I was recently gifted a pair of Heathkit W-5M amps and am getting ready to do a to the chassis strip down and rebuild. Since I'm going this approach, I'd like to also replace the tube sockets in addition to bringing in current quality caps and resistors. Suggestions on sources for reliable ceramic sockets would be most welcome. Thanks!
Not ceramic, but I have very good experience with Belton (octal and noval). Also NOS sockets from former USRR are good, but sometimes harder to solder (one has to clean the pins).
Before you do anything else, you might want to confirm that the output transformers are intact. These are among the best audio transformers ever made, but are fragile, and the circuitry has no protection for them from a variety of common component failures. DC (resistance) tests of the primary windings will give you some confidence level, and the same for the power transformers. The original power transformers have such a high secondary HV voltage that they could be used with a choke input and still provide plenty of B+, especially with modern mains AC voltages, which just exaggerate the fragility of the design.
As a separate issue, the original Heathkit implementation of the Williamson is not ideal for low frequency stability, and is an artifact of its time. You might want to read DTN Williamson's own later thoughts on his amplifier design.
But whatever you decide to do, please try to protect the output transformers; they're like a 1958 Ferrari - irreplaceable in the modern world.
All good fortune,
Chris
As a separate issue, the original Heathkit implementation of the Williamson is not ideal for low frequency stability, and is an artifact of its time. You might want to read DTN Williamson's own later thoughts on his amplifier design.
But whatever you decide to do, please try to protect the output transformers; they're like a 1958 Ferrari - irreplaceable in the modern world.
All good fortune,
Chris
It is a lot of work to change the tube sockets and new ones are not necessarily an improvement. Is it more that you are looking to create something modern from the old components? From a resale perspective a wholesale 'renovation' is not always beneficial. I would always prefer patina and originality over modernised.
Without question replacing sockets can be a lot of work. I recently replaced some cracked ceramic sockets on a pair of mono blocks and a preamp. The cracks occurred during tube rolling because socket pin design made removal of tubes very difficult. So much so that bending of tube pins occurred during removal . I elected to use teflon sockets thinking to eliminate possible cracking issues. Each pin on the teflon sockets had to be sized to accommodate ease of insertion and removal of tubes. Once done the sockets allowed rolling tubes so much easier.
What Chris said. The Peerless 16309 outputs were notorious for failing. Be sure to measure the primary resistance on yours. IIRC it's something along the order of 300 ohms from each plate tap to the center tap, with the screen taps about 160-170 ohms. The later ouputs were the 16458, which were more robust and reliable. The power trannie were also prone to failure so you should test those also for any shorts. I would isolate them from the chassis and bring them up on a variac to make sure they don't blow any fuses and voltages are correct.
Heathkit issued a service bulletin, which should be followed:
https://www.kevinchant.com/uploads/7/1/0/8/7108231/heathkit_w5service_bulletin.doc
The most important item there is the addition of a thermistor to reduce the turn-on surge.
Be sure to rate ALL caps, coupling and power supply, for at least 600VDC.
The W5 was probably the most stable of all the Heathkit Williamsons, with coupling cap values improved for low-frequency stability and measures implemented for high-frequency stability as well, so I would follow the original design exactly. The output transformers were specifically tailored for that circuit and will only work properly if you maintain the original design.
For sockets, I have found Belton to be the best, with extra-thick pins, tight coupling to the tubes and good resistance to bending or cracking. I've never thought Heathkits offered that much in the beauty department (unlike, say, Marantz or McIntosh) and my inclination is to ensure that they are brought up to the best possible working condition.
Heathkit issued a service bulletin, which should be followed:
https://www.kevinchant.com/uploads/7/1/0/8/7108231/heathkit_w5service_bulletin.doc
The most important item there is the addition of a thermistor to reduce the turn-on surge.
Be sure to rate ALL caps, coupling and power supply, for at least 600VDC.
The W5 was probably the most stable of all the Heathkit Williamsons, with coupling cap values improved for low-frequency stability and measures implemented for high-frequency stability as well, so I would follow the original design exactly. The output transformers were specifically tailored for that circuit and will only work properly if you maintain the original design.
For sockets, I have found Belton to be the best, with extra-thick pins, tight coupling to the tubes and good resistance to bending or cracking. I've never thought Heathkits offered that much in the beauty department (unlike, say, Marantz or McIntosh) and my inclination is to ensure that they are brought up to the best possible working condition.
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I appreciate the thoughtful responses and insights on the transformers. After receiving this pair of W-5Ms - actually while they were in route - I searched and located a few excellent threads in Audiokarma detailing renovations on this model. The power transformer was often mention in the same cautionary tone shared here. Last night, I found a thread detailing a replacement from Hammond, installed and verified.
https://audiokarma.org/forums/index...with-pix-and-values-help-please.186432/page-2
I plan to follow this lead and replace both it's PT as a precaution while doing the rest of the rebuild - seems worth it. Yes, that will alter the appearance - and while I regrets this visual change, I'll take it for the reliability boost. Within this thread is reference to another covering a full rebuild and the same comments on CL-90 / 120 additions.
Back to sockets - thanks for the inputs. I'll likely continue to research - will be reaching out to Audio Classics on what the current McIntosh units run as sockets - but the suggestions on Beltons seem to be a popular choice, always with good results noted. Thanks for your help!
https://audiokarma.org/forums/index...with-pix-and-values-help-please.186432/page-2
I plan to follow this lead and replace both it's PT as a precaution while doing the rest of the rebuild - seems worth it. Yes, that will alter the appearance - and while I regrets this visual change, I'll take it for the reliability boost. Within this thread is reference to another covering a full rebuild and the same comments on CL-90 / 120 additions.
Back to sockets - thanks for the inputs. I'll likely continue to research - will be reaching out to Audio Classics on what the current McIntosh units run as sockets - but the suggestions on Beltons seem to be a popular choice, always with good results noted. Thanks for your help!
Regarding sockets, I'm sure you are aware, but they are not all the same diameter.
And reliability, the failure of a transformer is usually the symptom of another issue, often capacitor related but could be overstressed tubes. I don't see why they should be replaced. Using Chris's Ferrari analogy, it is like shoehorning in a Toyota engine to cut down the servicing bill.
And reliability, the failure of a transformer is usually the symptom of another issue, often capacitor related but could be overstressed tubes. I don't see why they should be replaced. Using Chris's Ferrari analogy, it is like shoehorning in a Toyota engine to cut down the servicing bill.
There's nothing special about the Heathkit sockets. It was a kit, after all. It's quite a job to de-solder and strip the old pins, and they can be easily broken or bent. Assuming the OP plans to use these himself, a complete rebuild would frankly be much easier. And it's not going to hurt the resale value--quite the contrary, IMO.
Just measured an early (16309) chassis and its octal sockets are 1 1/8" (about 28mm) ID and 1 1/2" (about 38mm) fixing screw C-C. The miniature sockets are 7/8" (about 22+ mm) ID and 1 1/8" C-C (about 28mm). Totally common sizes in their day, but modern versions can differ.
All good fortune,
Chris
All good fortune,
Chris
