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Heath HW-101 bias question
Just recently got a HW-101, with low power out,I can get a few more
watts by adjusting the bias slightly above the 20ma mark, how safe is it this? Since I dont have spare 6146's what should I be looking for that could be a problem other than the finals? Thanks in advance...Gil |
gil wrote:
Just recently got a HW-101, with low power out,I can get a few more watts by adjusting the bias slightly above the 20ma mark, how safe is it this? Since I dont have spare 6146's what should I be looking for that could be a problem other than the finals? Thanks in advance...Gil Sorry, but the finals are the usual reason for low output. You will go through many sets of finals before you wear out the driver. Make sure that your replacement finals are 6146, or 6146A's, never B's! Note, 6146W's can be all three types. The later 6146W's are B's. Don't get creative with the bias. It has nothing to do with the power output, but everything to do with balancing tube life with low distortion. When your bias is low, your tubes are cut-off on opposite cycles, and you get cross over distortion. When your bias is high, the tubes are approaching class A operation where they make a good expensive short lived shack heater. -Chuck |
Hi,
The bias should be set to 40 mA with both finals installed. Set the bias by using push to talk mode in SSB, no audio. If you have another receiver, listen to the carrier output and adjust the internal notch controls for minimum carrier with no audio. Running the HW-101 at 20 mA bias would reduce the output, and worsen the distortion on SSB. You can check the balance of your finals by running one at a time, and setting the bias for 20 mA with a single tube. (remove the other tube completely, don't just disconnect the top cap). If the tubes aren't within 5 mA of each other, I'd look for around for a better balanced set of finals. I'd do this check on 80m, because by removing one tube, you are upsetting the neutralization. 73, Ed Knobloch gil wrote: Just recently got a HW-101, with low power out,I can get a few more watts by adjusting the bias slightly above the 20ma mark, how safe is it this? Since I dont have spare 6146's what should I be looking for that could be a problem other than the finals? Thanks in advance...Gil |
Make sure that your replacement finals are 6146, or 6146A's, never B's! I've got to challenge this statement. This rumor has been circulating for several years now. When I received my new HW-100 from Heathkit in 1968, it came with RCA 6146B's. There was a note enclosed that said that they(Heath) were having problems getting 6146A's and that the 6146B's would work fine. They did. The radio neutralized without any problems and stayed that way. I had the radio for about 10 years and when I sold it, it had the same tubes and still produced full output. Darrell |
Darrell wrote:
Make sure that your replacement finals are 6146, or 6146A's, never B's! I've got to challenge this statement. This rumor has been circulating for several years now. When I received my new HW-100 from Heathkit in 1968, it came with RCA 6146B's. There was a note enclosed that said that they(Heath) were having problems getting 6146A's and that the 6146B's would work fine. They did. The radio neutralized without any problems and stayed that way. That there are big differences between the 6146(A), and the 6146B is not a rumour. It shows up on the spec sheets as different interelectrode capacitances. The 6146B had a bigger plate size, and handled something like a third more plate dissipation. It would have been better if I had said that you must use which ever was certified by the manufacturer, straights, A's or B's. Heath had already made the necessary modifications to the final section of your radio. You would probably have had problems if you tried A's. The 6146B should have been issued a new number. -Chuck |
Darrell wrote:
Yes, there are diffences between the A and B versions. There are also differences between various manufacturers. However, that doesn't change the fact that the two tubes are generally interchangeable. All of the hoopla got started when an article was written about some problems Motorola had with some VHF gear that was designed around the 6146A and had fixed neutralization. Their attempt to stadardize around the 6146B caused them some problems. The bottom line is, if it will neutralize, it will work fine. Frankly, I've never found a piece of ham gear they won't work in. A partial list of radios I have used them in with NO PROBLEMS: COLLINS: KWM2A, 32S3A GONSET: Commander HEATHKIT: DX-60, DX100, HW-100, HW-101, Apache JOHNSON: Ranger, Valiant, Viking II KNIGHT: T-150 MULTI ELMAC: AF67, AF68 WRL: Globe Scout 680A There are others. Like I said, I've never found an example where they won't work, and work well. I haven't tried them on VHF equipment. I'll be the first to admit that there could be a problem there. Darrell I have used the A's and B's interchangeably in both Heath SB-102 and Collins S-line with no problems. Chuckie doesn't know everything even though he thinks he does. |
Yes, there are diffences between the A and B versions. There are also
differences between various manufacturers. However, that doesn't change the fact that the two tubes are generally interchangeable. All of the hoopla got started when an article was written about some problems Motorola had with some VHF gear that was designed around the 6146A and had fixed neutralization. Their attempt to stadardize around the 6146B caused them some problems. The bottom line is, if it will neutralize, it will work fine. Frankly, I've never found a piece of ham gear they won't work in. A partial list of radios I have used them in with NO PROBLEMS: COLLINS: KWM2A, 32S3A GONSET: Commander HEATHKIT: DX-60, DX100, HW-100, HW-101, Apache JOHNSON: Ranger, Valiant, Viking II KNIGHT: T-150 MULTI ELMAC: AF67, AF68 WRL: Globe Scout 680A There are others. Like I said, I've never found an example where they won't work, and work well. I haven't tried them on VHF equipment. I'll be the first to admit that there could be a problem there. Darrell Darrell wrote: Make sure that your replacement finals are 6146, or 6146A's, never B's! I've got to challenge this statement. This rumor has been circulating for several years now. When I received my new HW-100 from Heathkit in 1968, it came with RCA 6146B's. There was a note enclosed that said that they(Heath) were having problems getting 6146A's and that the 6146B's would work fine. They did. The radio neutralized without any problems and stayed that way. That there are big differences between the 6146(A), and the 6146B is not a rumour. It shows up on the spec sheets as different interelectrode capacitances. The 6146B had a bigger plate size, and handled something like a third more plate dissipation. It would have been better if I had said that you must use which ever was certified by the manufacturer, straights, A's or B's. Heath had already made the necessary modifications to the final section of your radio. You would probably have had problems if you tried A's. The 6146B should have been issued a new number. -Chuck |
The required screen voltage for the Bs is higher also.
73, K8AC "Chuck Harris" wrote in message ... Darrell wrote: Make sure that your replacement finals are 6146, or 6146A's, never B's! I've got to challenge this statement. This rumor has been circulating for several years now. When I received my new HW-100 from Heathkit in 1968, it came with RCA 6146B's. There was a note enclosed that said that they(Heath) were having problems getting 6146A's and that the 6146B's would work fine. They did. The radio neutralized without any problems and stayed that way. That there are big differences between the 6146(A), and the 6146B is not a rumour. It shows up on the spec sheets as different interelectrode capacitances. The 6146B had a bigger plate size, and handled something like a third more plate dissipation. It would have been better if I had said that you must use which ever was certified by the manufacturer, straights, A's or B's. Heath had already made the necessary modifications to the final section of your radio. You would probably have had problems if you tried A's. The 6146B should have been issued a new number. -Chuck |
Cmd Buzz Corey wrote:
Darrell wrote: COLLINS: KWM2A, 32S3A GONSET: Commander HEATHKIT: DX-60, DX100, HW-100, HW-101, Apache JOHNSON: Ranger, Valiant, Viking II KNIGHT: T-150 MULTI ELMAC: AF67, AF68 WRL: Globe Scout 680A There are others. Like I said, I've never found an example where they won't work, and work well. I haven't tried them on VHF equipment. I'll be the first to admit that there could be a problem there. Darrell I have used the A's and B's interchangeably in both Heath SB-102 and Collins S-line with no problems. Chuckie doesn't know everything even though he thinks he does. Thanks for the vote of confidence! -Chuck |
Cmd Buzz Corey wrote:
