HK A500 Output Tube Experiments (Again)
- Thread starter TriodeLuvr
- Start date
Making some progress. This is the rear view, machining and engraving complete on rear panels and top plates. Next step is to fab the subchassis, then paint the transformers.
Jack
Jack
Bought them up on the big auction site. They were already brushed and anodized, so that saved some work. Doesn't look like this will be an option going forward. I just checked this item, and the page now shows shipping cost at $380. Must be the new tariffs. 
Jack
Jack
Lavane
Lunatic Member
Bought them up on the big auction site. They were already brushed and anodized, so that saved some work. Doesn't look like this will be an option going forward. I just checked this item, and the page now shows shipping cost at $380. Must be the new tariffs.
Jack
man I'm glad I snagged the aluminum chassis I used when I did.I'm not even going to look for anymore at this time then. There's going to be a lot of sellers sitting on invantory for awhile.
Chatter on Chinese social media indicates some companies planning to move elsewhere (Malaysia, Vietnam, etc.), but many others simply closing down. Tomorrow is the end of de minimus, and I'm waiting to see if everything on eBay and Amazon reflect this. I guess it's possible that an item might be purchased as usual but then have the tariff applied later and get stuck in customs. Not sure yet how this is all going to work for individual purchases.
I'm not even going to look for anymore at this time then. There's going to be a lot of sellers sitting on invantory for awhile.
Jack
I wouldn't be too surprised to see things bouncing through other countries. Set up a satellite facility in some low-tariff country, ship in bulk to that facility and distribute from there.
This is all such a moving target anyway that it might all be different next week or next month though.
This is all such a moving target anyway that it might all be different next week or next month though.
Made some progress on these amplifiers. The transformers are painted now, and it was a huge improvement. The upper bells were scuffed and rusty, absolutely unsuitable for a new build. The rust was even down inside the lettering stamped into the bells, and I wasn't sure exactly how I was going to deal with this. It's the first set of transformers I've ever had to repaint, so it needed a bit of thought. I ended up leaving the bells attached, and a brass wire brush on a drill press cleaned everything up. It even dug down into the stampings and removed all that rust.The lams were dirty, but not rusty, so I didn't brush them. After the wire brush work, I wiped everything down with Xylene to remove dust and surface contaminants.
I sprayed the lams and upper bells with a rust converter, just to be sure any remaining oxide layer would be treated. Then I applied gloss black enamel. After three or four hours, I put them in an oven and let them bake at about 60ºC for a couple hours. This really sped up the curing process and produced a hard coat right out of the oven. Instructions on the paint say full cure takes 7 days, but I think this has probably been cut in half (or more) by baking it. Here's a shot of the transformers after painting and a pic of the paints I used:
And here are a couple pics showing progress on the chassis:
Jack
I sprayed the lams and upper bells with a rust converter, just to be sure any remaining oxide layer would be treated. Then I applied gloss black enamel. After three or four hours, I put them in an oven and let them bake at about 60ºC for a couple hours. This really sped up the curing process and produced a hard coat right out of the oven. Instructions on the paint say full cure takes 7 days, but I think this has probably been cut in half (or more) by baking it. Here's a shot of the transformers after painting and a pic of the paints I used:
And here are a couple pics showing progress on the chassis:
Jack
Almost done with the power modules. These will mount under the transformers on standoffs at the rear of the monoblocks. The capacitor board holds all the filter caps for the amps (there are a few more caps under the board). The transformer on the left is for bias. The long turret board has the HV rectifiers and bias supply components. Heaters will be elevated, and there's a provision to adjust heater voltage if necessary.
Jack
Jack
I compensated for that by using silver plated turrets. Seriously, they're silver plated, given to me by an ex-employer who must have had thousands in the bins. Plus - I'm using MAGA caps for coupling (Make Audio Great Again) to make sure the sound will be astounding, incredible, amazing and also very, very good.I don't see any boutique stuff in there... you sure its going to sound good?
Jack
Yes, I made both boards. They're cut from sheets of .063" G10. I wanted to use the drilled boards from AES for the long turret board, but nothing in their catalog was quite right. This work really slows down a project, but hopefully worth it in the long run.
Jack
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I'm sure you just offended someone here... but not me!I'm using MAGA caps for coupling (Make Audio Great Again).
There are heaps of jokes I'd love to make here but all of them will run afoul of moderation and probably get someone's panties in a bunch so I'll leave it be
but thats vastly neater construction than my laziness allows for. My stuff generally resembles typical mass production nonsense with things hanging in space and sub-optimal component placement that is usually compromised by a too-small chassis to begin with.
but thats vastly neater construction than my laziness allows for. My stuff generally resembles typical mass production nonsense with things hanging in space and sub-optimal component placement that is usually compromised by a too-small chassis to begin with.
All my chassis are too small. I thought it would be easier with monoblocks, but no. Maybe I'll copy a commercial layout in my next build, see if that's easier.
Jack