• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Radio craftsmen c400 monoblocks restore

I found a C400 in one of my first scores. I let it go, as I only had one, and did not look to see what the general opinion of them was. The guy who got it, looked about the garage, and from quite a distance, lit after it and put in in his pile. I had no idea...LOL Getting a pair at some point I will not pass up.
cheers,
Douglas
 
Awesome! Ill definitely keep the metal hole plugs in mind. Is there a spray paint that would kind of mimic the orignal chrome? If not i have a bunch of hammertone copper rustoleum paint. I could paint the chasis copper, repaint the trannies black, and possibly make some kind of bottom cover for extra protection underneath. So far the only mods i want to do is a power switch and maybe add a fuse. Im gnna keep this one on the back burner and finish up a few more projects. When i get around to messing with these ill update this thread. Also im not really familiar with the 6v6 tube. Any recommendations? All of my amps are either el84 or 7591 and ive never actually heard a 6v6 tube.
 
James Cox said:
Awesome! Ill definitely keep the metal hole plugs in mind. Is there a spray paint that would kind of mimic the orignal chrome? If not i have a bunch of hammertone copper rustoleum paint. I could paint the chasis copper, repaint the trannies black, and possibly make some kind of bottom cover for extra protection underneath. So far the only mods i want to do is a power switch and maybe add a fuse. Im gnna keep this one on the back burner and finish up a few more projects. When i get around to messing with these ill update this thread. Also im not really familiar with the 6v6 tube. Any recommendations? All of my amps are either el84 or 7591 and ive never actually heard a 6v6 tube.
Click to expand...
There is spray paint out there that mimics chrome. Check out Jay Leno trying it on Utube if you wish.
 
James Cox said:
Awesome! Ill definitely keep the metal hole plugs in mind. Is there a spray paint that would kind of mimic the orignal chrome? If not i have a bunch of hammertone copper rustoleum paint. I could paint the chasis copper, repaint the trannies black, and possibly make some kind of bottom cover for extra protection underneath. So far the only mods i want to do is a power switch and maybe add a fuse. Im gnna keep this one on the back burner and finish up a few more projects. When i get around to messing with these ill update this thread. Also im not really familiar with the 6v6 tube. Any recommendations? All of my amps are either el84 or 7591 and ive never actually heard a 6v6 tube.
Click to expand...

The 6V6 is a sweet tube. There are plenty of current manufacture varieties to choose from. The Tung-Sols look promising since their other re-issues have turned out very well. As for vintage, you can go nuts. They can get pretty pricey because they are popular with guitarists, but since they were also used extensively in military gear, there are a lot of nice JAN (Joint Army-Navy) and mil-spec ones out there. The Sylvania 6V6GTY is very nice, with low microphonics. The gold standard is the Bendix 5992, built like tanks and sound spectacular, but very expensive. You should be able to land a nice quad, new or vintage, for $100.
 
zackthedog said:
Plastic or metal hole plugs in a any number of sizes are available from Amazon or hardware outlets.
Click to expand...

last ones I made were from an old aluminum sign from work. I used a hole saw to knock out a round plug big enough cover a removed tube socket. The small hole in the middle was used to mount a test jack to.
 
FWIW if you keep the original chassis, I believe they are quite similar to my Model 2's, but with a different chassis layout and different output transformer. I replaced the power cord with a grounded one (three-prong), but put rubber feet on the chassis and ran the power cord out the bottom of the chassis. Then I used the hole that the original power cord went through to mount a power switch, without drilling any new holes.

I've always wondered how close the circuits are (the tube compliment is identical) but never seen a proper schematic of the c400, so if you get one or draw one and were willing to share I'd be glad to see it.
 
Good to hear tung sol has made 6v6 reissues. I love their 7591s! As far as the c400 being similar to a model 2, i heard that one of the designers of the c400 and c500 eventually left to work with Saul Marantz so its definitely possible! Let me try to find a schematic.
 
I had to take a screenshot because the pdf version i had was too big to upload. If you have trouble reading it i can post i link to download the pdf.
 

Attachments

  • Screenshot_20200814-162702_Write on PDF.jpg
    Screenshot_20200814-162702_Write on PDF.jpg
    33.8 KB · Views: 29
If you don't mind DM'ing me a link that would be great. It looks nearly identical except for the feedback cap, I can't quite make out the values in the image though to know for sure. Thanks!
 
Alright, its been awhile but i have an update. I originally went through amd changed just enough stuff to power them up and make sure they work. They did! So i then went throughand changed all the components out underneath for fresh parts of the same value. I went woth some vintage vitamin qs for the coupling caps and orange drops for the other bipolar cap. I went with the orignal style carbon comp resistors as well. Everything sounds great and im now just waiting for a few more tubes to show up and they willbe ready to be slipped into the main system for further testing. Now i just need to fimd a good vintage preamp to go with them and ill be set!
 
You must log in or register to reply here.
Back
Top Bottom