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
*Every post is created using Linux
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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 maybe their price lists are out of date but I have bought several tubes from these people and the price was as listed.?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
*Every post is created using Linux
|
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?
|
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
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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
|
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
|
I have received several direct responses to my connector offer. Here is what I would prefer if someone is willing to take on the project. I would donate all the connectors and cable I have in stock, including the crimp tool, at no charge except for a minimal shipping cost, to any person, club or group who would like to make up kits and distribute them. At 76 I am trying to declutter which my XYL would appreciate!
Rob, NC0B
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Rob Sherwood Sent: Friday, May 05, 2023 2:15 PM To: [email protected]Subject: Re: [DRAKE-RADIO] TR7 Connectors If anyone needs some of those tiny crimp-on RG-174 size connectors I have lots of them. Had to purchase 1000 of each for interfacing my 7-SP speech processor to the TR-7. (Product long out of production.) There is the chassis connector (called the lunar lander in some Drake documentation!), the coax tip female connector, and the coax crimp-on connector. I have the crimp-on tool, but I don't know how well a generic crimp tool would work. Rob, NC0B -----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Steve Wedge, W1ES/4 via groups.io Sent: Friday, May 05, 2023 2:07 PM To: [email protected]Subject: Re: [DRAKE-RADIO] TR7 Connectors I remember seeing them used on the clock boards for DECSystem 10 and 20. Million-dollar systems. The reasoning behind choosing them are the very small space requirements and the fact that these connectors were not designed to be disconnected/connected multiple times. 73, Steve Wedge, W1ES/4 Time flies like an arrow.? Fruit flies like a banana. Sent with Proton Mail secure email. ------- Original Message ------- On Friday, May 5th, 2023 at 3:57 PM, Gary Follett <xntrick1948@...> wrote: BTW: Even the ¡°great¡± Collins Radio Company used these junk connectors all over the very expensive KWM-380. All TenTec radios up through the Omni V, same deal.
Gary
W0DVN
On May 5, 2023, at 2:54 PM, sohosources kirk@... wrote:
Considering all of the innovations that went into the TR-series, I too have always wondered why they used those weird, probably failure-prone coax connectors... :)
--Kirk, NT0Z
Those connectors are REALLY chintzy. I think the center pin is just the center conductor of the coax itself. I wonder if one could upgrade them to SMA connectors?
- Jerry, KF6VB
|
Re: Using a resistor with 6BN8 filament
I am guessing it would. That¡¯s a pretty shoddy fix on Drake¡¯s part. I would consider rectifying and filtering the filament to this tube. Then you can use the very common 6BN8, of which I have a dozen or so.
Gary
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On May 5, 2023, at 4:45 PM, ve3fit@... wrote:
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
|
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
|
Re: 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: 2B Receiver voltages & resistances
I¡¯m still having trouble. Pulling all of the tubes didn¡¯t help, as the AGC voltage needs at least the 8BN8 and the 6BF6.
I¡¯ve started measuring voltages around the 6BF6 and they¡¯re not right. I¡¯m going to have to start lifting resistors and caps.?
I¡¯ve subbed tubes from my other 2-B and no joy, so it¡¯s not a tube.
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 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
|
Re: 2B Receiver voltages & resistances
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
|
Tektronix used something that sounds a bit similar:
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Steve Wedge, W1ES/4 via groups.io" <w1es@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Friday, May 5, 2023 3:07:09 PM
Subject: Re: [DRAKE-RADIO] TR7 Connectors I remember seeing them used on the clock boards for DECSystem 10 and 20.
Million-dollar systems.
The reasoning behind choosing them are the very small space requirements and the
fact that these connectors were not designed to be disconnected/connected
multiple times.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with Proton Mail secure email.
------- Original Message -------
On Friday, May 5th, 2023 at 3:57 PM, Gary Follett <xntrick1948@...>
wrote:
BTW: Even the ¡°great¡± Collins Radio Company used these junk connectors all over
the very expensive KWM-380. All TenTec radios up through the Omni V, same deal.
Gary
W0DVN
On May 5, 2023, at 2:54 PM, sohosources kirk@... wrote:
Considering all of the innovations that went into the TR-series, I too have
always wondered why they used those weird, probably failure-prone coax
connectors... :)
--Kirk, NT0Z
Those connectors are REALLY chintzy. I think the center pin is just the center
conductor of the coax itself. I wonder if one could upgrade them to SMA
connectors?
- Jerry, KF6VB
|
If anyone needs some of those tiny crimp-on RG-174 size connectors I have lots of them. Had to purchase 1000 of each for interfacing my 7-SP speech processor to the TR-7. (Product long out of production.) There is the chassis connector (called the lunar lander in some Drake documentation!), the coax tip female connector, and the coax crimp-on connector. I have the crimp-on tool, but I don't know how well a generic crimp tool would work.
Rob, NC0B
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Steve Wedge, W1ES/4 via groups.io Sent: Friday, May 05, 2023 2:07 PM To: [email protected]Subject: Re: [DRAKE-RADIO] TR7 Connectors I remember seeing them used on the clock boards for DECSystem 10 and 20. Million-dollar systems. The reasoning behind choosing them are the very small space requirements and the fact that these connectors were not designed to be disconnected/connected multiple times. 73, Steve Wedge, W1ES/4 Time flies like an arrow.? Fruit flies like a banana. Sent with Proton Mail secure email. ------- Original Message ------- On Friday, May 5th, 2023 at 3:57 PM, Gary Follett <xntrick1948@...> wrote: BTW: Even the ¡°great¡± Collins Radio Company used these junk connectors all over the very expensive KWM-380. All TenTec radios up through the Omni V, same deal.
Gary
W0DVN
On May 5, 2023, at 2:54 PM, sohosources kirk@... wrote:
Considering all of the innovations that went into the TR-series, I too have always wondered why they used those weird, probably failure-prone coax connectors... :)
--Kirk, NT0Z
Those connectors are REALLY chintzy. I think the center pin is just the center conductor of the coax itself. I wonder if one could upgrade them to SMA connectors?
- Jerry, KF6VB
|
On 2023-05-05 13:02, william stevens wrote: Gentlemen
I just got a handheld D104 in checking the wiring I found that the mic
cartridge is made in Japan. Is this correct? *** I was looking at those handheld D104's... Reviews were not good. Mostly, people said that the PTT switch was cheap & unreliable.
|
I remember seeing them used on the clock boards for DECSystem 10 and 20. Million-dollar systems.
The reasoning behind choosing them are the very small space requirements and the fact that these connectors were not designed to be disconnected/connected multiple times.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with Proton Mail secure email.
toggle quoted message
Show quoted text
------- Original Message ------- On Friday, May 5th, 2023 at 3:57 PM, Gary Follett <xntrick1948@...> wrote: BTW: Even the ¡°great¡± Collins Radio Company used these junk connectors all over the very expensive KWM-380. All TenTec radios up through the Omni V, same deal.
Gary
W0DVN
On May 5, 2023, at 2:54 PM, sohosources kirk@... wrote:
Considering all of the innovations that went into the TR-series, I too have always wondered why they used those weird, probably failure-prone coax connectors... :)
--Kirk, NT0Z
Those connectors are REALLY chintzy. I think the center pin is just the center conductor of the coax itself. I wonder if one could upgrade them to SMA connectors?
- Jerry, KF6VB
|
Jim Shorney
Rob Sherwood