Yes, it is a weird schematic.... BUT It also seems the B+ is listed at 440V instead of 540V which kind of defuses my whole "HOW WILL I GET THE B+ DOWN!?!?!?" point in the first place.
The preamp tubes were okay looking, old Phillips again, but the Power tubes were chinese made "INTERNATIONAL SERVICEMASTER" tubes... Look a little crap,a nd for all i know, until i get to dig around the circuit, maybe they were failing and that is the problem.
Orange drop caps in the chassis, labeled Mallory!?
That's one of the last versions of the YBA-1. It has an extra gain stage instead of the cathode follower. Does it have the sloped front panel like a blackface Fender chassis?
This version doesn't have cathode bypass caps either, which would bring down some gain, that is then recovered by adding a gain stage. First thing is to go over it and see why it was making such horrible sounds... then to work from there. I may just add another filter stage to it, to bring down the voltage if needed and to clean up some noise.
Traynor gear was honestly NEVER done... until the day they went out of production, its the same now. Stuff gets changed pretty regular during production runs.
Okay, dug into the amp a little today before starting work. First thing to be said, is The old tubes were SHOT! Put in a set of groove tubes after i checked it over, and it works, not amazingly, but it works. When i took a few readings, the B+ WAS a little on the high side.... as in, 450v caps in the power supply, being hit with 453 volts of juice! The 121.2 volts at the wall perhaps a little more than was expected with this amp design. SO, added a filter stage, with 2 100uf/450 caps in a stack, with 220k 3w balancing resistors. Added a BIG ASS 1k 25 watt resistor feeding the next filter stage which feeds the screens, voltage is a little happier 412 volts there. Reworked the supply into a series formation instead of a branch formation, and got the voltage on the tubes a little lower. No changes to the preamp AT ALL and it already sounds much happier. The 2 volumes are incredibly dirty, so they are next to go, and I may rework the preamp into a JTM50. since it isn't that far off already. Just need to figure a way to not piss off my co-workers when i test this amp, since I need to get it turned up and that is a little loud outside my workshop!
guittech wrote:Just need to figure a way to not piss off my co-workers when i test this amp, since I need to get it turned up and that is a little loud outside my workshop!
I know how that goes - around 1985 I tested an amp I had modded in a garage occupied by small engine repairmen. Lawnmowers, snow throwers, all that noisy stuff. When they started screaming at me "shut it off it's TOO LOUD" I knew I got it right. That amp measured all of 19W at clip.
Good going on the Traynor, looks like you got it just about done.
Funny thing about noise: when you are the one making the nouse, you're not nearly as bugged by it as those around you. I notice this every time I'm swinging a hammer vs. just being near someone who's doing the swinging.
Leo, I imagine those lawnmower guys never gave a second thought as to how their noise affected you!
JazzGuitarGimp wrote:Leo, I imagine those lawnmower guys never gave a second thought as to how their noise affected you!
Kee-rect, and my neighbors used to look at me as if I just stepped off a UFO when they saw me wearing shooters muffs while mowing the lawn & doing other noisy tasks. Funny thing, they all either got into ear protection or hired someone else to chop their lawns. "They're ALL doing it now." Leo the trendsetter, hah! That'll be the day. I'm just a dedicated follower of fashion. What? What's that you said? Huh?
Okay, i got my part from NTE and I may have learned a little lesson or 2 (Bout time!)
So the 10 watt Zener came in. Installing it brought the "DANGER WILL ROBINSON" Voltage from 464 (Not making life easy on those 450v caps) down to a more reasonable 422. I had already added an extra filter stage, with a cap stack, in case of voltage spikes, and i could safely bring the dump resistor i had used down to 250 ohms. I think the voltage settled around 415 volts, which makes me a little happier and in this amp sounds FAR better... the 1987 circuit running at higher voltage in this iron always sounded really rough.
I went through and tried a few more changes. I dialed back the Power supply cap feeding the first stage to a 22uf, instead of the 47uf i was using. That made it a little less flubby. I also tried using a .0022 cap in the bright channel instead of the .022 i had been using (the original schematic calls for .0022) It makes things a little too thin for playing that side solo, but it makes for a much nicer effect when mixing channels. I also tried a mod i saw in a gazillion places, where you use a 470k resistor like a bright cap in the normal channel... that made it more beefy, which again, worked well with the newer thinner bright channel. It still needs a few refinements but it is much closer to awesomeness now.
I am usually "All about the bass, bout the bass NO TREBLE" but It finally got through my head that adding TOO MUCH bass at the first stage made things a little too flubby and sloppy. a few tweaks here and there and i may be done.
OH, and i even tried feeding it with an overdrive pedal (a Klon-ish clone i got from a dude) and it soundede pretty damn sweet... I never really liked that Tube Screamer into a Marshall thing, since most of my marshalls were already newer high gain beasts... but it really does something good to these older circuits. Now maybe i need to do a rehouse, a mild overdrive and a volume boost in one pedal!
What? What's that you said? Huh?
