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I posted the message below to the Kenwood-Hybrid group but thought the information may be useful here. -------------------------------------------------------------------------------------------------------------------------- A while back there was a discussion concerning RF detector probes. Since then, I had been looking for a NOS or used Heathkit PK-3 probe but these don't seem to be as common as the Heath PK-1 universal scope probe. I decided to purchase a PK-1 probe with the intent to convert it into an RF probe and actually made it more functional than the PK-3. Because the PK-1 comes with a SPDT switch, I use it to my advantage to switch either high or low RF detection sensitivity. The PK-3 manual gives the builder an option of installing one, or up to three germanium detection diodes. So, the choice of probe sensitivity is chosen at the time of the build. With a switch, that decision is no longer a concern. Using a Dremel tool, I cut new circuit traces on the PK-1 PC board that allows for the switched probe sensitivity. The input cap can be seen at the lower edge. It's 0.001 uF NP0 SMD with a 1KV rating. All diodes are 1N60P. The original design calls for using uninsulated braid for the ground return lead. I decided to insulate it with blue heat-shrink tubing. Images attached. Paul, W9AC

Hi all, I still had, until recently, few “Bumblebee-coded” 0.01?F, 600V Sprague capacitors that passed all the leakage tests with flying colors. I believe that they were early production units of the 160P series. All the caps in the attached picture have no detectable leak (10nA or more) at their rated working voltage. I also found an extract of the 1972 Sprague catalog that describe the capacitors lines available at that time. To any useful purpose… 73, Jacques, VE2JFE in Montreal De : [email protected] <[email protected]> De la part de Richard Knoppow Envoyé : 25 mars 2024 05:08 ? : [email protected] Objet : Re: [HallicraftersRadios] SX-100 Repair Problems - Bumblebees! Well, the Sprague caps had problems from the git-go. Hammarlund changed to ceramic caps within a couple of years. What you say is true for most paper caps but the Black Beauty caps had special problems. Paper caps seem top suffer from a degradation of the paper dielectric that was well known long ago. Some text books point out that the expected life depends on the voltage on the cap in relation to the voltage rating, i.e. the lower the applied voltage in comparison to the rating the longer the cap will last. Oil filled caps, such as transmitting caps, seem to have considerably longer life but are much larger. Modern plastic film dielectric caps do not seem to have this problem at all but who knows what we will find in seventy or eighty years. At the time Sprague made Black Beauty caps (the actual trade name for the "bumble bee") there was a change from the earlier cardboard and wax type paper caps to molded jackets made of Bakelite or some other plastic. The early BB caps seem to have had a problem. After a couple of years Sprague dropped the name Black Beauty although they still referred to them as "These black beauties" in their advertising. They also dropped the coding stripes but that may have been for some other reason. You can find these ads in QST and trade journals of the time, about the early 1950s. Sprague was a well-established manufacturer of capacitors at the time with an excellent reputation. Note that the 600 volt BB caps were oil filled. Evidently through a tubular lead at one end which was sealed after filling by inserting a wire lead and soldering or welding. Those could develop a leak. I would be interesting to know what others have found, it seems to me that BB caps in some Hewlett Packard gear (like the 400 series voltmeters) never show cracks. Perhaps -hp- was better at soldering them than Hammarlund. The windings of the BB's I've dissected appear to be a combination of plastic on paper with metal foil. Similar construction is found on other makes. I've never taken a Vitamin-Q apart but they are a much more elaborate housing than the BB or other cast or molded plastic caps. On 3/24/2024 10:44 PM, Jim Whartenby via groups.io wrote: Richard What went wrong was that time took it's toll. These capacitors have survived much longer then their intended design life. Nothing is forever except perhaps entropy. I've been looking into what is causing the Bakelite housing to split. Nothing definitive has come up so far in an internet search but it seems that voltage has an effect. Caps in low voltage circuits appear to last much longer then those with a high voltage across them. I am sure that heat is also in the mix. See attachment. So caps in AVC circuits appear to still be long lived but coupling and bypass caps in plate circuits not so much. It might be as simple as outgassing causes the internal pressure to build up and split the Bakelite or that there are internal defects in the Bakelite caused by the molding process. I have noticed that the high reliability PIO caps are metal cased like Vitamin Q caps, also made by Sprague. Being metal, the housing should be able to withstand higher internal pressure. One thing I found interesting is that the color stripe caps are aluminum foil, paper and oil (PIO) but the Black Beauty caps with printed markings are Mylar or more properly metalized polyester. The later

I noticed a Hallicrafters rig in an old ABC News clip that appeared in a recent Last Week Tonight episode covering the history of UFOs, back to the WW2 era. I am curious if anyone has a guess on the model in this very low resolution snapshot..

