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A noninvasive SR-series Direct Reading Plate Current Meter
开云体育Sorry in advance if this has already been done.? I know people will often connect up a VOM to measure the voltage drop across the 10 ohm resistor in the PS-120 or PS-500 power supplies to monitor the Plate idle current.? As most know 0.7V for an equivalent 70mA current.I was contemplating a noninvasive method to provide a better ‘almost’ direct plate current measurement.? By noninvasive, I mean using the same 10 ohm resistor in the power supplies via their Tip Jack connections.?? Then it dawned on me, I have a decent assortment of meters, so why not use a 0-500uA meter and simply divert 1/1000th of the current going through that 10 ohm resistor.? Robbing 1/1000th your plate current will go without notice under normal operation.? For 200mA of plate current I’d be diverting 0.2mA of current, barely noticeable. Found a nice vintage Triplett 500uA FS DC meter in my junk box.? It was actually NIB!??? The schematic couldn’t be simpler.? I have essentially around 10K of adjustable resistance in series with the meter and it gets connected to the same power supply TIP jacks that everyone uses to monitor the idle & plate current (via voltage).? Even though the schematic shows a 5K fixed resistor and a 5K pot, I naturally used a 4.7K resistor and a 10K series connected (recommended) pot.? Ain't much current going through these components so high wattage is not of concern. Calibration is supper easy.? Either using a DC power supply or even a low voltage, one to three volt, battery connect the meter circuits leads to the DC source.? Then adjust the pot to correspond to which you measure with either your VOM or better yet with a decently accurate DMM.?? So for a battery that measures 1.5VDC you would set the meter to read 150.?? Once adjusted it will never need adjustment again! I installed the meter in a case, I also had lying around, and painted it in a similar two tone Hallicrafters gray, or the best I could get using off-the-shelf spray paint.? Notice, I just added a decal to the front of the meter face that indicates the reading is X1000.? So 70 on the meter is 70mA, 200 is 200mA, etc. No more old VOM’s needed and I have a continuous noninvasive method for monitoring the plate current on my personal SR-150 transceiver. 73 Don N9OO |
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Re: SR-150 VFO Lubrication
开云体育
Do not use oil. Clean the drive system first. Where you have two gears meshing, use a toothpick and put a small amount of white grease at three points around the smaller of the gears. Then turn from stop to stop several times and let the gears spread the
lub.?
As for the stiffness, some stiffness is desirable. This is to prevent mechanical drift or backlash when you release the tuning knob. Originally there was a felt disc between the tuning knob and the front panel. If your radio still has one check to see if
the knob set screws were tightened with the knob pushed in too tight.
Walt Cates, WD0GOF
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From: [email protected] <[email protected]> on behalf of Steve N7AQ <smoreen@...>
Sent: Tuesday, April 29, 2025 10:56 AM To: [email protected] <[email protected]> Subject: [HallicraftersRadios] SR-150 VFO Lubrication ?
I recently purchased a SR-150 in good condition and have been working through WD0GOF's wonderful guide in repair and restoration.? On page 92 there are notations on the lubrication of the VFO and Chassis Assemblies.? From
the perspective of someone with limited experience in cleaning and lubricating a VFO assembly, are there practical suggestions on how to service the VFO assembly and what kind of grease to use.? (Obviously 3 in 1 oil is easy to obtain.)
The assembly is working but unevenly stiff.? In my restoration efforts I want to make sure I do no harm to the assembly.
Thank you for any guidance.
Steve N7AQ
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Re: The First and Last Hallicrafters with Flywheel tuning?
开云体育Since a ?day ?ago [this is a late reply] we deviated to non-Hallicrafters also, my old heathkit AR-3 had ?some kind of viscous damping tuning for each of the main and BS caps. It is hard to believe how a slight torque will allow the Cap to turn very slowly. Just don’t lean down on the knob. It can’t be a simple planetary gear reduction; perhaps it is a Jackson ball drive? which seems to be classed as one form of vernier drive. But I always wondered what is in there ????? .. I missed my education somewhere! ? From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow via groups.io
Sent: Sunday, April 27, 2025 7:55 PM To: [email protected] Subject: Re: [HallicraftersRadios] The First and Last Hallicrafters with Flywheel tuning? ? There ete all sorts of variations of dial drives. For instance rhe Hammarlund SP 600 JX uses a gear reduction driven by a friction drive on the dial, it also has a flywheel. While it has both a main dial and band spread dial they are driven together. It is an extremely smooth drive.? In comparison, thr RCA AR 88 also has two dials which are driven together via gears but the main shaft is gear coupled to the dial mechanism, no friction drive. It also has a flywheel.? This is also a very smooth drive although the SP 600 is smoother.? ? ?
-- don??? va3drl |
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Re: The First and Last Hallicrafters with Flywheel tuning?
开云体育Why does every one forget the SX 32 lol. 73 tony WA4JQS On 4/28/2025 11:51 AM, Bill (Group
Owner) via groups.io wrote:
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Anthony W.DePrato WA4JQS CQ DX HALL OF FAME #39 DXCC HONOR ROLL CW PHONE RTTY CALLS HELD VP8SSI VP8BZL V31SS 3Y0PI ZS8JQS WA4JQS/KC4 WA4JQS/ZS1 |
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Re: The First and Last Hallicrafters with Flywheel tuning?
