Would the Real GLA-1000 Please Stand Up

Originally offered in the 1970s, the Dentron GLA-1000 was a clever little amplifier.  It was compact, reasonably priced, and promised 1200 watts PEP.    During the 70s I owned a ham radio store in Oklahoma, Derrick Electronics, and I was a dealer for Dentron.  They were an up and coming company and they made good equipment which could easily be described as, "Built like a battleship."   Even though I had already purchased one of their MLA-2500 larger amplifiers, I was impressed with the little GLA-1000 amplifier and bought one for myself.  I recall the oft-used nickname for this amplifier said the GLA stood for "Great Little Amplifier."

Dentron followed the GLA-1000 with the GLA-1000B which added a tuned input circuit, a 2-port antenna switch, an extra indicator light and perhaps something else.   I recently dug out my GLA-1000 amplifier after having used it only a very few hours.   A friend had been looking for his own amplifier on eBay and I had told him several things about the GLA-1000 but I obviously had forgotten several items.  When I opened my early version amp up to brush out the cobwebs and dust I discovered that mine had the tuned input switch and added PC board.  I vaguely remember removing a small PC board with a single wound toroid core and one high voltage door-knob capacitor and a couple of pieces of small (RG-174-sized) coax.  Seems like at that point I replaced it with the newer tuned input board.

Also I remember unsoldering the four tube sockets and reinstalling them on a new board I had received from Dentron.  Since I never seem to throw anything away I remembered I had the old tube PC board in the bottom drawer of my desk.  Digging around, sure enough --- there it was.  In the pictures below I have shown the old board and also the newer board, which is now installed in the amplifier.  Note that the new board, added to my original GLA-1000, is marked "GPA 1000B" so this was evidently an offering to original owners to upgrade their amplifiers to nearly the same features as the next model, the GLA-1000B.  In looking at the pictures it looks like I failed to clean up the solder flux when I reinstalled the tube sockets but since it hasn't caused me much problem for 25+ years I just decided to leave it like you see it in the pictures.

  The thing I am trying to remember is, were these two items (tuned input board and replacement tube socket PC board) sent to all purchasers of the original GLA-1000 or was it something I had to ask for and/or order?  I just don't remember.  If most other owners of the original GLA-1000 have these modifications, it must have been sent to all buyers otherwise it might have just been made available for an addition cost.  Too much time has passed for me to remember that.

It looks like there were really four GLA-1000 models:  (1) the original GLA-1000 with no tuned input, (2) the original GLA-1000 with the tuned input board and tube PC board from the B Model, (3) the newer GLA-1000B, and (4) a rare GLA-1000C which was not easily convertible to 10 meters but used that 10 meter switch position for 160 meters.

The pictures below show probably more views than necessary but may be helpful if you have an original GLA-1000 and would like to modify yours with features of the later models.  Also GI7BT had a .pdf file for building a tuned input board for the earlier GLA.  I tried to find the site on the internet where I had downloaded it but was unable to locate it.  GI7BT gets all the credit and it does say that Far Circuits had a PC board already made up.  The file can be downloaded by clicking on GI7BT's tuned input board.  There is the possibility that this board is no longer available from Far Circuits but it would probably be worth checking with them.


K5LAD's Dentron GLA-1000

Click on any image for larger version

Current PC board

Current PC board2

Front panel

Inside view of amp

Left side of amp

New on top - orig on bottom

New tube socket board

Old tube socket board

Original PC board

Rear panel

Relay - antenna

RF input

Right side amp

Tube boards comparison

Tube socket - LR - old

Tube socket LR - new

Tube socket UL - new

Tube socket UL - old

Tubes - new board

Tubes & parasitic chokes

Tuned input - left

Tuned input - right

Tuned input board addition
Code on pictures:

LR = Lower Right

UL = Upper Left


Information on Dentron Amplifier Tuned Input Circuits

Click here



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Updated 01/11/07 07:12 PM

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