[AMRadio] AWA Conference (long) somewhat OT
I just returned home from the AWA Annual Conference in Rochester, NY, last nite at about 8:00PM. I made the trip with Bruce, W1UJR. We arrived Tuesday nite and left around noon yesterday. I realize the conference is not over until tonight, but time and $ limitations prevented me from staying until the end. My primary interests were the flea market, the AWA Museum and Annex, seeing and meeting new friends, and the old equipment contest. On the last item, Sam Beverage, W1MGP, had given us an old Western Electric 25B amplifier to enter in the contest, as the theme this year was Western Electric, and then donate to the AWA museum. This amplifier is a compact by heavy floor-standing unit in an octagonal shape - it looks like it could be an electric space heater. There is no internal speaker, and it uses two type 205A tennis ball triodes. It's vintage is mid-20's or so. There were many extremely interesting items in the contest, for example: 1) the original breadboard superhet on which AVC was developed and first implemented - It used battery triodes (01's or 01A's, I think) throughout, 2) a homebrew rotating spiral-mirror mechanical television display, 3) Eddy Swyner's (VE3CUI) 1929 MOPA using a 27 driving a pair of 27's. (I looked for Eddy, as I would have loved to meet him in person after all these years, but our paths didn't cross. Eddy - were you there, or did you have someone else bring your rig to the conference?) We did not stay long enough to see the results of the contest. The flea market didn't have a great deal in the way of amateur gear - most of the stuff is related to collectable entertainment electronics. But there were a lot of vintage parts, tubes, sockets, ceramic insulators, stand-offs, etc., which are my main interest. I saw a Heath DX-60, a Hallacrafters S-38D, an HRO-50 or 60 (didn't look closely; too many other distractions), a couple of older HROs, a couple of National SW-3's. Stu, W2AO, was selling really cute homebrew transmitter with a single 807 in a wooden mini-rack, very nicely constructed. This is not a complete list, I'm sure there was other stuff I didn't pay much attention to and am not remembering now. As usual, there were plenty of wooden console radios, 20's battery sets, (very expen$ive) catalin radios, old transistor portables, tube-type high-fidelity gear, horn and cone speakers, and phonographs (some old mechanical ones). I came home with: 1) lots of breadboard-mount 4-pin tube sockets 2) some NOS adjustable grid-leaks (parallel cap integral with the adjustable resistor) 3) the Alice Schumacher (sp?) Hiram Percy Maxim biography 4) CQ Sideband Handbook by Don Stoner 5) a very interesting and somewhat ratty, but quite restorable, 1920's broadcast battery set (Buckingham, never heard of it), for $5. No tubes in it (probably uses 01's throughout), interesting ganged tuning arrangement, and an (intact!) moving-film dial arrangement. The panel is a unique, attractive simulated wood grain on metal with two strips of a machined swirl pattern on the metal - difficult to describe. There was no cabinet. 6) and yes, I bought one of the SW-3's - I've wanted one for a long time, but couldn't justify the typical asking price. This one is complete, and very restorable, and has one coil set (61, 12-23 MHz). Bottom plate is quite rusty, but otherwise the cabinet has a few places with minor surface rust and missing paint. It is the model using 2.5VAC tubes. The audio coupling unit looks good to my ohmmeter, but the voltage divider resistor has two open sections (no big deal). I'll be anxious to fire up this one! I was fortunate to have gotten this for $45. The AWA Museum and Annex visit on Wednesday night was as impressive and mind-blowing as my 1st visit 3 years ago. Just imagine OD'ing on old radio gear, and multiply the result by 100! There's no way I can describe it and come close to doing it justice, just make it a point to go there sometime. The James Millen (W1HRX) station in the Annex was up and running. This is James Millen's own homebrew AM transitter in 3 (yes, three) six-foot racks, and his own HRO receiver. I called several CQ's on 3837 KHz, then 3885 KHz, on Wednesday night, but could not get anyone to answer. We were putting out 250W of carrier, and