Traynor YBA1 Bass Master (1968) repair

[Arhythmic]

Hello

I've been a long time reader and now I finally decided to finally ask some questions directly!

A few days ago, I bought a very nice Traynor YBA1 Bass master amplifier with 2 X 15'' cabinet. I've been looking for a more powerful amp than my little Laney Cub 12 (with a Celestion Greenback) and this thing is definitely more powerful... Frighteningly so actually! So I've ordered a master volume kit (and a bias adjustment kit) from London Power website just to be able to get some crunch from it, because it stays very clean way above my listening pain threshold levels.

So while I'm waiting for those to arrive, I would like to fix (or at least try) a buzzing power transformer. I didn't notice it at the seller's house, or maybe it wasn't there, I'm not sure. I transported it carefully, on the passenger's seat, not in the trunk. Once home, I plugged it in and it was buzzing quite loudly, as soon as you power it up, even in the standby mode. For now it still has the good ol' two prong cord, which I will replace by a three prong counterpart first thing this week, maybe that will help. I tested the tubes just to make sure and both 3 12AX7s and 2 EL34s tested strong and with no shorts. I will remove the chassis tonight and will check if I can tighten the transformer's bolts. I will also take some pictures for your viewing please

Is there anything else I might want to look for? Loose filtering capacitors connections?
I'm a careful novice basically: I know how to do some clean soldering and how to discharge caps before starting poking around a tube amp, but I do not have sufficient theoretical knowledge to diagnosis everything by myself... despite reading a lot of books on the matter... so maybe starting to do actual debugging will help

Thank you all very much in advance!

[Leo_Gnardo]

I can tighten the transformer's bolts.

That would be a good start, right there. Both mounting to chassis bolts and the ones that hold the covers & laminations together. Good amp, good plan. And welcome aboard!

[DRH1958]

Hello
Is there anything else I might want to look for? Loose filtering capacitors connections?

Check to make sure the fuse is the same value and type as specified on the amp next to the fuse holder.

Also, as long as you're checking conditions around the filter caps, maybe check to see if they have been replaced. A 1968 model amp will likely benefit from a cap job. As long as you are there, check for possible overheating of power supply dropping resistors and any other components that look like they have been overheated. Just follow the wiring connected to these caps and you'll see these resistors.

Check to make sure the sockets connect with the pins of the tubes firmly. If you have some cleaner on hand, spray some on a cloth to make it damp, rub some on the tube's pins and then install, pull out, then re-install the tubes to clean the sockets. I personally don't like to spray the cleaner directly into the sockets. Make sure this cleaner is the type that leaves NO RESIDUE or lubricant behind. That lubricating type is for cleaning pots and leaves some lube behind for better operation.

Once you provide those gut shots, other more experienced eyes will be able spot other problems and offer other ideas.

These are general things that should be done regardless of that buzzing problem.

[Randall]

Have you tried reversing the AC plug at the wall outlet?

[Arhythmic]

Hello

Thank you all for suggestions and advise!
Randall, I tried reversing the AC plug, that was the first thing on my list. Unfortunately, no change in the transformer's buzzing. I'm also quite puzzled about the ground on/off switch on the back of the amp: how is it supposed to affect something that is not quite there?

Here's a nice shot of the super safe 2 prong cord, I get nervous just by looking at it


Some wicked this way came... wow...


The overall look of my YBA1:


The new can capacitors that previous owner's amp tech installed. Glad to see that those are not the cheapest kind:


However the installation (at the mechanical part) troubles my OCD...


The infamous gut shot:


As per DRH1958's suggestion I quickly checked around and the electrolytics seems to be remplaced and all the resistors seems to be in shape as far as I know. But I checked really quickly...
I also retightened the transformer's bolts (both output and power) but the buzz was still present afterwards. However I noticed this:


Was it something intentional and by-design or is it something I might want to correct? Because it certainly seems odd to me...
Also I tried firing the amp up without any tubes in it for a very brief moment and the buzz arrived instantly.
That's about it for now

[Leo_Gnardo]

I'm also quite puzzled about the ground on/off switch on the back of the amp: how is it supposed to affect something that is not quite there?

Lots of amps had those, some still do. The "ground" switch connects the chassis through a capacitor, to one side or the other of your AC power line. The idea was, you might be able to minimize hum. The drawback is, if it's the hot side of the AC line then your chassis and anything connected to it (your guitar for instance) becomes a shock hazard. As long as the cap is working well, you would get an annoying shock but limited to about 2 milliamps. If the cap fails short then you're directly connected to the AC line and the shock can be deadly, also you can weld your guitar to anything grounded, and some people have done that. YOU are going to replace your AC cable with a grounded cable set, right? Right! Without further delay. And when plugged into a grounded outlet then your only fear will be any other gear that isn't properly grounded. These days most is. And at that point you can remove your "death cap" and dispose of it.

Some wicked this way came... wow...

Looks like there was an arc in the output tube socket under that char mark. I hope the socket was replaced.

I also retightened the transformer's bolts (both output and power) but the buzz was still present afterwards. However I noticed this:

Woops looks like the amp was dropped. We see this all to often in amps. As long as the bracket isn't broken I'd just leave 'er alone. But that buzz . . . usually blamed on loose laminations. They are usually held together by a layer of lacquer plus the pressure of the assembly bolts. The fall may have loosened things up a bit, or time & heat may have done it. If the transformer is otherwise working I don't have much in the way of solutions. You might find a nearby outfit that works on electric motors & generators, see if they have a dip tank where they can soak your PT in whatever adhesive they use to hold windings & laminations together. If you remove the transformer you can try straghtening the mounting bracket at that time. A replacement is going to be costly no doubt, otoh yours was likely made by Canada's Hammond, and they very well may have an appropriate part that will fit properly & deliver what's needed for your prize.

