the material, eventually all the germanium xistors will fail.

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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: May Fri 13, 2022 9:02 pm 
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The 4-pin transistors in the Zenith TO-3000 were known for tin whisker problems due to the case being grounded through one of the pins. Just fold over or snip that pin and that may "fix" it.

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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: May Sat 14, 2022 2:19 am 
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"The only trouble is, Germanium Transistors can eventually start giving up the ghost as they age."

I don't believe this. I have a few thousand NOS 60'S dated and i use them building guitar fuzz pedals and i have no problem.


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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: May Sat 14, 2022 7:18 am 
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HALLI wrote:
"The only trouble is, Germanium Transistors can eventually start giving up the ghost as they age."

I don't believe this. I have a few thousand NOS 60'S dated and i use them building guitar fuzz pedals and i have no problem.

In fairness, he posted, "they can", not, "they will". I have a few score '50's radios, none of which have displayed this problem, other than maybe 2-3 converter Transistors I've had to replace.

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 Post subject: Re: Raytheon 8TP-2 with replaced transistor sockets
PostPosted: May Sun 15, 2022 2:17 am 
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The tin whiskers issue seems to be confined to the four-leaded AF1xx series RF transistors from the 1960's.
I have seen some mid 1950's transistors go bad for seemingly no good reason, in particular Sylvania's audio output transistors (like the 2N214). The usual issue is extreme leakage.

Raytheon's early plastic encapsulated transistors tend to be bad as well, especially ones where the glass base has cracked, which I have seen a few times myself. I would speculate that reliability issues are what drove them to use more expensive sealed metal packages.


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