Darrell wrote: COLLINS: KWM2A, 32S3A GONSET: Commander HEATHKIT: DX-60, DX100, HW-100, HW-101, Apache JOHNSON: Ranger, Valiant, Viking II KNIGHT: T-150 MULTI ELMAC: AF67, AF68 WRL: Globe Scout 680A There are others. Like I said, I've never found an example where they won't work, and work well. I haven't tried them on VHF equipment. I'll be the first to admit that there could be a problem there. Darrell I have used the A's and B's interchangeably in both Heath SB-102 and Collins S-line with no problems. Chuckie doesn't know everything even though he thinks he does. Here is a link buzz. If you can find someone to read it to you, you might find it illuminating: http://home.comcast.net/~k9sth/The_6...of_Tubes_1.htm And here's an excerpt from the above link: "RCA "claimed" that the 6146B was directly interchangeable with the earlier members of the 6146 family. Unfortunately, this did not hold true in most cases. Collins, Heath, and probably other companies, at first issued various documents saying that the use of the 6146B in their equipment was "fine". But, this soon proved otherwise! For example, when the 6146B was used in the Collins 32S-1, 32S-2, 32S-3, 32S-3A, KWM-2, and KWM-2A it was discovered that the components in the neutralization circuitry "burned up" in a very short amount of time. Thus, Collins had to retract the statement that it was "OK" to use the 6146B. Then, due to the fact that the United States military establishment wanted to "standardize" on the 6146W equivalent of the 6146B, the neutralization components had to be redesigned to allow the 6146B to be used. Fortunately, these changes did not affect the use of the earlier 6146 and 6146A in those transmitters manufactured to use the 6146B. All three types of tubes may be used without any problem in these transmitters. Replacing the 6146 / 6146A tubes with 6146B types often results in spurious emissions, parasitic oscillations, etc. This is due to the fact that there are different bias requirements, different inter-electrode capacitances, etc. of the 6146B versus the other two. It is often difficult to neutralize 6146B tubes when used in place of the 6146 / 6146A. If neutralization can be achieved, often it lasts for just a few minutes before the tube(s) goes into oscillation." Somewhere, in my files, I have the ECO sheets from Collins that discuss the 6146B, and the changes that need to made for the KWM2(A) to safely use the tube. Later model KWM-2(A) and 32S transmitters had these changes already incorporated when they came from the factory. The changes for the HW100, 101, SB100,and 101, can be found through a little light searching on the web. The SB102 always had the change, IIRC. -Chuck |
Darrell wrote:
There are others. Like I said, I've never found an example where they won't work, and work well. I haven't tried them on VHF equipment. I'll be the first to admit that there could be a problem there. Exciter for the RCA FM-1 broadcast transmitter needs a capacitor change if you go to the B version. Details are in the manual. This is a single-ended gain stage that drives about 10W into the final. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
The only difference in capacitance I see is Cgp, 0.24 pF for the 6146A
vs. 0.22 pF for the 6146 and the 6146B. Doesn't sound like any difference at all, unless maybe the average values are quite a bit different for the 6146B vs. the other two (but what would cause that?). I don't question those who say there's a problem with some rigs, but on paper all three tubes do seem to be the same (at the lower screen voltage the 6146 is designed for). Apparently RCA thought the same thing. No conclusions, just ruminations... 73, Mike, KK6GM |
"Mike Silva" wrote in news:1117989475.147628.191590
@f14g2000cwb.googlegroups.com: The only difference in capacitance I see is Cgp, 0.24 pF for the 6146A vs. 0.22 pF for the 6146 and the 6146B. Doesn't sound like any difference at all, unless maybe the average values are quite a bit different for the 6146B vs. the other two (but what would cause that?). I don't question those who say there's a problem with some rigs, but on paper all three tubes do seem to be the same (at the lower screen voltage the 6146 is designed for). Apparently RCA thought the same thing. No conclusions, just ruminations... 73, Mike, KK6GM There is no real difference. The 6146B was very popular in the 1960's. Everyone was switching over to them with no problems. Trust me, I was there. One guy writes an article expressing an erroneous opinion about them and it becomes fact. It's nothing but an internet myth. Maybe he wanted to corner the market on the 6146B's? Like I said, I'm still looking for a radio they won't work in. Darrell |
