Trace Acoustic TA-50 disassembly

[phantombox]

Hi guys
I just received a Trace Elliot Acoustic TA-50 amp, that blows the fuse as soon as you switch it on. I took out all the screws on the wooden enclosure but it still doesn't come out. Any ideas?

[TomCarlos]

Screws on the bottom? Screws on the side (the strap handle)? Maybe give it a light pry because the tolex came loose and rubbing against the chassis?

[phantombox]

Just got it out of the enclosure. It has the famous 2SJ162 / 2SK1058 MOSFETs, one went short. And its full of silicone hot glue. I also found a loose electrolytic, just as I opened it. I think I'll have to take the whole thing apart.

[phantombox]

The chassis was kind of glued to the bottom where the 3 screws are. I had to pry it loose.

[phantombox]

I have seen strange ways of assembly in amps before, but this one kind of tops it. After checking the AC power section, and a few blown fuses later, I found the primary windings on the power transformer have shorted. It works when I disconnect it from the power switch and voltage selector and feed 120VAC directly to it. But then it gets so hot that the contacts start to melt and smoke comes out. The switch and volt selector section seems to be ok, I meassure 120 VAC on the 2 pairs of cables that connect to each the trafos primary 120V windings. I'll either take this trafo for rewinding or try to find a new one. It's the older square type, not the toroidal rafo used on later models.
Any idea about the power consumption of this trafo? I could not find any specific info online.

[TomCarlos]

Phantom....

It's hard to find a schematic for the "TA50". But you can find one for the TA100 / 50R, Link and pdf below.

It looks like the input has a switch where you can select 115v input or double it up for 230v input. The output has two sets of windings, (1) 7.5vac and (2) 40-0-40 vac. I don't know if the 50R has another tap. Look in the upper right corner of the schematic.

If you look at this link, it says that the toroid replacement could work for the TA50 - https://britishaudio.com/collections/trace-elliot-parts/products/trace-elliot-ta50r-power-transformer

TA100 / 50R. Service Manual

Trace_TA50R_TA100_schematic.pdf

[phantombox]

I have the schematics for the TA100 / 50R. I need the consumption of this unit. Or the amount of power this transformer can deliver. Too low and the equipment will not work properly, too big and it wont fit in the tiny space available... I guess I could show the trafo to my transformer guy, he knows right away the correct specs.

[J M Fahey]

.

It works when I disconnect it from the power switch and voltage selector and feed 120VAC directly to it. But then it gets so hot that the contacts start to melt and smoke comes out.

Wait a second,and what about *secondaries*?

Are they FULLY disconnected from the rest of the circuit, with all ends insulated by tape?

I don´t trust:

I meassure 120 VAC on the 2 pairs of cables that connect to each the trafos primary 120V windings.

That does not match a shorted smoking transformer very much.

[phantombox]

I wanted to make sure nothing is connected to the trafo. It does put out 40-0-40 and 7.5-0,but only until it gets to hot to continue testing.

[J M Fahey]

Ok, if you sure all secondaries are disconnected and insulated, 115V primaries are in parallel and connected to mains, and it overheats in minutes, yes, you have a shorted turn inside.
Which means full rewinding.

Your transformer guy will know for sure, but in any case an SS Class B 50W amplifier needs a roughly 70-80VA transformer; preamp and reverb consumption is low, a couple W.

*Might* have a 100VA transformer, "just because they can" and TE is a serious company, but not larger.

Only problem is that small Acoustic Guitar amps tend to be ... ummmm .... "small" ..... that seriously limits space available.

Just for curiosity, post a couple pictures showing amp guts and transformer.

Maaaaybbeeee you could find a suitable transformer at the APEX toroids site.

[phantombox]

Ok. Here are some pics. The inner guts originally were full of silicone hot glue, I've already removed most of it.

[The Dude]

Are there any numbers/manufacturer name/anything printed on the transformer itself?

[phantombox]

Here is a picture of the trafo. My transformer guy said it is an 800 mA unit and would cost $60 to rebuilt. He didn't tell me how much it would cost to build a new one with these specs.

[phantombox]

800 mA is more or less what J.M. Fahey said

[The Dude]

Have you contacted Trace Elliot to see if a replacement is available?