were heard over at the museum a mile away, at least (!). Just no one listening at the time who wanted to talk to us, I guess. I must have called CQ on and off for at least 20 minutes; very unusual not to get a response that time of day in this part of the country. Finally, and the best part, we had a great time hanging out with and talking radio with the following folks: Bob Raide, W2ZM Ed Gable, W2MP Bill Fizette, W2DGB Dave, KA2J, who gave us a tour or his beautiful shack (~4 miles or so from the Conference) Tim W1GIG Jim KC1FB Bob WB2FOF Bob Mcteague Marty Reynolds, AA4RM Geoff Bourns Stu, W2AO Gary, WA4IAM Don, N9OO George Rancourt (can't remember George's callsign at the moment) Ken Owens This was the first time I
[AMRadio] A bit of Viking Valiant help
I'm in the middle of a long, slow project to get my Valiant back in service. I've changed out the bigger power tubes, solid-state replacements for the 866s, and partially re-capped the rig, specifically the RF power section. After finding (expensively) out that 'W' 6146s just don't work, I replaced the finals with new 'B's and power is now being transferred to the antenna / dummy load. Main bug: On the bands below 20M, however, and getting 'worse' as the frequency gets lower, the rig runs away after 15 - 30 seconds - the plate current rises fatser and faster and then needs to be shut down, lest another set of 6146s gets wasted. ;} I have neutralized the transmitter per the manual, seems ok. Bias also set per sepc. LV rectifier tubes have been chacked (on a Weston 686) and seem within spec, though their performance under load is measurable only in situ. I left the doorknob cap alone because it's fine electrically and not cracked or discolored. Do the sypmtoms sound familiar to anyone? Before I spend a bunch more hours wearing out the transmit switch, I thought I'd ask those who have a lot more experience than I do with the Valiant. I can add more info/observations as needed, specific caps replaced, etc. Thanks all! Cheers John KB6SCO
Re: [AMRadio] A bit of Viking Valiant help
Just a wild a-- guess, but I thought that the Valiant used only 6146's, not the B 6146. It is my understanding that sometimes subbing in the 'B for the early 6146 just doesn't cut the mustard. Regards, Gary...WZ1M - Original Message - From: John Lawson [EMAIL PROTECTED] To: amradio@mailman.qth.net Sent: Saturday, August 27, 2005 1:56 PM Subject: [AMRadio] A bit of Viking Valiant help I'm in the middle of a long, slow project to get my Valiant back in service. I've changed out the bigger power tubes, solid-state replacements for the 866s, and partially re-capped the rig, specifically the RF power section. After finding (expensively) out that 'W' 6146s just don't work, I replaced the finals with new 'B's and power is now being transferred to the antenna / dummy load. Main bug: On the bands below 20M, however, and getting 'worse' as the frequency gets lower, the rig runs away after 15 - 30 seconds - the plate current rises fatser and faster and then needs to be shut down, lest another set of 6146s gets wasted. ;} I have neutralized the transmitter per the manual, seems ok. Bias also set per sepc. LV rectifier tubes have been chacked (on a Weston 686) and seem within spec, though their performance under load is measurable only in situ. I left the doorknob cap alone because it's fine electrically and not cracked or discolored. Do the sypmtoms sound familiar to anyone? Before I spend a bunch more hours wearing out the transmit switch, I thought I'd ask those who have a lot more experience than I do with the Valiant. I can add more info/observations as needed, specific caps replaced, etc. Thanks all! Cheers John KB6SCO __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
RE: [AMRadio] A bit of Viking Valiant help
