Trace Elliot Speed Twin power xformer issue

[Mars Amp Repair]

Hello, I am new the forum. I have a Trace Elliot Speed Twin in which I replaced the power xformer & low voltage bridge diodes. The issue is that the new power xformer is getting WAYYYY too hot. I have systematically disconnected things & reconnected to see where the major current draw is that is causing this issue. Nothing else is getting inordinately hot.

The xformer gets proportionately warmer as I take it out of standby, then plug in the preamp board & systematically add preamp tubes (they're in series & fed dc off of a 24v regulator). The 6l6 outputs are biased at 35ma ea.

I guess what would be very helpful is if anyone has had experience with this amp & can tell me if they've experienced the same issue.

Anyway it turns out, I am not comfortable with how hot this xformer is getting & may add a separate filiament xformer to take some load off of this one.
I saw some info on this site about how pwr xfrmrs for many old amps were designed for 110v & now we have typically 126. Not certain this amp is old enough to fall into that catagory.
Any ideas appreciated. glen whatley - MarsAmpRepair.com Englewood, CO.

[Ray Ivers]

Glen,

Are you 100% sure you've found & repaired the problem that caused the old transformer to fail, and is the new one an exact Trace Elliot replacement?

Ray

[Mars Amp Repair]

Originally Posted by Ray Ivers

Glen,

Are you 100% sure you've found & repaired the problem that caused the old transformer to fail, and is the new one an exact Trace Elliot replacement?

Ray

Thanx for the quick response. Yes, the xfmer came from British Audio Service & is the original. There doesn't seem to be anything else wrong (aside from the LV bridge diodes I replaced) They don't get hot, either. The amp performs great all the way to clipping & puts out the expected wattage.
The 24v regulator I mentioned for the preamp tubes (fil in series) gets a bit hot, but Trace Elliot added a piggyback heatsink to that as a retro fix. Of course it only gets hot when the preamp tubes are plugged in.
So yeah, really difficult to determine when everything seems to be running fine...nothing with too high or too low voltages & nothing getting too hot.

I will say that it is weird that the line fuse did not blow before the xformer went bad. The new linefuse does not blow either. Also the old xformer looks like it was getting really hot before it blew...the holes in the bottom where the wires exit are brown from the heat & whatever was being exhausted from the blown xformer.
It's just one of those tough buggers where the real problem is illusive.
glen MarsAmpRepair.com

[Ray Ivers]

Glen,

Has the factory been able to shed any light on whether the transformer normally runs this hot, and if so, why? I assume not or you probably would have posted it... You mentioned disconnecting each PT load during troubleshooting; did you also measure each winding's current draw, finding all of them normal?

I'll hazard a guess; if this transformer normally runs super-hot, it will eventually fail as the first one did (kind of a no-brainer ). In light of this, your suggestion of an additional heater-only transformer sounds like a good one; I've done this more than once, though never for exactly this reason. Also, just FWIW; Heyboer Transformers winds custom PT's to your specs for very reasonable prices, and if this amp is a personal "keeper" amp you might consider spec-ing out an ideal PT for the amp yourself, as I did with my Marshall 6100.

Does the PT get warm with no loading at all, as have a number of Fender blackface PT's I've encountered? Does it pull appreciable primary current with no loading?

Ray

[Mars Amp Repair]

Ray,
I actually don't know where the factory service folks are...I've been in contact with Shane @ British Audio Service & he was unable to shed any light on the issue...Are you speaking of the folks in britain...if so, do you have a link to them.
This amp isn't actually mine, I am a servicer & it belongs to a customer.

Thanx, glen

[Mars Amp Repair]

Ray,
Also, I wouldn't really know what to expect as far as current draw on the windings. Haven't really had much need for that in the past.
The xfrmr doesn't not get hot when unloaded. In fact as I mentioned, none of the loads alone seem to draw exorbidant current from the xformer...only when everything is connected, does it seem to go over the point of being too hot.
The last thing I connect is the preamp board. That pushes it over the top of what I consider to be 'safe'.
I'll have to hunt get on the trace site & see if they have an e-mail to their techs. thanx, glen

[Ray Ivers]

Glen,

In fact as I mentioned, none of the loads alone seem to draw exorbidant current from the xformer...only when everything is connected, does it seem to go over the point of being too hot.

This sounds to me like you have the correct current-draw information for each load, and have made measurements that indicate each load is within specs... so I guess it's got to be an under-spec'd PT. I was thinking that you were just plugging in loads and checking for PT temp rise after each new load was connected, which obviously tells you nothing about whether or not that specific load is pulling more current than it should - especially considering the time lag between an increase in winding current draw and a perceptible temp increase at the outside of the PT.

Ray

[tim]

I repaired one of those last year (it was an OPT that I had to replace) and it was the second one in a year and a half that I had replaced in the same amp (the amp is not abused by any stretch). The third one I put in was defective right out of the box.....I haven't a lot of confidence in the design of the transformers in that amp. Shane was good about sending out a new transformer to replace the defective one....If their power tranny is built like their OPT, I would suspect a bad design (severely under rated)