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Marantz Lamps…200ma versus 250ma….THE MYTH

I have decided it is time to put this ridiculous myth to rest. You know the one. If you use 250ma fuse lamps in Marantz receivers it will melt the lamp housing assy. I have long maintained that this was nonsense and the melting, which really only occurred in two or three models, was a result of defective materials used in the construction on the lamps holders when the units were originally built. So, I put the lamps and the Marantz lamp holders to the test. The second part of this Myth is also addressed. The idea that using the 250ma lamps would put an additional strain on the power supply thus causing it to fail.

To do this I used a Marantz 2325 receiver, which is one of the couple models that had a big problem with the lamp holders melting. I purchased a set of 8v 200ma fuse lamps from a seller on Ebay. I have the 8v 250ma lamps here in stock. I inserted a digital thermometer inside the unit, laying it directly on top of the lamp holder assy. This would insure the full effect of the head coming off the lamps.

(1) I installed (7) 8v 250ma fuse lamps into the dial section of the Marantz 2325. I then laid the thermometer on top of the lamp holder assy. I left the black metal dial string guard off the unit to make sure the thermometer was not being shielded from the full heat of the lamps. I then laid the top cover back onto the unit. NOTE: the ambient room temperature was between 68 and 70 degrees during the tests. I turned the unit on and allowed it to run for 90 minutes. At the end of the 90 minute test period, I removed the top case and recorded the reading on the thermometer. When using the 250ma fuse lamps, the reading was 119.7 degs. F.

(2) I then turned off the unit and replaced the 250ma fuse lamps with the 200ma fuse lamps I had purchased on Ebay. The unit was left turned off with the top cover off for 1 hour to allow for a complete cooling of the lamp holder assy. I then again inserted the thermometer into the unit and laid the top case back on the unit. It was turned on and left running for a 90 minute period again with the 200ma lamps installed. At the end of the 90 minute test, I removed the top cover and recorded the temperature reading. This time the reading was 115.9 degs. F.

(3) I took a used lamp holder assy from a Marantz 2270 that I had laying around and tested it to see at what temperature it would begin melting. I set our kitchen oven at 150degs and allowed it to fully heat up to this temperature. I laid the plastic lamp holder assy in the oven directly on the rack and left it inside the oven for 30 minutes. I removed the holder and immediately tried to bend and mis-shape the holder. It was rock solid and had not softened at all. So I increased the temperature of the oven to 200 degs F. After allowing the oven to get up to temperature, I again laid the lamp holder inside the oven for 30 minutes. At the end of the 30 minutes I removed the holder and again tried to mis-shape it. It was ever so slightly pliable at this time but was still not what I would call soft or to the point of melting. I repeated the procedure with the oven at 250 degs F. At the end of this period, the plastic was very soft and pliable and would most likely deform itself if left at that temperature.

Conclusion: There was only a 3.8 deg F. difference in the level of heat produced when using the 250ma lamps as compared to the 200ma lamps. The lamp holder did not become at all soft until it reached at least 200 degs F. That is 80.1 degs F. more than the temperature inside the unit even when using the 250ma lamps. Differences in the ambient temperature (the temperature inside your house) will differ and may slightly change the temperature reading inside the unit. But the difference of 3.8 degs should still remain constant. The lamp holder is at least 80 degs from reaching the melting point with the 250ma lamps installed and at least 84.3 degs F from melting with the 200ma lamps. I think it is very clear that the 3.8 degs F. difference in the two types of lamps is negligible. In both cases the heat inside the unit is nowhere near hot enough to even begin to melt the lamp holders. So, unless you keep your house at about 150 degs. F, I do not believe you will ever experience any melting of the lamp holders in the Marantz units. The problem that existed in the Marantz 2325 and a couple of other units when they were new, was a plastic problem, not a lamp problem. The holders melted long before the original lamps had ever been replaced. The holders, now 30 years later, are probably hard and brittle enough that the problem that once existed in these units, is no longer a problem to be concerned with.

Excess Power Draw

With the 250ma lamps installed and the volume turned down to zero, the AC power supply amp meter read about 0.6amp (600ma). With the 200ma lamps installed it read exactly the same. So as you can see, (9) 8v 250ma lamps does not add up to a current draw of 2.25 amp (2250 ma). These components are not designed to operate at their maximum capacity. The ratings on the lamps are Max ratings and not would you expect to see with them in a circuit under normal operating conditions. I then turned the volume control up to approximately ¼ volume. The amp meter then read about 1 amp (1000ma). So any minute, undetectable difference in current draw between the 250ma and 200ma lamps pales in comparison to the different in current draw when operating the receiver at the lower end of its capacity. So, you can clearly see that the paranoia about burning up the power supply in your Marantz unit due to the wrong lamps being used just doesn’t hold up under scrutiny.

Now I realize that there will be some of you who will still say the 250ma lamps will melt the lamp holders or burn up the power supply. I am sure that the readers of this article, as well as myself, would be greatly interested in hearing and seeing any proof that you may have to back up these claims. I sincerely doubt any proof will be forth coming, but my email is always available if you would like to respond to this information.

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