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Old 08-16-2017, 12:49 AM
tubetwister tubetwister is offline
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Join Date: Oct 2010
Location: west blue coast conservative
Posts: 163
Quote:
Originally Posted by maxhifi View Post
So, how bad is the hum, anyway? Every time I fix up an AA5, there's always some residual hum, I think it's kind of the nature of the beast.
Right I understand that.even a lot of the old 1937-1946 and mid century transformer radios had a high nose floor and poor DC ripple or ground loop filtering to audio thats a given on an old discrete AM tube radio or these .

The common mode fixed hum , maybe not related to elevated thd+ n noting both are are too far from the mean and average and the hum can garble speech and usable volumes.

Lytics are new, 11 caps (some suspects ) and 4 NOS tubes that may cover all this are on the way ,Hum is originating before First Audio /AVC Dual Triode Diode plates if that matters

Could be leaky tube heater ,Heater Cathode tube short, Cathode circuit,tube heater wiring order out of proper sequence but I don't think so , hum originates way ahead of 50C5 beam power output tube where the AC hum would leak in with a faulty tube heater wiring sequence instead of a tube heater >cathode short or tube heater leak it may be ,could be leaky Vol. Pot cap or a bad (leaky ) VOL.pot , maybe 50C5 cathode circuit @ C32D 20uF 25v cap and maybe the R15 & R16 carbon resistors or any number of parts or tubes shipped that includes some of all if this this ,

I may have it coverd and it was getting all this in any case outside of the 50C5 cathode circiut and Vol. Pot, .

I can Jimmy Rig a pre conversion Tracer an Altoids Tin with a diode detector , .001 uF capacitor that can discern an AC hum ,an OP amp, a battrey and buffer caps & whatever for a Ti PDIP- 8 type op amp , most of that is probably here if its not a tube radio circuit part shipping. or for any tube rig part


The squakers in these Halli. S120 SWL AA4 radios like this are horrid but its not for music or games here just occasional bed time casual SWL propaganda or KCBS in AM if I'm not watching my 05.2017 NIB 2016 retina searing 4K HDR 1000 QDOT, SUHD Samsung 55" TV in here on the wall .


These class of radios out side of an AA6 class like a Zenith Transoceanic (my next project radio keeper) with an RF Amp up front + another tuned stage are nearly deaf in SWL anyway.

I bougt it for what it is (nostslgia) here not what it isn't but it's on my 100' end fed and grounded long wire like any SWL radio in here outside of webSDR.


SRSLY old school AM Carrier Wave Analog Mono broadcast on it's best day was /is maybe 40 Hz to maybe 7. or 7.5 Khz and none of these old dogs could hit either end until High Band FM and Phono High Fi on a spendy mid century Hi Fi set back then unless it was something like a 2 way speaker ~ 25 tube ~1939 Zenith Srat 1000 or a big Scott Radio Philharmonic , and like that that all cost more than a new Sr. Buick and maybe some Cadillacs or a ~ 1948 Scott Radio Labs Metropolitan. radio set up or a custom

I could put it to a sound analyzer here in the studio outback on my Lily pad and simulate a normal noise floor, give you +dB reading for hum and thd+n (distortion we can hear NOT Thd ,<<<long documented maybe 1950 + phsycoaucoustics +Audio codec study and PhD peer reviewed research collaborations here ) VOL. thd+n @1m but thats too much for all this but it can garble speech and usable volumes (annoyingly ) @ Zero VOL common mode hum you can hear across the room but I think I have it covered in any case,

Thanks for replying(not trolling) BTW but if you see something I haven't ,jump in

Last edited by tubetwister; 08-16-2017 at 01:27 AM.