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2-A S-Meter Reading
I have a very clean (for a 60 year old radio) 2-A that I'm checking out for selling. It has been my bench receiver for years and seems to work fine.? All voltages check out fine.? for a 50 uV signal on 40m, what should the S reading be? I'm getting S7.? All caps are the original and I've peaked the 455 KC transformer.??
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Re: Using a resistor with 6BN8 filament
Rick WA6III
On Sat, May 6, 2023 at 01:33 PM, william stevens wrote:
RickBill, You are absolutely right!?? I screwed up! (That never happens does it?) I see what I did now!!? Late last night I had both schematics on my desktop....? the 2-B? was a DJVU file and the 2-A has both.?? My browser will directly open the PDF but not the DJVU.? I have to save it first! (and I "saved-as" the 2-B as? 2A.djvu!!) The 2-A of course, uses a 6AV6 driving the 6AQ5 audio amp and the 2-B uses the 6BN8 (triode section) to drive the 6AQ5. Drake was clearly trying to save pennies and keep the tube count down and used the tri-section 8BN8 and/or 6BN8 Then they really reduced it in the 2-C That 2A schematic from Bama was particularly bad resolution..... -- 73/RickWA6III*Every post is created using Linux |
Re: Using a resistor with 6BN8 filament
My 2B is s/n 2974 and it uses an 8BN8. May 1961 is printed on the S-meter rear cover.
Food for thought: if all of the filaments were floating, instead of being grounded on one side, would this 'rectified' hum problem manifest itself? Maybe not, but production would be a bit more labour intensive. Drake employed bean counters too.73. Ken, VE3FIT |
Re: Using a resistor with 6BN8 filament
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On May 6, 2023, at 4:50 PM, william stevens via groups.io <197174stevens@...> wrote:
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Re: Using a resistor with 6BN8 filament
¿ªÔÆÌåÓýRick?The 8bn8 is used for 3 things bias rect,noise Lim, audio amp see attached On May 6, 2023, at 3:35 PM, Rick WA6III <myr748@...> wrote:
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Re: Using a resistor with 6BN8 filament
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On May 6, 2023, at 3:35 PM, Rick WA6III <myr748@...> wrote:
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Re: Using a resistor with 6BN8 filament
Rick WA6III
On Sat, May 6, 2023 at 11:53 AM, william stevens wrote:
FolksIndeed! I have bought several tubes from them!? They have so much "good stuff" that even if I want only 1 tube I usually get 2 or 3 and I always need other tubes and stuff too!? I am a little late to this Drake 2B party? but when I looked at the BAMA manual for the 2B, it didn't show an 8BN8 in the schematic. The 2A does.? Does the (very) early 2B's use it too? and if they do, whom ever has one, could you scan your manual and put it on BAMA?? It would sure help someone else that has an early one with no manual..... ? -- 73/RickWA6III*Every post is created using Linux |
Re: TR7 Screws
On Fri, 05 May 2023 15:39:40 -0700
"jerry-KF6VB" <jerry@...> wrote: Mine is missing some. Looks like the screws that hold the top on,They are 4-40. I've seen both slotted and Phillips used depending on the age of the gear. Could be round or pan head I suppose, I never gave it much thought. Use what suits you. Don't over think it, it is just a screw. Also missing a few internal screws - the ones that hold the bottomCorrect. ISTM that they are #4 sheet metal screws. On one of my rigs the upper card cage cover rear screws long ago graduated to the next size up. With the thin sheet metal some of the threads are delicate. Especially the screws for card cage covers. Tighten them snug but do not over tighten them! All of the cage cover screws need to be there and snug for RF tightness. 73 -Jim NU0C |
Re: Using a resistor with 6BN8 filament
¿ªÔÆÌåÓýI have a Kenwood TS-820S that received fine but would not transmit. The AGC voltage was way off. I looked at it on and off for months, hobbled by the fact that Kenwood did not provide a table of voltages with the schematic diagram. I finally found a disc ceramic cap that measured 35,000 ohms that was dragging down the high impedance AGC line. First time in many decades of repairing radios to find a bad disc ceramic cap, and this one only had 4 volts of stress on it.73, Graham, N6GH On May 5, 2023, at 5:10 PM, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
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Re: TR7 Screws
Cabinet screws are flat heads.?? On Fri, May 5, 2023, 18:39 jerry-KF6VB <jerry@...> wrote: All, |
Re: enhancing the speaker in the Ac-4 power supply?
As others note, the speaker, the enclosure, and the audio amp you have there are all compromises.? Add in age, and possible slight misalignment of your receiver (which can make audio less clear), and you have what you have.? I had considered many of the suggestions others have made, but took a different tack.? I installed one of the BHI DSP audio amps into the MS-4 enclosure ? I put the keyboard on the bottom, so that it looked otherwise stock.? The built-in amp (5W?) allowed me to run the Drake amp at a lower level with lower distortion.? Add in a touch of DSP noise reduction when needed, and it greatly enhances the audio from the old girl. I no longer feel like I need to upgrade the speaker, but know that the extra power available would allow me to choose a replacement based on sound rather efficiency and oval form factor.? As others have noted, round speaker cones generally sound better.? If you still decide to swap the speaker, a small speaker such as those in guitar "practice" amplifiers might be interesting to try, especially if you can get one for free from a non=working amp.
Good luck! Eric WK3B |
Re: Using a resistor with 6BN8 filament
Lesson learnt. I was trying to quickly find one and you see what that got me.? Carry on¡ Steve Wedge, W1ES/4 Time flies like an arrow. Fruit flies like a banana. Sent from Proton Mail for iOS On Sat, May 6, 2023 at 00:09, Rick WA6III <myr748@...> wrote:
Oh, and by the way for everyone,? I have also found that eBay is not always the best (or cheapest) place to find tubes. |
Re: Using a resistor with 6BN8 filament
Rick WA6III
On Thu, May 4, 2023 at 02:20 PM, Steve Wedge, W1ES/4 wrote:
Steve, I just looked for 8BN8's and found a few vendors that were "out of stock" but the one below appears to have them and the price is somewhat less than $30..... ? maybe their price lists are out of date but I have bought several tubes from these people and the price was as listed.?
3.00 Just click below and find your tube Cheers, Rick -- 73/RickWA6III*Every post is created using Linux |
Re: Using a resistor with 6BN8 filament
I¡¯ve been looking more closely at the schematic and there¡¯s something around V6 that isn¡¯t right.? I know that ceramic caps don¡¯t commonly leak but I¡¯ll need to check them all around the supply.? 73, Steve Wedge, W1ES/4 Time flies like an arrow. Fruit flies like a banana. Sent from Proton Mail for iOS On Fri, May 5, 2023 at 19:22, Richard Knoppow <1oldlens1@...> wrote:
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