당신은 주제를 찾고 있습니까 “heathkit w 6m – Heathkit W6M / Extremely Rare“? 다음 카테고리의 웹사이트 Chewathai27.com/you 에서 귀하의 모든 질문에 답변해 드립니다: Chewathai27.com/you/blog. 바로 아래에서 답을 찾을 수 있습니다. 작성자 seamaster969 이(가) 작성한 기사에는 조회수 1,011회 및 좋아요 7개 개의 좋아요가 있습니다.
heathkit w 6m 주제에 대한 동영상 보기
여기에서 이 주제에 대한 비디오를 시청하십시오. 주의 깊게 살펴보고 읽고 있는 내용에 대한 피드백을 제공하세요!
d여기에서 Heathkit W6M / Extremely Rare – heathkit w 6m 주제에 대한 세부정보를 참조하세요
The setup is made out of a pair of Heathkit W6M \u0026 W6A along with a pair of Mcintosh C8 preamps. The cages for the amps \u0026 faceplates of the C8 were refurbished by Deco Metal Finishing (decometalfinishing.com) in Escondido California. The electronics for both items have gone through a complete restoration
heathkit w 6m 주제에 대한 자세한 내용은 여기를 참조하세요.
Heathkit W-6M-70 chạy bóng 6550 Push Pull
Heathkit W-6M-70 chạy bóng 6550 Push Pull.
Source: vnavshop.net
Date Published: 2/29/2022
View: 973
Heathkit Model W-6M High-Fidelity Amplifier (1957)
Talk about big iron! This Heathkit W-6M monophonic amplifier was at the top of many shopping lists in 1957. Teamed with a Heathkit WA-P2 preamplifier, and FM- …
Source: antiqueradio.org
Date Published: 7/2/2022
View: 5653
Heathkit W-6M 6550 Tube Amplifier with Cage. Peerless 16431
It powers up and the meter moves, it’s the perfect candate for restoration and is being sold as-is for parts or repair. It calls for two 6550 power tubes, one …
Source: reverb.com
Date Published: 2/13/2022
View: 4430
Heathkit W-6m, finally got a pair. – Audiokarma
Everybody likes pictures, I finally got a pair of Heathkit W-6m’s. They are truly massive, beautiful transformers.
Source: audiokarma.org
Date Published: 10/23/2021
View: 1390
Heathkit W-6M (W-6A) Vintage, Mono, Tube, Power Amplifier
Classified: FOR SALE – Heathkit W-6M (W-6A) Vintage, Mono, Tube, Power Amplifier – FULLY RESTORED!! asking for $1000.00.
Source: www.usaudiomart.com
Date Published: 4/15/2021
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Schematic – Heathkit W-6M Tube Amplifier @ AmpsLab.com
Heathkit W6M. Vintage Vacuum Tube Power Amplifier….
Source: www.ampslab.com
Date Published: 10/20/2022
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Heathkit W-6M amp and WA-P2 preamp with hum
A Heathkit W-6M amplifier just landed here (with a thud — this thing is HEAVY). I’m not an audio guy, although I have restored lots of tube radios and TVs.
Source: www.antiqueradios.com
Date Published: 9/7/2021
View: 5081
Heathkit model W-6M High-Fidelity Amplifier 1957 – Pinterest
Oct 9, 2017 – Heathkit model W-6M High-Felity Amplifier 1957. … Heathkit model W-6M High-Felity Amplifier 1957 Speaker Design, Vacuum Tube,.
Source: www.pinterest.com
Date Published: 11/24/2021
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주제와 관련된 이미지 heathkit w 6m
주제와 관련된 더 많은 사진을 참조하십시오 Heathkit W6M / Extremely Rare. 댓글에서 더 많은 관련 이미지를 보거나 필요한 경우 더 많은 관련 기사를 볼 수 있습니다.
주제에 대한 기사 평가 heathkit w 6m
- Author: seamaster969
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- Date Published: 2016. 8. 18.
