Drake 4-Line LED Lamp Replacements FAQ

What lamps are used in the SPR-4 Receiver?
On the SPR4 you can use a regular MOD-4LINESET set for the meter and PTO, but for the preselector window you would use a 12.6VAC PTO style lamp. For that bulb you can order the same PTO lamp as used in the RV4 series VFO's or P/N MOD-RV4PTO that is designed for 12.6VAC operation. That combination should have you glowing blue on the SPR4

Will these lamps work in the L4 or L4B amplifiers?
Yes, the lamps work fine in the L4 series amplifiers. Two different methods have been tested by users.

Method 1:
Each amplifier would use two of the MOD-4LINEPTO lamps. Installation does require a bit of work and I include the information in the next paragraph that was kindly provided by Stew K3ND.

"Installation did require the entry holes to be reamed out slightly. I first removed the top and bottom case and then the tubes and chimneys. There is no way to ream out the mounting holes without removing the outer front panel. To do this, you remove all the knobs, unsolder the wires (4) to the two indicator lamps, and the front panel comes right off by removing the six mounting screws. I then used a tapered reamer from the front side to open up both holes a bit. I just reversed the process to put everything back together. As I recall, it took me a little over an hour to do the whole job."

Method 2:
Each amplifier would use two of the MOD-4LINEMTR lamps. This method does not require the entry hole enlargement encountered by Method 1. However, the illumination intensity will suffer somewhat. This methods result is best summarized by Tony KF8MW and I quote his results in the next paragraph.

"Got the lamps today. Both are installed in the L4B and I asked the wife, a non ham, to give it a look-see. She said the blue looked very nice and no mention of it needed to be brighter. I imagine there would be a group of Drake users-collectors who like me just don't want to drill (enlarge) holes. I could have done it but those smaller bulbs do a fine job!"

Why are there different lamps for the T-4XC and RV-4 Models?
Drake designed some of their equipment to run the lamps directly across a 12.6VAC source or in series with a small valued current limiting resistor. All other 4-line units operate across 6.3VAC or have series connected lamps across the 12.6VAC source. For the directly connected 12.6VAC units it requires that a larger current limiting resistance be built into each lamp base. That is why I have special lamps specifically listed for these models.

Is there an alternative method for installing the meter LED into the T4XC transmitter?
John Chevalaz KB2LOZ provides insight into his method for installing the meter LED. Its somewhat of a bear to try to slide the bulb mount DOWN as its real tight. I was like " what am I going to do". Then I remembered that when the bulb went bad years ago, I did the following to get at it. I removed the PLATE knob by just pulling on it. Make sure not to loose the springy metal tang that holds the knob to the shaft. Then pull the shaft out away from where it attaches to the junction inside the radio. Carefully draw the shaft out of the radio. This exposes the light bracket for easy removal. And the shaft is slotted on both ends so it goes back as removed.

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