Mike Silva wrote:
The only difference in capacitance I see is Cgp, 0.24 pF for the 6146A vs. 0.22 pF for the 6146 and the 6146B. Doesn't sound like any difference at all, unless maybe the average values are quite a bit different for the 6146B vs. the other two (but what would cause that?). I don't question those who say there's a problem with some rigs, but on paper all three tubes do seem to be the same (at the lower screen voltage the 6146 is designed for). Apparently RCA thought the same thing. No conclusions, just ruminations... 73, Mike, KK6GM Hi Mike, Neutralization is more than just interelectrode capacitance. It is also affected by plate to everything outside the tube capacitance, and, of course, the layout of the transmitter finals cage. The plate of the 6146B is bigger than the 6146, or 6146A. It has about 33% more plate dissipation as a result. There is more coupling between this bigger plate, and the outside world. As was pointed out by another poster, it also requires a higher screen voltage. In order to accomodate the 6146B, Collins completely redesigned the neutralization circuitry on the S-Line transmitters, and the KWM-2(A). The old circuitry had a 8-50pf PA neutralization capacitor, the new circuitry has a 1.8-8.7pf PA neutralization capacitor. If you put 6146B's in a KWM2(A) with the 8-50pf neutralization cap, you will be replacing all of the neutralization circuitry in the near future. -Chuck |
Chuck Harris wrote: Hi Mike, Neutralization is more than just interelectrode capacitance. It is also affected by plate to everything outside the tube capacitance, and, of course, the layout of the transmitter finals cage. The plate of the 6146B is bigger than the 6146, or 6146A. It has about 33% more plate dissipation as a result. There is more coupling between this bigger plate, and the outside world. I don't have an example of both tubes in front of me, but I don't remember the plate structure of a 6146B being larger than a 6146(A). Can anybody confirm that the 6146B plate structure is bigger? I thought the higher plate dissipation was due to some combination of different plate material and/or thicker plate material. Is it possible that the Collins neutralizing capacitor range was marginal to begin with, and that the higher power that the B tubes were capable of just brought the problem to the surface? Just wondering... 73, Mike, KK6GM |
Mike Silva wrote:
Chuck Harris wrote: Hi Mike, Neutralization is more than just interelectrode capacitance. It is also affected by plate to everything outside the tube capacitance, and, of course, the layout of the transmitter finals cage. The plate of the 6146B is bigger than the 6146, or 6146A. It has about 33% more plate dissipation as a result. There is more coupling between this bigger plate, and the outside world. I don't have an example of both tubes in front of me, but I don't remember the plate structure of a 6146B being larger than a 6146(A). Can anybody confirm that the 6146B plate structure is bigger? I thought the higher plate dissipation was due to some combination of different plate material and/or thicker plate material. Is it possible that the Collins neutralizing capacitor range was marginal to begin with, and that the higher power that the B tubes were capable of just brought the problem to the surface? Just wondering... 73, Mike, KK6GM Hi Mike, Collins went from a 7-50pf, to a 1.5-8.7pf. They made a few other tweaks in the neutralization circuitry too. I have worked on both pre, and post neutralization modification KWM-2's, and I can tell you that when used with the proper tubes, the caps in either end up in the center of their range. The KWM2A that is in my station right now has 6146W's, and the 1.5-8.7pf neutralization cap, and the cap is in the center of its range. The heaters on my 6146W's barely glow, so they are probably 6146A's. I don't recall, are the B's dark heater too? You get the same power out on the KWM-2 with any of the 6146 family, so I don't think excess power output is the problem. Collins said that the original neutralization circuitry tended to burn up with the 6146B tubes. I'm willing to trust Collins to know the why's and wherefores. You can view the complete Heathkit SB101 ECO notes somewhere on the net. Heath said there is something different about the 6146B's that requires changes in the PA section. [ They also had a tremendous problem with variations in other tubes made by different manufacturers. They out and out banned certain manufacturer's tubes from use in their rigs.] That the 6146B is different isn't just the rumblings of some flaky ham. Collins and Heath made the necessary changes shortly after the B came out, and long before I ever owned a rig using a 6146. -Chuck |