Discovered an issue with the pot for the sensitivity. Having intermittent connection and losing audio. That pot was a real pain to get out but managed to work it out. Its a 10k linear, but looking around online, not seeing something similar. Tons of stuff for a guitar amp. But those dont quite fit the bill size wize. Suggestions? I have taken the pot apart and will try to clean it and lube it but not sure it will be successful. Was buttoning up the radio after putting on the faceplate thats when the problem surfaced. Wife said should have left it off and let it play.....I didnt say anything...she just doesnt understand. lol

The SR2000 is working great now with thr offset fox in place. Today was time to go through the P2000 The high voltage meter was reading way low. I took the supply apart. Cleaned it, removed the meter bezel and adjusted the needles to zero. They where both below the lines Next I found the smaller of the two 2 Meg meter resistors was reading 7.5meg! I replaced it and now the meter reads correctly. I used my fluke HV probe to find 2050 volts low and 2950 volts high. I also found screen at 320 low and 426 high. My line voltage is 126 today. The PS had been recapped but the can cap and the screen cap where factory. I replaced the screen with a new 20mfd 500 volt sprauge. I don't have the can cap. I do have a 30/30 at 450 volt FT cap. It's very high quality. I have reservations about running 426 volts on a 450 cap though. Maybe I get look at the data sheet. Otherwise I will have to order 500volt caps.

The tubes have gone to a local ham except for one mailed East. Plus he (the local ham) purchased a National and two Hallicrafters radios. Thank you for the feedback on the postings. Skip Magnuson W7WGM Spokane, WA

I am looking for a choke for an SX-16 PN: C1003, CLI on schematic (MB CL1). Either an original or replacement. 73, de Larry, W6YH

Working on adding #18 to the collection. Picked up this 5T no-Boy dial receiver that matches up with the Rider drawing attached. Completing preliminary checks and metering out the IF cans showed: First IF, primary and secondary each at 8.5 ohms. Second IF primary at 95 ohms and secondary at 30 ohms. (?) Physically it looks fine. I've searched and found no data and have nothing to compare against to verify the Second IF coil measurements. I read where a S-19 may be a close comparative model but I don't have one and the S-19R I do have is a different beast. Power transformer metered out OK. Field coil is open, dang it. Tubes tested - The 80 tube had an open filament which was resolved by re-flowing solder into the pins, the 6F7 fails "very weak" a portion on the pentode side but no shorts. Caps done, electrolytic 4 and 8mfds replaced with 10mfds each. Some dogbones out of tolerance and one 100pfd mica replaced. Subbed in a 1500 ohm for the open FC. At initial power up on the variac and at 40vac input the 5 and 6vac reached enough that the 80 kicked in and a low B+ came up, lamps and filaments glowed. Bringing up to 60vac sound was heard and at 80-90vac I could clearly tune in a BC station. B+ at 250-255v. Then, as if you threw a switch, a dominant "power" hum kicked in and the clear sound became garbled under that hum, the hum being constant despite volume position. The power transformer began to heat up excessively, I heard a crackle or two coming from it. And R4 (25K replaced with a 27K 1W, off B+ / screen of 6A7 in drawing) gets VERY hot. R6 is also replaced with a 27K. The rig is now on a test bench transformer for its supply (320-0-320), a test speaker with audio transformer, the field coil subbed by a 1500 ohm 10W wire-wound. No change in the operation, symptoms, all supply voltages come up as expected, the B+ remains pretty steady at 245-250v even when the hum kicks in 10-15 seconds after power up. The hum may drop out and reception is clear for a few seconds before it returns, its present most of the time. I do have a 6F7 on order as its hum suspect #1 but doubting its the root of my problem with R4 heating up. Also, an appropriate replacement transformer is on order. -- Dan K1DTS

Didn't notice this previously when testing, but, when the tube bias is set per the manual, the idling current continuously drifts upwards. For example, I can set the bias at .9 V (read across the 10 ohm resistor) and it will drift up to 1 V over the next minute or two. After repeatedly adjusting the bias, it's no longer possible to achieve the 1 volt reading with the bias pot turned full clockwise. Seems to be that the new tubes I purchased are likely soft? The plate voltage at the test pins on the power supply is 682 VDC. The range of adjustment of the bias pot as measured at the wiper is -111 VDC to -154 VDC. What do you say? 73, Floyd - K8AC

Thanks in advance. 73, gary/K5JWK

This is the third selection of some old tubes. One tube was purchased from the first offering, then after the second listing I posted, there is an “all tubes” offer, and then a local telephone number (I think) with an interest in “tubes/gear”. I’ll try to keep requests in order but local means no hassle with packing and shipping for me which is inviting. My primary objective is to find a “happy home” for the tubes. The third list: Silverton 247 - 22X National Union 82 GE 5U4G Marshal Electric 6AS7G Hytron HY4OZ RCA 872A RCA 8005 Taylor Tube 866 Jr RCA 872A GE 872A Continental Electric 2J-872-A / VT-42A (2 ea.) United Electronics 972A (2 ea.) ? 6LF6 Sylvania 6JS6C Sylvania 6BK4A / 6LX6 Westinghouse 3DB3 / 3CY3 RCA 73-26 RC D35P 73s Skip Magnuson W7WGM PS Easiest for me is email to <magnuson@...>

