2:90 poweramp NOISE issue

[STUART]

Gary what a guy ...great info !!

Just looking out my Fluke multimeter right now will post back results soon ....
Yep for sure channel B appears to be running half power here constantly
with no difference in volume level when voicing is switched off and on.
Channel A working flawless...

Stu.

 

[STUART]

UPDATE

Gary

Removed the 100uF 10 v cap and yes noises no longer present wahooo..

I have replaced this 100 uF cap with new one but channel B still does not switch to 1/2 drive...
I have now ordered a replacement LDR from Mesa distributors and should be with me early next week ..
Hopefully this should do the trick and cure my 2:90 :wink:
By the way that resistor R372 i cannot locate ,all these components are tight to the board and identification is a bit difficult
Not to worry will post a result when this LDR is installed along with 100uF capacitor ..

Have a nice weekend !!

Stu

 

[Blueracer]

Hi Stu,

Good to hear progress is being made. It is clear you are hitting the right area. The voltage measurement would be useful and would indicate whether the LDR or the resistor is more likely at fault. A little hit and miss with component replacement is ok though. As long as it gets you there. Have a great weekend and I am glad to hear this is getting resolved.

Gary

 

[STUART]

Hi Gary ,

Ok heres the script , parts arrived at my home today from MESA distributors.

Up until till now i had already removed the old and replaced with a new 100uF 10 volt capacitor at LDR 1. This cured the "wind" like noise running through channel B...
When this cap had been replaced the noises had gone but channel B still did not switch to 1/2 drive .

LDR 1 ( VTL5C9 ) has now also been replaced and the 2:90 now switches perfectly to 1/2 drive on channel B

I now have a 2:90 in perfect working order !! Wahoooo...

Gary i honestly cannot thank you enough for sharing your knowledge and first class advice throughout this post .

All the best freind !!

Stu.

 

[Blueracer]

Hi Stu,

I am delighted that the amplifier is again in working order. It was fun helping out on this. Take care my friend and if I can help again in the future feel free to contact me.

Gary