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  1. aeyb701

    Sony PS-X60 Thump Through Speakers with Each Revolution

    Hello everyone, Just got a Sony PS-X60 direct drive turntable and noticed when playing through quieter parts of ANY record I hear a 33-1/3 rpm “lub dub, lub dub,...” through the speakers, not unlike the sound of a heart beat through a stethoscope. When I put my ear to the deck or try and feel it...
  2. aeyb701

    CR-2020 Intermittent Hum

    Thanks-you for chiming in Avionic. Yes. Same thing with AC plug reversed, but the fm antenna fully connected didn't induce the hum this time. Oddly someone had marked the polarity of the plug for some reason, perhaps ground loops encountered with other components. Maybe a cold solder joint...
  3. aeyb701

    CR-2020 Intermittent Hum

    I have a Yamaha CR-2020 I found at a waste station last year, and since then I've performed the service bulletin(s) and between me and a technician whom I trust hav replaced many capacitors in the power supply, hoping to sort a 120Hz (I think, maybe it's 60) hum. The hum is not there until, on...
  4. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    one of the Tungsol 6550's had the positioning key missing which I forgot and when I tried it smoke started from below, a resistor I believe, but again shut her down fast. Tough old bird. So to all, it is possible to use keyless tubes but make sure it's oriented!
  5. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Thanks gadget. BTW that GE 6550 that had the loose getter disc: tested fine on the B&K no matter how I shook it up down and sideways. With caution I tried it in the amp and what a light show: blue lightning like in Frankenstein, but turned it off fast having been at the ready to do.
  6. aeyb701

    Question on Manufacture of Old 6550 KT88 Tubes

    Scanning the web the consensus is that all "coke bottle" 6550's were made by Tungsol of New Jersey. I have one though labelled GE (not uncommon) but with EIA (mfr.) code 247, which means RCA from a plant in Penna. can someone explain that? Also I have a Sylvania "6550" NON-coke bottle that is...
  7. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Well a few weeks with things tickety-boo: nice sound and no hum (yay!). Have a pile of good used Tungsol, RCA and GE-branded coke bottle 6550's and have been comparing them sound wise against Valve Art (Chinese) 6550's that came with it when purchased from "plink" a few years ago and find the...
  8. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Or paint the black cap silver, so two front ones look OEM :) Thanks Gadget.
  9. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    In the setup, with Altecs, CJ PV-7 pre, Technics SL-10 linear tracker and Marantz SACD player. That is an MC-2100 in the wings and a couple open reel decks.
  10. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    The brown cap is there for looks, it's not hooked up. Its replacements are beneath.
  11. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Finally received the resistors, and installed the requiired 1.5Kohm 1W at R203 instead of the 3.3K. Biased up in perfect range, and idling about 65mA per 6550 cathode. No more hum. Playing Angela Hewitt, Bach on piano (DG vinyl pressing 1985), through Altec A7-500 Magnificents, or my build of...
  12. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Got a new diode, 1N5408, put in and grounded what needs groundin'. Numbers all settled down. 100VAC in and -70 or so DC out from diode. By the way NO HUM. Have yet to put any signal on it yet, but there is audio at speakers as shown by a crackle when I touch certain test points with the probe...
  13. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Today I finished reconnecting loose ends, and making sure of no shorts. When I fired it up (cocky doing so without a dim bulb tester) no smoke, no smell and no light show. Neither did the output tubes glow much. I heard no hum so touched the input jacks to see if I could create hum with my body...
  14. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Actually the socket it fine, but I knocked the tube sideways while the amp was inverted. Ref. Trobbins advice, I could operate it inverted and use the 6550 :) What does that metal disc under the tube top do, btw?
  15. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Thanks Gadget, I just now noticed that in the pictorial map. I thought that too, since both ends on ground would be the same as no shield and having the single wire running next to the (ground) chassis just where it was. When powering up do you think it wise to have any tubes in, or none?
  16. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Fwiw I noticed that the shielded black wires from the RCA inputs to the front "lab/normal" switches did not have their shields grounded, per the pictorial colour diagrams in my manual. I decided to do so by stripping further back and soldering a piece of wire to the shield to recover some length...
  17. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Identifying outer foil is hard visually if not marked, so I saw a video how a scope can determine it. So in say between the 7199 and power tube the outer foil end would point toward the 7199? As you say, though, it doesn't matter that much unless near an AC line etc, which I've taken steps to...
  18. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    The phone app which I take it uses the phone's mic and not a wire. I have a 2007-ish iMac so I'll see what's compatible software wise and hookup to item tested.
  19. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Teaching point: remove tubes when working with the unit upside down. While installing can caps I dislodged a driver tube which fell to the ceramic tiles below. A Sylvania 7199. Double ouch. I have three more fortunately.
  20. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Thanks Mr. Robbins: To identify noise spectrum do you mean an oscilloscope? It has been a thought, based on youtube tutorials by one such as "Uncle Doug" (he explains electronics generally and tube amp basics in particular quite well). I also pondered that axial capacitors can have polarity...
  21. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Thanks Gadget. I hope to leave enough lead wire to allow placement of caps away from tubes and resistors, I checked various threads on other forums , and the schematic and indeed the negative cap lug/wire goes to negative voltage supply, with positive ends to a common ground ie chassis, much as...
  22. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    I constituted the 75uf x 4 common-positive cap (C1) from 4 80uf ones (450v : unnecessary but there it is). The negative voltage from the solid state diode (Out of picture) connected to the resistor at lower right feeds the negative terminals of C201 per schematic and also a 220-ohm resistor in...
  23. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    I got a good copy of the assembly manual from RadiolaGuy.com with colour parts and wire diagrams as in the original, in which I drew the service bulletin updates from 1962. I got a supply of new caps from tubesandmore.com as well as a few resistors. My aim is to rebuild the power supply as...
  24. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Abandoning trying to figure out how my power supply is made from 4 50-50/500v JJ cans. Too many hours. I ordered replacements in values close to the revised Scott schematic as well as couplers and a rsistor that was absent. Shot gun, yes, but I hope the hum is gone when I finish. The connections...
  25. aeyb701

    Scott LK-150 Low Level 60Hz Hum at Speakers: Transformer-Induced?

    Shout out to my man Sam for supplying me with the assembly manual for this amp by email (no where on web could I find that didn'tt set off malware detection!) since max image size on the forum precludes much enlargement. I think I'll replace the 4 double 50uF/500V cans with 2 double 35's (can...
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