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  1. 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.
  2. Tom Bavis

    Stromberg Carlson ASR-120 OT ohms?

    Yes, 20-100 KHz or wherever it stopped being nice. Here's a better transformer:
  3. 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...
  4. 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.
  5. 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...
  6. 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.
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. 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...
  12. 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
  13. 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.
  14. 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...
  15. 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...
  16. 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.
  17. Tom Bavis

    Voltage drop problem

    The LM350 should do it. The heaters may draw triple the hot current at start-up, and LM317 has a current limit plus a thermal cutoff (sound like it's nor reaching the latter). One way that might get around this is to add a resistor in parallel with the regulator - output will still be...
  18. Tom Bavis

    RCA Victor Model 4RC84 hum fix -- first steps?

    The orange cardboard cap is the first suspect for hum - probably a two-section electrolytic. I'd guess that all of the wax covered caps are electrically leaky - with effects that depend on where it is in the circuit. I can provide a scan of the Sams folder (schematic, parts list and ID) or an...
  19. Tom Bavis

    Is there an inexpensive power supply I can use with my tube preamp? Paragon System E

    The Antique Wireless Association sells a preamp power supply PCB; it includes four voltage regulators but they don't need to be fully populated - for instance, you could use the two 12V regulators for DC heaters and install an RC filter in place of the HV regulator (and split to two R-C filters...
  20. Tom Bavis

    Does anyone have a schematic for a early 60s Boulevard Emperor amplifier?

    Guess they couldn't decide - Emperor or Empress... Sams covers a few mono amps under the Boulevard name, no stereo amps. Transformer numbers may help ID the maker if it's a rebrand (many were).
  21. Tom Bavis

    Let's start over trying to solve this amp distortion problem

    The floating paraphase inverter has the resistor values swapped, and 2% feedback isn't doing much. Using a 12AX7 should help a lot. But there could be a DC balance problem too - measure the output transformer resistance and then you can get the plate currents from the voltage drops across it...
  22. Tom Bavis

    Is this resistor okay???

    Out of spec, but doesn't matter - it's a "parasitic suppressor" - preventing high frequency oscillations. 50 to 100 Ohms should be fine, with no measurable or audible difference. I'd use it, and forget about it. There are places for 1% resistors, and places where 50% will make no difference...
  23. Tom Bavis

    8 ohm tube amp output to 16 ohm speaker?

    So don't drive it into clipping - has always been good advice. Otherwise, tube life is almost entirely due to idle current (plate dissipation) and hours of operation. Drive it into clipping with no load and the output transformer is at risk (as are output tubes and sockets).
  24. Tom Bavis

    8 ohm tube amp output to 16 ohm speaker?

    Maximum power will be reduced, amp won't care.
  25. Tom Bavis

    high res. 9303 schematic needed

    I tried attaching the schematic but forum software resized it, result wasn't great. PM your email address.
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