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 Post subject: Strange Drake TR-4
PostPosted: Sep Mon 06, 2021 6:52 pm 
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Joined: Sep Mon 06, 2021 6:18 pm
Posts: 7
Hello, I have an unusual Drake TR-4. I am looking for a schematic or any info on this unit. The serial number is 31090. It has what looks like a factory mounted 4 pin mic plug, a vertical circuit board where the OA2 regulator goes. A noise blanker board with lots of wires and no plug-in socket, a orange light just under the vfo window mounted under the tuning knob and lots of factory looking circuit boards. Anybody recognize this animal? I will send some pictures soon. Thanks


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 Post subject: Re: Strange Drake TR-4
PostPosted: Sep Tue 07, 2021 2:12 am 
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Location: Ohio 45177
Here is a description of differences in early and later production models: http://www.zerobeat.net/drakelist/drakemod/drmod91.html
Don't know if any of them describe your discoveries. The boards in your unit are obviously commercial production items, whether factory or after market mods. All I can say is google around for more pictures of the insides of that model. You might keep the pictures to show to someone on this site, as they have seen alot more than I have in old Drakes: http://www.wb4hfn.com/DRAKE/DrakePageHome.htm

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 Post subject: Re: Strange Drake TR-4
PostPosted: Sep Tue 07, 2021 3:34 pm 
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Joined: Jan Sat 12, 2008 12:25 am
Posts: 281
Location: Kingwood, Texas
While the differences in your radio are very well done, they are not factory. Your radio had a significant number of user executed modifications. One exception may be the noise blanker. For a relatively brief period, the noise blankers were in fact, wired directly into the radio.

Darrell


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 Post subject: Re: Strange Drake TR-4
PostPosted: Sep Wed 08, 2021 1:31 pm 
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Update, After careful examination I can not find any sign of parts removal or modifications. For example the audio output transformer has no holes drilled to mount it. This radio has a solid state output amplifier with no transformer. Excellent craftsmanship on every item. I have also found the connector for the ac-4 power supply are different on this critter. Most pins are the same but a few are different. When you plug in the ac-4 it powers up without turning the power switch on the unit. The only thing that lights up are the 12 volt tubes none of the 6 volt tubes light. The finals are wired differently than my other tr-4's one side of the filament now goes to ground rather than feeding the 6 volt chain like my other tr-4's. I am trying to reverse engineer the wiring and trying to get the power plug back to a standard ac-4 configuration. Just an FYI I am not a stranger to Drake equipment this will be number 7 of my restorations. Never encountered one of these before, maybe a prototype? Attached is a picture of another TR-4 I am using for comparison.


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 Post subject: Re: Strange Drake TR-4
PostPosted: Sep Wed 08, 2021 4:47 pm 
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Location: Costa Mesa, California
I would suggest you make a power adaptor cable so that you don't need to re-wire what is obviously a well thought out radio. This looks like it may have been a prototype or a radio someone working at Drake built for themselves.

Norm

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 Post subject: Re: Strange Drake TR-4
PostPosted: Sep Wed 08, 2021 7:52 pm 
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Joined: Jan Sat 12, 2008 12:25 am
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Location: Kingwood, Texas
Norm Johnson wrote:
I would suggest you make a power adaptor cable so that you don't need to re-wire what is obviously a well thought out radio. This looks like it may have been a prototype or a radio someone working at Drake built for themselves.

Norm

I suppose anything is possible, but all I see are some well performed modifications done on someone’s workbench.


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 Post subject: Re: Strange Drake TR-4
PostPosted: Sep Thu 09, 2021 5:03 pm 
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Found some history on this unit. It came from a silent keys estate. He was in fact an employee back in the day of Drake. He may be responsible for the mods/construction. Made an adapter cable and the beast came alive with exception of no audio. Found the audio IC had a hole blown out and is dead. Signal tracer at the input of the audio amp gets audio and received signals on 40 meters. I may have a problem identifying the IC as the part number was part of what blew up. Time to design my own audio output stage. at least it's alive.


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 Post subject: Re: Strange Drake TR-4
PostPosted: Sep Thu 09, 2021 6:37 pm 
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Location: Montreal, Quebec
What does the audio IC look like? Sherwoodhad an article about a solid state amplifier for a Drake, I think it was an LM383, kind of a TO-220 package but with more leads.I

There's nothing to suggest this uses it, but we can wonder.


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 Post subject: Re: Strange Drake TR-4
PostPosted: Sep Sun 19, 2021 7:29 pm 
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Looked at the Sherwood audio amp board and it is nothing close to the one in this radio. I am figuring out the pin-out now.


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