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 Post subject: The Motorola 66T1 --- long sought project...
PostPosted: Dec Thu 07, 2017 3:47 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4959
Location: Indianapolis, IN
Hello All,

This was one of a couple radios at the top of my "wish" list since the 56T1, 76T(1 & 2) sets already reside in collection, and had been looking quite awhile for a decent example in my price range that had the external IF capacitors... Saw this one on Ebay with what seemed to be no interest until end of auction---so put in a bid (more than I really wanted to pay) in the last seconds and got it !

The chrome is in really good shape for its age and the distortion on the top which makes it appear dented is an illusion (as I'd hoped !). The tuning knob is warped and cracked, but usable. The grille needs painted, but fortunately have some black satin Krylon left and kept my home-made "exhaust box" intact which was built just for the purpose... Handle is in great shape with just a few scratches on top. Fabric covering on back does have some scuffs and wear, but should clean up nicely. There was some battery leakage residue inside, but was mainly contained by the holder. The end of battery holder is broken on one end, but a previous owner had rolled up some paper to wedge it against side of back cover which worked well and also absorbed a good amount of the battery fluid which protected rest of radio.

Applied power and audio seems fine (jumpered coupling cap temporarily), but no reception. Converter is not oscillating and the E & B voltages are much higher than service info specifies---but will investigate further since it may be something other than transistor... Of course, will replace electrolytics first !

Know that a few of you have these, so please post your experiences with them...

Ebay pic below...

Stay tuned !

John


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Fri 08, 2017 3:56 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4959
Location: Indianapolis, IN
Played with this a bit tonight and did a little more interior cleaning. Noticed some strands of what looked like steel wool on speaker magnet and am wondering if that's what a previous owner used to clean the battery contacts---that could be a problem !!!

John


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Fri 08, 2017 11:54 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25688
Location: SoCal, 91387
Hey John, I have a couple of 'em; definitely an improvement over the 56T1. Replace the E-Caps.

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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Sat 09, 2017 1:31 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4959
Location: Indianapolis, IN
Thanks Richard---hope to make some progress on it this weekend !

John


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Sun 10, 2017 2:53 am 
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Joined: Aug Wed 26, 2009 1:50 am
Posts: 1219
Location: Mount Pleasant UT 84647 (from Coventry, UK)
That’s an interesting looking radio.

Colin


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Sun 10, 2017 7:00 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4959
Location: Indianapolis, IN
Colin---it's one of Motorola's first three transistor radios and not easy to service !

Replaced the four electrolytic caps today and found that the converter transistor IS bad ! Pretty weird that once in awhile when power first turned on it would oscillate and radio would work great for a second or two and then stop. Removed transistor and installed a socket on pigtails to find a transistor that would work (it's an NPN, unfortunately). Tried several silicon RF transistors and they just oscillated "wildly"---so this set is on hold until I can find an NPN germanium RF transistor that will work properly...

On to other projects !

John


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Sun 10, 2017 11:53 pm 
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Joined: Aug Sat 16, 2014 2:19 am
Posts: 984
Location: Palos Verdes, CA
John - A few years ago I bought 2 Motorola 66T1s from a seller on eBay as parts radios. The handle was missing from one 66T1, with the other suffering from major battery leakage. I figured I would just remove the chassis from one 66T1 and put it in the other radio, which did take a lot of effort. Unfortunately, all I got for my efforts was static. I haven't had much luck in replacing the electrolytic capacitors in Motorola transistor radios, with the exception being with the 56T1. I replaced all of the capacitors on a Motorola 7X23E and only could get static. I hope you get the Motorola 66T1 working as it is a neat radio! - Mark


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Mon 11, 2017 12:10 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25688
Location: SoCal, 91387
I have a small number of Motorola's, and I would agree they can indeed be a PITA to work on, esp with the damn double sided traces on the PCB. And, as you both are noting, although the caps are the first suspects to replace, unfortunately all to often they aren't the only culprits. Also, for whatever reason, the oval Transistors in this brand seem to have a higher failure rate than the same type in other maker's sets. I too have had to replace at least one converter (can't remember if I had to replace more than one). Glad to say though, that all of mine do work.

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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Mon 11, 2017 3:34 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4959
Location: Indianapolis, IN
Had a bit of luck today---at least temporarily !

Realized I had a weak NPN IF transistor removed from a '58 Olds Transportable and decided to give it a try---the radio came to life and worked pretty well for awhile. While trying to peak the ANT trimmer on my favorite DX station, it stopped oscillating again---cycled power and it started again for a couple more minutes. E & B voltages better than original, but still high---so need to continue to search for a good RF NPN germanium transistor. Wish they'd used PNP's !

John


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Mon 11, 2017 8:41 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: SoCal, 91387
John, what difference would PNP's make?

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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Mon 11, 2017 3:12 pm 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 3828
Location: Sunnyvale CA
fifties wrote:
John, what difference would PNP's make?



You can easily get them.

Brett


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Mon 11, 2017 9:48 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25688
Location: SoCal, 91387
Brett_Buck wrote:
fifties wrote:
John, what difference would PNP's make?



You can easily get them.

Brett

Afraid I don't understand; why would Germanium NPN's be any tougher to locate than PNP's? In fact it seems that NPN's were more commonly used back then, so ?

John, give me some NPN part numbers and I'll look in my stash; I have quite a few.

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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Tue 12, 2017 3:52 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4959
Location: Indianapolis, IN
Hey Richard,

Yes, they were used more in the early days, but most radios starting in late '50's went to PNP's. The junk sets I have are all PNP, and have very few germanium NPN's in parts stash---and none for RF/IF applications... All the transistors in this 66T1 are T.I. units and from date codes I've found, seems this radio was made in 1956.

Are your germanium NPN's all from mid '50's or do you have any from the '60's ? You know what's in the Motorola's, but I can look for other numbers that would work when I have time---thanks much for offer ! Haven't yet looked to see if there are any Russian NPN units available...

John


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 Post subject: Re: The Motorola 66T1 --- long sought project...
PostPosted: Dec Tue 12, 2017 3:04 pm 
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Joined: Apr Wed 21, 2010 12:01 am
Posts: 297
In the early days of germanium transistors, i believe
the PNP's were easier to make. The alloy junction transistors utilized the connecting metal as a p-type junction with the n-type germanium piece. That's if my memory is correct. At my age, It's questionable. Ken


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