I had one of the first Heathkit HW-100's. I was on a waiting list before
they ever made the first shipment. Mine came with 6146B's. If there was any change, it would have to of been made in the first few hundred. Like I have said, the card that came with my HW-100 said they were equivalent. I've seen dozens of them with both versions. They all worked just fine. I still say it's nothing but an internet myth. Darrell Mike Silva wrote: Chuck Harris wrote: Hi Mike, Neutralization is more than just interelectrode capacitance. It is also affected by plate to everything outside the tube capacitance, and, of course, the layout of the transmitter finals cage. The plate of the 6146B is bigger than the 6146, or 6146A. It has about 33% more plate dissipation as a result. There is more coupling between this bigger plate, and the outside world. I don't have an example of both tubes in front of me, but I don't remember the plate structure of a 6146B being larger than a 6146(A). Can anybody confirm that the 6146B plate structure is bigger? I thought the higher plate dissipation was due to some combination of different plate material and/or thicker plate material. Is it possible that the Collins neutralizing capacitor range was marginal to begin with, and that the higher power that the B tubes were capable of just brought the problem to the surface? Just wondering... 73, Mike, KK6GM Hi Mike, Collins went from a 7-50pf, to a 1.5-8.7pf. They made a few other tweaks in the neutralization circuitry too. I have worked on both pre, and post neutralization modification KWM-2's, and I can tell you that when used with the proper tubes, the caps in either end up in the center of their range. The KWM2A that is in my station right now has 6146W's, and the 1.5-8.7pf neutralization cap, and the cap is in the center of its range. The heaters on my 6146W's barely glow, so they are probably 6146A's. I don't recall, are the B's dark heater too? You get the same power out on the KWM-2 with any of the 6146 family, so I don't think excess power output is the problem. Collins said that the original neutralization circuitry tended to burn up with the 6146B tubes. I'm willing to trust Collins to know the why's and wherefores. You can view the complete Heathkit SB101 ECO notes somewhere on the net. Heath said there is something different about the 6146B's that requires changes in the PA section. [ They also had a tremendous problem with variations in other tubes made by different manufacturers. They out and out banned certain manufacturer's tubes from use in their rigs.] That the 6146B is different isn't just the rumblings of some flaky ham. Collins and Heath made the necessary changes shortly after the B came out, and long before I ever owned a rig using a 6146. -Chuck |
Darrell wrote:
I had one of the first Heathkit HW-100's. I was on a waiting list before they ever made the first shipment. Mine came with 6146B's. If there was any change, it would have to of been made in the first few hundred. Like I have said, the card that came with my HW-100 said they were equivalent. I've seen dozens of them with both versions. They all worked just fine. I still say it's nothing but an internet myth. Darrell Doing some casual research, I find that Heath did indeed know about the problem, as early as January, 1978, but in 1979, when they had no choice, they gave approval to use the 6146B. -----------------------QUOTED FROM HEATHKIT's CHANGE BULLETINS--------------------- ************************************************** ***************************** JANUARY 20, 1978 HW-101 BULLETIN NO: SSB TRANSCEIVER HW-101-18 RF CHOKE IN FINAL PLATE CIRCUIT OVERHEATS OR DIFFICULT TO NEUTRALIZE ON 10 METER & 15 METER BANDS 6146B tubes in the final amplifier may be causing this problem. To correct, replace with 6146A tubes. A label will be installed on the back panel of the HW-101 recommending the use of 6146A tubes only. The 6146B tubes should not be used as a replacement. ----------------------------------------------------------------------------- ------------------------------------------------------------------------------ NOVEMBER 20, 1978 HW-101 BULLETIN NO: SSB TRANSCEIVER