Quad Revision Live: Walters' Quads revision
I rarely saw a series of Quads (33 - FM3 - 405) in such excellent condition as those Walter brought me last week. He bought them around 25 years ago and spent half his life listening to excellent music. I'm almost jealous ;-)
I have to revise and upgrade them although they work fine already. Of course , after 25 years a midlife-upgrade is obvious...
Step 1: Let's start with the FM3 Tuner.
In the original FM3 there were 4 light-bulbs, 1 to give light on the front-panel (12V) and 3 indicator-lamps (2 for tuning and 1 for FM-stereo) (7V, 1 is broke). Those have to be replaced by LED's anyway.
Led's live forever - at least till 2500 - and they don't influence the power-supply rail like old neon-lamps do. I replaced them with yellow Led's and a 390R resistor. I sticked them in with 2-component glue.
For the rest I only changed one very old 220 mF capacitor for a new one.
I won't care about changing the Tantalum capacitors, the FM3 perfoms a lot better than the FM-broadcast quality anyway, so there is no reason to care about high-end components like we'll do in the 405 or in the 33.
Steps 2 ...
Well, sometimes it goes fast ;-)
The 33 and the 405 were upgraded and Walter is listening to them as we speak.
He says the sound-quality has improved a lot but the level of the Record-Player input of the 33 is too low and there is a lack of dynamics.
Fortunately it is very easy to modify the sensitivity of the PU-input of the 33 (changing 4 restintances on the board allows for almost every possible sensitivity of MM-elements). MC-elements might not be applicable because of the low output, although I heard there alternatives for that too now.
He'll buy a new PU-element and then we'll adapt the sensitivity to it's specs.