YBA-1 decisions UPDATE! With an UPDATE on the UPDATE!

[guittech]

Hey guys,

SO... the reason i got my "Big Ass Chassis" is because i was at the junk shop picking up a YBA-1 baby bumper type head for another project.

I am a little conflicted on what to do with this one. It's currently "Semi Functional" It works, makes noise but sounds TERRIBLE. I paid around $200 for it plus a couple pedals out of my unloved pile. It was described as "all original, no mods" which had me thinking i would just make sure it works and play it for a while.... Well, there are no CRAZY mods, but it's got a handfull of orange drops (definitely not original) and it isn't working right. Again, it's at home, and my workshop is at work, so I don't have a chance to get my hands dirty yet, just evaluating.

Since it DOESN'T work and isn't original, I don't feel bad about doing mods to it... but I am torn, I was going to build a clubman, but now i have the BIG ASS CHASSIS that i might put an octal clubman in... so then i thought of maybe a hotrod Marshall, but i already have that. Lately I have been torn between restoring it (with a subtle tweak or 2) OR maybe leaning it a little towards a Marshall vintage type, a JTM50 or a 1987.... But i have decided i don't want to go TOO crazy, and start punching holes or covering up stuff.... The Marshall circuit will fit nicely, and in lieu of a Master Volume mod, I may just put a DrZ Brakelite in the cabinet to tame the volume a little.

SO, in essence, non working, non orginal chassis. What would you guys do? Restore it to happiness? Or subtly mod it in the direction of a vintage Marshall?

[Regan]

Isn't it just a few parts off of a plexi? why not go that route?
Regan

[guittech]

The 2 amps i am leaning towards JTM50 and 1987 are 50 watt plexi era amps. Just use el34's instead of kt66's I've tried a few times and never gotten the "magic" of kt66 tubes. I like the midrange characteristic of the el34 better.

I say "move towards" instead of rebuild since the changes are pretty minimal, Regardless with this amp, It's a Junk store find, sold by a bunch of kids who had NO IDEA of what constitutes a "working" amp... It's pretty scary. I talked to their "electronic dude" who had NO IDEA about tube amps, yet he was replacing parts on a few (mostly pots) I think he's been spraying wd40 into the pots too.... eeesh. The look of shock on their face when the amp was acting screwy shows they have no idea what they are doing, they claimed if i put wd40 in the pot it would be fine, meanwhile the amp has blocking distortion and is cutting out severely, even after working the pot in... It needs some TLC. But i digress... since it is a junk shop find, it certainly hasn't been tested properly, or assessed for issues. It's noisy as heck, has crappy chinese power tubes and questionable orange drop caps in here and there... It needs some real love to get back to where it could/should be. I might add a choke and more filtering, see how that turns out. Not looking for miracles, but I'd like it to be quiet as possible At least power-wise

[Leo_Gnardo]

Put your Traynor schematic and JTM50/1987 side by side, you'll see they're near as dammit, so that's a good direction to go. Traynor nicked their design from Fender 5F6A Bassman, with a couple minor changes, much like Marshall.

Orange drops, maybe not your fave, but they are reliable in all their varieties. Who knows, maybe those kids knew enough to pinch the mustard caps often found in old Traynors. No matter, the OD's are OK, and you can replace 'em with whatever you want if you don't like 'em. I like Mallory 150's for a good clear tone and affordable price, but go with whatever floats your boat.

Traynor hi voltage typically a bit north of 500V, tough on EL34's. Think 6CA7 instead. When I bought my first amp, a YBA1A in 1971, that's what was in it & I ran that thing at hundreds of gigs & rehearsals into 1976. KT66 would likely not like the hi voltage, that would be an expensive experiment. Save those for amps with B+ 450V or lower.

Chinese power tubes vary all over the place in quality too. As far a crappy ones, there have been some real doozies. The Shuguang-made tubes currently sold by Ruby fare much better. I use them regularly with satisfied amps & customers. Some folks get a 5+ year run out of a set. On the other hand I've had customers who took it on themselves to spend extra on current Russian made fake TungSol - because they're "supposed to be premium" - and wind up with a set of vacuum-loaded maracas rattly as hell.

Haven't found much advantage using chokes in the Traynor hi voltage supply. You might consider putting a larger resistor to the screen grid filter, also individual screen grid resistors. Yes you'll lose a couple watts of audio power, big deal, you'll buy a lot more output tube life with screen grid voltage brought down a bit.

I wonder if the "expert" at your electronic junque shop read Cesar Diaz's article in Guitar Payer. Almighty Cesar recommended hosing down pots with carb cleaner, or was it brake cleaner, either way lots of people wound up dissolving their pots' interiors with his advice . WD-40, I could see using it in a pinch, if I was stuck in with a noisy-pot amp and HAD to make it work by show time only an hour away. The problem I run across, some folks think "more is better" and keep spraying until the interior of the amp is swamped with WD-40 oil making for a fire hazard. One spark - then WOOF! Not the thing to do. FWIW I find 40 year old pots found in Traynors often require replacement anyway, if they don't respond to cleaning even with the prime Caig sprays.

