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 Post subject: Building the Stancor Williamson Amp: 807 PP
PostPosted: Mar Fri 16, 2018 4:36 am 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Hello All,

A local Craigslist ad had a pair of power supply and amp chassis as well as what appears to be the proper transformers to build the Stancor Williamson amplifier. The price was too good to pass up, so now I have a new adventure - and questions for the community.

1. One of the output transformers has an open winding. Where is a good place to get it rewound? I believe Heyboer can do it, but perhaps there are other recommendations out there.

2. For the resistors in the amp, should I stick with carbon comp or go with metal film? The power supply resistors will be the ceramic or sand type I suppose.

This should be lots of fun and I plan on keeping the parts 'industrial' as there is no paint on the transformer bells and the chassis are copper plated with patina from years of storage. No rust or gross corrosion seen. My plan would be to just use a clear coat for long-term protection, hopefully not too glossy.

For reference, I will be using the ultralinear circuit found here: http://www.tubebooks.org/file_downloads ... matics.pdf

Wish me luck!

Best Regards,

Greenhorn


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Mar Fri 16, 2018 4:54 am 
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Location: Detroit, MI USA
Heyboer makes very good quality transformers, I have used them on several occasions and been pleased with the results and the turnaround time. They will wind you a brand new one to the exact specs of the original part, or to any specs you give them.

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Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Mar Fri 16, 2018 7:31 pm 
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Posts: 3985
I've fixed a few, very few, open transformers by peeling back the insulation and resoldering the lead to the terminal. It might be worth checking out.


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Mar Sat 17, 2018 2:08 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2284
Location: Saskatoon
I know that Williamson OPT's have an interesting interleaved winding arrangement, but if the output winding is still on the outside as it is with most OPT's, then it may be an easy fix, as Macrohenry suggests, without having to resort to a complete rewind.


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Mar Tue 27, 2018 11:54 pm 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Update:

I was referred to a place in Maine (TRS in Orono) that can repair/rewind transformers.

Both output transformers were shipped today, with the goal of confirming the 'good' one is truly good and to test/repair the one with the open leads. The testing charge is waived if I use them for the repair.

Budget is kinda tight for this project so I may need to pinch some pennies elsewhere. I will also keep my eyes open for a Stancor A-8072 output transformer for sale somewhere. I did find one on Canuck Audio Mart for a price much lower than the rewind cost, but the ad was from November, 2017, and I doubt it's still available.

Stay tuned!

Best Regards,

Greenhorn


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jul Thu 05, 2018 2:15 am 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Update on the project:

Got the output transformers back. One was fully rewound and both were tested, dipped, and given nice long leads.

Now comes a tricky part: Where do I find the equivalent of the can capacitors used on the original chassis? The power supply uses 3x 30 Mfd, 475 WV and the amp chassis uses 1x 30 Mfd, 475 WV and 1x 250 Mfd 50 WV.

I am looking for the original sized cans as the chassis parts I have are, I think, original and already have the holes punched/drilled. The insulator mounting hole centers are 1 7/8" apart (center to center) and the large hole diameter is 1 9/16".

Any suggestions or leads to help me purchase these would be greatly appreciated.

Best Regards,

Greenhorn


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jul Wed 11, 2018 6:05 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1630
Location: Silver Spring MD, USA
Greenhorn wrote:
Update on the project:

Got the output transformers back. One was fully rewound and both were tested, dipped, and given nice long leads.

Now comes a tricky part: Where do I find the equivalent of the can capacitors used on the original chassis? The power supply uses 3x 30 Mfd, 475 WV and the amp chassis uses 1x 30 Mfd, 475 WV and 1x 250 Mfd 50 WV.

I am looking for the original sized cans as the chassis parts I have are, I think, original and already have the holes punched/drilled. The insulator mounting hole centers are 1 7/8" apart (center to center) and the large hole diameter is 1 9/16".

Any suggestions or leads to help me purchase these would be greatly appreciated.

Best Regards,

Greenhorn


If you're looking for new cans, CE Manufacturing makes the Mallory cans using the same tooling.

https://www.cedist.com/products/capacit ... ufacturing

The other option would be to place a WTB ad in the classifieds here for cans in those sizes. Then gut them and restuff. It might take longer to get all of the correct physical sizes, but might be cheaper.

