Hallicrafters S120 hum at no vol and hum with volume

[old_coot88]

Originally Posted by Electronic M

...the heater string... does not need to be wired with the tubes in any fixed order.

Um.. by convention, in a series heater string, the first audio tube is usually at the bottom (ground) end of the string to minimize hum pickup. The OP might want to verify that the 1st audio tube's heater is indeed at the bottom of the string, in regards to his hum problem.

(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.

[tubetwister]

Originally Posted by old_coot88

Um.. by convention, in a series heater string, the first audio tube is usually at the bottom (ground) end of the string to minimize hum pickup. The OP might want to verify that the 1st audio tube's heater is indeed at the bottom of the string, in regards to his hum problem.

(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.

^^^ Interesting and makes sense electrically unless the fundamentals have changed since I was in school

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

[tubetwister]

Originally Posted by Electronic M

If by millennials your referring to me....Don't, I'm not like 99.9% of those around my age.

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.

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

[old_coot88]

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

[tubetwister]

QUOTE=dieseljeep;3188044]
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.[/QUOTE]

, 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![

Right AFAIK AA5 wasn't a metal Lytic ,that I recall and sometimes wax paper covered lytics laid in with the circuits instead of on top like this radio that sounds thats reckless or stupid on that radio you fixed good eye !


Setting aside the selenium rectifier and Zenith T.O. with an RF amp , the last AA5 tube radio was basically a clone of a 1936 reference AA5 even the Japanese radios and that time they were not uncommonly rubbish products anyway IRRC one could get get a chep no name or maybe regency Japanese or Taiwan AA5 for less than $10.00 in the mid '60s with the currency exchange rates back then.

IRRC Sony never made AA5 tube radios but I may be wrong and they got into the first Sony pocket transistor radios instead of rice cookers late like 1955 I think .

I read the Japanese S120 Hallicrafters AA4 had Japanese parts or a lot of them ,thats one way they said to tell if they had a Japanese made S120 AA4 or whatver

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.

I had a number of boat anchors and comm, radios , 2 Hallicrafters S38 AA5 and a National Radio S54 AA5 and a Hammerlund HQ 170A (w/a squaker ) like all that and the marine radios on my offshore power boat money pitts I had so I know about comm. radio speakers and that audio.

OTOH This radio has elevated thd +n way more than it should or my other AA5 radios and the other radios above and the fixed hum that is too loud and garbles speech at the lower volumes .

Again SRSLY 50C5 beam power output tube has the Wrong value control grid cap and that cntrl. grid is over volting +6v + more if factor in the negative volt spec. but its a work in progress . I will know more with the new tubes and parts it could be tube and or circuit faults or something ahead of the 12AT7 AVC First audio contl. grid see below

The radio gives me the same distortion and same hum at the VoL. pot and center tap .head of the 50C5 output tube


Lets allow an argument that I didn't buy this deaf SWL AA4 for music . Bd'cast AM Frequency response is typically 40 Hz–7 kHz with a 50 dB S/N ratio at best and this radio can't make either end .

I been an Audio enthusiast since the mid 1960s & studied the popular digital audio codecs in depth more recently but not like what snob audio fools think hires is ,they knew what we could hear in 1950 and 16 bits is plenty if its done well ,

LOL those snob audio fools think they can hear different color tube plates in an amp with ~1% thd+n and a difference of adequate CT11000 copper wires & cables and AC cords vs the exotic metal cable fool stuff too and hires over good 16 bit in the same production but the industry is banking on those fools daily !

Lets allow an argument I may not the guy to be talking to about loudspeakers

Originally Posted by dieseljeep

I never worried about being electrocuted on a hot chassis receiver, as I've been doing it for over 60 years!
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.

Lets allow an agrumant that if you have a post 1936 AA5 it wasn't basically any different at all than a 1936 AA5 unless it had an RF amp in the first tube on the radio side of the antenna like the Zenith T.O or a tone circuit pr phono in. or it was an AA6 variant but the same anyway as far as AC and B+ ,you can only do so much without a transformer in these .

I don't know if you attended electronics school but belive it or not we did learn some things an enthusiast may or may not know in some corners but we weren't on a TV radio curriculum for the most of it at all especially being near Silicon Valley if you know what I mean and we were all recruited back then ,

I changed study and career paths that ultimately paid and kept me more engaged and some would say well traveled
I ended up with a generous fortune 100 company corporate retirement plus , at 55


.

I never worried about being electrocuted on a hot chassis receiver, as I've been doing it for over 60 years!
I also worked as an Industrial Electrician for 30 years, so I'm no stranger to even higher voltages.

Well then ,then you must be very lucky or know what not to touch & how not to put yourself in harms way here with these lethal contraptions 99.99 % of consumers simply won't know today given that my radio is 52 yrs old and that would apply to a higher number of folks today without the tribal knowledge about all this so perhaps spreading FUD on web about all this or just minimizing this hazard anecdotally is reckless or no?

.