- Video Url link: https://www.youtube.com/watch?v=HLQY1wjo1Uw
Heathkit Model W-6M High-Fidelity Amplifier (1957)
Heathkit Model W-6M High-Fidelity Amplifier (1957) Talk about big iron! This Heathkit W-6M monophonic amplifier was at the top of many shopping lists in 1957. Teamed with a Heathkit WA-P2 preamplifier, and FM-3 Tuner it formed the core of many a hi-fi enthusiast’s dream system. Here is my restored W-6M; the second photo shows it with my WA-P2 preamp and FM-3 tuner. Finding a W-6M Amp I got this amp in a trade with a fellow collector in 2013. I wasn’t interested in replicating a 1950s hi-fi system, but I did need an audio amp to watch TV on my RCA TM-10 color monitor. The TM-10 monitor was used in TV studios and it was engineered to display the finest color picture possible in the mid-1950s. Like the ground-breaking RCA CT-100 color TV, it was based on the 15GP22 picture tube. Like most video monitors, it displays a picture with no audio. Of course, I could use a modern audio amp, but the W-6M is a more fitting companion. By joining these two best-of-breed components, I’ll enjoy a 1950s television experience that few people could have witnessed outside a broadcast studio. General Description With a list price of $109.95, the W-6M was Heathkit’s most powerful and expensive amplifier. Below is an advertisement from the September, 1957 issue of High Fidelity: The W-6M uses a pair of 6550 tubes to pump out 70 watts. It is a Williamson amplifier, a type that was popular in high-fidelity circles during the 1950s and 1960s. You can find a brief description of Williamson amps in a Wikipedia article. More details appear in these technical articles by the designer, D.T.N. Williamson. Williamson amps are characterized by massive transformers. The W-6M weighs over forty pounds and most of that weight lies in its big black transformers. Click the next icon to view the first dozen pages of the W-6M owner’s manual, which includes the schematic diagram and many technical details. By purchasing this amp in kit form, an audio enthusiast could save a considerable amount of money. The comparable amp from McIntosh (model MC-60) retailed for over $200, double the price of a W-6M. Front Panel Here’s another look at the W-6M with its tube cage removed. On the left are the beefy 6550 tubes: The front panel has four controls and a meter. From left to right, the controls are: the damping factor control, the bias meter switch, and two bias adjusters (one for each 6550 tube). The bias meter lets you balance the bias voltages for the two 6550 output tubes, a critical factor in a circuit of this type. The bias switch has three positions (OFF-1-2) and the meter has a red line near the top of its scale. To set the bias for the first output tube, you set the switch to 1 and use the first adjuster to bring the needle onto the red line. Then you switch to 2 and repeat the adjustment for the second tube. After the bias voltages are balanced at the same level, you return the switch to its OFF position. What is a Damping Control? The amplifier’s damping control was unfamiliar to me, so I asked for clarification on the Antique Radio vintage audio forum, eliciting these remarks from two forum members: (From K7MCG): That damping control, like the similar control on the Fisher model 50, uses feedback to adjust the output impedance of the amplifier, thus adjusting the damping on the motion of a driven woofer. It can’t do much to improve a good speaker, but can sometimes make a cheap woofer sound much better. It can also partially compensate for the effects of too much speaker cable resistance between the amplifier and woofer. (From dberman51): Speakers of the 1950s varied as to how much amplifier damping they needed for best bass, so this amplifier senses speaker current and uses it to drive the negative feedback loop. The damping control determines how much current gets fed back. Modern speakers want maximum damping. Another note describing this control appears on the last page of the W-6M manual. Why No Volume Control? If you’re looking for a volume control or tone controls on this amp, don’t bother. They don’t exist! As noted in the advertisement, this amp was designed to be used with a companion preamplifier, the Heathkit WA-P2, which provides those functions and also lets you switch among various inputs such as a phono turntable or FM radio tuner. In this rear view, we see the various input/output connectors, including an eight-pin socket for the cable that powers the WA-P2 preamp. The back of the output transformer sports a Peerless label and serial number. From left to right on the panel, we see the audio input jack, the eight-pin preamplifier power socket, the fuse, and two 120-volt AC sockets (switched and unswitched) for