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 Post subject: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Sat 08, 2020 7:32 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6351
Location: Indianapolis, IN
Hello All,

Since it's the second consumer transistor radio (and first from Raytheon) ever made, had been looking for an "affordable" Raytheon 8TP project set for awhile without success and recently thought of Bob McGarrah and the excellent web-site he once had online that contained a great article on these radios. I found his site many years ago while searching for info on my RCA 9-TX-2 which he also had an example of and discovered he was from the same small town in Illinois (Canton) as my Mom & Dad. We corresponded several times via e-mail at that time discussing radios and families. Decided to locate and contact him and see if he might have an extra Raytheon 8TP "project set" stashed away. He responded and sent pics of a nice looking 8TP-4 with an untouched original chassis, but having battery leakage damage at bottom edge of cabinet back and a decent 8TP-2 cabinet with parts he stripped from a badly corroded chassis he discarded. His suggestion was to transfer the good chassis to 8TP-2 cabinet, but I now wanted to keep the 8TP-4 together as I'd grown to really like the "flashy" red & black style. Was thinking of making an attempt to fabricate a chassis for the 8TP-2 since all critical parts except transistors were in "package", but now would like to find a junked original to try and refurbish to keep set as close to stock as possible...

I stopped by Bob's place near Peoria to purchase radios while en-route to visit Cousin's farm . The price was fair reflecting current market value and am in process of selling some items to fund my "extravagance". Had a great conversation and really enjoyed seeing and discussing his excellent collections.

After returning home, I applied power and only got a fairly loud "hiss" at all volume levels with no reception. Pulled the untouched chassis and saw that it had a 2 uF, ceramic-encased IEI audio coupling cap at volume ctl. Used clip leads to bridge it with new part. Hiss decreased a bit and could somewhat receive strong local. Swapped the socketed transistors in front end with "once NOS" CK760's I had in my stash and could now receive a couple locals after alignment, though very distorted. Got out signal tracer and the signal sounded fine at output of detector and could actually hear a few other stations now while tuning. The voltages were off on both pre-amp & driver transistors, so very carefully desoldered two of each of their leads to disable. Resistors measured fine. Used clip leads to connect two good RCA 2N408 transistors in their place and had same distortion and bad voltage readings ! Bridged all other electrolytics with new parts using test leads and no noticeable change whatsoever. Then looking closer at the schematic, wondered about the biasing ! Carefully reattached and soldered leads of original transistors and connected a 10K pot in series with a 470 Ohm resistor between base of driver and -5V rail---adjusted for best sound quality which occurred around -.6V. Audio now near normal with little distortion ! Measured total resistance which was close to 560 Ohm and installed fixed 1/4W resistor. The pre-amp bias was closer and used a 39K resistor in series with pot to determine needed resistance of 43K for clearest audio. Much of the hiss was now also gone. Would sure like to understand exactly what had happened to transistors to cause the need for re-biasing ! Carefully removed one lead of the original audio coupling cap from center volume ctl terminal and covered it with short piece of snug fitting teflon insulation before installing new part. All repairs were carefully and neatly made so that they could be easily removed to return this historic radio's chassis back to original state. Since bridging the other electrolytics had no effect on performance or AGC action, am leaving them untouched.

The cabinet was pretty clean as purchased, but detail cleaned all surfaces including trim edges (where dirt had accumulated) with water-dampened, then dry soft cotton cloth pieces. Used nothing more on leather which would affect original appearance. There was a thin layer of dried battery leakage residue on area of inside bottom of cabinet and it took a couple hours of very careful cleaning using small pieces of paper towel folded and clamped in tip of hemostats with Windex to remove it. Used toothbrushes with dishwashing liquid solution on knobs being very gentle around the numbers and lettering.

The date stamped on inside of cabinet is: Jun 16, 1955

Still need to seal the cabinet bottom wood damaged by the leakage as everywhere I set the radio, it "deposits" a small amount of fine black powder---will probably use thinned clear shellac...

And am now on the hunt for a junked chassis so that the 8TP-2 can be rebuilt !

Project pics below in two groups---the last one shows radio with red 1958 Western Electric 500 phone (thought they looked good together)...

How many out there have one of these historic radios ? Know that Bill & Mark do...

John


Attachments:
01ARF 8TP4 LABEL.jpg
01ARF 8TP4 LABEL.jpg [ 554.26 KiB | Viewed 638 times ]
02ARF 8TP4 CHS BOT BOT.jpg
02ARF 8TP4 CHS BOT BOT.jpg [ 489.46 KiB | Viewed 638 times ]
03ARF 8TP4 CHS BOT TOP.jpg
03ARF 8TP4 CHS BOT TOP.jpg [ 502.97 KiB | Viewed 638 times ]
04ARF 8TP4 CHS BOT.jpg
04ARF 8TP4 CHS BOT.jpg [ 726.52 KiB | Viewed 638 times ]
05ARF 8TP4 CAB INS CLN.jpg
05ARF 8TP4 CAB INS CLN.jpg [ 496.57 KiB | Viewed 638 times ]
06ARF 8TP4 SPKR SHRD CHS SCRWS.jpg
06ARF 8TP4 SPKR SHRD CHS SCRWS.jpg [ 372.98 KiB | Viewed 638 times ]
07ARF 8TP4 HNDL PRTS KNBS CLN.jpg
07ARF 8TP4 HNDL PRTS KNBS CLN.jpg [ 244.97 KiB | Viewed 638 times ]
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 Post subject: Re: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Sat 08, 2020 7:44 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6351
Location: Indianapolis, IN
Below are the remainder of projects pics---please see previous post for first group...


