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.
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."
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.
are guaranteed to be free from defects in
material and/or workmanship and to perform as advertised when properly
installed, used, and maintained in accordance with published
instructions. Failure to adhere to and/or comply with operation manual
instructions will void all associated warranty obligations. Should any
part(s) prove defective within thirty days from date of purchase,
it(they) will be replaced without charge provided the defective part(s)
is returned with transportation charges prepaid.