HW-101-39 IDENTIFICTION OF THE 6146A TUBES The 6146A tubes [PN 411-75] used at V8 and V9 of this unit are marked '6146A' in white ink on the side of the tube. These tubes may also have '6146B' etched in the galss. These tubes have been reworked by G.E. and are acceptable for use in the HW-101. Most tube cartons will contain the following insert to explain the situation to the customer: IMPORTANT INFORMATION; THE TUBE SUPPLIED WITH THIS NOTICE IS TYPE 6146A, AS PRINTED ON ONE SIDE OF THE TUBE, EVEN THOUGH THERE MAY BE A 6146B ETCHED ELSEWHERE ON THE TUBE ENVELOPE. ALWAYS REPLACE V8 AND V9 WITH 6146A TYPE TUBES Replace the backing from this label and place the label at any convenient location inside the cabinet top. ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ May 15, 1979 HW-101 Bulletin No: SSB Transceiver HW-101-49 Changeover To 6146B Finals The 6146A final amplifier tubes are no longer available from the manufacturer. Future productions runs will use the 6146Bs. These are GE brand tubes and have been tested in the HW-101. No difficulty was encountered in neutralizing the finals; nor did the RF choke in the final plate circuit overheat. The tube replacement label [PN 390-146] should be removed from all units brought in for service. ------------------------------------------------------------------------------- -----------------------QUOTED FROM HEATHKIT's CHANGE BULLETINS--------------------- I haven't yet found the bulletin mentioned by Zook, but everything he stated fits the above bulletins. To recap, he said that 1) heath forbid the use of 6146B's 2) Heath switched to B's when GE stopped making A's 3) Heath came to regret it. I need to find the Bulletins from past 1979. That is where the meat is. -Chuck Harris |
"Chuck Harris" wrote in message ... gil wrote: Just recently got a HW-101, with low power out,I can get a few more watts by adjusting the bias slightly above the 20ma mark, how safe is it this? Since I dont have spare 6146's what should I be looking for that could be a problem other than the finals? Thanks in advance...Gil Sorry, but the finals are the usual reason for low output. You will go through many sets of finals before you wear out the driver. Make sure that your replacement finals are 6146, or 6146A's, never B's! Note, 6146W's can be all three types. The later 6146W's are B's. Don't get creative with the bias. It has nothing to do with the power output, but everything to do with balancing tube life with low distortion. When your bias is low, your tubes are cut-off on opposite cycles, and you get cross over distortion. Huh? The tubes in the HW-101 are in parallel, not in push-pull!! |
BFoelsch wrote:
Don't get creative with the bias. It has nothing to do with the power output, but everything to do with balancing tube life with low distortion. When your bias is low, your tubes are cut-off on opposite cycles, and you get cross over distortion. Huh? The tubes in the HW-101 are in parallel, not in push-pull!! A senior moment, and audio habits, made that phrase come out. Sorry! A resonating tank circuit makes how you think of Class A, AB, B, and C operation somewhat different, though. (A = 360 degree plate conduction; AB1 = less than 360, but more than 180 degree conduction, no grid current; AB2 = less than 360, but more than 180 degree conduction, w/some grid current; B = 180 degree plate conduction; C = less than 180 degree plate conduction.) The tank "free-wheels" through the areas of non-conduction in the RF signal, effectively taking the place of the second tube in a push-pull amplifier, thus making AB, B, and C modes of operation usable with one tube. But the tank does nothing to improve amplification linearity. The correct amount of bias is still chosen for the same reasons as in the push-pull amplifier: so that the stage remains suitably linear under normal operation, and tube life is adequate for the mission. In this case, the correct bias puts the stage in the Class AB1 region. The OP was running a pair of 6146's, at 20ma bias, and commenting on how turning the bias up a bit made his too low output power rise a little. I assumed he meant 20 ma each tube, as the usual bias for a pair of 6146's (ala Collins) is 40ma, 50ma if you are running into a linear. If he was indeed running 40ma to a pair of 6146's, and his output power was still too low, the usual reason is he has a used up pair of finals. And the thread went (some would say downhill) from there... -Chuck |
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