Graetz Sinfonia 3262 Another Odd Fault

[cathoderay57]

I use a Graetz Sinfonia 3262 for daily listening on FM. Another odd fault developed yesterday - crackling and rustling and fluctuating deflection on the magic eye. I fitted replacement valves temporarily one by one (except the magic eye) but the fault was still present. Exercising the piano key switches had no beneficial effect. The noise was still present with the volume control at zero, and also when gram or tape inputs were selected, although then the magic eye was stable at zero deflection. I changed the anode load resistors on the EABC80 triode to no effect. Shorting the EL84 grid 1 to chassis produced silence - no crackling. Well, to cut a long story short in the end I traced the fault by disconnecting C199 (1.5nF) from the EL84 grid 1. Similarly the fault disappeared if the EM34 magic eye was removed. The fault was heavily oxidised pin sockets in the EM34 magic eye valve holder. A couple of doses of Deoxit and careful scraping with a needle file did the trick. Variations in the magic eye anode current were coupling onto the EL84 via C199. Not what I had expected at all. The various couplings to the magic eye on this circuit are more complicated than many I have seen. I think the various capacitor inputs are intended to damp out deflection of the eye resulting from AF modulation of the received signal, particularly on FM. I post this in case it helps somebody else. Cheers, Jerry

[Joe_Lorenz]

Hello Jerry,

great job on a not-so-straight-forward set! Sometimes you need a lot of patience to figure out what is wrong. On the other hand these Graetz Sinfonias have always been recognized for their good sound, so very well worth the effort.

Regards, Joe

My youngest son has got a Graetz Sinfonia 422 "Schallkompressor" (Sound Compressor) in use on daily basis that he had located in our attic a while ago. It was used by the local school in it's hey-days. Here it is:

[cathoderay57]

Hi Joe, thanks for the reply. I have been very pleased with the Graetz radio (once I got used to the cabinet colour - it has been painted maroon/purple). I do not know if it is the original cabinet finish because all the other ones I have seen are like your son's, just varnished wood. The sensitivity on FM is excellent - even though it sits on the floor in a downstairs room and I am not in a particularly strong signal area. I repaired a Grundig valve radio of a similar age a couple of years ago and it was just as good. Here is a link to an earlier thread in which I attempted repair of the Graetz radio electrostatic tweeter, which was only partially successful but the audio quality is still excellent. https://vintage-radio.net/forum/showthread.php?t=154009 Kind regards, Jerry