Member Since 02 Dec 2004
Offline Last Active Nov 19 2015 08:36 AM

Posts I've Made

In Topic: Macro Tech 3600vz, plea for assistance...

16 November 2015 - 08:57 AM

Just as a note : The flyback diodes are used to empty any back-emf from the speakers. These components are also used to monitor the output devices : If you were to observe a hv rail short (if measuring the flyback diodes you discover that you have a short on a diode) it would indicate an output device failure! Very rarely will these diodes fail in normal circumstances. Usually, an output failure is due to excessive heat buildup in the output section. After a few years of use, all amplifiers should be verified for their cooling properties. The output components transfer heat to the heat sinks via 'thermal compound'. This thermal compound will dry up with use and will need to be replaced, eventually. If heat cannot be evacuated efficiently, the output devices will fail.

Do not worry about the back emf : it is just a behavior of a reactive load (speaker) in regards to the output section.

Note : Because the amp has a grounded bridge design, any short with the output section will disable the psu voltages. So, instead of a blown fuse, you will find an unbalanced rail scenario!

Has your tech verified the input board for cold solder connections?
Has your tech verified the CMRR adjustment?
Are the bias voltages correct (@ 330mV)?



In Topic: Macro Tech 3600vz, plea for assistance...

13 November 2015 - 10:42 AM

Hello Duggy,
Why shouldn't the customer (user!) get help from the 'experts'? :-)
A few things come to mind :
- verify for intermittent solder connections to the driver section; I've seen weird issues because of a crack in the solder that was not visible;
- verify the CMRR adjustment (See the manual for explanations); the small potentiometer could be intermittent and dirty and can cause weird issues as the one discussed; sometimes, just touching the control can bring it back; Just splash a little DeOxit on the resistor tracks, if attainable; Replace if necessary or if part is available;
- verify all the flame proof resistors (5R6, 22R, 100R, etc);
- Can the noise be reproduced by tapping on the board? If so, remove the speaker and tap to your liking while monitoring on the oscilloscope; I've often used a paint brush successfully!
- bias controls (250R) : when a refurb is needed, these are the first to be replaced and readjusted;

I hope that one of these tips may work!


In Topic: Delat/Omega 2000 Alignment revealed

13 November 2015 - 10:21 AM

Hello Crowndog!
Good work. Unfortunately, I don't know or haven't seen/repaired any Delta/Omega 2000 equipment.
I googled and what a beast! 2000W per side was huge fore the times. You still see some of these units around?

In Topic: X4000

06 October 2015 - 09:55 AM

It seems to be class AB. Not D or I!


In Topic: CT-400 not working properly

03 September 2015 - 12:09 PM

Thanks for the info! I wasn't aware of these intricacies with the transformers. Good to know.