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Old 17th March 2013, 11:39 AM   #631
Desmo is offline Desmo  Denmark
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Quote:
Originally Posted by rab28 View Post
Sad development with my Tram2: the second time i turned it on (without an extremely noisy airconditioner running in the background this time), i could hear a loud hum from one channel. Based on some of the reports earlier in this thread, i blamed the cheap Chinese rectifier tube radiating EMI to the closest of my EML 45 tubes.

So then i borrowed a NOS RCA 5U4G rectifier tube and tried that: even louder hum! So the next night i went back to the Chinese rectifier, but the entire channel was now dead. I also noticed that the 45 tube on that side was not glowing any more. I swapped the tubes and found that the tubes are fine: the Tram2 (heater supply?) has a problem. :-(

As it happens, this coming week I was already going to take the Tram2 to a technician to get the Coleman regulator boards installed, but now it seems he has some repair work to do first!

- richard.
Richard, I think your own diagnosis is correct: You have a dead DHT regulator board... If you have been following the thread you will know that many of us have had that experience. These regulator boards are really the weak link in this preamp..!

Go ahead and have the Rod Coleman DHT regulators installed instead... Sound will be improved by a wide margin, noise will be lower and reliability will be improved. No need for repair-work, since the Rod Coleman regulators goes in instead of the regulators you use now. So out with the old ones, and in with the new ones and your preamp is back on track...

EDIT: Remember to specify that you use 45's when ordering the Rod Coleman regulators... You should try the Tram II with 2A3's also, for even better sound...
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Last edited by Desmo; 17th March 2013 at 11:43 AM.
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Old 17th March 2013, 11:49 AM   #632
kazap is offline kazap  Australia
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Yes and with the Coleman regulators in you can also cut out the crap across the filament pins.
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Old 17th March 2013, 12:02 PM   #633
kazap is offline kazap  Australia
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Quote:
Originally Posted by Desmo View Post
EDIT: Remember to specify that you use 45's when ordering the Rod Coleman regulators... You should try the Tram II with 2A3's also, for even better sound...
The regulator pack I got from Rod Coleman is the generic kit with all the components for 2A3/45/26's. The info sheets reads:

2A3: fit R1=0,68 +r2 = 1R
Trimmer range 2.2A to 2.7A

45: Fit R1=0.68 ONLY
Trimmer range: 1.4A to 1.7A

My question then

is it possible to have both configurations installed and selectable e.g. with an external switch, so we can easily roll between 2A3 and 45's?

Im sending my Tram2 down to Decky tomorrow for my Coleman make over.
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Old 17th March 2013, 12:08 PM   #634
Desmo is offline Desmo  Denmark
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Originally Posted by kazap View Post
The regulator pack I got from Rod Coleman is the generic kit with all the components for 2A3/45/26's. The info sheets reads:

2A3: fit R1=0,68 +r2 = 1R
Trimmer range 2.2A to 2.7A

45: Fit R1=0.68 ONLY
Trimmer range: 1.4A to 1.7A

My question then

is it possible to have both configurations installed and selectable e.g. with an external switch, so we can easily roll between 2A3 and 45's?

Im sending my Tram2 down to Decky tomorrow for my Coleman make over.
You have more or less given the answer yourself: YES, you can just install a switch on r2...

BUT remember..! These current sensing resistors are critical for the sound, and I don't think that a switch + additional wiring on this critical place will do anything good for the sound quality. This current sensing resistor is the one I have upgraded to 12W Mills 0,47 ohm = better sound. Also, you will not be able to just flip the switch and run different tubes, you still need to adjust filament current/voltage...
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Last edited by Desmo; 17th March 2013 at 12:13 PM.
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Old 17th March 2013, 12:17 PM   #635
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Yes, the recent kits for TRAM are able to support 2A3 (2.5A) or 45 (1.5A) or 6A3/6B4G (1A).

A switch in the resistor connexion would allow quick trials of 45 vs 2A3, but the switch should only have short wires, or there will be a risk of noise pickup.

Or, you can just disconnect one end of the resistor, to try 45s, and reconnect for 2A3.

But for best long-term results, it's a good idea to choose the DHT and fix the regulator to suit that.
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Old 17th March 2013, 12:18 PM   #636
kazap is offline kazap  Australia
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Originally Posted by Desmo View Post
I don't think that a switch + additional wiring on this critical place will do anything good for the sound quality.
I see. Thanks. Im going to have to commit to the 2A3 then.
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Old 17th March 2013, 12:21 PM   #637
Desmo is offline Desmo  Denmark
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Originally Posted by kazap View Post
I see. Thanks. Im going to have to commit to the 2A3 then.
Have Decky upgrade the cap + resistor on the modules while he is at it... With the limited space in the Tram II, they are a pain to fit later on...
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Old 17th March 2013, 12:27 PM   #638
kazap is offline kazap  Australia
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Originally Posted by Desmo View Post
Have Decky upgrade the cap + resistor on the modules while he is at it... With the limited space in the Tram II, they are a pain to fit later on...
Is there an alternative upgrade capacitor you might suggest that's just a bit less space hungry then you went with?

Its just that Im getting Decky to do side mounting of the Coleman regs to conduct the heat away from the internals so they can cope with the ambient heat my Tram2 has to deal with here in Australia. I think that makes the huge cap too big to fit?
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Old 17th March 2013, 12:37 PM   #639
Desmo is offline Desmo  Denmark
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Originally Posted by kazap View Post
Is there an alternative upgrade capacitor you might suggest that's just a bit less space hungry then you went with?

Its just that Im getting Decky to do side mounting of the Coleman regs to conduct the heat away from the internals so they can cope with the ambient heat my Tram2 has to deal with here in Australia. I think that makes the huge cap too big to fit?
Huge caps..!? They are not huge... (I don't know what you are talking about)...

As mentioned several times: I choose the 220nF Amtrans mylar caps because they are rated for high temperatures, they are relatively cheap, and reportedly they sound good. You can use any good quality 220nF capacitor, but when shopping around you will notice that the better they are, the bigger they are and these are not ''huge'' when comparing to other 220nF quality caps... Also, you can spend a lot of money on these if you wan't to use the best quality coupling caps: V-Cap copper, Duelund or what ever, but I don't think they will be worth the investment in this application. And they are certainly bigger than the Amtrans Mylar's...

When side mounting the regulators the wiring is critical. Long wires running high AC currents is ''poison''..! The RAW DC supply should be kept a close to the mains transformer as possible, for the shortest possible AC wires from the transformer to the rectifiers + first caps.
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Old 17th March 2013, 12:40 PM   #640
sjs is offline sjs  United Kingdom
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Kazap, many thanks for reading my post and offering a reply, however as Desmo has already pointed out I was specifically asking about the Mk3 version of the DiyHifiSupply filament regulator boards, and a direct conflict between the Tram2 manual and the manual for the regulators, and not the Rod Coleman boards.

I guess as there is no experience here, and I have never had an answer from Simon to a direct question, I will just have to experiment myself
My guess is that the board output of about 1.8mV ripple (as stated in the manual) remains too high for a line preamp, hence the bit slug of capacitance across the filament

Be assured, I read the entire thread prior to buying the Tram2, and am very aware of the issues with the earlier reg modules, but that the Mk3 appears to be ok, if not as good sounding as the Coleman boards. I am also aware that I probably need to add drop resistors to the AC feed to the filament boards in order to minimise the power dissipation.

I have a pair of Rod's boards, but not the other parts required to make them operational yet, that is for the next stage of work.

Should be entertaining.
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