-K

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Crawls Backward When Alarmed: Guitars, amps, vintage radios and more.


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jul Wed 11, 2018 6:42 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12549
Location: Mpls, Minnesota
Hayseed also has the capacitors you need.
https://hayseedhamfest.com/

Dave


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jul Fri 13, 2018 7:29 pm 
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Location: Ohio 45177
For half watt resistors, you could use the common carbon film types that are usually available. But I see Sal in his website has nice metal film types for real cheap. Unless you have the parts on hand and they test good, and you are about saving just a little money, I would not put CC in place of CC. Especially if the originals test right, in that instance. Probably all the wirewound power types are good if undamaged. Metal films in the preamp stages at low levels, such as in phono stages, are likely to be a bit more quiet than carbon. Inconsequential in higher level stages if you have, say some new carbon films that will work. Restuffing metal cans with the small modern lytic caps is doable and I have done that, but it is a little time consuming. Remove the cans, then fiddle with getting the phenolic end covers out, and yanking out the innards. I have done little work with the new can replacements due to the high cost.

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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jul Sun 15, 2018 1:28 am 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Hello,

Thanks for the comments and helpful suggestions, everyone. I truly appreciate them.

I will check out the Hayseed site for the capacitors as, frankly, I would rather not have to find cans to restuff.

For resistors, I believe I have some metal films on hand. For the power supply filter, I am not worried between using ceramic, sand cast, etc., but I might as well go with tighter tolerance metal films where possible as the schematic does call for matched pairs.

Again, thanks to everyone for their helpful comments.

Best Regards,

Greenhorn


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Nov Fri 30, 2018 4:32 am 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Update:

Piece parts ordered. Filter caps will just be whatever I found and will be mounted on some phenolic sheets where the original cans would have been. The DigiKey BOM Manager was pretty useful.

I generally ordered parts with tighter tolerences when I could find them and increased the power rating on the resistors as well. For the 1/2 or 1 watt resistors this was easily done with generally no concern for physical size. The higher wattage parts may crowd the undercarriage but I guess I will deal with that as assembly progresses.

The chassis and transformer covers were sandblasted by the previous owner. I will just spray paint them with matte finish clear. Flat black would look good on the transformers and maybe some other color would be cool for the chassis, but I think the current look of vintage/industrial/scratched with a matte finish should be fine. Maybe it will just look junky...

I now need to get the power supply cables and plugs made. The schematic just calls for 4-pin connections, but I want an earth ground between them as well so I am looking for 5 or 6 pin plugs and sockets. I will use female sockets on the chassis and male plugs on the cables. That way I won't have exposed power pins sticking up for fingers to touch.

That's it for now.


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jan Mon 07, 2019 4:57 pm 
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Joined: Jan Sun 06, 2019 2:59 pm
Posts: 5
Location: Orlando
How is the restoration going?


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jan Wed 09, 2019 6:18 am 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Hello All,

Hope your holidays were enjoyable and relaxing.

I have assembled a few more parts and have begun the assembly. The power transformers were tested and the secondaries matched rather well between the two. The two chokes measured differently, both in DC resistance and inductance. I was worried about that until I looked up the specs in an old Stancor reference. Turns out the spec window was really quite wide and they both meet that published criteria.

My original plan was to spray clear matte finish over the transformer bells and chassis...but I got lazy and it's cold outside. Thus they will remain in their industrial patina finish and will age accordingly.

All the tube sockets are ceramic, so there are no heat worries. (The spring clips were a pain in the neck.) I also ordered higher wattage resistors where practical just to add some margin of safety. Other than the modern 3 prong power connection, the outsides will look relatively vintage.

While I could not find exact matches for the can capacitors, I did find a reasonable way to hide the modern filter capacitors: cut a piece of 1" copper pipe and place a copper end cap on it. This just fits into the hole where a can capacitor would have been mounted and the modern dual filter caps on the amplifier chassis juuuust fit within the pipe walls. I plan to bend narrow strips of copper sheet and solder one tab to the copper pipe. Drill a hole in the other tab to match the #6 screws next to the cap locations. Right now they stand about 1.5" tall, looking like young copper mushrooms. Not sure if taller covers would look better, but with relatively wimpy soldered brackets planned to hold them in place I cannot have them too tall lest a bump leave them at an angle.