powering accessories such as a phono turntable. At far right are the speaker terminals and a four-position load selector that lets you choose a speaker of 4, 8, or 16 ohms, as well as a 70-volt output. The previous photo also shows a power switch between the two big black transformers. This non-stock switch was added by the original owner. The W-6M amp contains the power-supply circuitry needed to power itself and the WA-P2 preamp. The On-Off switch is located on the preamp, but all power comes from the W-6M. In addition to 120-volt AC for the master power switch, the connecting cable carries 6.3-volt AC for the preamp tube filaments and 300-volt DC for their plates. Adding an auxiliary power switch to the amp lets you use it with an input other than the WA-P2 preamp. In that case, you simply leave the WA-P2 power socket disconnected, but your alternate input will have to provide whatever volume control or tone controls you desire. Restoration Let’s get started with the restoration! Although sophisticated in design, the W-6M amp is much simpler to restore than most of the radios and TVs I have tackled before. In this discussion, I’ll refer to the following schematic: Getting Started Here’s a photo of the unrestored chassis: In the upper compartment we see five large cans, which hold seven of the amp’s eight electrolytic capacitors. The lower compartment contains the signal circuitry and five solid-state power-supply rectifiers. Our first glance is encouraging. This amp was assembled precisely, with tidy solder joints and proper lead dress, exactly as shown in the building manual. In a high-fidelity device, every component and wire is precisely located to prevent distortion or background hum. The original owner did a very professional job! Looking more closely, I see evidence of overheating (or at least aging) in this pair of 22K resistors on the 12AU7 tube. These resistors are connected to the second section of the 12AU7 tube, which operates as a phase splitter, feeding the audio signal to the 12AX7 push-pull amplifier stage. It’s critical that they have the same value; Heathkit specified that they have 1% tolerance, whereas most resistors in tube radios and TVs have a 20% tolerance. Even though the old resistors test very close to the specified value, I’ll replace them for peace of mind. I have selected a pair of new resistors whose values measure well within 1%. Finding no other surprises, I proceeded to do some clean-up and other preliminary tasks, such as testing the tubes and cleaning the tube pins and sockets (see First Steps in Restoration. One of the old 6550 tubes was dead, so I ordered a new matched pair. You normally can’t tell much about a tube’s condition from its outer appearance, but in this case I can see that the old tubes racked up many hours of playing time. Note the difference between the new and old tubes: The new tube’s “getter” is thick and silvery, while the old one is dull and depleted, nearly transparent. The getter is a thin deposit of metal (often barium) inside the tube’s glass envelope. Its purpose is to adsorb any stray molecules of gas that were left behind when the tube was evacuated during manufacture. As more and more molecules are neutralized during the tube’s working life, the getter changes appearance. Don’t conclude too much from appearances, however. A depleted-looking getter isn’t necessarily a death sentence: a tube that has been used long enough to fade its getter may still have plenty of life left. Both of my old tubes looked superficially similar, but one of them tested with very strong emission, and I would have been willing to use it indefinitely—if I could find another one that matched its characteristics. If I had bought only one new tube, there’s a chance that the strong old one would have worked acceptably with it, but it was simpler to buy a new matched pair that’s guaranteed to work. Replacing Capacitors As noted in my recapping article, capacitor replacement is a routine part of restoring every vintage tube device. I’ll begin, as usual, with the big electrolytics. Of these five cans, the one on the left contains three caps and the others contain one cap per can. Electrolytic can bases are sometimes hard to access, but these are out in the open. I’ll warm up with a couple of simple ones. These two cans on the right end of the row each contain a single 150-mfd cap and the replacements will easily fit inside after I hollow out the cans. In the next photos, I have removed the cardboard cover, sawed open and emptied the old aluminum can, installed the new cap, epoxied the metal can to the base and refastened the cover. (You can read more details of this “restuffing” process in various articles which have links in my recapping article.) Bada-bing, bada-boom! The