The S-20R was first built in 1939 I believe, so it is close.? Interesting history on these radios. John WD5ENU On Mon, Apr 28, 2025 at 09:12 Gary Schulz via <mail=[email protected]> wrote:
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Re: The First and Last Hallicrafters with Flywheel tuning?
So I decided to ask Gemini AI assistant the question about flywheel tuning in Hallicrafters receivers, how many had it.? The interesting answer is below.
While it's challenging to provide an exact count of all Hallicrafters shortwave receivers that featured flywheel tuning without access to a comprehensive historical database of every model and its specifications, we can identify several prominent examples known for this feature. Based on available information, here are some Hallicrafters shortwave receivers that incorporated flywheel tuning for smoother operation: ? ?? Hallicrafters SX-28 "Super Skyrider": This is a well-known receiver and its tuning mechanism is described in detail, explicitly mentioning the use of heavy flywheels for both main tuning and bandspread. The design allowed for rapid spinning of the dial across the bands using the momentum of the flywheels. ? ??? Hallicrafters SX-28A "Super Skyrider": As a successor to the SX-28, it's highly likely that the SX-28A also retained the flywheel tuning system, as it was a highly regarded feature of the original. ? ??? Hallicrafters SX-88: This top-of-the-line receiver from Hallicrafters also featured gear-driven tuning knobs weighted with heavy flywheels, contributing to its smooth tuning feel. ? 1. Hallicrafters SX-88 and SX-99 - DXing.com ? Source icon www.dxing.com ?? ? Hallicrafters SX-96: This model is described as having "smooth flywheel tuning," indicating its inclusion of this feature for ease of operation. It's important to note that flywheel tuning was often a characteristic of higher-end communications receivers as it provided a more refined and user-friendly tuning experience compared to direct drive mechanisms. Therefore, it's plausible that other models in Hallicrafters' lineup, particularly those marketed as "Super Skyrider" or high-performance communications receivers, also included flywheel tuning. ? The more basic or entry-level models, such as the Hallicrafters S-38 and S-120, are generally not noted for having flywheel tuning. Reviews of the S-120 specifically mention the lack of a flywheel and the effort required to tune across the bands. The service bulletin for the S-38 details the dial cord stringing without any mention of a flywheel. ? To get a more precise number, a detailed examination of the specifications and features of each Hallicrafters shortwave receiver model produced would be necessary. However, the SX-28, SX-28A, SX-88, and SX-96 are confirmed examples of Hallicrafters receivers that utilized flywheel tuning. K2WH |
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Re: The First and Last Hallicrafters with Flywheel tuning?
开云体育No problem Gary.? That's what makes these queries interesting.? The Hallicrafters books can't possibly answer it all and just a little investigative work goes a long way.? It's also nice seeing people craftsmanship work on these fine old radios.73 Don N9OO On 4/28/25 8:41 AM, Gary Schulz wrote:
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Re: The First and Last Hallicrafters with Flywheel tuning?
开云体育Oh excellent Jim.? There the freewheel 'be' on the Radiomuseum underchassis view.? Great going!? The new winner at 1936 the SX-10.?Now we have the first, the 1936 SX-10 and the last, the 1969 SX-146.? Any dissenters out there? 73 Don N9OO On 4/27/25 11:59 PM, Jim Whartenby via
groups.io wrote:
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Re: The First and Last Hallicrafters with Flywheel tuning?
The SX-10 is most likely the first hallicrafters with flywheel drive.? Radiomuseum has several photos of the insides showing the mechanism.? The SX-10 dial is the first to have an engraved dial of some 300+ degrees.? Looking at the SX-9 photos at the RM, it appears to have a direct drive so the 180 degree dial makes perfect sense.? I assume that the sets made before hallicrafters began production with the S-9 are also 180 degree dials? The SX-10 set the standard for later production models.? The rumor is that only 200 were made but I think that there must have been more made then that.? Is this early trendsetter in anyone else's collection? Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Sunday, April 27, 2025 at 02:46:48 PM CDT, Bill (Group Owner) via groups.io <k2wh@...> wrote:
My SX-17 has direct tuning via a fly wheel.
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K2WH
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Hallicrafter HT-37 and S-76 Need new homes and TLC
开云体育I just posted the following 2 ads on QTH and thought that ops on this server could be the Better solution: ? ? SEE ATTACHED PIX: ? A S-76 RECEIVER on top at 46lbs with the right most large microvolt/S-meter glass removed and the mechanicals of the meter/indicator shot. Cosmetically pretty beat; bottom front case rust, but no internal penetration. Was capable of 538khz thru 34 mhz in its day. will need work!
Ok/nice cosmetics.... clean and very repairable. All dial tuning/bedspread controls work smoothly as well as other pots, swts, toggles ? ALL offers considered and replied to.?? TU and 73 ? ? STAY SAFE AND STAY WELL! ? Respectfully, NJ DOH Licensed EMT;? PHTLS, AMLS, PHPEC Millenium EMS ARC N.E. BioMedical Services ARC N.E. Disaster Cycle Services ? |
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Re: The First and Last Hallicrafters with Flywheel tuning?
开云体育Thanks Bill.? Well that gets us to the current oldest honor of 1937.73 - Don N9OO On 4/27/25 2:46 PM, Bill (Group Owner)
via groups.io wrote:
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Don Buska - The Radio Lab Works
waltcates
Mark Dinsmore
don Root
Anthony W. DePrato
Bill (Group Owner)
Jim Whartenby
Thomas K. Lanieri
