ROTEL amp sounds dull - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 26th March 2009, 08:43 AM   #31
Account disabled at member's request
Join Date: May 2006
Those output transistors are good, they are factory originals. Your pic is good, one can clearly see. The one thing I do notice from that pic is that the bias transistor is not mounted upside down on to the output transistor but at a 90 degree angle. Im not sure on this model but on most its always mounted in line. The reason is that when mounted in line it has larger surface contact with the output transistor which is important for thermal tracking and correct biasing. As it is the metal tab on the back of d600 has very little contact on that d1047. Have a look at the attached pick in this post, its a different model but about all rotels that I have seen are mounted like this. The transistors in question are the ones with the orange wires. After that adjust the bias a little higher than factory spec with the amp warmed up, around 15 mv is good.

Before replacing the zobel resitor test to see if they are ok, before they fail the factory ones tend to turn brown as if burnt, if they are measuring good and look ok leave them be.

After this the amp should be performing close to factory spec, with only maybe the age of the capacitors having any real effect.
  Reply With Quote
Old 26th March 2009, 08:46 AM   #32
Account disabled at member's request
Join Date: May 2006
Here is a pic.
Attached Images
File Type: jpg dsc_1847.jpg (72.2 KB, 273 views)
  Reply With Quote
Old 26th March 2009, 09:00 AM   #33
Join Date: Apr 2005
Location: Stockholm
how are you?
Those output transistors are good, they are factory originals.
It does matter, however.
  Reply With Quote
Old 26th March 2009, 04:59 PM   #34
Account disabled at member's request
Join Date: May 2006
Hi Lumba

Im good, yourself ??

Drop me a email through link on my profile and Ill point you to a online shop where you can purchase those powersupply caps if you thinking of replacing them, without denting your bank account too much. The manufacturer is the supplier to rotel for those caps. I assume it uses for 4 10000uf caps so it would cost around 55 euros to replace all with same and go up to double the price for superior quality ones.

The zobel resitor is r669 and r670.
  Reply With Quote
Old 28th March 2009, 05:31 PM   #35
Bartt is offline Bartt  Netherlands
diyAudio Member
Join Date: Feb 2009
I checked the zobel resistors and they seem to be fine (+/- 11 ohm). I couldn't mount the bias transistor upside down, because it would have less contact than before. So I turned it straight up (see picture). The wires do make contact though with the small heat sinks. Is that a problem? The're not gonna melt are they?

The heatsink of the output transistors seems to be a bit hotter than before 41 C (left) and 45 C(right). The small heatsinks in between are quite a lot hotter, around 73 C

I've set the bias at 15mV. The left channel got back to 11 later and doesn't deviate more than 10% since. The right channel increased to 18mV and when cooling down for a while to 13mV. The strange thing is that the right channel seems to increasing or decrease during the measuring, while the left channel doesn't: is that normal?
Attached Images
File Type: jpg img_4232 (medium).jpg (67.3 KB, 173 views)
  Reply With Quote
Old 28th March 2009, 07:43 PM   #36
Account disabled at member's request
Join Date: May 2006
MMM maybe we shouldnt turn the bias up that much, i was expecting the temp rise on the outputs but not so big a diffrence on the drivers. Maybe keep it around 12mv max. I sure hope when you say contact you dont mean electrical contact, that could be disaster. I see space is tight there. Something is up with that right channel, but i cannot think what is is. It will vary a bit with voltage and power fluctuations but im not so sure its should be changing like that all the time. In later models rotel improved the vbe multiplier for use with triples, ill have a look and let you know if something can be done without messing with the circuit, maybe a darlington transitor as the temp sense.
  Reply With Quote


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
Rotel RCD950 sounds distorted Bartt Digital Source 1 27th March 2009 09:53 AM
Dull mind looking for speaker help justn Multi-Way 8 11th August 2005 06:50 PM

New To Site? Need Help?

All times are GMT. The time now is 11:28 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2