Hammond Pwr Trans 374BX Diagnosis - Page 2 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Tubelab

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Reply
 
Thread Tools Search this Thread
Old 5th September 2012, 02:42 AM   #11
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
replace both D1 & D2 with DSEI12-12A.
There have been issues with the IXYS parts ever since IXYS changed something about 3 years ago (probaly a process geometry change). I have been reccommending a Fairchild part that doesn't blow, ISL9R8120P2 It has been discussed in the Tubelab forum before.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 5th September 2012, 03:33 AM   #12
Junior is offline Junior  Singapore
diyAudio Member
 
Join Date: Jun 2004
Location: Singapore
the original one that blow is Farchild.
anyway, let me try it out tonite and hope that the 12A (DSEI12-12A) version will hold.
finger cross

Left - Good
Right - Bad
Click the image to open in full size.

Last edited by Junior; 5th September 2012 at 03:39 AM.
  Reply With Quote
Old 5th September 2012, 02:01 PM   #13
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Junior: as Tubelab mentioned above, you don't need the diodes if you are running a tube rectifier...........so feel free to power up the amp after the diode-ectomy as see if the transformer quiets down.
  Reply With Quote
Old 5th September 2012, 02:07 PM   #14
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Quote:
Originally Posted by Junior View Post
anyway, let me try it out tonite and hope that the 12A (DSEI12-12A) version will hold.
Junior: It's not the current rating that is a problem. It's a voltage spike at turn-on from the power transformer, with the Hammond units being especially prone to this. Depending on where the AC mains waveform is when you hit the power switch, the transformer can send a voltage spike (sometimes in excess of 2KV) to the rectifiers, and the 1200V rated parts get toasted.

Tubelab has discussed this in a thread around here somewhere, having flipped the power switch over and over while looking at the diode voltage with a scope. So leaving them out altogether if you are running tube rectification will save you from future issues.
  Reply With Quote
Old 5th September 2012, 03:11 PM   #15
Junior is offline Junior  Singapore
diyAudio Member
 
Join Date: Jun 2004
Location: Singapore
Hi boywonder,
Understand the part that George mention that I do not need the SS rectifier. But I had already drilled hole in the front panel for it.

Good New:
Finally, I manage to stop the humming (vibrating) from the Hammond 374BX after replacing D1 & D2. The fried D2 caused the short circuit on the high tension resulting in the humming.

Bad New:
Hooked up the SSE, No output. I mean no music.
Please suggest where can i start to determine the cause.

For the time being, I will be looking at all my wiring all over again.


Thanks
  Reply With Quote
Old 5th September 2012, 08:28 PM   #16
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
Junior: It's not the current rating that is a problem. It's a voltage spike at turn-on from the power transformer, with the Hammond units being especially prone to this.
Actually the voltage spike occurs at turn off. If turn off happens when the current through the transformer secondary is at a peak, it will try to continue causing a voltage spike in excess of 2 KV. This has been known to blow diodes, and even 5AR4's. You don't know the rectifier has failed until the next turn on. The exact mechanism for failure is an avalanche breakdown in the SS diode. The diode conducts in the reverse direction trying to clamp the spike in a manner similar to a zener diode. The IXYS parts are not rated for avalanche energy, while the Fairchild parts are. This is the first I have heard of a Fairchild part blowing.

Quote:
Hooked up the SSE, No output. I mean no music.
Start with basic voltmeter checks. With the negative voltmeter lead on ground, check the plate voltages on the output tubes. It should be over 400 volts. Look for 35 to 45 volts on the cathodes. Check for about 175 volts on the 12AT7 plates.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 6th September 2012, 05:19 AM   #17
Junior is offline Junior  Singapore
diyAudio Member
 
Join Date: Jun 2004
Location: Singapore
Hi George,
Thanks for the quick reply.
I will perform the measurement tonight.

Let me share with you my wiring for UL/Triode Select and Able/Disable Feedback & Spk Ohm Select implementation:

UL or Triode Select
Click the image to open in full size.

Able/Disable Feedback & Spk Ohm Select
Click the image to open in full size.

The output transformer secondaries' was connected in reverse and is it applicable to Hammond 1629SE OPT that I am using?
  Reply With Quote
Old 6th September 2012, 03:30 PM   #18
Junior is offline Junior  Singapore
diyAudio Member
 
Join Date: Jun 2004
Location: Singapore
Hi George,
Power up the SSE with all tubes in. It glows nicely with no anomaly.

I check the supply voltages from the power transformer on the connectors on the SSE PCB. All reading is good at: 5.28VAC, 6,28VAC & 785VAC.

I measured the voltage across the output tubes and 12AT7 as suggested and I get near to 0V (both AV and DC setting). The only sensible reading I get is the heater AC voltage.

Please advice what can I do next. Thanks
  Reply With Quote
Old 13th September 2012, 02:07 AM   #19
Junior is offline Junior  Singapore
diyAudio Member
 
Join Date: Jun 2004
Location: Singapore
Quote:
Originally Posted by Junior View Post
Hi George,
Power up the SSE with all tubes in. It glows nicely with no anomaly.

I check the supply voltages from the power transformer on the connectors on the SSE PCB. All reading is good at: 5.28VAC, 6,28VAC & 785VAC.

I measured the voltage across the output tubes and 12AT7 as suggested and I get near to 0V (both AV and DC setting). The only sensible reading I get is the heater AC voltage.

Please advice what can I do next. Thanks
After days and weeks of struggling, blowing fuse and diode, I had finally got to the root of the problem.

Recall the fired FRED. Tt had caused the discontinuity in the plated thru' hole (D2 Anode) and that why I did not have any VAC reading between the plates for the 5AR4.

Currently, I had the SSE wired with NO FEEDBACK and in TRIODE mode.

I wish to had it wired to be selectable for:
1) Able/Disable Feedback Select,
2) UL/Triode mode Select and
3) 4ohm/8ohm Spk Out Select.

The below diagram are my wiring implementation and please help me check if there is any error. Thanks in advance

Click the image to open in full size.
  Reply With Quote
Old 18th September 2012, 03:00 PM   #20
Junior is offline Junior  Singapore
diyAudio Member
 
Join Date: Jun 2004
Location: Singapore
Quote:
Originally Posted by Junior View Post
After days and weeks of struggling, blowing fuse and diode, I had finally got to the root of the problem.

Recall the fired FRED. Tt had caused the discontinuity in the plated thru' hole (D2 Anode) and that why I did not have any VAC reading between the plates for the 5AR4.

Currently, I had the SSE wired with NO FEEDBACK and in TRIODE mode.

I wish to had it wired to be selectable for:
1) Able/Disable Feedback Select,
2) UL/Triode mode Select and
3) 4ohm/8ohm Spk Out Select.

The below diagram are my wiring implementation and please help me check if there is any error. Thanks in advance

Click the image to open in full size.
Finally, I manage to solve all the problems that I had encountered.
Now my Tubelab Simple SE is singing again.

Thanks to all who help in one or another way.
  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
Diagnosis please bullpeters Tubes / Valves 19 31st July 2012 06:47 PM
Bad Tube in my "new" Hammond C2 Organ preamp? HELP w/ diagnosis!! jeffstev Tubes / Valves 10 24th November 2011 05:59 PM
Simple SE using pwr trans without ct stoolpigeon Tubelab 1 24th May 2011 10:00 AM
driver diagnosis agrobler Multi-Way 3 26th April 2006 12:58 PM
Diagnosis needed! fender4 Solid State 14 3rd July 2002 09:18 AM


New To Site? Need Help?

All times are GMT. The time now is 01:38 AM.


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