Are tube shields in place. Are speaker wire near the antenna coil? Since the squeal is very high pitched a small cap across the output transformer may stop the noise? You could try .0047 mf?
Don't think alignment would help.
Norm
:The squeal is very high pitched. It will diminish and dissapear when the volume is turned down. It is much worse on the low end of the dial,and is there on the high end, but not as bad. I replaced all wax caps with new ones. They are the yellow polyester type. If the volume is turned up the squeal is terrible and the sound breaks down. The e-cap was replaced with a 60 and a 20, which is what the schematic calls for. I do not have a signal generator to align it.Could that be it,and is there another way?
ZUJ'ing
Edd
73's de Edd
73's de Edd
http://img101.imageshack.us/img101/7388/fpyschemacrosley56tfhe8.jpg
Its a medium J-peg...so drag across...and then….Beam me up Scotty !
The prior test steps were numbers 1-3. To confirm in test 1 if the "noise" ceased with the blocking of all signal prior to the AF amp stages. Then test 2 shuts down the input of the IF amp and [[[[Revised]]]]] Test 3 shuts down the mixer input.
The Test 4 (Green markup) would involve just a short disabling of the output stage to see IF the SEPARATELY mentioned...HUMMMMMM.... is then
eliminated just during that testing instant, with the sets volume control being at its MINIMUM setting. Another rare possibility, would be Evaluation #5
with there being cathode to filament eakage...within the inter elemental structure of the 50L6……test by subbing in another 50L6.
If that ..HUMMMMM... was still present after the last two tests I would tend to think that a bit heftier values of filter capacitors were in order. I certainly do remember seeing my share of 80/50 ufd values used for those electrolytic filter caps, both with your 35Z5 and its later 35W4 repro used in the miniature tube lineup.
Jumping back to your "noise" situation, another rare possibility would be a microphonic 12SQ7, but I've never seen one ...what with the mass of the heavy
internal formed glass envelope PLUS the additional conformal metal shells mass. Tapping the tube should confirm that fact, in order to see if it acts like
Mr Microphone.
The two final tests on the sequence would be in the second IF transformer, with it being in the large rectangular alum can and its variable tuning being accomplished by varying its C value with adj mica compression caps . But ALSO, hidden within, are two small value caps for a Hi Freq RF stripping /bypassing.
[Considering it to be one particular brand, they liked to have those small units made of mica with a healthy pure silver deposited on both sides of their units mica wafer. (Electro-sputtering within a vacuum for its deposition). Then their fatal shortcoming, with ttttt-iiiii-mmmmm-eeeee, was their accompanying technique of utilizing a clamping action and using a dissimilar a metal against those wafers to make the connective function. Now I ask you, who has seen WWII- ---> Korean vintage silver plated RF connectors...and egg-zact-lee WHAT shade of BLACK were they ?...e.g. with a very heavy onset of AgO2.....or how you Crazy Americans say... silver oxide. Those connectors trace silver was in a harder state and additionally, was being buffed up in its final production stage....but it DID oxidize with time and its oftimes subjective environs. Whereas, those mica wafers were receiving a purer state of the base silver, required in their vacuum deposition process, and the accompanying deposition layer being in more of a micro-porous matte surface. Now have a unit constructed in that aforementioned way and just wait for the /any atmospheric elements wafting about to find their way to those contact junctions. Take some of our omnipresent nitrogen , sulfur, chlorine, ammonia and their oxide counterparts...from our auto emissions, heating , cooling ,factories , farming, manufacturing, construction sources, etc....and don't over look the highly reactive ozone emission from common nearby lightning storms, along with the all important…in the formula…..humidity induced moisture and take those elements starting the reaction with a primordial buildup on that silver coating, ever creeping inwards into each accessible area. Upon adequate scale build up, it then walks down the chemical activity list and starts its attack on the copper, brass and phosphor bronze metals present in the mix. Eventually, creeping up and leaving ever less effective electrically contacting / conducting surface area.]
So much for that IF units failure mode analysis..what you would want to do now is to ohm out the secondary connections to that 2nd IF's secondary and the two connections without continuity will be the caps outsourced connections. They also should be connected to points A and B on the reference. So take those connections totally out of the circuit and sub in the two external caps depicted in their schema reference inset (in violet).
Fire up the set and see if that potential loss of a final "tweet" filtering could have accounted for an induced self oscillaion in the IF stage and the source of your "noise" creation.
Should that not have been the solution, the final thing in mind would be to get the unit miss behaving in its worse state again, and then observe the 2 mica compression trimmer capacitors that tune each transformers 2 internal coils. Looking at the slots in their 1/4 - 5/16 " pan head screws would reveal that the slot on top could be referenced for gauging the movement of a tuning screw in a one turn rotation and could typically index out as taking 20 peripheral slot widths (*****) in rotation thru one 360 degree turn of that trimmer screw. Sooooooo, using that referencing, take note of where the slots are and go to one end of the screw slot and mark an indexing position (a blue micro tip permanent Sharpie works best) on the aluminum shielding access hole, just aside to that slot, and place a dot on the particular slot end of the screw head that you are referencing to. Now, the screws can be repositioned to where they were started from initially !!!...as / if required. With the set in its worst "noisy" mode adjust the trimmer screw of the plate coil of the second IF xfmr NO MORE than an 1/8 turn CW and then back past starting position, and 1/8 turn CCW.
If this noise was RF / IF induced....feedback /or/ oscillation...one should expect the tone to change or the effect to abate or completely disappear altogether within that degree of tuning shift. If not, reset the trimmer to its initial position and move on to the 1st IF's plate coil and look for tone shift or abatement / elimination of your "noise".
If not then re-zero its tuning and move on to the less likely and effectual IF amp's grid coil and then finally on to the 12SQ7 detectors coil in enacting the the same testing procedure. Those operations should confirm if this was / is an IF/ RF type of induced problem.
Referencing(******):
In olden times working with ultra high performance communications receivers, I had my alignment procedure refined to the point that I was tuning into a stable , but very weak, distant RF reference signal and grounding the frontal stages AVC feeds such that the Rf stages / IF stages were running at MAX gain with a fierce developed AVC voltage at the detector and then taking meter referencing onto that level. The degree of preciseness of adjustment was such that I was rockimg within that mentioned 1 screw slot widths, latitude of adjustment, to find my optimal adjustment peak.
If none of the prior evaluations confirmatively pan out , the next question would be the reception capability, within your area, of a station sitting upon a 910 Khz..operating frequency...or submit your reception location and I will research them.
73's de Edd
:The squeal is very high pitched. It will diminish and dissapear when the volume is turned down. It is much worse on the low end of the dial,and is there on the high end, but not as bad. I replaced all wax caps with new ones. They are the yellow polyester type. If the volume is turned up the squeal is terrible and the sound breaks down. The e-cap was replaced with a 60 and a 20, which is what the schematic calls for. I do not have a signal generator to align it.Could that be it,and is there another way?