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  1. Tom Bavis

    McIntosh MC2152 vs MC70

    Future collectible? Special 70th Anniversary edition.
  2. Tom Bavis

    Filthy Scott console, newbie questions

    Looks like a 16A, 1948 or so. Sams folder is on my site: https://www.audiophool.com/hifistuff.html
  3. Tom Bavis

    Weber WS1 in a Dynaco ST70 without modification?

    It will raise the B+ voltage, which will require more negative bias voltage.
  4. Tom Bavis

    AWA Learn it, Build it, Fix it classes

    Multiple classes at the Antique Wireless Museum in Bloomfield NY. Tube Amp Boot Camp is weekend after next, with Monday bonus of a total eclipse. It says register by 3/15, but I believe a few seats are left. https://www.antiquewireless.org/homepage/learn-build-fix-classes/
  5. Tom Bavis

    Output Transformer without Common, Identification

    Green wire went to the output connector, wasn't from the transformer. As far as measuring resistance, it's pointless unless you have a meter that can resolve milliOhms. The 5 Ohm one (Orange 1) is the (70V?) line tap. Put 100 to 120V across the primary, common will be the one with the highest...
  6. Tom Bavis

    Output Transformer without Common, Identification

    I see 3 primary wires. Five secondary wires is the minimum for 4,8,16 and a line output (one tapped winding) Must be grounded already as I see a green wire which would be feedback. As Dave said, line outputs are sometimes isolated, but there aren't enough transformer leads.
  7. Tom Bavis

    MPX decoders with LA3401 chip

    510 value is often marked 511. One per channel. You could also change the adjacent 100Ks to 150K, would also give 75 uS time constant.
  8. Tom Bavis

    12 Volt Tubes

    12AB5 is a 9-pin tube, a bit larger physically than the 6AQ5. Same pinout as 6973. Speaking of 12V6, I built this Champ clone with 12V6, 12SJ7 - using the PCB available from Antique Wireless Association: No choke but completely hum free - a little hiss with your ear at the speaker
  9. Tom Bavis

    Heathkit AA-100

    So don't switch it to tape mode. Seriously, there is no reason to use a tape head input - have you ever seen a tape deck without electronics? It might help to put shorting plugs into the tape inputs - I'd rewire them for something useful myself.
  10. Tom Bavis

    Question: Where to find good replacement for 60uf-450V axial Capacitor ???

    I was about to suggest the same - 68 uF is 21 (7/8") x 38 mm (1 1/2") with 34 mm (1 3/8") leads. Should just reach. 60 uF is not a standard value any more. Axial caps have gotten harder to find.
  11. Tom Bavis

    Stromberg Carlson ASR-120 OT ohms?

    Yes, 20-100 KHz or wherever it stopped being nice. Here's a better transformer:
  12. Tom Bavis

    Stromberg Carlson ASR-120 OT ohms?

    I was employed then. Our Engineering lab had a Wayne-Kerr impedance analyzer, and it was sitting there unused during lunch hour... so we lined up some transformers to measure. I still need to collate all the data and put it on my web site - one more project I need to get to. The Sams folder...
  13. Tom Bavis

    Stromberg Carlson ASR-120 OT ohms?

    I have measured one - part number 161000-184 - it was 10K when terminated with 8 Ohms. One of Sams numerous errors.
  14. Tom Bavis

    Voltage Doubler Power Supplies

    Out of curiosity, I looked in the 1961 Radio Shack Industrial catalog. 600PIV diodes, rated for 600 mA were $6-8 each; a pair of 60 uF 250V caps were $3 vs. a single 30 uF @ 500V at $1.50. 1000PIV and higher were available, but low current or much more expensive. Surge current ratings were...
  15. Tom Bavis

    Mystery amp

    Construction is impressive. Looks like there's a second transformer secondary connected for feedback, so there at least two speaker impedances available. BTW, 6201 tube is a military/industrial 12AT7, 6189 is likewise a 12AU7.
  16. Tom Bavis

    What actually makes the gain in a tube?

    Gain exists in two forms - amplification factor, or voltage gain, and transconductance, which is current change vs. voltage. To get voltage gain, you need a closely spaced grid. Since this doesn't allow a large current of electrons, transconductance is lower. To get high transconductance, the...
  17. Tom Bavis

    Ordering passives

    5% values for feedback resistors will control gain to within 0.2 dB. Other than plate resistors in a phase inverter, many other resistor locations could be +/- 20%, even 50% without an issue. One place you'd want 1% is current sample resistors for the output tubes - which might be matched to...
  18. Tom Bavis

    Westinghouse H-1793A Stereophonic Record Cabinet Info/Repair Inquiry

    Anything connected to the AC line needs to able to withstand 1500V spikes (common on power lines) - if one fails, it can put line voltage on the chassis. Common to find these exploded in older equipment. Y type capacitors are tested by a safety agency at 1500V or more. You want safety agency...
  19. Tom Bavis

    Westinghouse H-1793A Stereophonic Record Cabinet Info/Repair Inquiry

    The .068 uF cap is connected between the chassis and one side of the power line, This calls for 'Y' rated cap, which typically don't come in such a large value. Reason is that ground leakage (what you feel touching the tone arm, say) increases with the value of that cap. It provides a ground...
  20. Tom Bavis

    Bell 2122 mono questions

    Looks like only three terminals are wired. Confusing - schematic shows 8 Ohms, tapped at 4, parts list says 16 Ohms, tapped at 4. (the 'C' version has 4/8/16) And no input selector? Guess you just turn on whatever source you want...
  21. Tom Bavis

    Westinghouse H-1793A Stereophonic Record Cabinet Info/Repair Inquiry

    160V seems to be standard these days. 33 will be easier to find than 30 uF. (Justradios.com carries the 30 uF, but they have a $30 minimum order.) Tony' Capacitor Corner has axial caps: https://62bf1c-2.myshopify.com/collections/all
  22. Tom Bavis

    Trying to decide what power amplifier I want to purchase to pair with my Mcintosh c220

    Fix the Pilots or the the Citation - I'm not sure a Mac will be any better. Amps don't really suffer from use (playing loud is no worse for it than leaving it on without signal). Clean up, touch up paint and replace questionable parts, and they'll be good for another 60 years.
  23. Tom Bavis

    Westinghouse H-1793A Stereophonic Record Cabinet Info/Repair Inquiry

    No, that's two caps in one package. Two caps to replace - will be smaller, so should fit. It's covered in Sams Photofact folder 701-12 (circuit diagrams and parts list) - I can get a copy from the Antique Wireless Association on Tuesday when I'm there, or a scan if there aren't any duplicate...
  24. Tom Bavis

    HH Scott 330 Tuner

    I kept a copy of the HH Scott site, and also I have the Sams folder (348-12) if you need it. 16 page data sheet for LA3401: https://pdf1.alldatasheet.com/datasheet-pdf/view/40053/SANYO/LA3401.html - has typical circuit values. 20K input impedance, much lower than the 335 MPX, so .47 or 1 uF...
  25. Tom Bavis

    Bogen AP-60 found in the dust

    Bulb is #12, Bogen liked those for some reason - used to be common, still can be found. Agree on diode ratings - I have a few lower voltage ones, but wouldn't buy less than 1000V.
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