(Side story: I went to a local Menards store to buy the caps and the first ones I found were not cut nice and straight on the open end. I thought I would need to go to another store, but I saw a bin of caps further down the aisle. These had a groove in them that is already filled with solder, appeared a bit beefier in construction and had a nice edge on the open end. Same price, too, as the not-so-pretty ones.)

Here are a few pictures:

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The industrial (rat rod, steam, etc.) look should be ok once everything is finished and the tubes are installed. Kinda wish I had brass hardware everywhere, but just not practical at this point.

Stay tuned for further updates.

Best Regards,

Greenhorn


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jan Wed 09, 2019 6:50 pm 
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Location: Beautiful Downtown Burbank CA
You may want to check out 1" copper test caps. Very thin and almost invisible compared to a standard cap.
Image


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Jan Wed 09, 2019 8:43 pm 
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Joined: Jan Sun 06, 2019 2:59 pm
Posts: 5
Location: Orlando
Since you added an IEC connector, be sure to use a good ground method to avoid ground loops. The attached topology is what I have used for many years and I never had any hum, noise or ground loop issues.

I have a large stash of Panasonic 0.0047uF X caps so I use that value. Also, a resistor of 75 to 150 will work well too.


Attachments:
Earth_Signal Ground Scheme_010619.jpg
Earth_Signal Ground Scheme_010619.jpg [ 17.35 KiB | Viewed 1400 times ]
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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Mar Sun 03, 2019 9:11 pm 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Hello All,

Thanks for the tip on the RC connection between circuit and earth grounds. Will poke around and see if I have the parts. I am tempted to finish the project without the trick just to see if I do get some hum and if the RC circuit will help.

I have finished wiring the two power supplies and ran into the typical problem of soldering old wire. Sometimes the old wire just does not want to get wet with solder. I have a bunch of vintage cloth insulated wire I want to use (courtesy of an old Baldwin organ) and it really bothered me that the stuff just would not behave properly.

After several frustrating hours of generating dull joints and language that I am not proud of, I did a little research on good solder. Purchased some new Kester "44" 63/37, 0.5mm, solder and a small bottle of Kester 186 flux. Now I can cut, strip, tin, and solder much more smoothly.

I also made a rookie mistake: Thought I was done with the power supplies until I remembered that two power resistors needed to be installed in each one. There I was, all happy and proud with (relatively) shiny joints and wiring that does not look too awful. Then, when double-checking the schematic, I was reminded of what else needs to be there. Nuts. Luckily they fit nicely, although not exactly per the pictures from the old Stancor literature. Enough space between the resistor bodies and surrounding wiring, too.

Next up are the amp chassis. These ought to be a hoot trying to figure out how to cram everything in.

Currently in the 'thinking' phase: The construction of the cable between the power supply and amp chassis. It would be really cool (pretty) to get some woven copper braid to act as the outer cover and I could use it as the earth ground connection as well. I do have a good length of 4-conductor wire within a green cloth covering, but I am not confident that two of the conductors are beefy enough to handle the filament current. The filament current total between one power supply and its amplifier is 3A (a pair of 807's and a pair of 6SN7's).

Thanks again for everyone's tips and comments.

Best Regards,

Greenhorn


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Apr Sat 13, 2019 5:11 am 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Update for a Friday night....

Working on the first amp chassis and just looping the leads into the socket terminals and terminal strips. This is turning out to be a somewhat of a pain in the neck. The picture from the original Stancor documentation shows large components that can stretch from one socket to another and fit juuuust right into their respective locations. The modern components are much smaller and the leads are not as long as some vintage parts. Thus I need to add terminal strips all over the place and the undercarriage is beginning to look like a sloppy rats nest of wires.

On top of that, I am reading various posts of Williamson amps and see various mentions of instability, the need for grid stop resistors, resistors for the plate connection hidden in the plate cap connector, and/or graphite beads for the plate wires. I will leave that bit of investigation for after the soldering is completed.

