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Re: R4C BFO leakage into 50Khz IF
¿ªÔÆÌåÓýLook at This may not address your problem, but in any case I am sure you might find it interesting as might others. Regards Martin, HS0ZED
On 4/23/21 16:52, Lionel B wrote:
Hi Steve, |
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Re: OT: SOLA CV Transformer
The old capacitor checks about as close to the stamped value as one could expect. It's stamped as ".5uF" and my inexpensive component checker showed it to be 500nF and some change. Very close. ESR wasn't horrible but I suspect a lot of that changes as it heats up as well as being under load voltage.
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Since 0.5uF isn't all that common anymore, I'm considering a 0.47uF. The original cap is rated at 660V and, when I checked it last night, that wasn't exactly uncalled for. I'm pretty sure the waveform across that capacitor isn't at all very pure and that probably affected my Fluke DMM's reading, but I was seeing a bit over 700V there. Also, unloaded, the output ran at 7VAC. Loaded, about 6.4VAC which I'm attributing to the old capacitor. I'm hoping a new capacitor will at least cure the regulation. Thanks, Barry - N4BUQ ----- Original Message -----
From: "Richard Knoppow" <1oldlens1@...> |
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Re: OT: SOLA CV Transformer
Sola transformers also have capacitors. If the value of the capacitor changes it will change the regulation and may make it run hot. I have had a couple of CVTs, not Solas but other makes, go bad in Boonton instruments, they use CVTs to directly drive the rectifiers. I have never been able to find a fix other than just replacing them. The normally run quite hot but should not melt the potting compound. I also have a couple of Sola free standing transformers where the output voltage is wrong and where I could not correct it with new capacitors. I don't know what happens to them but suspect it may be a change in the air gap in the core.
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On 4/23/2021 6:26 AM, n4buq wrote:
Looking for some help with an older SOLA CVT. Please reply off-list if appropriate but others may be interested. --
Richard Knoppow 1oldlens1@... WB6KBL |
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Re: 2B Crystals
Michael:
It certainly acts like it could be a fundamental.? With 1V P-P 18mhz signal applied to one lead and the other lead hooked to the scope, it produces a very clean and stable waveform of 256MV.? This is pretty much the same level as the other crystals. Both 18mhz xtals result in 20db over S9 on 14.2mhz with about 100micro volt signal input to the antenna.? Doesn't appear to be any obvious distortion using the new xtal but I'm going to poke around with the scope out of curiosity. John |
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OT: SOLA CV Transformer
Looking for some help with an older SOLA CVT. Please reply off-list if appropriate but others may be interested.
I'm working on an ancient VTVM, a model 800A made by Technology Instruments Incorporated (later became Acton). There are some pictures of one like mine here: The SOLA started overheating after several minutes of powering the meter and would eventually drop the output voltage dramatically (spec'd at 6VAC output and dropped to around 2VAC as I remember). The transformer is(was) housed in a tar-filled metal box and, instead of digging around very much in that tar at unknown entrails, I decided to freeze the entire assembly and then some rather caveman-like activities to force the transformer out of the box. That process caused a few of the transformer's laminations to "fan" out a bit and, given the odd frequencies that are generated in this CVT, it buzzes somewhat more than it did. I've powered it back up outside of the box and, while it takes a bit longer to fail, it does eventually drop the output voltage when the capacitor overheats (I'm planning to replace that cap). Would it be a bad thing to drill some small holes through the laminations and secure them with small nuts and bolts (4-40 or smaller)? I can clamp the laminations and silence it significantly but not sure if small holes with additional metal through the laminations would affect the operation of the transformer. From what I can tell, two rivets extend through the laminations at both ends of the transformer and lock them to the core. I'm not sure, but I think it's possible to remove those rivets, remove the laminations, flatten the laminations that need it, and then reassemble it with small nuts and bolts. That might be a better alternative but, again, not sure what effects that might have. Any advice appreciated. Thanks, Barry - N4BUQ |
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Re: R4C BFO leakage into 50Khz IF
Lionel, is this early or late design (i.e., does it have the 6EJ7 third mixer)? Steve Wedge, W1ES/4 Time flies like an arrow.? Fruit flies like a banana. Sent from ProtonMail for iOS On Thu, Apr 22, 2021 at 15:56, Lionel B <N5LB@...> wrote:
I've seen an article about this topic and unfortunately cannot find the document. The receiver has been "on the shelf" in an air conditioned shack for about 20 years and now I've been going through and aligning per the manual.? When rotating the passband tuning from LSB to USB there is a peak at center that moves the S meter up to about S4 while on either end it falls to S0.? I've had this rx since 1976 and have aligned many times, but this seems new. |
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Re: Looking for a good working 3-500Z
Rob, even with that other tube, the power out seems low. I¡¯ve worked on AL-80¡¯s and they put out at least 500W (closer to 700, actually).? Something else is wrong. Is the output this low in all bands, into a dummy load? Steve Wedge, W1ES/4 Time flies like an arrow.? Fruit flies like a banana. Sent from ProtonMail for iOS On Thu, Apr 22, 2021 at 02:11, Roberto - YS1RS via groups.io <ys1rs@...> wrote:
Hi. As per title.... I am looking to buy a good working 3-500Z. |
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R4C BFO leakage into 50Khz IF
I've seen an article about this topic and unfortunately cannot find the document. The receiver has been "on the shelf" in an air conditioned shack for about 20 years and now I've been going through and aligning per the manual.? When rotating the passband tuning from LSB to USB there is a peak at center that moves the S meter up to about S4 while on either end it falls to S0.? I've had this rx since 1976 and have aligned many times, but this seems new.
