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Dentron Tuner Cap Mount

S

SLR_65

Active Member
Dec 27, 2014
104
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Hi Guys,

I picked up a Dentron MT-2000A antenna tuner. It's a nice enough unit for a piece of 1978 equipment, but the tuning caps seemed loosed and could be moved left and right. I lifted the lid and found that it looks like it's missing a couple mounting nuts. The caps mount to plexiglass rails and it appears there's a screw mounted upside down and recessed into the rail that's supposed to hold the cap and both are missing the front nuts. It looks like it either had a star washer or a flanged nut with serrations.

Anyone know what it originally had, and what size and thread pitch they are?

[photo="medium"]3315[/photo]
 

Thanks BJ!

I got time tonight so I dug into this - if you take the bottom off there's an access hole to the this screw, so it's a simple fix.

Unfortunately once I had the lid off i dug into it further....someone has done something funky to this thing! The operate/ground switch is gone. The seller said it was gone when he bought it, but it worked fine. I could see where it could be a bit dicey if you left it grounded and fired the rig up, so i figured someone removed it to avoid that (though in retrospect, why wouldn't you just unhook it instead of removing it?). The seller has several references on the net and seems a straight shooter.

I noticed that the antenna cap isn't hooked up! The coil mount has also been cut off!

I think someone fired the thing up while it was grounded and damaged the cap and coil so they by passed the cap and rigged the coil!

I sent a note to the seller showing him the problems, and I imagine he didn't know because I imagine it still sortta does tune an antenna, just doesn't do it as well as it should. I offered to split the shipping back to him, or if he wants to list it as a parts/repair item I'd be happy to ship it to it's new home for him to avoid the trip back to him.

We'll see if he's an honest guy and works with me, if not I'll be happy to share his call sign for others' reference.

Ahhh, the joys of buying online!

Here's a pic:

Here's what it should look like under the hood:
[photo="medium"]3317[/photo]

 
Got a note back from the seller...wow, is he embarassed! He's taking care of it hassle free, so I can't complain.

Now to hunt down another tuner...
 
From the bypassing of the antenna side cap I have to wonder if someone did not modify it to function as an L-network tuner. L networks only require a single cap and inductor. Also I have to say that if the schematic is correct I really dislike Dentron's idea of a lightning protect switch. It only works when the tuner is inline and hence offers a false sense of protection as it may only protect the tuner and not the gear it is connected too. If it is bypassed the switch is not across the antenna line and does nothing at all. It should have been straight from the antenna input jack to ground.
 
I agree on the lightening switch, and from what I've read it wasn't real popular in the day and that's why it didn't appear on any other of their models.

Dentron did make a one cap/coil unit so I wondered if that's not how they reconfigured it, but why would you do that? I'm thinking the other cap is damaged is why.

Why did they cut and discard the coil mount also?

Something odd has gone on.

No matter, the seller is taking care of it, so I'll just look for another.
 
If the tuner was modded to make it an L network it would be because the owner had a really high impedance antenna usually a random or long wire type and L networks work better and are more efficient with those types of antennas. Simpler to use also.
 

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