I came by these tubes from a friend and now SK. Some are exotic looking and most will be hard to find references to. Price is $1.00 each for my dusting them off and packing plus shipping cost which I estimate from $5 to $15 each. The first list is: RCA JAN CBC810 RCA VT136 GE JAN-872A Eimac 4-65A RCA JAN CRC-3529 GE JAN CG-2C40 Eimac 7034/4X150A The next list, in a day or two, will have more easily referenced tubes. Skip Magnuson W7WGM Spokane, WA

Second list of tubes. I came by these tubes from a friend and now SK. Some are exotic looking and most will be hard to find references to. Price is $1.00 each for my dusting them off and packing plus shipping cost which I estimate from $5 to $15 each. Ting-Sol JAN CAHG-4832 RCA 866-A (2ea.) GE GL-4-125A/4D21 (3 ea.) 12AU7A (how did that get in?) RCA 4-65A (5 ea.) Eimac 4-65A JAN 3BP1 (~3” dia. Oscilloscope tube) and a Electro Voice Mic. 605 HiZ More to come. Skip Magnuson W7WGM Spokane, WA

Newbie here. Thanks for welcoming me and I hope this post is appropriate. Not tested, requires evaluation to determine condition and desired restoration. This is from the estate of a long-departed SK and idle for over 30 years. I have kept it sleeping and have not applied power for any evaluation. I understand it will likely require recapping. Visual Inspection It is complete and in good cosmetic condition. All components above and below chassis appear original with no visible deformities or arcing. Two cables have been added that extend out and terminate in RCA plug/socket connectors. This appears to break out the speaker with the ability to loop back providing choice of internal or external speaker. It has a 230V line cord/plug with a 115V adapter and is wired for 115V. Photos attached. I will not ship this 60-pound boat anchor. I will be attending Dayton this year and could deliver it there, along my route or it’s available for pickup in Minneapolis, Minnesota. Asking $700 or best offer, COD. ~Pat -W?YES

These radios drop approximately 40 cycles on TX. This is annoying in modern times. This drop happens in ALL modes. I isolated the VFO from the radio and found the issue is the VFO itself. It's not a voltage regulation problem. The 12ba6 is an odd ball vfo tube and why they used a sharp cutoff tube like this I do not know. Rather than rebuild and modify the radio, my friend, Jim k7jeb and I decided to offset the TX voltage to the varactor. This is done with a 1meg resistor and a 10K. Place the 1meg from terminal 12 on relay to the ground terminal next to it. Next, unhook the wire from pin 8 on relay. Insert a 10K resistor in series with relays terminal and the wire. That's it. The offset is gone..it will be within a cycle. The rit and cal pot all work normally. Hope this helps someone.

Hello And thank you for allowing my participation in the Hallicrafters Group. Have been in amateur radio quite a while and restored several Swans, Hammarlund, Heathkit and Hallicrafter. After wishing for an SX for some time, obtained two SX-101 MK3 in fairly good condition, same owner for 15 years. Best to ask before doing something regretful, so three basic questions. 1. How to remove chassis from cabinet, I see four screws on the bottom of the case, along with those on front panel ? 2 How to remove Front Panel, as glass has dropped down on one SX ? 3 Does anyone have a Mk 3 schematic to share that can be enlarged for old eyes ? Thanks to all. Charles W5CRY

Looking to purchase subject diode for my power supply. Maybe 1 or 2 extra just to have around. Please reach me off list. Thanks, & 73, Jeff W8KZW

After much patience, the SX100 is working nicely. Very pleased with the results. Pays to not rush. Thank you all for the pointers. Still working on final tweaks, but it’s playing now where before, it was nothing.

Mine has a 25uf 25V electrolyte built in. Von: [email protected] <[email protected]> Im Auftrag von Tony Lunsford Gesendet: Donnerstag, 25. April 2024 07:43 An: [email protected] Betreff: [HallicraftersRadios] R-48 speaker Hello everyone. Does anyone know what value of the capacitor in this speaker is? Thanks

The 51E schematic is missing from the K9AXN website. This change was listed to fix the 30hz offset on RX and TX. My radio has this problem. Does anyone have a copy? Or does anyone remember what this change was? I spoke with Jim last night and he was very helpful but does not have a copy of the change. The website describes this here: 4. SERVICE NOTE 14A VFO 3rd harmonic reduction (k9axn.com) As you can see the Link for the schematic is gone. C