Updating Vintage YBA3

[bcmatt]

Don't be fooled by the high voltages. Crank one of these amps up to full shred and observe how the screens DO NOT glow like they do in most vintage amps with high screen supplies. This is because the B+ dips down (sags) significantly, which keeps screen dissipation in check. I've measured this a few times. Increasing the main resovior just for the sake of 'bigger bass' may not be advantageous since it would stiffen the supply and perhaps push the screens and plates into over max dissipation when cranked. However, this would probably not be a big deal if the amp was being operated cleanly for bass.

So, perhaps we should try it out before ordering new caps to see if the stock values are fine. I think I would lean toward going for stock. If she needs more solid lows, she could pull out her 600W MarkBass.

[bcmatt]

And I had the version with the master. I don't really think it's necessary for bass since you probably have it all the way up anyway for max headroom. Depends on how much grit you want, and at what volume. But I'm guess this thing is gonna be considerably quieter than the Markbass, and seems more colored and gritty even at "clean" settings.

I like the sound of this.

[billyz]

You need to replace the 10uf 400v caps as well, they are part of the power supply. I would not jack this amp up, it is a nice high quality Vintage amp. They sound great too.

The two white tubular things may be Avalanche type rectifiers instead of the 3 per side diode string.

Correction, the round gray balls are the diodes. Those White tubes are connected to the plates and look like a flyback protection diode.

[Gaz]

I didn't realize you were from Canada either (and this may be my American ignorance), but I think it's illegal to mod a Traynor in Canada. I've heard about guys sending them to the US to get modded, but the border patrol are trained to find mods, which is why they have to put the schematics in the amps. In my opinion, it's not worth the jail time (although I also hear Canadian prison is quite accommodating). I guess the upside is that's how Garnet and O'Connor got their starts, as Mounties.

[bcmatt]

I didn't realize you were from Canada either (and this may be my American ignorance), but I think it's illegal to mod a Traynor in Canada. I've heard about guys sending them to the US to get modded, but the border patrol are trained to find mods, which is why they have to put the schematics in the amps. In my opinion, it's not worth the jail time (although I also hear Canadian prison is quite accommodating). I guess the upside is that's how Garnet and O'Connor got their starts, as Mounties.

Hahaha!
You are right. I should only replace with RCMP approved updates. I don't need jail-time right now. All the Tim Horton's and X-Box would wreak havoc on my figure at this point in my life...
Although, I wouldn't mind scoring a free electronics course, and the Lord knows I'm not meeting any eligible young ladies on the outside...

[bcmatt]

So, this is perhaps a stupid question, and I guess I should really know this, but:

I assumed the changing of all electrolytics for new ones, but what about cathode bypass caps in the preamp? What's the standard for those? No one seems to mention them so far. Should I actually be leaving them in?

And Power tube grid resisters? Is it not standard to change those? They should be fine as long as all seems to be running fine?

So, the amp is officially purchased and should be in the mail very soon.

[Gaz]

I'd say, while you're at it, replace all the electrolytics, that way you won't need to worry about it for another good 20+ years. Those eyelet boards are very easy to desolder, and it should be a breeze to replace the ones on the board.

The only resistors that sometimes need to be replaced (which haven't failed completely) are carbon compositions that have gone noisy or drifter. I think there may be one or two in the power supply you could check, but it's probably fine. As far as the grid stops, those should be fine.

[bcmatt]

I'd say, while you're at it, replace all the electrolytics, that way you won't need to worry about it for another good 20+ years. Those eyelet boards are very easy to desolder, and it should be a breeze to replace the ones on the board.

The only resistors that sometimes need to be replaced (which haven't failed completely) are carbon compositions that have gone noisy or drifter. I think there may be one or two in the power supply you could check, but it's probably fine. As far as the grid stops, those should be fine.

Thanks Gaz!
would you be in the same boat about going with the external cap cans instead of all axials on the inside for caps?

I'm realizing that this amp is even older that I originally assumed. serial number is in the 1300s and it is pre-bumper cabinet with the removable lid. I think that puts it around 1968-69. Apparently this was the most powerful bass amp on the North American market (and possibly the world) when it came out in 1967; 120W sine wave with no clipping.
What will we do with all that power!??!

[Gaz]

I dunno, which caps are the cans, and which are the axials? I can't remember.

[billyz]

I dunno, which caps are the cans, and which are the axials? I can't remember.

The dual 40/40 are the cans, the internal ones are the axial 80uf.
JJ makes 80 and 100uf 500vdc axials. JJ also has the dual 50/50 cans and clamps at Antique Electronic Supply.

[bcmatt]

I dunno, which caps are the cans, and which are the axials? I can't remember.

The dual 40/40 are the cans, the internal ones are the axial 80uf.
JJ makes 80 and 100uf 500vdc axials. JJ also has the dual 50/50 cans and clamps at Antique Electronic Supply.

I think that's what I will go with:
2x 50/50 cans and three 80uF Axials, so that the replacements just go where the originals are. Then there are the 250s in the preamp and the 2 8uF as well in the power section.

It seems that this is an earlier model than I thought and that's why there are no 10uF caps at all in the power section. Those were later mods.

Now that we have this and it sounds pretty great and it is all original, I think I'll stay with the same layout and circuit (just replacing the caps with the same values). I am thinking I won't do the mods that Pete Traynor made over the first few years to the original design.... any thoughts on this? Did the 10 uF caps just serve to tighten things up a bit more?

[billyz]

The 10uf might just be used instead of the 8 if. Same difference .

[bcmatt]

The 10uf might just be used instead of the 8 if. Same difference .

No, actually, the 8s both remain. There are 10s added.... one at a time chronologically over a couple years.

[billyz]

Ok, the two 8uf are part of the bias supply. The 10uf model does not have a choke, maybe they were needed to smooth out the b+ ripple. If yours has the choke you don't need them.

[renshen1957]

Ok, so is it safe to assume that the 2 sections weren't used in order to get higher voltage handling? I figured it wouldn't be since they are used with an 80uF 450V in series anyways...

So, I could just forget about the 2 40uFs and replace with an 80uF or 100uF as long as it is rated for about 500V?
Maybe it would be more economical and convenient to just order 5x 80uF 500V axial caps then instead of the 4x 40 and 3x 80.
Also, I was thinking I would just replace all electrolytics. Is that not just the standard?

Hi

First thing to do get a schematic (http://www.lynx.bc.ca/~jc/721005_YBA3.gif) or better yet, a copy of The Ultimate Tone Vol. 3 and read Chapter 13 and Chapter 14.

The YBA-1A had a 540 Volt B+ and the 2X6CA7 amplifier put out 90 watts with its high voltage power supply. The YBA-3 Custom Special has the same power supply in essence and 4X6CA7

Best Regards,

Steve