[Arhythmic]

Thank you for all the information Leo_Gnardo!

The 3 prong is going in and the death cap is going out, no doubt! I'm wondering why the previous owner didn't change it while his tech was working on the amp...
The tube sockets seem to be replaced, yes. They were also screwed down with a metal screws, not with bolts and nuts.
The amp is still working, so the transformer is not an urgent replacement, but it still bothers me a lot. I will look around my area if there are shops that are able to reseal it in low viscosity epoxy.
I also checked Mercury Magnetics website and they do have replacement power transformer for YBA1 but it is 281$US + shipping + import taxes and everything... Ouch...
Hammond also do have nice models for Bassman (so it should work for YBA1, right?), but I also read that YBA1's transformers were oversized and overbuild, which I like very much So I thought maybe getting 291FX (http://www.hammondmfg.com/pdf/EDB291FX.pdf. If the replacement is necessary, that is. I would love keep those vintage transfos...

Thanks again!

[Leo_Gnardo]

IYou could contact Hammond on email, give 'em the part number on your PT & see if they have a recommended replacement. Yes anything Mercury is deadly expensive, add shipping & customs, sorta drives you right to Hammond don't it? If you're lucky and the dimensions work out, you might be able to swap the bells so you can mount it upright as original. It would be a big PIA to have to hog out a big hole in the chassis for "lie-down" mounting.

I hope you can skip all that if the pros at a motor shop can sort that transformer out for you.

[g1]

Those ground lug connections on the big caps look very poor. They need to be real solid to provide all the current for those caps.
You need a real big iron to heat up those chassis connections enough to get a good solder joint.

[g1]

IYou could contact Hammond on email, give 'em the part number on your PT & see if they have a recommended replacement.

If they are not allowed to tell you about OEM parts, contact Traynor directly and ask them what they use for subs. You will need to tell them the exact sub-model (1, 1A, MkII ?) and the serial number probably helps date it too.

[mozz]

That's the famous Traynor second story drop test. I would take it apart, try to straighten it the best i could and retry.

[Justin Thomas]

While I don't advocate their use in NEW builds, in this instance I'd spring for new CE Dist. can caps, or pretty close Mallory copies, that would fit the mounting holes and the previous grounding scheme, without the chintzy clamps and the sheet metal screws... I would think I could be fairly safe saying that the original product did not have a grounding problem as issued from the factory?!?! I just don't trust the replacements to be mechanically secure as mounted, and I'm with g1 - the ground soldering is spotty. Get out the big iron for that job...

I guess some see these as "cheap mod platforms," but I think it'd be worth the investment to dress it up nice... sometimes, it <IS> worth doing nice, even if it does cost you half or more of what you paid for it... of course, fix the buzzing first! As far as new iron, go with a "suitable" Hammond - they're conservatively rated, so even a "regular" Bassman Hammond will probably be more than "adequate."

Justin

[Arhythmic]

Thank you all again for suggestions! I really appreciate it!
I will replace those can capacitors but I have a question: should I go with 32uF or 40uF? I read somewhere that boosting to 50uF (from Traynor's original 40uF) will make the amp ''stiffer''. Is it something relatively scientific or is it perception based only?
Based on Justin Thomas' suggestion I found this as a replacement: https://www.cedist.com/products/capa...-525v-404040uf (rated to 525V instead of 450V original).
Also, I don't think of this amp as ''cheap JTM45 or poorman's Marshall'' and I would like to preserve it as much as possible in it's original state, or at least some easily reversible mods (1 meg audio instead of 4 meg linear volume pots for example).
I will unsolder the power transformer and try to straighten the brackets and putting it back to see if it fixes the buzz. If not, try to find a shop that will be able to reseal it. If not, Hammond replacement
G1, I totally agree with you: those ground connections look unreliable! However, what is the proper method of mounting those can capacitors? Should I use the mounting clamps/rings?

[Leo_Gnardo]

I will replace those can capacitors but I have a question: should I go with 32uF or 40uF? I read somewhere that boosting to 50uF (from Traynor's original 40uF) will make the amp ''stiffer''. Is it something relatively scientific or is it perception based only?

I use 50+50 uF / 500V for this sort of thing. They're held in place with brackets. You have to wire from terminals to your circuit points, no need for a giant soldering iron. F&T & JJ make them now, Ruby also (Ruby the tubes distributor, not Rubycon), back in the day it was LCR. Of course there will be some "purists" who spend all day tapping on their keyboards, parroting what they read in some other expert's blog, I doubt they could really tell any difference between 32, 40 or 50 in a double blind (triple blind in this case?) listening test. If you went whole hog, say to 220 uF then maybe there's a case to be made for "stiffness" but I've worked on amps with this much and more filtering in the main B+ supply, they didn't sound bad. And there sure wasn't any hum from an insufficiently filtered B+.

[Justin Thomas]

The can caps' original mounting tabs can be seen leftover in spots. The can would come with the positive terminals for the different sections, and then there are four other tabs that are the shared negative ends of the sections. Those four tabs were usually bent over the sides of the hole and soldered to the chassis. Which is why you need the Big Iron.

Alternatively, Ampeg and some others used a wafer isolation base, which was mounted by two rivets to the chassis, then those four ground tabs on the cap can were twist-locked on the wafer. Then you run a ground wire to wherever you want.

Personally, I try to stick with the factory way. If you DO choose to stick with the clamps, I'd definitely clean up those leftover tabs and screw holes, and stick with some better mounting hardware (machine screws). But that's all just me.

Justin