B&W 5100

[W7VM]

I am restoring a very nice B&W 5100 transmitter and have located, on BAMA ,a factory  addendum to the manual which reports production changes.  One of the changes places two 100 K 20 watt resistors accross the secondary of the modulation transformer (I am doing this at work and may have the values wrong) There is capacitor involved.  I have looked in verious references including a 1947 version of the Editor's and Engineer's Ham Radio Handbook (not the ARRL) which otherwise is a wonderful resource for AM rigs and can't find any references explaining why B&W would do this.  It is a pair of 6146 tubes modulated by a pair of 6146s so there is lots of audio available.  Can anyone explain this?  I am putting in all of the other minor changes since  they all make sense and my late serial number unit has many of them already.

Dave

[DMOD]

I think you meant 2, 2W 100K resistors in parallel across the Mod transformer.

I think they had a bassy audio problem, so adding these would widen the bandwidth of the Mod transformer taking the low frequency peak out of the mod audio.

C44 in the multiplier of the final is supposed to be 0.005 uF, if that's waht you are referring to?

Phil - AC0OB

[The Slab Bacon]

they probably had some kind of impedance mismatch, and used the resistors to either load down the mod tranny, or suck up some excess audio power.

[KD6VXI]

I think you meant 2, 2W 100K resistors in parallel across the Mod transformer.

I think they had a bassy audio problem, so adding these would widen the bandwidth of the Mod transformer taking the low frequency peak out of the mod audio.

C44 in the multiplier of the final is supposed to be 0.005 uF, if that's waht you are referring to?

Phil - AC0OB

I'd say Phil is correct on this, but only by heresey.

The 11 meter crowd removes those, to get the "BASSY" audio out of the "Barkers" as they are known.

NICE transmitters, wouldn't mind having one, and the SSB adapter, myself


--Shane