restuffed can has been installed. Notice the empty base hole in the previous photo. Before installing the fresh can, I removed its neighbor to make a little elbow room. When all of the cans were in place, my fingers couldn’t reach behind to reinstall the innermost mounting nut (note the circled screw holes in the photo). When it was time to install the final can, I temporarily taped the tiny nut and washer to the eraser end of a pencil and sneaked them in that way. Fast forward: in the next photo, I have restuffed three more cans. The remaining can will hold three caps. Wiring three caps onto the base takes a little patience, but there’s still ample room to epoxy the empty can back on. The next photo shows the fresh cans back at home. This project is more than half done, and the remaining work involves small, easy-to-reach components. While I had those associated resistors disconnected, I checked them to make sure their values hadn’t drifted out of tolerance. After testing the remaining resistors, I proceeded to replace the handful of small paper (and plastic-coated paper) capacitors. At this stage I gave the amp a cautious trial, bringing up the power on a variac and metering the current draw to make sure it didn’t exceed a safe level. It worked! I also checked the voltages on all of the tubes, comparing them to the W-6M manual’s voltage chart. All of them were in the right ballpark. Upgrading the Rectifiers Although the old rectifiers are working for the moment, it’s prudent to replace them. Old selenium rectifiers are notoriously unreliable, and three of the four silicon rectifiers have already been replaced, showing that the originals had a high failure rate. In the next photo, yellow arrows identify all five rectifiers. The big blue component is a selenium rectifier. Next to it is the last remaining electrolytic capacitor. In the four-rectifier stack at left, only the cylindrical one at the bottom is original. A technician has already wired newer rectifiers (two “top hats” and one bead-style) around the snap-in terminals for three of the fuse-like originals. This photo shows how I used type 1N4007 silicon diodes to replace all of the old rectifiers. The old selenium unit has been taken out of the circuit, but I used one of its terminals as an anchor point, enclosing the new diode in a white sleeve. Restoration Complete After replacing nineteen components, my W-6M project is finished. These photos show the chassis before and after restoration. Although the amp’s voltages looked reasonable in the earlier trial, I rechecked the voltage on every pin of every tube, as well as the supply points at the electrolytic capacitors and on the power connector, comparing them to the voltage chart in the manual. Now the measurements look better than ever. I should be able to play this amp for many hours without worrying that a marginal old component will conk out. One Last Tweak Before buttoning up the W-6M, I made a little change, disconnecting the 120-volt AC line from the WA-P2 preamp power connector and routing it to the amplifier’s onboard power switch. Now, when the amp and preamp are used together, they are turned on at the amp rather than the preamp. (The power cable still supplies filament and plate voltage to the preamp, as always.) This change silenced a slight background hum resulting from that connection and it lets me use another input such as an iPod without being tied to the preamp. You can read more about the hum issue in my WA-P2 article. Final Thoughts I haven’t finished restoring my TM-10 color monitor—that was the original reason to get this amp, remember?—but in the meantime I enjoy using my W-6M with its matching preamp and FM tuner: Paired with a good speaker like one of my Klipsch Quartets, you’d be surprised how good a 1950s-era hi-fi system can sound!
Heathkit W-6M 6550 Tube Amplifier with Cage. Peerless 16431
This amp was introduced in 1957, it is in 100% original condition, so it could use a going through and a bit of Heathkit gold touch-up in places. It powers up and the meter moves, it’s the perfect candidate for restoration and is being sold as-is for parts or repair. It calls for two 6550 power tubes, one 12BH7A, one 12AX7 and one 12AU7 and it features the Peerless 16431 output transformer, which many consider the best ever produced. There were only 2,000 estimated to ever be produced. The tubes are not included with this amp. If you have any questions please feel free to contact me. I am also selling a Heathkit W-6A which is nearly identical to this unit, but even harder to find, and a Heathkit SP-2 stereo pre-amp with some cool accessories that is perfect to feed these amps, so check my other auctions!!! Thanks for looking.
read more…
Heathkit W-6m, finally got a pair.
