DHT OTL Linestage - Tram 2 - Page 17 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > DIY HiFi Supply

DIY HiFi Supply Parts and Kits from Diy HiFi Supply

Reply
 
Thread Tools Search this Thread
Old 9th June 2011, 11:09 AM   #161
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by DECKY999 View Post
I checked all the wiring inside. PSU voltages are fine (a bit high due to 246V mains) - B+ at around 270V. All LEDs are ON everything seams to be working but no sound this time. Any suggestions?
+B at 270V suggests to me that the valves are not drawing enough current.

What is the cathode voltage to ground and the grid voltage?

Ciao T
  Reply With Quote
Old 9th June 2011, 02:13 PM   #162
diyAudio Member
 
DECKY999's Avatar
 
Join Date: Jul 2007
OK, firstly do not forget that the mains voltage is close to 250V (246V to be exact). Therefore the output voltages are a bit higher than specified in the manual. For example the bias DC is -110V instead of -74V. I do not know if that makes any difference or not.

Measured grid to GND is around -9V. For the cathode ; pin 1 to GND is 2V; pin 4 to GND is 0.48. Heater supply is stable at 2.500V. For this ; plate to GND is 128V and reasonably stable. This is all with 45 valves.

I also noticed that it takes at least 30 minutes for plate voltages to stabilize and the bias is not the same as I left it - I do not know any more - I think I am getting a bit paranoid.
__________________
The only true way is no way.
  Reply With Quote
Old 9th June 2011, 02:16 PM   #163
diyAudio Member
 
Join Date: May 2003
Location: UK
Decky, I wish you all the best in sorting out the preamp.

All the recent discussions made me finally get around to putting 45s back into my Tram II. As expected I needed to reset the heater volts but what I've not found before is that I had to reset one CCS which was showing 100V. I swapped the tubes around but they weren't to blame. I had recently noticed that one channel was a little noisy (rustling sounds). It was this channel that needed resetting, I expect a component has drifted, maybe the CCS variable resistor, it is very sensitive to adjustment in the first place. Anyway, I mention this as it's probably worth checking voltages every few months just in case of drift, heat from 2A3s could be a contributory factor.
  Reply With Quote
Old 9th June 2011, 02:16 PM   #164
diyAudio Member
 
DECKY999's Avatar
 
Join Date: Jul 2007
Also there is - again - a significant coupling between the plate voltages when I try to adjust them. It really feels like chasing a ghost.
__________________
The only true way is no way.
  Reply With Quote
Old 9th June 2011, 02:19 PM   #165
diyAudio Member
 
DECKY999's Avatar
 
Join Date: Jul 2007
Quote:
Originally Posted by clivetjm View Post
Decky, I wish you all the best in sorting out the preamp.

All the recent discussions made me finally get around to putting 45s back into my Tram II. As expected I needed to reset the heater volts but what I've not found before is that I had to reset one CCS which was showing 100V. I swapped the tubes around but they weren't to blame. I had recently noticed that one channel was a little noisy (rustling sounds). It was this channel that needed resetting, I expect a component has drifted, maybe the CCS variable resistor, it is very sensitive to adjustment in the first place. Anyway, I mention this as it's probably worth checking voltages every few months just in case of drift, heat from 2A3s could be a contributory factor.
Thanks. In my case one pot is very sensitive and the other very lazy. The trouble is when I am close to around 100V if I adjust one the other one is changing - it is very hard to balanced them. I though before that it is CCS to blame - but they are brand new now.
__________________
The only true way is no way.
  Reply With Quote
Old 9th June 2011, 02:23 PM   #166
diyAudio Member
 
Join Date: May 2003
Location: UK
Quote:
Originally Posted by DECKY999 View Post
Thanks. In my case one pot is very sensitive and the other very lazy. The trouble is when I am close to around 100V if I adjust one the other one is changing - it is very hard to balanced them. I though before that it is CCS to blame - but they are brand new now.
Both of mine are VERY sensitive and I have zero interaction between channels so what you have seems strange.
  Reply With Quote
Old 10th June 2011, 11:33 AM   #167
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by DECKY999 View Post
Also there is - again - a significant coupling between the plate voltages when I try to adjust them. It really feels like chasing a ghost.
There still seems to be something really wrong.

Can I suggest that you do some more trouble shooting.

It isolate issues I would suggest you temporarily replace the CCS with 560 Ohm / 5W. This creates a simple SRPP and the +B should settle at around 200V and you should see 0.38V across the two 12 Ohm resistors to ground at the DHT's.

This way you can be sure that the whole biasing circuit and the power supplies work 100%.

I would suggest to then test the CCS's by themselves (you can use a 9V Battery) and to set them, together with the parallel resistor to 31.6mA outside the Tram 2.

Then you can put everything back together.

The circuit is really quite simple, it should be pretty easy to find what the problems are.

Ciao T
  Reply With Quote
Old 10th June 2011, 12:43 PM   #168
diyAudio Member
 
DECKY999's Avatar
 
Join Date: Jul 2007
OK thanks for the help - will try that tomorrow morning. I assume when you say CCS you refer to the whole PCB that holds the Ixys chip?
__________________
The only true way is no way.
  Reply With Quote
Old 10th June 2011, 02:35 PM   #169
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by DECKY999 View Post
OK thanks for the help - will try that tomorrow morning. I assume when you say CCS you refer to the whole PCB that holds the Ixys chip?
Yes, whole PCB.

Just a thought, the CCS & PCB require a modification, as the CCS chip requires a "gate stopper", if diyhfs send you new chips and PCB's you may be missing this mod?

Ciao T
  Reply With Quote
Old 10th June 2011, 02:49 PM   #170
diyAudio Member
 
DECKY999's Avatar
 
Join Date: Jul 2007
Also just to clarify, I should put 560R between the +B and the anode and leave the output not connected?

Can you just explain in more details how to set the CCS by themselves?


I do not know about that mod - I am reading the assembly manual R1.34 and the CCs PCB looks the same as the one I have (I have not checked all the resistor values). What is the gate stopper? You mean that cut track under the 5.1K resistor?
__________________
The only true way is no way.

Last edited by DECKY999; 10th June 2011 at 02:57 PM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
C3M linestage costa23 Tubes / Valves 15 23rd August 2009 08:53 AM
C3m linestage bequerel Tubes / Valves 32 14th April 2009 06:03 AM
48V B+ linestage hirafu_boarder Tubes / Valves 24 11th May 2008 05:57 PM
Another linestage...... kianbach Tubes / Valves 11 28th June 2005 05:34 PM
:: linestage [Bryston B60] :: dhengkoel Solid State 6 26th September 2002 03:32 PM


New To Site? Need Help?

All times are GMT. The time now is 03:27 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2