Sir Jesse. . . . .

Anyone got any ideas where to look.. Where to start.

AM WORKS WELL.. FM IS NONE>>>>> HELP?????????????????

You been associating with G berg ?

(Jes' messin' wit' your mind )

I certainly did, and gave them back to you waaaaay back on :

http://www.nostalgiaair.org/forums/Messages/963/M0078963.htm

No comeback on testing what-sum-ever . . . .

We KNOW with what you info that HAVE given us, that the set is in order in its power supply, and the audio amplification stages and the speaker.

Now in going back to my initial help offering and ALSO there is the additional need for the checking of the presence and voltage level of all B+ feeds to tube screen grids and plates of the sets frontal RF tubes . Compare the resultant readings against the schematic estimated values.

Pee Ess . .gettting the plate readings on the 6AQ8 can be accomplished by taking a single strand of AC line cord's bare copper wire. Then you do a tweezer twirling of a few turns around each of the the plate pins, with two separate wires and separate and tape across them at the top of the tube to hold them taut against the envelope.

Then place an insulative tab of paper between the bare wires and the tube shield. plug in, fire up and take your readings
up at the exposed wire ends.

Now, we are trying to ascertain the sequential link down the FM section that is failing.

When you monitor at the 1st grid of the limiter tube, (That is pin 1 of the V5-6AU6 tube) you can confirm that all of the FM frontal RF string up to that point is OK.

It lets you know, by the presence of a negative voltage there. Expect, that as you tune into a FM station, the negative level will rise and peak as you are " right on " the station, then the reading will diminish as you tune on past and off from the station.

The level of - reading is proportionate to the strength of the signal.

The highest negative voltage readings will be experienced from your very strongest stations.

Then, if you are finding swinging voltage levels with the tuning in to stations, YOU'SE GOTS a working FM radio . .UP to that circuit point, and we need to be moving on to the evaluating of the FM detector stage, as that is the next stage before reaching your audio, which you have already confirmed as working.

Initial HOT reference thread . .hottamus link-a-caticized . . .:

Rotomola / Quasar B-100

73's de Edd

Sir Jesse. . . . .

Looks like it might have been toooooo long since you last visited that chassis .

Just look at the FM tuner construction aspect and see if you don't see it being built in an all enclosed pot metal box , with zero access to the a bottom socket area of the 6AQ8, to access for plate voltage readings, without a teardown.

Less than desirable, other options, for access:

The use of a plug in 9 pin extender test socket . . .bet you don't have one of those . . plus it's something you wouldn't expect to use operationally on that FM tuner section, due to its upsetting effect via its extra inline inductance added along with its added extra stray capacitance. . . .this is high frequency FM, not very low frequency AM.

The unplugging of the 6AQ8 and a QUICK movement of + probe to the top of the tube socket, probing down inside, to measure, hoping that the socket is not a wafer style which would require a probe tip close to the pin size of a mini tube pin.

Downside 1 to that procedure is the tubes other elements being out of circuit, therefore it would not be a dynamic test of plate voltage under true operation.

Downside 2 on the same procedure, the overall B+ supply will start rising in value, as the AF output tube starts cool down and takes away, its hormal high level of loading of the B+ supply.

Now I hope you see why I suggested the "Money for nothing and chicks for free" utilization of fine wires, taped to the side of the 6AQ8 glass envelope, to "remote" connections of those plate pin connecions up to the top, such that they are then accessible for access in the taking of the tubes two plate voltage readings