The BFO seems to be getting into the 50Khz IF.? Its a mystery.? I seem to recall reading an alignment doc that has you test for minimum BFO feedthru as shown by the S meter, and a way to correct the problem.? Am I making any sense at all? Has anyone encountered this on an R4C?? |
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Re: Where to buy solder?
Here it is and this is good stuff.
On Thursday, April 22, 2021, 8:51:18 AM EDT, amfone via groups.io <amfone20000@...> wrote:
Isn't there a Kester 88 too which works very well? Tim WB8UHZ
On Thursday, April 22, 2021, 8:32:52 AM EDT, Gregory Beat via groups.io <w9gb@...> wrote:
Kester Solder is now owned by Illinois Tool Works (ITW) For a number of years, Kester sold Pocket Paks for Electronics Hobbyists, in smaller sizes. NTE asked Kester to continue this product line, a few years ago. Pocket-Paks come in Lead-Free, as well as 60/40, 63/37, and Silver formula Alloys. For Lead-solder, I use ¡°44¡± an?Activated Rosin Flux Designed for Instant Wetting Action Used in the energy, automotive, aerospace, medical, general manufacturing, electrical, industrial, fabrication fields. You can purchase from Electronics Distributors OR NTE Parts Direct. Mar-Vac Electronics in Costa Mesa, CA is a good distributor based in Costa Mesa, CA |
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Re: Where to buy solder?
Isn't there a Kester 88 too which works very well? Tim WB8UHZ
On Thursday, April 22, 2021, 8:32:52 AM EDT, Gregory Beat via groups.io <w9gb@...> wrote:
Kester Solder is now owned by Illinois Tool Works (ITW) For a number of years, Kester sold Pocket Paks for Electronics Hobbyists, in smaller sizes. NTE asked Kester to continue this product line, a few years ago. Pocket-Paks come in Lead-Free, as well as 60/40, 63/37, and Silver formula Alloys. For Lead-solder, I use ¡°44¡± an?Activated Rosin Flux Designed for Instant Wetting Action Used in the energy, automotive, aerospace, medical, general manufacturing, electrical, industrial, fabrication fields. You can purchase from Electronics Distributors OR NTE Parts Direct. Mar-Vac Electronics in Costa Mesa, CA is a good distributor based in Costa Mesa, CA |
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Re: 2B Crystals
John,
Additional thoughts concerning my reply yesterday: Concerning the greater output of the oscillator with the new crystal, rather than a fundamental-optimized crystal, I expect that this new crystal is a series overtone, higher than the third; this would supply a lower impedance at resonance to the cathode circuit of the oscillator, and decrease negative feedback increasing the output of the oscillator. ?The manual does not specify what series overtone is used. ?I have received information from others that Drake used the third overtone for optimal design. An oscillator input voltage higher than expected for optimal design could, actually most probably would, create an under-modulated AM signal: the difference frequency (sideband) voltage would be less than optimal. ?The (higher) oscillator frequency is being modulated by the RF signal (lower) frequency. ?With the Preselector circuit of the RF amplifier peaked and the RF signal power constant to the inductive-coupled coils (L2), an increase of the oscillator injection signal would create under-modulation and decrease the difference frequency (lower sideband). ?Whether over-modulated or under-modulated, the result would be the same: decreased receiver sensitivity. ?Unity (100%) modulation at the first mixer will provide the best receive-sensitivity performance. ?You could use a high-impedance oscilloscope to inspect the AM signal modulation on the input to V2 (Pin 2) if the scope has enough sensitivity, and the output of the first mixer, convenient at V3 (Pin 7). Comparing the receive sensitivity using the new and old 18 MHz series-resonant crystals will quantify the effect of different oscillator injection levels, at a difference of |-0.6| - |-0.2| VDC. ?How the receiver sounds during normal operation will qualify performance. 73, Michael Smith |
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Re: Where to buy solder?