No worries, $200 is an OK buy price for a restorable Traynor. It'll be a project & you'll wind up with a great sounding amp.

[guittech]

Oh, when i say NO IDEA I mean it, he had ZERO... No idea the amount of voltage he was dealing with... I doubt he could read a schematic. Didn't know what i was talking about with "discharging caps" before working on an amp.... I doubt they pulled any parts because they wanted them, it was more like they had no idea what the originals would have been! The ones in there look a little different, again, just a cursory look, they may be cheap knock off OD's, I'll know more when i get it to work and on my bench.

The other amp i got from them, they had no idea that it wasn't working properly.... Again, it needed a couple new tubes and some filter caps, noting major... They could have sold it for more if it didn't hum and rattle when being tested... but they had no idea what might be wrong.

And yeah, the 1987 is so damn close it might as well be the same amp... just a few subtle tweaks.

[fusionbear]

I converted one of these into a 1986 Marshall circuit and it came out sounding awesome. My customer was very, very happy.

[IMG768]http://i169.photobucket.com/albums/u223/fusionbear/YBA-1%20conversion%20to%201986%20specs/IMG_3255_zpsaab72345.jpg[/img]

http://s169.photobucket.com/user/fusion ... 86%20specs

[guittech]

Hey FusionBear, looked at the pics and It looks like it has a choke. What Choke did you use?

I only have a little Fender type one laying around, need to track down one of them big arse Marshally ones

[Leo_Gnardo]

Didn't know what i was talking about with "discharging caps" before working on an amp.

Then they're bound to learn the hard way and someday they will. Hope there's no permanent damage.

Fusionbear, your Traynor looks awesome I'd say, that's what you wanna do.

[fusionbear]

Hey FusionBear, looked at the pics and It looks like it has a choke. What Choke did you use?

I only have a little Fender type one laying around, need to track down one of them big arse Marshally ones

This one had the Hammond choke in there already. But any 3hy to 5hy will do IMO...

[fusionbear]

Didn't know what i was talking about with "discharging caps" before working on an amp.

Then they're bound to learn the hard way and someday they will. Hope there's no permanent damage.

Fusionbear, your Traynor looks awesome I'd say, that's what you wanna do.

Thanks! You have to move a few things around, but not too much, the volume pots must be changed to 1Meg. I changed the B+ string to match the 1986 circuit, added an adjustable bias supply. Added a Lar/Mar PPIMV Added the 30uf's for the preamp and CF. There is a lot of room in there...

[Leo_Gnardo]

Hey FusionBear, looked at the pics and It looks like it has a choke. What Choke did you use?

I only have a little Fender type one laying around, need to track down one of them big arse Marshally ones

This one had the Hammond choke in there already. But any 3hy to 5hy will do IMO...

If you must have a choke, yes the Twin Reverb type will be plenty sufficient, take up less space, & more affordable besides.

What not to do: one of my customers had his Traynor "modified" by some California flavor-of-the-week hack who insisted on installing a huge Mercury 10 Hy unit. Said hack bolted in the choke, charged list price plus shipping for it, didn't bother hooking it up. "You're amp's 10 pounds heavier now, pay me $125." Amazing what some people get away with.

[guittech]

Well, it's not so much a "must have" a choke, I just happen to already have one. It's from Allen Amps, I need to double check, but I thnk it's the 3Hy one they use for Bassmans. It's pretty tiny. Just want to get the power section as clean as possible, and the part is gathering dust.

I'll have to see how the filter caps are performing... amp is currently noisy and not working for shit... has original can caps, so they might have to be replaced. Once i figure out why it isn't working, and whether the crappy 3 prong plug is even wired correctly, I'll know what I am woking with... Replaced the filter caps in my Bassmate and it went SILENT!

well, Damn close at least.

[dorrisant]

+ 1 on Fusionbear's advice to change the volume pots to 1M.

I just rebuilt one not that long ago. I haven't changed anything about it since the last post here:

https://tubeamparchive.com/viewtopic.ph ... aynor+yba1

Don't see any reason to change it other putting in a PPIMV. I really like the pots with the switch.

[guittech]

So my troubles continue.....

Got a chance to look at this amp today, and it's actually a version I've Never seen before! it doesn't match any of the schematics I have seen online! Grrr.

It's a late 70's The schematic under the hood shows a revision from late '75. It uses a bridge rectifier, but there is no center tap on the Transformer winding for B+. just the center tap from the rectifier circuit. I was hoping to use the "zener diode trick" or something similar to drop down the B+ a bit. but without a center tap wind I would have to put the zeners on the line back from the bridge rectifier correct? I could switch it to the Marshall style rectifier circuit, (full wave? I am horrible with names) but there is no center tap on the transformer.

I will try to take a quick pic of the schematic to put up. until i can get home to my scanner.

[guittech]

[IMG768]http://i871.photobucket.com/albums/ab273/guittech/IMG_5188_zpsnp8xrjyj.jpg[/img]