Heathkit W5M Thoughts

[8xlaxx]

For the outputs on a W5m, I'd not bother if you're doing a new build. The easily available S265 from Heyboer is quite fine, especially at voltages and currents that would make a 16458 say 'Uncle'. The new S265 can have taps installed in any set of 10% increments you ask for( and especially in multiple sets ). Can't get that in a '458...let alone the undersize '309.
cheers,
Douglas

Thanks Doug. So far, everything is testing out OK. I made a bone head testing mistake at first but all seems to be within spec, so I’m going to soldier on with what I have.

It is my hope that pops, old man time, and temperature didn’t put the hurt down too much on the 16309 W5M#1 amp. I’m willing to take a risk (if it shorts) to get it running.

 

[8xlaxx]

https://www.audioasylum.com/cgi/vt.mpl?f=tubes&m=166015

Interesting read about Surgistors and the PT in these amps.

 

[8xlaxx]

Any recommendations on how to clean or polish the oxidation or rust off of the bolt heads/threads and nuts?

I'm sure a Dremel w/ wire brush can make quick work of this but the hardware that holds the 9 pin sockets down are very tiny (everything is quite small actually!).

Would my time be better spent in replacing all the hardware? Just wondering what others have done,...

Thank you.

 

[mike567]

8xlaxx: How much time do you want to spend to polish 2 or 3 dollars worth of screws?

 

[chinacave]

Stainless steel bolts, washers 'n nutz from someplace like 'boltdepot' those are all 8-32, maybe some 6-32 bolts, common enough stuff. I'd only Polish them if they were some unique or odd-ball size or head.. ymmv.

 

[primosounds]

Any recommendations on how to clean or polish the oxidation or rust off of the bolt heads/threads and nuts?

I'm sure a Dremel w/ wire brush can make quick work of this but the hardware that holds the 9 pin sockets down are very tiny (everything is quite small actually!).

Would my time be better spent in replacing all the hardware? Just wondering what others have done,...

Thank you.

If not reusing the original hardware it is better to replace them. I prefer to use brass but they are a little more expensive than stainless. The really small nuts and bolts are probably 4-40 size.

 

[8xlaxx]

^^^All good points. Ace Hardware Rewards (no affil.) bonus card arrived today!

Applying that towards the new hardware. IMO, it's gonna be more than a few dollars even for the zinc stuff.

Brass is a good idea to match the chassis.

 

[8xlaxx]

Any decent looking SPST On/Off switch that would marry will with the A/C outlet openings in the chassis?

 

[heyraz]

Any decent looking SPST On/Off switch that would marry will with the A/C outlet openings in the chassis?

I use dpdt slide switches and paint the plates with black nail polish before mounting to match the slide.
The screw holes are perfectly spaced.

 

[Mike Sweeney]

Any recommendations on how to clean or polish the oxidation or rust off of the bolt heads/threads and nuts?

A solution of citrix acid will clean off the rust nicely. This link is one version of many using electrolysis to remove the rust. https://www.instructables.com/id/Electrolytic-Rust-Removal-aka-Magic/

 

[8xlaxx]

Reviving thread,... noted a recent W5M build here on AK, got that itch in me going to think some more things through about this project.

A member from '08 had used a 4MFD 1000V oil-filled cap in place of some other components. (pic below)

1) Why would this be an added protection for the PT and in rush current? 2) What components were bypassed or replaced to insert such a cap?

Looks as if one side of the oil filled cap goes to pin 2 of rectifier. Can't make out the other side of the cap.

3) Are the two can caps bypassed with the insertion of the oil filled cap?

 

[zackthedog]

Reviving thread,... noted a recent W5M build here on AK, got that itch in me going to think some more things through about this project.

A member from '08 had used a 4MFD 1000V oil-filled cap in place of some other components. (pic below)

1) Why would this be an added protection for the PT and in rush current? 2) What components were bypassed or replaced to insert such a cap?

Looks as if one side of the oil filled cap goes to pin 2 of rectifier. Can't make out the other side of the cap.

3) Are the two can caps bypassed with the insertion of the oil filled cap?

That looks like a replacement for the 10uF input cap specified in the original design, perhaps something the builder had on hand. A 10uF Mundorf M-Tube cap takes up a fraction of the space and is a better solution, given that old oil caps can suffer from considerable current leakage.

 

[8xlaxx]

Thanks @zackthedog

See Post #18
https://audiokarma.org/forums/index.php?threads/yet-another-heath-w5m-rebuild.553493/

Here's the first filter section. Since the original can caps are just for appearance, the first filter section (before the choke) is a 4uF 600VDC oil filled cap with a 1M bleeder and a .01Uf 1kv bypass cap.