One question I have has to do with the bias jacks. One posting mentioned just putting in 1-ohm resistors in place of the jacks and just measure their voltage to check the bias. I planned on wiring the jacks as shown on the original schematic for now.

My second question reflects my inexperience: How do I actually measure/set the bias? I have stared at the schematic and imagined what the circuit would be if each jack has a 1/4" plug in it and then connected to a meter. From what I can tell, I would measure the current going to each side (each 807 tube), so I would need two meters to read simultaneously unless I would want to go back and forth to each one. I would then adjust the bias pot so each side would read the same.

The more I think about it, the idea of 1-ohm resistors is sounding far more practical.

That's it for now. Thanks in advance for any comments and suggestions.

Best Regards,

Greenhorn


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Apr Sun 28, 2019 11:46 pm 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Another update (28 April, 2019).

Wired up the first amplifier chassis. Used 1-ohm resistors across the bias jacks to measure voltage rather than current. Double-checked routing, audited a few connections (this one connects to here which then goes there...). Thought about testing the tubes before installing but it was late on Saturday. I had already ohmed out all the transformers to ensure there were no shorts between the windings, so I was feeling pretty good.

Sunday morning I attached an 8-ohm speaker, installed the tubes, connected the umbilical, added a music source (Joni Mitchel's Court and Spark CD), brought the assembly up nice and slowly using a Variac and was greeted with a nice loud hum. I figured I wouldn't panic and just do some poking around later on today...then I noticed the heater within one of the plates for the 5V4G wasn't glowing very much while the other was looking fine.

Hmm... No matter, just get that other 5V4G. Turned everything off. Waited for a time for the caps to dissipate, etc. Replace the rectifier tube and slowly bring things up with the Variac.

As I slowly turned up the Variac I heard the hum and then >pip!<. A nice little blue spark in the rectifier and a blown fuse.

With hindsight being 20/20, it would have been nice to test the rectifiers before powering up. I was admittedly skipping a step as, frankly, I would like to complete this project and move along in life. In other words, I was lazy. I did test them this afternoon on my TV-7: the first tube used was extremely weak on section 1 but fine on section 2. The second tube (believed to be NOS) tests absolutely dead on section 1 and fine on section 2.

So now I am in debug mode. Will be checking the voltage outputs of the power transformer without the rectifier tube installed (checked fine last year) and triple-check the wire routing.

Suggestions welcome.

Best Regards,

Greenhorn


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: Apr Mon 29, 2019 12:45 am 
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Joined: Sep Tue 15, 2015 1:16 am
Posts: 532
Location: 18424 PA
Sounds like you have something shorted, you should have checked all the wiring before going full on the variac when you had hum.


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 Post subject: Re: Building the Stancor Williamson Amp: 807 PP
PostPosted: May Wed 08, 2019 3:05 am 
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Joined: Dec Wed 18, 2013 6:03 am
Posts: 310
Location: Inver Grove Heights, MN 55076
Hello All,

It works!

Double checked the power supply chassis - no shorts.

Double checked the umbilical cable - no shorts.

Double checked the amp chassis and saw the connection between pins 2 and 4 was unsoldered on pin 2. Soldered that connection.

Installed the circuit ground to earth ground resistor/cap combination in the amp chassis as long as the iron was hot and the chassis was upside down. Thanks again to THD+N for the suggestion.

Plugged everything in and connected a CD player. Slowly upped the voltage via the Variac and heard the pleasant voice of Joni Mitchell. Interesting how I was able to get nice volume with the Variac at only 80 volts. Slowly proceeded to just under 120 on the Variac and everything is running fine.

Here are some pictures. Please excuse the messy work table.

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Amp is dead quiet between songs. Playing The Suburbs now and enjoying the music of my younger years.

Next steps will be to build the other channel and then fabricate the covers for the external electrolytic caps. I will replace the wires for the 807 plate caps with thicker wires. Right now they are just connected directly to the output transformer leads, which looks wimpy. Maybe use test lead wire.

Thanks to everyone for their comments and suggestions. I appreciate your support!

Best Regards,

Greenhorn


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