John, I am not a Valiant owner, but you sure seem to have a annoying and expensive problem. I keep thinking that your DC operating point is wrong somehow. Since the finals are class C, there should be enough bias to completely cut off the finals in the absence of drive. Maybe try this on CW mode and see what the key up cathode current is. I think it should be zero milliamps. Today's line voltage is typically higher than back in the 50-60's, so spec bias may not be enough today. Got a Variac? What is your filament voltage? Seven volts is too high. Also the screen voltage might be a little high too. I'd concentrate looking at this in CW mode, and Linear SSB mode. I seem to recall that a Valiant has some kind of switch to allow a SSB adapter to drive it and the 6146's run in linear mode. If you have no cathode current in CW key up, and linear mode is idling fine without a rising cathode current over time, then the tubes, and DC parameters are not the problem. I suspect however that you will have trouble with these tests, and the problem is seen static, in the absence of RF drive. I might be wrong, so read on. If the problem is seen with drive, and on the lower frequencies as you mention, then think that the RF plate load impedance is wrong, and tube efficiency is so poor that they get hotter and hotter by the second, and go into a thermal runaway. I see this problem when trying to make a poor 6DQ5 work on 6 meters in my Gonset G-76. No can do, 6 meters on a G-76 is a joke. I am not sure what a Valiant can do, but my guess is that 200 watts DC input on AM should give you about 150 watts RF output (150/200 * 100 = 75%). A 6146 normally should not show any color in the plate. Are yours blushing? If the RF plate impedance is wrong, and efficiency is poor, then it's time to scrutinize that pi-network for problems. Some of the loading capacitors may have gone south, and are only used on the lower frequencies. If you suspect a VHF parasitic oscillation, look for sudden jumps in grid current , or cathode current while adjusting the controls for plate and grid tuning. Also a neon bulb near the plate of a 6146 (can mount to a pop sickle stick) should glow orange. The color turns more purple at VHF. Keep in mind that this is general advice, and that others with more first hand Valiant experience may nail this with one stab instead of me with my buck shot approach. Hope this helps. Why would this be: It is my understanding that sometimes subbing in the 'B for the early 6146 just doesn't cut the mustard. Could it be that we need to adjust the DC parameters for the 'B' like lowering the screen voltage a little, or a little more fixed grid bias? Or is this tube unsuitable for use in a Valiant for some other reason? The 'B' was used a lot in AB1 liner use with plate voltages up to 1000 volts. Maybe the 'B' is not tame in a Valiant, and wants to go into a destructive VHF parasitic oscillation often enough to make us curse them? Regards, Jim Candela WD5JKO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of GBrown Sent: Saturday, August 27, 2005 1:01 PM To: Discussion of AM Radio Subject: Re: [AMRadio] A bit of Viking Valiant help Just a wild a-- guess, but I thought that the Valiant used only 6146's, not the B 6146. It is my understanding that sometimes subbing in the 'B for the early 6146 just doesn't cut the mustard. Regards, Gary...WZ1M - Original Message - From: John Lawson [EMAIL PROTECTED] To: amradio@mailman.qth.net Sent: Saturday, August 27, 2005 1:56 PM Subject: [AMRadio] A bit of Viking Valiant help I'm in the middle of a long, slow project to get my Valiant back in service. I've changed out the bigger power tubes, solid-state replacements for the 866s, and partially re-capped the rig, specifically the RF power section. After finding (expensively) out that 'W' 6146s just don't work, I replaced the finals with new 'B's and power is now being transferred to the antenna / dummy load. Main bug: On the bands below 20M, however, and getting 'worse' as the frequency gets lower, the rig runs away after 15 - 30 seconds - the plate current rises fatser and faster and then needs to be shut down, lest another set of 6146s gets wasted. ;} I have neutralized the transmitter per the manual, seems ok. Bias also set per sepc. LV rectifier tubes have been chacked (on a Weston 686) and seem within spec, though their performance under load is measurable only in situ. I left the doorknob cap alone because it's fine electrically and not cracked or discolored. Do the sypmtoms sound familiar to anyone? Before I spend a bunch more hours wearing out the transmit switch, I thought I'd ask those who have a lot more experience than I do with the Valiant. I can add more info/observations as needed, specific caps replaced, etc. Thanks all! Cheers John KB6SCO