Your welcome and I wish you luck for your search for a pair of Fairchild amps but considering how rare the 275’s are you might want to settle for even a pair of 255’s or 260’s
Heathkit W-6M amp and WA-P2 preamp with hum
Heathkit W-6M amp and WA-P2 preamp with hum
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[ 21 posts ] Go to page 1 , 2 Next Previous topic | Next topic Author Message philsoldradios Post subject: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Dec Tue 03, 2013 2:05 am Dec Tue 03, 2013 2:05 am MemberJoined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA
Can anyone point me to a manual or schematic? The purpose of the front “damping control” is not immediately apparent. It also has a multi-pin “preamp power” jack in the rear, which raises the question whether it can be used at all without the right preamplifier.
Regards,
Phil Nelson
Phil’s Old Radios
http://antiqueradio.org/index.html A Heathkit W-6M amplifier just landed here (with a thud — this thing is HEAVY). I’m not an audio guy, although I have restored lots of tube radios and TVs. I assume it will need recapping, etc.Can anyone point me to a manual or schematic? The purpose of the front “damping control” is not immediately apparent. It also has a multi-pin “preamp power” jack in the rear, which raises the question whether it can be used at all without the right preamplifier.Regards,Phil NelsonPhil’s Old Radios
Last edited by philsoldradios on Apr Wed 23, 2014 2:58 pm, edited 1 time in total.
Top tubeR Post subject: Re: Heathkit W-6M amplifier manual? Posted: Dec Tue 03, 2013 2:49 am Dec Tue 03, 2013 2:49 am Member
Joined: May Wed 06, 2009 6:01 pm
Posts: 933
I just uploaded a copy of the schematic at
http://www.ohio.edu/people/postr/bapix/ARF/w6m.gif
— Rich Hi Phil,I just uploaded a copy of the schematic at– Rich
Top K7MCG Post subject: Re: Heathkit W-6M amplifier manual? Posted: Dec Tue 03, 2013 2:55 am Dec Tue 03, 2013 2:55 am Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 3862
Location: Seattle WA US Phil-
That damping control, like the similar control on the Fisher model 50, uses feedback to adjust the output impedance of the amplifier – thus adjusting the damping on the motion of a driven woofer. It can’t do much to improve a good speaker, but can sometimes make a cheap woofer sound much better. It can also partially compensate for the effects of too much speaker cable resistance between the amplifier and woofer.
–Chuck
Last edited by K7MCG on Dec Tue 03, 2013 3:27 am, edited 1 time in total.
Top dberman51 Post subject: Re: Heathkit W-6M amplifier manual? Posted: Dec Tue 03, 2013 3:00 am Dec Tue 03, 2013 3:00 am Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 4938
Location: Boston, MA USA
Location: Boston, MA 1) Damping control — speakers of the 1950s varied as to how much amplifier damping they needed for best bass, so this amplifier senses speaker current and uses it to drive the negative feedback loop. The damping control determines how much current gets fed back. Modern speakers want maximum damping.
2) Preamp power — this is a tap to provide B+ and heater power to an attached preamplifier without its own power supply. You do not need to connect a preamp to use this amplifier but it looks like you might have to short a couple of pins together on the preamp socket to turn the line power on. Evidently the amplifier is wired to have its power controlled from a remote switch on the preamp.
-David
Top philsoldradios Post subject: Re: Heathkit W-6M amplifier manual? Posted: Dec Tue 03, 2013 4:38 am Dec Tue 03, 2013 4:38 am Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA Thanks, that schematic should get me started. I see what you mean about line power going through the preamp socket. There is a toggle switch on the top of the amp — perhaps the builder wired around the socket and added a power switch. I may not be able to look underneath right away. My shop is in a jumble as the result of some remodeling.