Attachments:
08ARF 8TP4 CAB TOP B4 KNBSLABEL.jpg
08ARF 8TP4 CAB TOP B4 KNBSLABEL.jpg [ 404.37 KiB | Viewed 637 times ]
09ARF 8TP4 CMPLT TOP.jpg
09ARF 8TP4 CMPLT TOP.jpg [ 449.71 KiB | Viewed 637 times ]
10ARF 8TP4 CMPLT REAR CVR INS.jpg
10ARF 8TP4 CMPLT REAR CVR INS.jpg [ 817.92 KiB | Viewed 637 times ]
11ARF 8TP4 FRT W-BK CVR.jpg
11ARF 8TP4 FRT W-BK CVR.jpg [ 726.02 KiB | Viewed 637 times ]
12ARF 8TP4 CMPLT INS.jpg
12ARF 8TP4 CMPLT INS.jpg [ 632.64 KiB | Viewed 637 times ]
13ARF 8TP2 BASKET CASE.jpg
13ARF 8TP2 BASKET CASE.jpg [ 711.62 KiB | Viewed 637 times ]
14ARF 8TP4 HOLLOW-8TP2.jpg
14ARF 8TP4 HOLLOW-8TP2.jpg [ 354.78 KiB | Viewed 637 times ]
15ARF 8TP4 CMPLT REAR ANG.jpg
15ARF 8TP4 CMPLT REAR ANG.jpg [ 697.8 KiB | Viewed 637 times ]
16ARF 8TP4 CMPLT FRT.jpg
16ARF 8TP4 CMPLT FRT.jpg [ 644.8 KiB | Viewed 637 times ]
17ARF 8TP4 58WE500.jpg
17ARF 8TP4 58WE500.jpg [ 366.61 KiB | Viewed 637 times ]
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 Post subject: Re: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Sat 08, 2020 8:40 am 
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Joined: Jan Thu 16, 2020 12:29 am
Posts: 292
Wow !

What a great radio, and your attitude and the approach to the problem of restoring it is equally impressive.


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 Post subject: Re: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Sun 09, 2020 6:30 am 
Member

Joined: Dec Wed 16, 2015 10:31 pm
Posts: 266
Location: Toronto ON
Hi John:

I have one that looks okay at a glance, but has some issues. I haven't shown it in my thread as it is still a work in progress.
You'll notice that the speaker has been changed as well as a couple of the transistors. I have a good CK760 for one but have yet to come across a blue CK721 that won't break the bank. I've repro'd the pull tab on the rear panel as it was nothing but a rivet, and the handle needs a 'skin graft' at one end. It has some corrosion on battery contacts and rust nearby on the chassis, evidently from a battery spill. Much of the stitching on the outside is either worn or missing completely. I don't see a way to remove and re-stitch without making a mess so that will probably never happen. The cabinet was made on the very same day as yours!

Joe


Attachments:
8TP2 front.JPG
8TP2 front.JPG [ 367.77 KiB | Viewed 554 times ]
8TP2 inside.JPG
8TP2 inside.JPG [ 381.21 KiB | Viewed 554 times ]
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 Post subject: Re: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Sun 09, 2020 5:51 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6351
Location: Indianapolis, IN
Thanks much, ACORNVALVE !

Joe---Really neat that the cabinet was made on same day as mine and both are pictured in this same ARF thread ! What are the chances of something like that happening ?

The CK721 for the pre-amp was probably black like the other three as in mine, but probably still difficult to find.

I agree, the very thin leather would probably fall apart if you tried to remove from cabinet. Have been thinking of modifying the "eye" of appropriate size sewing needle by grinding it down to a shallow "[" and using that to grip and push new thread into holes after very carefully inserting a tiny drop of clear drying glue---would be very tedious and time-consuming as you'd have to wait for glue to dry before doing same to next hole, but should look good once complete. Could be tried on a less valuable radio first for "practice"... Maybe you could be the first to try this idea as you have much more patience than me ???

John


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 Post subject: Re: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Sun 09, 2020 6:48 pm 
Member

Joined: Aug Sat 16, 2014 2:19 am
Posts: 1498
Location: Palos Verdes, CA
Joe - I noticed that your Raytheon 8TP has an open slot where it appears that a transistor is missing. Your radio could be one of the early versions where Raytheon used 8 transistors. I've noticed that the Raytheon 8TP which uses the later "blue" transistors is a better performer than those that use the earlier "black" ones.


Attachments:
2 Raytheon 8TP radios.JPG
2 Raytheon 8TP radios.JPG [ 107.42 KiB | Viewed 513 times ]
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 Post subject: Re: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Sun 09, 2020 7:20 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6351
Location: Indianapolis, IN
Mark---I also noticed the transistor socket opening in Joe's chassis and believe that the steel panel was a production carry-over from the earlier 8RT1 8-transistor chassis.

John


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 Post subject: Re: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Mon 10, 2020 2:51 am 
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Joined: Aug Wed 26, 2009 1:50 am
Posts: 1602
Location: Mesquite NV 89027 (from Coventry, UK)
A beautiful piece of history you have there.


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 Post subject: Re: Historic Raytheon 8TP-4 & 8TP-2 projects...
PostPosted: Feb Mon 10, 2020 5:26 am 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6351
Location: Indianapolis, IN
Thanks much, Colin ! it's one of those radios I didn't think I'd ever have, started a serious search for, and kinda went overboard with the spending... Was only asking Bob about a project set and when he offered more than I expected, just couldn't pass 'em by !

John


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