Re: Using a resistor with 6BN8 filament
Rick My 2 B is SN. 9200 and it uses 8BN8’s
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On May 6, 2023, at 3:35 PM, Rick WA6III <myr748@...> wrote:
?On Sat, May 6, 2023 at 11:53 AM, william stevens wrote:
Folks
Surplus sales of Nebraska has 8BN8’s for $ 2.50 but he requires a min buy on most of his stock and they could be very old stock
Bill
WB2UFC
Indeed! 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/Rick
WA6III
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Re: Using a resistor with 6BN8 filament
On Sat, May 6, 2023 at 11:53 AM, william stevens wrote:
Folks
Surplus sales of Nebraska has 8BN8’s for $ 2.50 but he requires a min buy on most of his stock and they could be very old stock
Bill
WB2UFC
Indeed! 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/Rick
WA6III
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Re: Using a resistor with 6BN8 filament
Folks
Surplus sales of Nebraska has 8BN8’s for $ 2.50 but he requires a min buy on most of his stock and they could be very old stock
Bill
WB2UFC
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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,
are UNC 4-40 - look like about 1/4 inch long. But what sort of head?
There is an impossible variety of screw heads out there. 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 bottom
cover. Those seem to be self-tapping sheetmetal
screws. One of the holes has graduated to the next size :(. Correct. 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
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Re: Using a resistor with 6BN8 filament
I 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
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On May 5, 2023, at 5:10 PM, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
?
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.?
I tried removing all tubes except the ones involved in the bias supply, with no luck. Negative voltages everywhere are off from spec.?
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: Should read 5 ohms.?
-------- Original message -------- From: Richard Knoppow <1oldlens1@...> Date: 5/5/23 4:07 PM (GMT-08:00) Subject: Re: [DRAKE-RADIO] Using a resistor with 6BN8 filament
Along about 1945 (very approximately) it became common to run 6H6 tubes used as series noise limiters with reduced filament voltage. Typically any Ohm resistor in series with the filament.? Thisbwas.toneliminate hum.? I have never seen it discussed in any text. I can't remember the correct term but think it was to reduce a space charge virtual cathode.? ?Not seen it used for detectors. I also don't remember if it's applied to 6AL5 tubes.? It's possible a series resistor on a 6BN8 might work in place of the other tube.
-------- Original message -------- From: ve3fit@... Date: 5/5/23 2:45 PM (GMT-08:00) Subject: Re: [DRAKE-RADIO] Using a resistor with 6BN8 filament
The 8BN8 filament spec is actually 8.4V and .45A. So, Drake runs them at 3/4 of their rated voltage to eliminate
the hum. Would running a 6.3V tube at 3/4 of it's rated filament voltage have the same effect?
My calculations show that a suitable dropping resistor to do this would be dissipating almost a watt.
I guess that using an 8BN8 was a cost-effective solution at the time.
Ken, VE3FIT
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Cabinet screws are flat heads.??
On Fri, May 5, 2023, 18:39 jerry-KF6VB < jerry@...> wrote: All,
? ? Mine is missing some.? Looks like the screws that hold the top on,
are UNC 4-40 - look like about 1/4 inch long.? But what sort of head??
There is an impossible variety of screw heads out there.
? ? Also missing a few internal screws - the ones that hold the bottom
cover.? Those seem to be self-tapping sheetmetal
screws.? One of the holes has graduated to the next size :(.
? ? ? ? ? ? ? ?- Jerry, KF6VB
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R-4C wire with no end stop
On the back of the print on the MODE/FILTER switch in my R-4C there is a 3 cm wire with no end stop. It is soldered onto the shield of the coax cable, and the solder looks original. Any idea what it is supposed to do? Serial number 18xxx.
Thanks.
Peter OZ8CTH
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Re: Using a resistor with 6BN8 filament
Like Dan mentioned,? thanks for posting your work Steve (and others).? It's great to learn from your experiences.
John K5MO
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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
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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.
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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.
--
73/Rick
WA6III
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Re: Using a resistor with 6BN8 filament
Oh, and by the way for everyone,? I have also found that eBay is not always the best (or cheapest) place to find tubes.
--
73/Rick
WA6III
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Re: Using a resistor with 6BN8 filament
On Thu, May 4, 2023 at 02:20 PM, Steve Wedge, W1ES/4 wrote:
It won't come up to 1.5V.
?
I have another 8BN8 coming in and that's fine, as I like to have a spare ($30 hurt a little, though!).?
?
Steve Wedge, W1ES/4
?
Time flies like an arrow.? Fruit flies like a banana.
?
Sent with secure email.
?
------- Original Message -------
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.?
8BN8
3.00
Just click below and find your tube
Cheers, Rick --
73/Rick
WA6III
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Re: Drake C Line Service Information CD
Go to the web site and look?
Jim W7RY
On 5/5/2023 10:23 PM, aa5wg via
groups.io wrote:
What was the last version? for the R4C
Service CD?
--
Thanks and 73, Jim W7RY
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Re: Drake C Line Service Information CD
What was the last version? for the R4C
Service CD?
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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.?
I tried removing all tubes except the ones involved in the bias supply, with no luck. Negative voltages everywhere are off from spec.?
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: Should read 5 ohms.?
-------- Original message -------- From: Richard Knoppow <1oldlens1@...> Date: 5/5/23 4:07 PM (GMT-08:00) Subject: Re: [DRAKE-RADIO] Using a resistor with 6BN8 filament
Along about 1945 (very approximately) it became common to run 6H6 tubes used as series noise limiters with reduced filament voltage. Typically any Ohm resistor in series with the filament.? Thisbwas.toneliminate hum.? I have never seen it discussed in any text. I can't remember the correct term but think it was to reduce a space charge virtual cathode.? ?Not seen it used for detectors. I also don't remember if it's applied to 6AL5 tubes.? It's possible a series resistor on a 6BN8 might work in place of the other tube.