Regards,
Phil Nelson
Top tinwhisker Post subject: Re: Heathkit W-6M amplifier manual? Posted: Dec Wed 11, 2013 12:29 am Dec Wed 11, 2013 12:29 am Member
Joined: Feb Sun 17, 2008 10:36 pm
Posts: 1868
Location: Dayton, Ohio You definitely want to overhaul the bias supply and check the bias voltage before inserting those expensive 6550’s.
I had switched power outlets on the rear of my pre-amp in the mid 60’s. I never used that option, as I thought the power amps could shorten the life of the on-off switch.
I used an external switch to power everything to extend the life of the pre-amp switch, which was also stacked with four potentiometers (volume control). That could be expensive and hard to find.
Charlie
Top philsoldradios Post subject: Re: Heathkit W-6M amplifier manual? Posted: Apr Sun 13, 2014 8:22 pm Apr Sun 13, 2014 8:22 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA
The amp sounds peachy except for background hum. The hum is there even with the preamp volume turned all the way down, and it sounds like your classic 60 Hz hum leaking in from the power supply. The construction was very tidy, with nice short leads and everything routed exactly as shown in the assembly manual.
The previous owner installed a power switch between pins 6 and 8 of the 8-pin preamp socket. It’s mounted on top of the chassis between the two big transformers. Since it’s the only non-stock thing in sight, I’m inclined to suspect that before anything else.
Any other ideas?
Phil Nelson
Phil’s Old Radios
http://antiqueradio.org/index.html I recapped the W-6M amp, checked the tubes & resistors, cleaned the controls, etc. I also acquired and restored a Heath WA-P2 preamp.The amp sounds peachy except for background hum. The hum is there even with the preamp volume turned all the way down, and it sounds like your classic 60 Hz hum leaking in from the power supply. The construction was very tidy, with nice short leads and everything routed exactly as shown in the assembly manual.The previous owner installed a power switch between pins 6 and 8 of the 8-pin preamp socket. It’s mounted on top of the chassis between the two big transformers. Since it’s the only non-stock thing in sight, I’m inclined to suspect that before anything else.Any other ideas?Phil NelsonPhil’s Old Radios
Top dberman51 Post subject: Re: Heathkit W-6M amplifier manual? Posted: Apr Sun 13, 2014 8:52 pm Apr Sun 13, 2014 8:52 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 4938
Location: Boston, MA USA
Location: Boston, MA Tube with H-K short?
-David
Top philsoldradios Post subject: Re: Heathkit W-6M amplifier manual? Posted: Apr Sun 13, 2014 9:37 pm Apr Sun 13, 2014 9:37 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA Hold the phone. I just found a note in the assembly instructions about a wiring change to make when the amp is used with the WA-P2 preamp. There is a second note describing changes to make in the WA-P2 preamp if it was manufactured prior to the first five months of 1957. I guess I will need to open the preamp again to sort that out.
Stay tuned . . . .
Phil Nelson
Top philsoldradios Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Wed 23, 2014 3:19 pm Apr Wed 23, 2014 3:19 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA
That change reduced the hum, but it’s not entirely gone. You can hear it across the room with the volume turned all the way down. It seems to be in the WA-P2 preamp, not the W6-M amp. If I disconnect the preamp output from the amp, the amp is dead silent. The hum is present with nothing plugged into the preamp inputs. Adjusting the preamp’s “hum” control doesn’t affect this hum.
I have tried a few obvious things; I double-checked the wiring and lead dress, and substituted the preamp tubes one at a time with known good ones. I checked voltages at all of the tubes in the preamp and amp and they all look reasonable. Following a tip in the manual, I even tried lifting the ground connection at one end of the cable that connects the preamp output to amp input.
Is there a systematic way to go through the preamp and isolate the hum? I have an audio generator and an oscilloscope. I don’t claim to be an oscilloscope wizard, but I regularly use it to view waveforms in tube TVs.
Here is a portion of the WA-P2 preamplifier assembly manual including the schematic:
http://antiqueradio.org/art/Heathkit_WA … Manual.pdf
The W6-M amplifier schematic is here:
http://antiqueradio.org/art/HeathkitW-6 … ematic.gif
Thanks for any advice.
