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Heathkit W-5M First Tube Amp Rebuild

I got the chassis back home today. The finish looks awesome for the most part. It seems pretty durable as well. I contacted the seller and he advised me against baking or clear coating. When I sprayed them the shop was not well lit in the area I had to work in and I think the top of my chassis may have suffered a bit from this. The tops are not as even as the sides but the good news is the big transformers and chokes will cover most of the inconsistency. Plus I will probably run them with the cages on most of the time. My improvised badges turned out pretty nice as well despite my rookie mistake. Overall I am pretty pleased for a noob. I will probably be up late tomorrow mounting everything. I can't wait to pickup my hardware order. :)

My smaller grommets had disintegrated upon removal but luckily Home Depot had some suitable replacements. I got 5/16 sized grommets and they fit perfectly.

It is overcast at the moment and I could not get a good shot of the original color next to the new color. The color seems to be close but not exactly right and it is more textured. The WA-P2 finish seems to be much smoother. This could likely be my finishing method though...
 

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Outstanding man, I envy you for those cages, I don't have a single heathkit cage, but a buttload of gear.:thumbsdn: They don't come up, I think folks tossed them.:tears:
 
I am trying to decide if I want to refinish them or not (cages). They are a little bit rusty on the inside and have some chips but I just love the texture. I have also decided to leave my transforms and chokes blemished. So a little wear and tear on the cages might not be a bad thing.

If you have an extra PT (Chicago 54-32) please PM me. I might get stuck here in a week or so if I cannot scrounge one up. I am even having trouble finding the Stancors mentioned earlier. My only lead is a company that will build me a new transformer from scratch with the necessary specs but I would need to pull the original out of the can and insert the new one. Might end up being a huge mess.
 
Got my hardware and went to town. Ill probably have to stop here for a bit as I try to locate a replacement PT and save some money for some more parts. I wanted to leave the spira-shield in place as I will be using the octal socket on the back as a terminal strip for my AC connections but with the heat shrink on they no longer fit. Any problem just running them along that path without any sort of shield? I could pick up a long spring but I don't know if its worth it.

Jim: When you are working on these how do you have them upside down on the bench? I as planning on just leaving the cages on and flipping them to work but am scared of all the weight on the cage from the transformers over time. Any thoughts?

PS - I can never get by on this project without matched specialty parts being junk. 2 bad PTs so far, one bad PIO cap... When i started installing my tube sockets I found two octals had been cracked and broken in shipping...
 

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Your W-5M's are looking very nice! Very detailed restoration.

I've had a pair for many years that I get out and listen to every so often.
I use KT66's and they sound very nice. I did the easy 12AU7 to 6CG7 swap which made a noticeable improvement in sound.

The PT's come up often on Ebay. I bought an extra years ago, just to have if one gave up.

Good luck on your rebuild :yes:
 
vendo81 said:
Your W-5M's are looking very nice! Very detailed restoration.

Good luck on your rebuild :yes:
Click to expand...

Thank you for the encouragement. I am using ab0ez's builds as a guide. This will become more and more apparent as I move forward. I am excited to start wiring and really wrap my head around this circuit.
 
I stole one of the good tube sockets from my second amp so I could get started on the first. I have two replacement tube sockets on the way for the cracked ones. For now I am moving forward on initial wiring of my chassis that has a working PT. I have flipped the V2 9 Pin socket as Jim did. I do not know if it was intentional but it made it a lot easier to wire in the filament leads. The purple wire is 18GA stranded. It was a pain to stack two wires inside of the 9 pin holes. I am glad I got 20GA for the rest of my hookup wire.

I dry fit the big PIO capacitor to confirm spacer height. I am bumping these up a lot. About 9/16"
 

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Looking good on your rebuild!

Had a little bit of time to finish up one of the chassis tonight. I'll finish up the second one tonight and do some preliminary checkout tomorrow. Once I think all is good, I'll ship them out to their owner and publish the schematic.
 

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The chassis is grounded via the power cord, however there is a separate audio ground bus that is isolated from the chassis ground. If one desires, a jumper can be installed to bridge the two if that is needed for a particular situation.

Yes, it's for safety and hum reduction.
 
Also related to 120VAC... My switch location is not ideal, but I was trying to fill the extra hole in my chassis. I like the way you dressed the 120VAC input around the right side and back, avoiding most of the amplifier circuitry. I think I could do something similar having the leads for my switch run along the left side behind my PIO cap. The only thing that I would cross with 120VAC would be the RCA jack...

I was also thinking about using the switch to trigger a 6VAC relay located somewhere less sensitive in the chassis but I am probably completely over thinking it. The best solution for me will probably be using the back octal plug as a terminal strip running my AC along the apron. Problem is I will have 120VAC running parallel with the OT secondaries...
 
Wow... my brainstorming was fatally flawed. Cannot get 6VAC from the the PT if its not on. Forget I even brought it up :)

So a better question is how important is it to have the 120VAC mains separated from sensitive amplifier circuity. Which parts would be most susceptible to negative effects? The original design has 120VAC going from the outlets across to the octal plug. I would just be adding another connection from around the RCA jack to the octal plug.
 
I think crossing underneath the RCA jack and dressing my switch leads around the back is going to be best. That way I don't have the primary wires for the PT running right through all of the bias circuitry without any shielding.
 
Any crossing you need to do with wires, make sure you try and cross them at 90 degrees. This will reduce any tendency for cross coupling.
 
ab0ez said:
And, by the way, are you sure this is your first tube amp rebuild???
Click to expand...

Yes this is my first amp rebuild. I just get a lot of practice with circuits at work. I work for a company that is primarily a home theater installer but I get roped into all kinds of stuff like LED lighting. Gate control, motorized shades, etc. I have invested in some very nice tools as well which makes projects like this go a lot smoother. A good soldering station and cutters go a long way. I use a Weller WESD51 and this cutters is probably the best tool I have ever owned:

http://buy1.snapon.com/catalog/item.asp?item_ID=644767&group_ID=682172

They do break easily if they are dropped or misused but we have Snap On truck that comes every week and they always get replaced for free. I think I am on my third set. They are perfect for cutting zip ties off flush, and the sharp end makes it easy to trim long wires in tight spots like tube sockets.
 
Update:

Finally located a replacement PT. I ended up tracking one down by messaging an auction site seller who was listing other W-5M parts. The Chicago 54-32 arrived today. I had him do some resistance tests before shipping. Everything seemed in the ball park. Confirmed resistance measurements on arrival and ran some AC on the primaries. It measures a little bit higher than my other PT but all of the windings seem to be intact.

I may have to extend some of the leads. Any suggestions on secondary wire gauge? I will be covering all of the leads in heat shrink so matching the original cloth is not a concern. I have some 18GA stranded left from my filament connections. Will this be sufficient?
 
I have some extra cloth covered wire I can send you that may help out. If you look at the pics of my builds, I covered all of the transformer wires with heath shrink. I did this because in the past I've had a few problems with old wire and arcing from a wire carrying HV being placed placed close to ground. It manifested itself in an intermittent static/ticking noise that just about drove me insane before I found it. Try and make the additional wires you add about the same gauge as the original. There were undoubtedly small cracks in the insulation on the cloth covered wire that allowed arcing. The heat shrink stopped that.

On the voltage measurements, are you measuring both transformers out of circuit with no loading on the secondaries?
 
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