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-   -   DHT OTL Linestage - Tram 2 (http://www.diyaudio.com/forums/diy-hifi-supply/156854-dht-otl-linestage-tram-2-a.html)

GeirT 28th November 2012 03:34 PM

Hi Clive,
My mounting of the regulator boards may be a bit dramatic; I simply glued them with 'super-glue' to the chassis sides. The regulators have electrically non-conducting packing that avoids short-circuiting.
If I had done it over again I would have soldered the regulators on the upper side of the boards so that are domewhat easier to remove/replace in event of failure.

Thank you about the tip to remove capasitor over the filament pins.

Geir

Desmo 30th November 2012 04:03 PM

Hi Geir,

Thanks for the pictures, it's always cool to see other implementations :-)

The epoxy coating of the chassis is quite bad at dissipating heat, meaning that the junction temperature inside the transistors will be very high in your set-up. Don't expect the transistors to have a long life...

Also: You MUST remove the capacitors on the the filament pins, otherwise they will both color the sound and work as filters that alter the freq response. With those caps in place I understand why you heard a mellow bass, basically the cut off the bass range when used with the Rod Coleman regs.

GeirT 30th November 2012 06:42 PM

Thank you Morten,
I was about to get a second opinion about removing the caps over the filament pins.
Now I'll open the chassis and just remove them.

Not so sure about the heat build-up though as the regulators are not so very hot to the touch. But thanks for your advices anyway.

Geur

GeirT 30th November 2012 07:05 PM

That helped,
More air around the instruments :-D

Just bought a 'vintage' reel-to-reel tapedeck, a Revox B77 with new heads.
My oh my, I've never believed that this machine from mid-seventies could be so transparent and seemingly uncoloured!

I'm a happy guy :-)
And it's Friday

Geir

GeirT 30th November 2012 07:10 PM

It's off-topic but I simply love my new favourite toy;
The famous Revox B77 taperecorder

Geir

GeirT 1st December 2012 07:04 PM

Now I've measured the temp of the Coleman heater regulators with a thermo-couple I bought for the purpose today. It measures 40 degrees C directly onto the regulater 'plate'. It feels somewhat higher using my fingers but still that should be OK shouldn't it?

Geir

Desmo 1st December 2012 07:16 PM

What is a ''regulator plate''..? Do you mean the housing of the transistors? If you have 40deg celcious on the transistor housing then all is fine. I think it will be higher though, as your test with the fingers also indicate. If you can hold your finger on the transistor for a few seconds, then that indicate a temperature on around 60 deg celcious - and that is fine, especially if it's with 2A3 tubes...

Rod Coleman 1st December 2012 07:23 PM

Yes, that's right - 40 to 60 deg C is OK.

70 deg C is the maximum temperature for the transistor case, or the heatsink (near the transistor).

Must be a good heatsink!

Desmo 1st December 2012 07:28 PM

Quote:

Originally Posted by Rod Coleman (Post 3266012)
Yes, that's right - 40 to 60 deg C is OK.

70 deg C is the maximum temperature for the transistor case, or the heatsink (near the transistor).

Must be a good heatsink!

He is not using a heatsink..! The transistors are just super-glued to the epoxy painted chassis. I'm a bit surprised if the temp is this low since a thick layer of epoxy paint + super glue between the transistor and the aluminium chassis could be a serious barrier for heat transfer... But apparently it works...

kazap 23rd December 2012 06:17 AM

Id like to buy a used Tram2 - please PM me if you know of one sitting on a back shelf.

Otherwise I wonder if anyone could build a two box version for me with the power and heater regulation in its own chassis to keep the tubed chassis cooler?


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