-------- Original message -------- From: ve3fit@... Date: 5/5/23 2:45 PM (GMT-08:00) Subject: Re: [DRAKE-RADIO] Using a resistor with 6BN8 filament
The 8BN8 filament spec is actually 8.4V and .45A. So, Drake runs them at 3/4 of their rated voltage to eliminate
the hum. Would running a 6.3V tube at 3/4 of it's rated filament voltage have the same effect?
My calculations show that a suitable dropping resistor to do this would be dissipating almost a watt.
I guess that using an 8BN8 was a cost-effective solution at the time.
Ken, VE3FIT
|
Re: Using a resistor with 6BN8 filament
I guess I was the first. I asked this question in the Drakelist in 2007. Here is K7OAH's answer. There is also some discussion in the thread about using a 6BNN8 with resistor. 73 -Jim NU0C On Fri, 05 May 2023 16:07:30 -0700 "Richard Knoppow" <1oldlens1@...> wrote: Along about 1945 (very approximately) it became common to run 6H6 tubes used as series noise limiters with reduced filament voltage. Typically any Ohm resistor in series with the filament.? Thisbwas.toneliminate hum.? I have never seen it discussed in any text. I can't remember the correct term but think it was to reduce a space charge virtual cathode.? ?Not seen it used for detectors. I also don't remember if it's applied to 6AL5 tubes.? It's possible a series resistor on a 6BN8 might work in place of the other tube.
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MCX would be easier bit still a PITA. They are closer in size and come in right angle and also in-line male and female cable connectors that should fit through holes. You would need transition cables in some limited space areas. Haven't got to that point yet as I have had no failures. Unless you have your own crimp tools you would need to order pre-made cables to your spec. Expensive either way. 73 -Jim NU0C On Fri, 5 May 2023 14:54:25 -0500 "Gary Follett" <xntrick1948@...> wrote: Converting to SMA would be a pretty labor intensive job, and the resulting SMA cable would not get through the hole in the DR7 to reach its destination. Fixing the existing connector is a better bet.
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Re: Using a resistor with 6BN8 filament
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-------- Original message -------- From: Richard Knoppow <1oldlens1@...> Date: 5/5/23 4:07 PM (GMT-08:00) Subject: Re: [DRAKE-RADIO] Using a resistor with 6BN8 filament
Along about 1945 (very approximately) it became common to run 6H6 tubes used as series noise limiters with reduced filament voltage. Typically any Ohm resistor in series with the filament.? Thisbwas.toneliminate hum.? I have never seen it discussed in any text. I can't remember the correct term but think it was to reduce a space charge virtual cathode.? ?Not seen it used for detectors. I also don't remember if it's applied to 6AL5 tubes.? It's possible a series resistor on a 6BN8 might work in place of the other tube.
-------- Original message -------- From: ve3fit@... Date: 5/5/23 2:45 PM (GMT-08:00) Subject: Re: [DRAKE-RADIO] Using a resistor with 6BN8 filament
Has anybody actually tried a 6BN8 in a 2B to check for "rectified hum" ? How bad is it? The 8BN8 filament spec is actually 8.4V and .45A. So, Drake runs them at 3/4 of their rated voltage to eliminate the hum. Would running a 6.3V tube at 3/4 of it's rated filament voltage have the same effect? My calculations show that a suitable dropping resistor to do this would be dissipating almost a watt. I guess that using an 8BN8 was a cost-effective solution at the time. Ken, VE3FIT
|
Re: Using a resistor with 6BN8 filament
Along about 1945 (very approximately) it became common to run 6H6 tubes used as series noise limiters with reduced filament voltage. Typically any Ohm resistor in series with the filament.? Thisbwas.toneliminate hum.? I have never seen it discussed in any text. I can't remember the correct term but think it was to reduce a space charge virtual cathode.? ?Not seen it used for detectors. I also don't remember if it's applied to 6AL5 tubes.? It's possible a series resistor on a 6BN8 might work in place of the other tube.
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-------- Original message -------- From: ve3fit@... Date: 5/5/23 2:45 PM (GMT-08:00) Subject: Re: [DRAKE-RADIO] Using a resistor with 6BN8 filament
Has anybody actually tried a 6BN8 in a 2B to check for "rectified hum" ? How bad is it? The 8BN8 filament spec is actually 8.4V and .45A. So, Drake runs them at 3/4 of their rated voltage to eliminate the hum. Would running a 6.3V tube at 3/4 of it's rated filament voltage have the same effect? My calculations show that a suitable dropping resistor to do this would be dissipating almost a watt. I guess that using an 8BN8 was a cost-effective solution at the time. Ken, VE3FIT
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Re: 2B Receiver voltages & resistances
? 6U8's and 6U8A's are completely interchangeable since the A version only has a slightly different heater warmup time. Either should be fine in the 2-B. I have a couple of sleeves of 6U8A's from my earlier Collins S-Line days.
Dan
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On May 5, 2023, at 5:25 PM, ve3fit@... wrote:
?I replaced the 6U8, V2, with an NOS RCA 6U8A, date code 1970. The AVC circuits can now be adjusted as per the manual
and the STDBY / RECEIVE? switch operates as it should.
I measured the signal waveform on the cathode of the 6BE6, V3, with a 10 Meg, 13 pF Tek scope probe. I'm seeing 3 Vp-p at the correct frequency
which seems reasonable. Looking at the control grid upsets the frequency, but does show about a volt or more positive bias.? The published 6BE6
voltage reading is still a mystery to me. I was taught that tube oscillators have a slight negative grid bias if they're working properly. Oh well.
Ken, VE3FIT
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Jim Shorney
