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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 26th Nov 2020, 11:42 am   #1
leakysump
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Location: Oxford, Oxfordshire, UK.
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Default Farnell LFM3 signal generator

I recently acquired an LFM3 because it has a wider frequency range (10Hz-10MHz) at the higher end than my LFM4 (10Hz-1MHz) albeit lower voltage range (1mV-3V) than my LFM4(1mV-12V). It also has a larger nicer volt meter. However it is a bit older by the looks of things, and I have heard they have overheating problems. How do the two compare in component reliability? Many thanks in advance, Adam
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Old 26th Nov 2020, 7:54 pm   #2
turretslug
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Default Re: Farnell LFM3 signal generator

IMHO, it's a victim of over-specification- in deciding that it it ought to range to 10MHz, instead of the typical 1MHz of a workbench Wien bridge oscillator, the designer was forced to adopt amplifier circuit techniques that resulted in unusually high power consumption. There can't be many other "AF" oscillators that are brimming with heavily-heatsinked 2N3866s! I wouldn't be surprised if its power consumption of around 40W is more than some of the basic thermionic LF oscillators from the likes of Advance. Yes, it does run hot, with a fair amount of current taken from its +- 25V rails and the generous pre-regulator headroom doesn't help- there's nearly 100V between the reservoir capacitors in this modest-looking box. By contrast, the Radford LDO3 here only consumes around 12W and achieves what's useful for AF-range testing, really.
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