Panel Hardware for the GPT-750

This page provides some information about replacing missing hardward on the GPT-750 panels.  Examination shows that the hardware that secures the drawers into the GPT-750 cabinet consists of two parts:  a swaged-in "nut" that captures the panel screw, permanently attached to the panel, and the panel screw itself, which has a 3/4" hex head that is also slotted (NB: don't ever use a screw-driver on these things!).

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This is the typical panel retaining screw on the GPT-750. You can thread the screw out of the swaged-on retainer.  Here it's show nearly threaded out.  There's never any need to take the screw out, normally, but that's how most of them get lost, most likely! Here's the back view of the swage-on captive hardware..


.. and the screw itself.


Note:  as of 6/2015, I am in the process of having a bunch of captive screws and bushings manufactured for the GPT-750, according to the original TMC drawings!  Watch this space and the For Sale page over the coming month or so, when I'll have them for sale!

Swaged Capture Bushing

Bruce Berman, the expert in matters of careful TMC restoration, provided the following information about the bushing that is permanently swaged onto the panel:

The swaged-in-place fasteners used on the front panel of the GPT-750 are manufactured by Amatom Electronic Hardware of Cromwell, CT. Phone 1-800-243-6032, The Amatom part number for an exact reproduction and replacement of these swaged threaded fasteners is 66666-5081. In 2009, I had purchased 31 each of these at a unit cost of $10.38 each, so they are not cheap, and the price varies significantly as a function of the quantity. They must be installed by a suitably equipped machine shop with the proper pneumatic-powered tooling; you cannot swage these fasteners to the panel by hand.
I purchased these so I could make an exact reproduction of the modulator unit with the front panel (variant GPT-750B-1), and the blank front panel for the radiotelegraphy-only variant (GPT-750A-1) as used in the GPT-750 series. If you wish to refinish a front panel properly, the factory-installed fasteners must be removed by drilling them out prior to refinishing the panel, and new ones installed if you want to do the job right.

Captive Screw

It appears that the captive screw was a TMC custom part.  Indeed it is SC-139 (click to get the drawing).  As things stand, you will need to get a local machine shop to make some of these things for you.  However, if there is interest, I could get 100 or so of these things made and make them available for sale--they won't be cheap however.  If you're interested, please get in touch at .

Here're Bruce Berman's comments on the captive screw:

The stainless-steel hex-head screws which are captured by these fasteners (and which secure the front panel/drawer assembly to the cabinet) were custom to TMC. I seem to recall the TMC part number for them was SC-139, and if the dwg can be found in Bob's archives, any suitably equipped machine shop can fabricate these exactly. Fortunately, the GPT-750 I obtained from Tony Faiola had all of these screws in place, and the slotted heads (which so frequently got chewed up in the field) were in perfect shape, so I did not have a need to reproduce them. As a matter of fact, Tony had several of the ones on my rig fabricated locally by a machine shop, and they look absolutely identical to the original screws from Mamaroneck.

Rack Handles and Ferrules

The rack handles, and the little black-anodized ferrules that help secure them to the front panel, are also hard-to-replace items.  Bruce supplied the following information about them (they're also available from Anatom):

Amatom can also supply the rack handles and ferrules as used by TMC on the front panels of their equipment. As the handles on my GPT-750 were in good shape, to get to the as-new from the factory look which I always try to strive for, I had them re-plated by a guy in Connecticut who does chrome plating for classic auto restorations, and the ferrules were refinished in black anodize using the same process TMC utilized.