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Re: SX-117 noise limiter behavior
I had hoped that someone who has actually seen and used an SX-117 would respond.? I've only been restoring receivers for 40 years or so, but over that time I've learned that you can save a lot of time by consulting with someone else who owns the same radio when observing an odd behavior.? You might be surprised how many times "they all do that" is the undesirable but true answer.? As I said, I have not dug into this particular problem yet.? What I do know is that the SX-117 does not have a "noise blanker" as seen in later or more sophisticated receivers like the Drake R4C.? It is described as a noise limiter.? This particular SX-117 has been completely restored with all new tubes and many capacitors replaced, as well as a few out-of-tolerance resistors.
Spraying old switch sections with anything is a really bad idea.? All switches in this unit have been carefully cleaned using De-Oxit and Q tips and tooth picks to apply the cleaner in small amounts where needed.?? |
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SR-2000 load cap
开云体育
I got lucky. Simple fix. When I got the load cap out, I could clearly?see the rotor was too far to the rear. I adjusted the end play screw and centered the rotor plates and all is fine. That is when I notice that the lock tight seal was only on the retainer
nut and did not cover the adjustment screw. I think I will drill a hole in the rear plate to allow access to that adjustment.
Walt Cates, WD0GOF
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Re: Parting out an SX-100
On Fri, Jun 7, 2024 at 11:40?AM trekkersteve via <trekkersteve=[email protected]> wrote: Donald, |
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Re: SX-117 noise limiter behavior
开云体育As far as I can see, there is a form of Noise Blanker implemented into the SX-117. Two silicon diodes, polarised by the signal from the last IF amp that de-sensitizes the input directly at the antenna connexion. Maybe the two diodes (CR1 and CR2) are busted…. And that the antenna signal is shorted when the “NL” is activated… Look at the schematic. ? 73, Jacques, VE2JFE in Montreal ? De?: [email protected] <[email protected]> De la part de Richard Knoppow ? Clarify a little, do you mean a desired signal falls off that much On 6/7/2024 9:02 AM, Floyd - K8AC wrote:
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Re: SX-117 noise limiter behavior
Floyd Have the tubes been checked for conduction, leakage and shorts?? Are you planning to recap the radio or at least check some coupling and bypass caps for leakage?? Have you done a critical look to see if there are any signs of stress on components and the like?? Sprayed?all pots and switches with your your favorite contact cleaner? I would do all of the above before applying power, to any radio.? It will save a lot of time troubleshooting. Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Friday, June 7, 2024 at 12:17:41 PM CDT, Richard Knoppow <1oldlens1@...> wrote:
Clarify a little, do you mean a desired signal falls off that much or background noise? If its a desired signal it sounds like the blanker is blanking or blocking the signal all the time. A noise blanker is supposed to cut or blank the signal path for short periods to eliminate the effect of impulse noise, like ignition noise. Mostly to prevent it from activating the AVC and desensitizing the receiver. Don't know how its arranged in the SX-117 but it sounds like its blanking all the time. On 6/7/2024 9:02 AM, Floyd - K8AC wrote: Haven't dug into this yet, but wonder what other SX-117 users see when --
Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
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Re: HT45 Loudenboomer working now with new power supply
Thanks for posting that article!? That stuff never changes with time does it!!
The original transformer is rated at 6750 (CT).....so with 12V the secondary should yield 675(RMS)? and Yes.....? The peak would be right up there too!. (With 12v RMS, the peak is about 17V) I know there are many high voltage plate supplies that have placed the choke in the CT.? It actually is a pretty good way to reduce the total voltage on the choke.? Doesn't do much for the rectifier filament transformer though. Don't forget to post pictures! We love pictures! -- 73/Rick W4XA __________________________________ All posts are created using OpenSuSE Leap 15.5 x64 Linux |
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Re: HT45 Loudenboomer working now with new power supply
Using the Duncan Amps power supply designer (/g/duncanampspsud) I modeled the factory supply with 866As, with diodes, and with different bleeder and capacitor values. Long story short, everything other than design values increase transformer/choke current, HV, or both.? Took bottom cover off the RF deck and found: Rattling to be a small nut and washer that do not appear to be part of the amp; RF deck filament transformer good; 3-400Z heater continuity, Grid not shorted; Ig and Ip metering resistors are open(Ig resistor blown open :-); Meter works; Lots of dust, dirt, and cat(?) hair.? Hope to find some suitable 0.25 ohm resistors in the junk box. HP45: 10k resistor for the HP45 NE51 lamp is missing.? Hope the tube is not gassy. Use the ~10kV P to P transformer secondary with some current limiting to check for gas in the tube? Why not! What to do once working? Move RF deck fuse holder to HP45 chassis and use that hole for a HV connector to run HV+ with wire that's good for at least 3kV. Assemble TR relay(s) with 'PTT' keying circuit for tube bias as suggested in manual. 73, -bob ah7i |
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SR-2000 load cap
开云体育
I need the PA load capacitor for the SR-2000.
C156 3 section Halli. Part #048-000629.
I think someone else had the same need a short time ago. I cannot find the topic in the archives. Hope someone remembers the outcome or has a parts unit.
Walt Cates, WD0GOF
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Re: HT45 Loudenboomer working now with new power supply
Hi Rick and readers,
Had a little time this AM to study the supply. If I understand the RCA ham tips article: he 200K 50W bleeder, if the only load, gives ~10% ripple. That puts 3300V peaks on the paper cap that's rated for 3kV.? I'm OK if it fails, there is the fuse, and can replace with modern polyester film caps. I'm curious if adding some C will increase the peak current in the HV transformer. For anyone who has not seen one, the original transformer has big radiator fins! Operating at full ratings, it's making at least 100W of heat. I'll fire it up with 12 V AC? to verify ripple and max voltage with the 200k. With only 12 VAC on the primary, there is still close to 1 kV on the transformer secondary (P to P)!? Any reason to not move the swinging choke to the center tap lead and get the high voltage to ground off of it? Speaking of unobtainable parts, I also have a Johnson Thunderbolt. I was keeping an eye out for whichever bit of iron is bad for so long that I forgot what it needs. Poor thing has been on a little furniture dolly under the bench for over 30 years :-).? RF deck? Something is rattling under the chassis. But, the top looks good. Will get to it once the supply and HV interconnect is sorted out. |
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Re: Parting out an SX-100
I think you’re looking for these Steve? On Thu, Jun 6, 2024 at 10:32?AM trekkersteve via <trekkersteve=[email protected]> wrote: Hi Donald, |
Floyd - K8AC
waltcates
Donald J
Jacques_VE2JFE
Jim Whartenby
Rick W7IMM
Bob ah7i