Phil Nelson
Phil’s Old Radios
http://antiqueradio.org/index.html The wiring change was simple (moving one lead). I guess the object is to isolate the filament supply in the preamp.That change reduced the hum, but it’s not entirely gone. You can hear it across the room with the volume turned all the way down. It seems to be in the WA-P2 preamp, not the W6-M amp. If I disconnect the preamp output from the amp, the amp is dead silent. The hum is present with nothing plugged into the preamp inputs. Adjusting the preamp’s “hum” control doesn’t affect this hum.I have tried a few obvious things; I double-checked the wiring and lead dress, and substituted the preamp tubes one at a time with known good ones. I checked voltages at all of the tubes in the preamp and amp and they all look reasonable. Following a tip in the manual, I even tried lifting the ground connection at one end of the cable that connects the preamp output to amp input.Is there a systematic way to go through the preamp and isolate the hum? I have an audio generator and an oscilloscope. I don’t claim to be an oscilloscope wizard, but I regularly use it to view waveforms in tube TVs.Here is a portion of the WA-P2 preamplifier assembly manual including the schematic:The W6-M amplifier schematic is here:Thanks for any advice.Phil NelsonPhil’s Old Radios
Top Tube Radio Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Thu 24, 2014 4:00 pm Apr Thu 24, 2014 4:00 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 21973
Location: Warner Robins, GA Ground loop.
The preamp is grounded both through the power socket and the signal cable.
What you need to do is either make an RCA cable that only has one end of the shield grounded or replace the RCA jack on the preamp or power amp with the isolated type which mounts to the chassis, but is isolated from it and leave the jack ungrounded.
That way the only ground is through the preamp power connector.
Reason I suspect this is because the hum only happens when the preamp is connected. What you can do is connect a short wire between the output jack of the preamp and the inoput jack of the amp just as a rtest to see if it is a ground loop problem. If the hum goes away then you have found your problem. If not then further investigation is required.
Top philsoldradios Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Thu 24, 2014 4:45 pm Apr Thu 24, 2014 4:45 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA Tube Radio wrote: What you need to do is either make an RCA cable that only has one end of the shield grounded Yes, I tried disconnecting the shield at one end of the RCA cable connecting the preamp output to the amp input. That is mentioned in one of the manuals. I guess I can try disconnecting both ends of the shield, or make an unshielded cable to use as a test.
Thanks,
Phil Nelson Yes, I tried disconnecting the shield at one end of the RCA cable connecting the preamp output to the amp input. That is mentioned in one of the manuals. I guess I can try disconnecting both ends of the shield, or make an unshielded cable to use as a test.Thanks,Phil Nelson
Top Tube Radio Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Thu 24, 2014 5:12 pm Apr Thu 24, 2014 5:12 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 21973
Location: Warner Robins, GA If disconnecting one end of the shield didn’t solve the hum problem then it has to be something else.
One thing you can try is disconencting the power wires from the preamp power jack on the amplifier as a test to see if the 120 Vac wiring is causing the hum.
If the hum then goes away you can just leave them disconnected and use the added switch on the amp to turn it on and off.
Top philsoldradios Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Thu 24, 2014 5:43 pm Apr Thu 24, 2014 5:43 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA Yes, I just disconnected both ends of the shield on that cable, and the hum is still there.
The preamp gets its power from the amp, so I can’t power the preamp on its own and turn on the amp with its own power switch.
I wonder if this was a common problem with these preamps. Tucked into the front cover of the preamp manual that I bought are plans for building a separate DC filament supply for the preamp.
Phil Nelson
Top Tube Radio Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Thu 24, 2014 8:02 pm Apr Thu 24, 2014 8:02 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 21973
Location: Warner Robins, GA Given the preamp gets its power from the amp the amp’s power switch would turn on and off the preamp as well.
Did you disconnect the 120 Vac wiring from the preamp power socket on the amp yet?
If not try that and if hum isn’t gone then it is time to check where things ground to the chassis.
