Stax SRM-T1 hot trafo over 70 Celsius degree

[Pirx]

Hello Everyone

This is my first post here. I have done some research about T1 troubles here and didn't find any topic about hot trafo.

In my opinion this trafo is too hot but I don't have another SRM-T1 to check.

I have removed tubes and then trafo is only warm - seems ok.

Picture shows where I put temp sensor (blue wire).

Did anyone had similar problems?

P.S. I have just bought SR-Omega with Mk1 driver and SRM-T1 - amazing sound My previous system was SRM-727 and SR-507 and it wasn't so good.

[wink]

P.S. I have just bought SR-Omega with Mk1 driver and SRM-T1

.

Were these on ebay from wiktor or rotkiw ?

[n_maher]

There is some disturbing discoloration on that transformer, in my non-professional opinion. I would make sure that the amp is setup for the proper line voltage (assuming it's adjustable like other Stax amps) and after that get a known good set of cheap tubes to try in there. Could be that one of the 4 tubes is going bad and drawing more current than it should be. Otherwise, I don't know enough about that amp to be really helpful.

[Pirx]

.

Were these on ebay from wiktor or rotkiw ?

Yes, from Wiktor

There is some disturbing discoloration on that transformer, in my non-professional opinion. I would make sure that the amp is setup for the proper line voltage (assuming it's adjustable like other Stax amps) and after that get a known good set of cheap tubes to try in there. Could be that one of the 4 tubes is going bad and drawing more current than it should be. Otherwise, I don't know enough about that amp to be really helpful.

There are only 2 tubes. Trafo is set to 240 V. In my opinion discoloration and temperature doesn't look good.

I have schematic from SRM-006 only, but I am not sure if it is the same or similar to T1

There is no hum or noise in headphones, amplifier seems to work good.

[kevin gilmore]

You need to measure the high voltage rails to know more.

If they are 20% high, then what you really have is

the transformer wired for 200v running on 240v.

And then the transformer gets very hot.

[spritzer]

That transformer should not look like that so first things first, change the tubes as they are a likely culprit. Second, check the actual socket wiring on the Stax voltage selector as it might be wrong.

The SRM-006t is pretty much identical to the SRM-T1 but here is the schematic since I have it. Not the best scan but it will do.

[Pirx]

Thank you for your interest, Kevin.

You need to measure the high voltage rails to know more.

After one hour of working I can read AC voltages: 251 V, 268 V and 6,25 V.

If they are 20% high, then what you really have is

the transformer wired for 200v running on 240v.

I have no idea if it's right for T1.

But I have SRM-006 schematic and there are very similar voltages: 250 V, 270 V, 6,3 V.

[Pirx]

That transformer should not look like that so first things first, change the tubes as they are a likely culprit. Second, check the actual socket wiring on the Stax voltage selector as it might be wrong.

The SRM-006t is pretty much identical to the SRM-T1 but here is the schematic since I have it. Not the best scan but it will do.

Thank you Spritzer, the schematic helps a lot

Voltages in my T1 are very close to those from schematic.

Schematic my T1

320 V 319 V

350 V 344 V

48 V 48 V

I have no idea why this trafo is so hot, everything seems to be ok

[spritzer]

Too much current through the tubes would be my guess.

[Pirx]

Too much current through the tubes would be my guess.

Measurements shows about 4,5 mA/triode (probing voltage drop on anode resistors = about 150 V).

But I have discovered this time there was not +320 V but only +308 V. That amp drives me crazy ;-)

[kevin gilmore]

output dc on the tubes should be close to 0. 150v is not right

[Pirx]

output dc on the tubes should be close to 0. 150v is not right

Sorry, I wasn't clear. Every triode has two 33k resistors in series. 150 V is on one of them, that gives 150/33000 - more less 4,5 mA. Output is close to 0 V (flows around zero).

I suspect, this is the way my amp should work. It is very strange to me but everything seems to be ok but temperature of trafo.

I need to look around for another T1 and check it.

[n_maher]

I wonder if some past event didn't cause damage to the trafo (before the current ownership) and it's now no longer capable of performing properly even under the best of circumstances?

[Pirx]

I wonder if some past event didn't cause damage to the trafo (before the current ownership) and it's now no longer capable of performing properly even under the best of circumstances?

Yes, it is possible. Who knows what history is behind this amp.

[spritzer]

4mA seems about right but I'm with Nate here, the terminals on these transformers are open so they are easy to short. If something like that occurred then who knows what happened internally.

[Pirx]

4mA seems about right but I'm with Nate here, the terminals on these transformers are open so they are easy to short. If something like that occurred then who knows what happened internally.

True.

I got this amp for two weeks. I can always replace this trafo in the future.

Thank you All for help and suggestions.

P.S. Perfect reason to build my own amplifier

[renrossi]

Hi Everyone,

 

My first post here and like Pirx I'm having trouble with my SRM-006tA transformer, HV rails have no voltage.

 

According to the provided SRM-T1 schematic (it's identical to SRM-006t, right?), it looks like secondary voltages are: orange 250V, red 270V and blue 6.3V.

 

I was wondering if somebody could please confirm the above and also the current rates, so I can replace it.

 

Pirx, you said "I can always replace this trafo in the future.". Do you know where I could get a replacement for that? I know Stax had it customized from Bando but I guess there are other transformer models out there that could fit.

 

Thanks in advance!

[kevin gilmore]

here is the problem. everyone rates transformers in different ways, and since the power supplies

in this unit are completely unregulated, and if the dc voltages go to high (more than +320/-350)

parts start to blow up, there are issues. so take your best shot at what you think the under load

voltages should be and hope for the best. second issue will be getting a transformer to fit

in that size hole.

[renrossi]

Hi Kevin,

 

Thanks for the answer.

 

So, am I right when I say that for SRM-006t transformer, orange is 250V, red is 270V and blue is 6.3V? And SRM-006t circuit is identical to SRM-T1?

[renrossi]

Thank you for your interest, Kevin.

After one hour of working I can read AC voltages: 251 V, 268 V and 6,25 V.

I have no idea if it's right for T1.

But I have SRM-006 schematic and there are very similar voltages: 250 V, 270 V, 6,3 V.

 

Hi Pirx,

 

Could you please provide a copy of your SRM-006 schematic?

 

Thanks!