Jump to content

Yamaha BX-1 Mono's.... I MUST BE CRAZY!


paul79

Recommended Posts

Awhile back a customer contacted me to see if I would take these things on for restoration. After being turned down by a couple other technicians, and the simple fact that he actually has these things, I said I would tackle them. I like the abuse.

 

These are Class A monsters making 100WPC @ 8 ohms. These things running will heat a small house.

 

They were in working condition upon receipt, all the way from Flushing Mi, and I am fixing to dig in. Wish me luck! I might even post some pics along the way.

 

19638-4-yamaha-bx-1-pure-class-a-mono.jp

Edited by paul79
  • Like 5
Link to comment
Share on other sites

So mainly just recapping or what? What's being restored? I am curious.

Mainly yes. All new electrolytic caps including the big main filter caps, relays, bias trimmers, some of the hot running pass transistors, and relay drivers. I also see allot of VD style diodes that will need replaced. They are 34 years old and all original. I have worked on about all the vintage amplifiers, but have never seen these before. Can't wait to plop them in the system for testing  ;)

Edited by paul79
Link to comment
Share on other sites

Yep. All passive cooling, and likely "just enough" heatsink. They designed it pretty well with regards to keeping the caps away from the output section. I haven't seen any heat damage anywhere.

 

Waiting on a couple more relays to finish the second. These take 8 12v relays between the two of them. I am working on a SX-5590 right now while I wait for the parts.

Edited by paul79
Link to comment
Share on other sites

They are complex for sure. Allot of trick stages in these things, and allot of FET's. Should sound pretty good. I don't have super high hopes for them though, because there is so much circuitry in them. IME, this usually gets you further from the music in favor of better specs, so the amp will do some things superbly, and other things not so much, but we'll see. Like all amps though, there is a speaker that will work wonders with them.

Link to comment
Share on other sites

That is a lot of amp!  Getting a little more than 100wpc now?  ;)

Right at 130wpc at rated distortion. Not too shabby! I'll clip them here in a bit.... Still fine tuning the bias. These things run HOT! sitting 8ft away on the computer, and I can feel them. Jeez.....

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...