If the grounds are through rivets that will be a bit harder to fix, but if the grounds are through nuts and bolts then you can undo the nuts, clean the chassis and the terminal that goes on the bolt then use a star washer to ensure positive chassis contact.
Top philsoldradios Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Fri 25, 2014 7:10 am Apr Fri 25, 2014 7:10 am Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA Tube Radio wrote: Did you disconnect the 120 Vac wiring from the preamp power socket on the amp yet? Yay, that did the trick!
I disconnected the 120 VAC leads from pins 6 and 7 of the amp’s octal connector and routed them through the existing switch. No more hum.
If the amp hadn’t already had a power switch, I might not have drilled a hole in the case to accommodate one, but the original owner had already done the deed, lucky for me. As tinwhisker pointed out, this setup also saves wear on the preamp’s switch, which seems a little flimsy, to be honest.
Thanks for the advice,
Phil Nelson Yay, that did the trick!I disconnected the 120 VAC leads from pins 6 and 7 of the amp’s octal connector and routed them through the existing switch. No more hum.If the amp hadn’t already had a power switch, I might not have drilled a hole in the case to accommodate one, but the original owner had already done the deed, lucky for me. As tinwhisker pointed out, this setup also saves wear on the preamp’s switch, which seems a little flimsy, to be honest.Thanks for the advice,Phil Nelson
Top Tube Radio Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Fri 25, 2014 10:28 am Apr Fri 25, 2014 10:28 am Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 21973
Location: Warner Robins, GA You’re welcome.
Either the hum was getting in the circuit through the AC wiring itself or more than likely with the switch on the treble control it was getting in through there unless the switch was in the neutral side of the power wiring.
Top philsoldradios Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: Apr Tue 29, 2014 7:33 pm Apr Tue 29, 2014 7:33 pm Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 5478
Location: Woodinville, WA USA
http://antiqueradio.org/HeathkitW-6MAmplifier.htm
http://antiqueradio.org/HeathkitWA-P2Preamplifier.htm
Thanks again for the advice!
Phil Nelson
Phil’s Old Radios
http://antiqueradio.org/index.html This project turned out well, so I wrote little articles about the amp and preamp:Thanks again for the advice!Phil NelsonPhil’s Old Radios
Top engineer Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: May Thu 01, 2014 11:18 pm May Thu 01, 2014 11:18 pm Member
Joined: Nov Thu 09, 2006 11:24 pm
Posts: 3147
Location: Thornhill, Ontario, Canada I use a couple of WA-P2 pre-amps with several monobloc power amplifiers, including a W4-AM and a home-brewed Williamson. As part of the general “de-humming” I put a 100 ohm resistor in series with the B- ground wire from the amplifier octal plug to the WA-P2 (under the PA chassis at the socket.) This “opens” the ground loop that exists made when a grounded audio cable from the WA-P2 to the power amp is connected (pre-amp B- current now goes via the audio cable shield – no problem with this.) You can also open this loop by opening a ground in the audio cable, but that makes it a custom cable – I don’t want that as my audio cable collection gets used randomly in several systems, so you can be too clever! BTW never open the B- ground in the octal power cable! If you do that that the WA-P2 gets B- though the audio cable shield (still works), but if this gets unplugged, the pre-amp chassis goes up to B+! Very nasty!
Cheers,
Roger
_________________
Roger Jones,
Thornhill, Ontario
Ontario Vintage Radio Assoc. _________________Roger Jones,Thornhill, OntarioOntario Vintage Radio Assoc. http://www.ovra.ca
Top Sal Brisindi Post subject: Re: Heathkit W-6M amp and WA-P2 preamp with hum Posted: May Fri 02, 2014 1:15 am May Fri 02, 2014 1:15 am Member
Joined: Jan Thu 01, 1970 12:00 am
Posts: 3825
Location: Freehold NJ 07728 Very nice restoration on the amp and preamp Phil. Well done!
Sal
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Need capacitors, resistors and other parts–> _________________Need capacitors, resistors and other parts–> http://www.tuberadios.com/capacitors
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