Kester Solder is now owned by Illinois Tool Works (ITW)
For a number of years, Kester sold Pocket Paks for Electronics Hobbyists, in smaller sizes. NTE asked Kester to continue this product line, a few years ago. Pocket-Paks come in Lead-Free, as well as 60/40, 63/37, and Silver formula Alloys. For Lead-solder, I use ¡°44¡± an?Activated Rosin Flux Designed for Instant Wetting Action Used in the energy, automotive, aerospace, medical, general manufacturing, electrical, industrial, fabrication fields. You can purchase from Electronics Distributors OR NTE Parts Direct. Mar-Vac Electronics in Costa Mesa, CA is a good distributor based in Costa Mesa, CA |
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Re: Where to buy solder?
? I have? 3? x? 1 lb rolls of the old stuff...and a bit left on the end of a? 5 lb roll.? ?I shoulda snagged some more when I had the chance.?
The new? rohs? compliant stuff melts a full 38 deg C? higher.? What I have not tried..yet is silver solder.? ?That? will be used in a few applications. Jim? ?VE7RF |
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Looking for a good working 3-500Z
Hi. As per title.... I am looking to buy a good working 3-500Z.
Someone who may have one in excess to his needs? Will pay via Paypal shipping to Miami, Fl. This is for my recently restored Drake L75. My amp produces 200W with 20W input from the exciter. If I push it a little more that 190 mA it shuts down. Does not produce output and the mA go higher with no output, which could damage the Amp. So in order to use the Amp I have to bring down the exciter to 15W, just to produce only 100 to 150W output. So I rather shut down the amp and use the radio without it. This on 40M Band. Borrowed a well used tube from our Radio Club's Kenwood Amp and this old tube produced 300W output at the antenna connector with 20W input from the exciter and I may push it up to 210mA producing 325W with 30W input. Didn't want to try more not to risk the Tube and the Amp that has a lot of elbow grease already in it. Is there someone willing to sell one? 73 de Rob YS1RS 73 Rob YS1RS |
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Re: 2B Crystals
John,
Sometimes more is not better. ?As you are seeing a significantly larger grid-leak bias magnitude, this indicates the feedback voltage to the oscillator grid is larger, which indicates the output voltage of the oscillator is significantly greater. ?Mixing, at the first mixer, is occurring by modulating the input RF through transformer modulation (see L2), ?with the output of that amplitude modulated signal (two fundamentals, sum, and difference frequencies) capacitively coupled through C72, to the first mixer tube grid, V2. ?If modulation is not balanced properly so the modulation index is unity (100%), harmonic distortion will be produced, and linearity no longer exists. ?Not knowing the value of L2, but knowing that L2 never changes value indicates that L2 and C72 are not series resonant, and they shouldn¡¯t be with this signal varying in frequency. ?So the input is not resonant, but the output of V2 is resonant. ?This resonant tank output may attenuate undesired harmonics, but if harmonics are produced, signal power is lost in the harmonics, taking desired signal power from the desired difference sideband signal. ?This would reduce the sensitivity of the receiver. ?Intermodulation distortion could also increase. ?Without more information and in-depth analysis, I can¡¯t predict circuit performance of the first mixer using the new crystal and -0.6 V grid-leak bias. I suggest you perform an input sensitivity test. ?Compare?the new crystal in circuit with the intermittent one, that is much closer to Drakes specified value of -0.1 V (if you can keep it oscillating). ?With the much increased grid-leak bias associated with the new crystal, I expect this crystal is either operating at series fundamental, not third overtone, or the equivalent series resistance is much, much lower than an original crystal design. ?Beyond this test, how does the radio sound operating on 20 M, comparing use of the two oscillating crystals? 73, Michael Smith |
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Re: Where to buy solder?
Alpha Metals has a 60/40 rosin core solder available through Amazon. I just bought a 4 ounce spool to replace Alpha solder purchased many years ago and it appears to be the same product. According to reviews on Amazon, it is available at Ace and TrueValue hardware stores. Alpha is a New Jersey company now making solder in Mexico. The product is labeled Alpha FRY. The solder is available in 0.032 and 0.062 diameters.
Amazon also has a few other choices including 63/37 and 60/40 rosin core solders. I tried one of them and it appears to be a close second to the Alpha solder. 73, Kent AA6P |
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Re: 2B Crystals
N4KZO de K8NN
Michael: Well, sometimes it actually is a weak and intermittent crystal.? Received the new 18Mhz crystal from WD8DAS, popped it in and boy did it take right off.? Checked the negative voltage on the test point per the manual's instructions and it was at least three times (approx. -6vdc vs -2vdc) what I had been seeing with the other crystals and solid as a rock.? No drop out when pushing it around with a finger tip.? If I was going to keep this radio, I'd invest the $$$ and put all new crystals in it. Touched up the alignment and now only have to put on the polarized line cord and add a thermistor and it can go back in the case and onto the auction block.? Will then move on to my other 2B which was butchered by a previous owner and will be a challenge just to get back to the original circuit, never mind repair. Thanks for all your help and will probably be calling on you with the next one. de K8NN |
Greg W9GB
Roberto - YS1RS
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