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Also don't assume I'm not knowledgeable on tube radios. I've owned well over 200, worked on ~80% with a 95% success rate, and have over 130 presently...Not to mention all the tube TV work I've done. I say vague on your pulling the first/last two in the string vs using the function names since you could be referring to the signal chain (which is a standard topology), or the heater string which does not need to be wired with the tubes in any fixed order.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#2
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(Edit) Also, the rectifier (e.g., 35W4 etc.) is conventionally at the top of the heater string to minimize heater-to-cathode voltage. The audio output (e.g., 50C5 etc.) is usually the next one down the string. Last edited by old_coot88; 08-12-2017 at 02:09 PM. |
#3
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IIRC even some transformer heater wiring and lead dress was very specific in something like a boat anchor comm radio or spendy audio gear and a there were a only a few AA5 variants and virtually AA6 radios , the pre 1936 AA5 variants and the different tube envelopes & sockets for the same bloody AA5 circuits and the superior Zenith T.O. variants Your edit that makes perfect sense . I tried to stay away from AA5 and AC/DC rubbish in the hobby but my 2 exceptions today are this deaf SWL specific model Hallicraftors S120 nostalgia radio for me and maybe a Zenith Transoceanic H500 legitimate AA6 variant . Benching TV & radios at a Magnavox AD when I was doing that there at 1967-1970 , Most of us understood a given signal path or output path tube order to function because you had to know it to fix the bloody things and where to start anyway . we didnt have all these web forums and web sites or FUD But your info here is not FUD .☺ EDIT 08.15.2017 20:30 PDT I just assumed anyone replying to me would know the mid century AA4-AA5 tube order to function order correlation that hasn't changed much since 1936 and we had had to know all that in our sleep in school and how to to build an AA5 in the lab too .and that was H.S. advanced electronics lab before college which wasn't tubes anyway 3 periods a day BTY Last edited by tubetwister; 08-15-2017 at 10:33 PM. |
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EDIT : without an electronics or EE education (~ 3yrs EE study at a universality like CAL State Electronics and Solid State Engineering study (like me) or bench tech experience (like me >part time + short timer ) and concomitant qualifications all that sounds like unqualified and hobby opinions to me and you are wrong about the heater wires ( I was informed below ) on these radios anyway stick to your day job mate I Last edited by tubetwister; 08-15-2017 at 07:49 PM. |
#5
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Dude, just to reiterate, check the heater wiring to verify that the 1st audio tube's heater is at the bottom (ground) end of the string. If it's not, it could be introducing hum downstream of the vol. control
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Audiokarma |
#6
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SRSLY no joke and it exact matches mica caps all over that radio and its a .0046 uf Mica vs an .001 presumably film cap it's supposed to have there per the schematic and the AA5 reference design that can go to .002 uf also who knows what else they did . I'm obviously not an AA5 or even radio expert like most of you here , so the input is all good and teaching me thank's During my career ,some of those screw ups and product were butt of inside humor or more or a PITA , IOW some misplaced wires would not suprise me in a USA mid century home radio ,they already put the wrong output tube cntrl.grid cap in that crude radio with 1936 AA5 budget model ciruits in a deaf SWL 1965 radio . It's almost criminal and that radio or a AA4/AA5 would be today because it can electrocute us without much provocation ! You cant make that up Last edited by tubetwister; 08-13-2017 at 03:52 AM. |
#7
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I also worked as an Industrial Electrician for 30 years, so I'm no stranger to even higher voltages. I have one of those receivers in my warehouse, somewhere. I remember working on it and it had a floating B- line. Trying to remember if it's U/L listed. On mine, someone replaced the 'lytic with a metal can type and installing it tied the B- to the chassis, which made it a shock hazard. I corrected that right away. Those type of SWL receivers generally didn't sound that great, mainly they were made for speech or code reproduction and not really for music. Also, that receiver was one of the last ones built in USA. They seemed to shift their production to Japan. Possibly, they used what left over! |
#8
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EDIT : Well it was a cardiologist and sudden coronary by pass surgery without more than a days delay , wholly unexpected by me or my GP or anyone that knew me at all including the gym trainers . The analogy here is these radios are lethal and you are being dismissive about that and your GFI outlets are not foolproof and neither was my significant exercise regimen .if you can not see the analogy here perhaps have someone explain it to you . .True story here and ......We never know when the bogey man is coming . Last edited by tubetwister; 08-15-2017 at 07:21 PM. |
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BTW, I'm a little more than just a hobbyist, plus I have four years of Tech school, associated with my Electrician Apprenticship. Plus, several years of practical experience, that no tech school can offer! Why do you think, I knew exactly what set you were working on, if I didn't have experience with the faults of the set. Another thing, I've been equipping my workshop with GFCI receptacles, ever since they became available, something like 30 years. It minimizes a shock hazard when working on equipment like this! |
#10
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Including the 2 Vol.pot caps and 50C5 final beam power tube correct uF cntrl.grid cap , I have 4 NOS not spendy tubes shipped and ~10 discrete circuit caps with the uF # @630v values from Hayseed Ham-fest ready made made cap kit parts listing for this radio but USA name brand caps not whatever they sell there and noting new Lytics are installed in this radio anyway so pricing was more favorable this way and total $2.50 USPS . Instead of getting stuck up for small order at Amazon, E bay, Mouser or Digikey I found them all cheap at Tube Depot store with the over priced tubes I wont buy there :LOL If all that does not fix it I will jimmy rig a sig. tracer and diode detector with a Ti PDIP- 8 op amp and some buffer caps and a battery & whatever else it may I need all I probably have sine its nit tube radio stuff & I can use the Senns. HD280 phones and for the amp/tracer a capacitor /diode detector series probe for the radio sig path before AF conversion ofc with a cap uF verified that passes the AC hum and see if I can find the origination of the AC hum if it is not the bloody tube heater wire order you kindly informed me of ,they could have skewed that too , noting the 50C5 outpt. cntrl. grid cap is way wrong uF from factory ,will keep advised, OTOH i could use my Schitt Audio Magni headphone amp it is very quiet and runs on DC wall wart .what do you think about that + diode and cap probe instead of op amp and maybe a cap on audio in to HP amp ground or no ? full stop. regards Last edited by tubetwister; 08-15-2017 at 08:53 PM. |
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