Why a 4uF cap? Two reasons: 1) Heath ran the daylights out of the output tubes and today's higher line voltages are a sure-fire recipe for shortened output tube life. The 4uF input cap to the choke will knock a few volts off of the B+ and get it down to about where it should be. 2) The power transformers on the W5Ms have a reputation of being somewhat fragile on the high voltage windings. Couple that with the quick warm-up characteristic of the 5R4 rectifier trying to feed a large capacitor load at start up, and you get the idea.

Of course, surgistors will also be added in series with the AC input on the primary side of the power transformer.

Just wanted to sort this out to protect these amps. Anything helps, really. I have these oil filled caps on hand.

 

[8xlaxx]

This AK member's thread here, gives me a ton of inspiration:
https://audiokarma.org/forums/index.php?threads/heathkit-w5m-rebuilds.165950/

He mentions the oil filled cap in Post #10, replacing (2) caps. Would like to figure this circuit out and preserve the components as much as possible.


First filter cap

I took a step beck at this point and read all I could about the W5's and some of the typical problems that they were having both after decades of use and decades of sitting.

The problem of dead power transformers was often mentioned as well as problems with the rectifier tube socket. Well, that socket was already replaced, so problem dealt with.

But what about these power transformer problems? Heath did modify the design a few years down the road to include a surgistor to give the amp a soft-start characteristic and lessen the turn-on strain on the transformer. Both amps have now been modified to include new surgistors placed in the primary path of each power transformer.

Looking a bit further in the design, you have two 40uF 450VDC electrolytic capacitors in series to effectively create a 20uF 900VDC cap that operates as the first filter cap in the power supply. Electrolytics get leakier and leakier over the years and you also have the added 100K bleeder/equalizing resistors in the circuit.
So, I decided to use a 4uF 1000VDC GE Pyranol oil-filled cap mounted in the space below the power transformer. With today's higher line voltages, I wasn't too worried about the B+ being much lower than if the original 20uF value was used. Additionaly, since the B+ is taken after the choke, I also wasn't too worried about excessive ripple voltage on the B+.

This should help lessen the initial turn-on stress.

After some further reading, I connected the center tap for the 6.3VAC heater line to the elevated ground grid. This was recommended by Heath if the amps were not going to be used to power a preamp.

 

[zackthedog]

This AK member's thread here, gives me a ton of inspiration:
https://audiokarma.org/forums/index.php?threads/heathkit-w5m-rebuilds.165950/

He mentions the oil filled cap in Post #10, replacing (2) caps. Would like to figure this circuit out and preserve the components as much as possible.


First filter cap

I took a step beck at this point and read all I could about the W5's and some of the typical problems that they were having both after decades of use and decades of sitting.

The problem of dead power transformers was often mentioned as well as problems with the rectifier tube socket. Well, that socket was already replaced, so problem dealt with.

But what about these power transformer problems? Heath did modify the design a few years down the road to include a surgistor to give the amp a soft-start characteristic and lessen the turn-on strain on the transformer. Both amps have now been modified to include new surgistors placed in the primary path of each power transformer.

Looking a bit further in the design, you have two 40uF 450VDC electrolytic capacitors in series to effectively create a 20uF 900VDC cap that operates as the first filter cap in the power supply. Electrolytics get leakier and leakier over the years and you also have the added 100K bleeder/equalizing resistors in the circuit.
So, I decided to use a 4uF 1000VDC GE Pyranol oil-filled cap mounted in the space below the power transformer. With today's higher line voltages, I wasn't too worried about the B+ being much lower than if the original 20uF value was used. Additionaly, since the B+ is taken after the choke, I also wasn't too worried about excessive ripple voltage on the B+.

This should help lessen the initial turn-on stress.

After some further reading, I connected the center tap for the 6.3VAC heater line to the elevated ground grid. This was recommended by Heath if the amps were not going to be used to power a preamp.

Okay, well that makes sense. If you have some on hand go for it.

 

[fredtroy]

About 15 years ago, I was buying vintage KT66's for use in Quad II amps (which turned out to be a mistake). One pair came in a Heathkit W5M of unknown status. Meaning the price of the amp was less than what KT66's were going for. I finally got around to looking at the amp and it had a bad PT. There are a number of current production PT's that are close to original specs. The one I used cost me $100. I bought a second W5M and converted both to Radio Craftsman 500 design. Both W5M and Radio Craftsman 500's are Williamson designs so the changes weren't too bad. The biggest change was replacing the 12AU7's with 6SN7's. The surprise was how good they sound. They easily beat both updated Marantz 8B and Citation II amplifiers driving Quad ESL63 speakers.

Regarding reliability, I did add CL30's and haven't had any problems.

 

[8xlaxx]

Kinda ran into a snag with this project. Was looking to change out all the octals (4).

Big mistake,...the newer 8-pin Beltons, from AES, do not fit at all.

Beltons - 1" 3/16

Hole - 1" 1/8