I never worried about being electrocuted on a hot chassis receiver, as I've been doing it for over 60 years!
I also worked as an Industrial Electrician for 30 years, so I'm no stranger to even higher voltages.

Lets allow an argument that aside from perhaps being reckless downplaying the lethal potential of these radios there may be folks without yours or an understanding of electrical current paths reading all this or have no idea what these 52 yr old plus radios can do to them without much provocation :

no need to debate all that ,the science around this is settled science )

[Titan1a]

???

[tubetwister]

Originally Posted by Titan1a

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hint :

yes it was wordy see the edit ,

[tubetwister]

Originally Posted by Titan1a

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yes it was wordy see the edit ,

[maxhifi]

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.

[tubetwister]

Originally Posted by maxhifi

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

[maxhifi]

Bed time listening in a quiet room is when the hum really drives me nuts. Any of my AA5s sound great during the day but unless it has an additional stage of power supply filtering, like some of the early 60s AM/FM sets do, hum is clearly obvious at night when volume is way down low and the house is silent. For this reason some of my favourite AA5 radios are the little cheap Japanese ones with a 3" speaker.. It just can't reproduce any hum due to high resonant frequency of the speaker.

How does it sound during the day time with the volume turned up a little?

[tubetwister]

Originally Posted by maxhifi

Bed time listening in a quiet room is when the hum really drives me nuts. Any of my AA5s sound great during the day but unless it has an additional stage of power supply filtering, like some of the early 60s AM/FM sets do, hum is clearly obvious at night when volume is way down low and the house is silent. For this reason some of my favourite AA5 radios are the little cheap Japanese ones with a 3" speaker.. It just can't reproduce any hum due to high resonant frequency of the speaker.

How does it sound during the day time with the volume turned up a little?

All over room has elevated hum add in thd+n or not it sounds poor beyond the mean and average (<<that is self explanatory engineering /research term "mean and average " BTW and @ any loudness 24/7 IOW ....its broke even.for these radios

if you will note my studies and education further back 6 years electronics and EE studies combined and audio codec + psycho acoustic studies + PhD peer reviewed research collaboration (s) directly above around all that, this issue would be settled or I can bring in any number of nationally prominent PhD and recording industry luminary's that mentored my later studies and were in or lead the research projects to explain all this to you if you like .

But Thanks for replying

[tubetwister]

Originally Posted by maxhifi

Bed time listening in a quiet room is when the hum really drives me nuts. Any of my AA5s sound great during the day but unless it has an additional stage of power supply filtering, like some of the early 60s AM/FM sets do, hum is clearly obvious at night when volume is way down low and the house is silent. For this reason some of my favourite AA5 radios are the little cheap Japanese ones with a 3" speaker.. It just can't reproduce any hum due to high resonant frequency of the speaker.

How does it sound during the day time with the volume turned up a little?

This deaf SWL AA4 radio may replaced for use by a far better sounding and tuning AA6 class (AA6) H 500 Zenith Transoceanic when I finish that yet to acquire project radio and this cam just be a mid century bauble in here which it is far better suited for since day one when it was made

pfftt....you know its basically nearly & literally 1936 AA5 radio or no ?

[/B]
All over room has elevated FIXED hum (you know what that is? ) add in thd+n or not it sounds poor beyond the mean and average (<<that is self explanatory engineering - research language "mean and average " BTW and @ any loudness 24/7 IOW ....its broke even.for these radios

If you will note my studies and education further back 6 years electronics and EE studies consecutively & much more recent digital audio codec and psycho acoustic studies + PhD peer reviewed research collaboration around all that, (5 + years there) this issue would be settled or I can bring in any number of nationally prominent PhD and recording industry luminary's or a nationally prominent EE + PhD too (<<<dude has more brains than a person should have ) most of these luminary's mentored our group studies + our research projects to explain all this to you if you like .

SRSLY at that level it could be academically and argumentatively BRUTAL for Month's on end and it often was like that , not High school >not Audio Karma> not ignorant snob audio we ridicule or the prominent snob audio pundits and editors we justifiably ridiculed unmercifully or never cheer leading it was knock down drag out scientific research and >> NOT COGNITIVE BIAS or SUBJECTIVE OPINIONS EVER just verifiable and repeatable DATA


BTW some of the labels ,S.E.'s ,mixers and perhaps coders use our results but its not a new wheel invention or a new codec it is something subtle likely you don't understand and it has to do with the usual lower Nyquist rates , digital artifacts , noise floors and dynamic range like any digital content or production or media specific mix like commercial CD ,24 bit studio masters CD replication mix ,club mix ,hires mix or steaming music &

^^^^ The above is in use here in the THX PM3 Pro digital content creation studio for our projects albums ,beats and catalogs s

[benman94]

The personal insults need to stop. Now. If you don't like the advice you're being given, ignore it, move on, and put your EE to use and fix your radio yourself.

I'm closing this thread; it's devolved into nothing but mudslinging and inane sniping.