Avalon U5 need power LED

[pucho812]

Hi! I just wanted to share with you my experience repairing this piece of equipment. From one day to another it stopped working. I am in EU so the mains switch was set at 230V. I switched it to 115V and conected it to a 115V autotransformer and it worked! So I guessed that one of the primary windings was open. Once I put a new transformer, the unit didn't turn on. Well, some audio was passing trough but the power led wasn't lit. So, as Pucho812 said:

That was it. Once I secured the connections, the unit was working again!

View attachment 115468

Nicely done. These units sound so good as a DI it would be a shame to not have them working.

 

[Jules123]

Hello,
Ive got a similar problem, U5 with distorted audio and no power led, switches (were) working.
I checked transformer secondaries which were ok, then I found C11 being open circuit.
Replaced it and when powering on, R50 burnt out... So C11 may not have been the main problem.
Then I removed C11 completely and switched on again, not a good idea, now R84 was burning...
So, can anyone help me out? I also need the values for R50 and R84.
Thanks!

 

[pucho812]

Hello,
Ive got a similar problem, U5 with distorted audio and no power led, switches (were) working.
I checked transformer secondaries which were ok, then I found C11 being open circuit.
Replaced it and when powering on, R50 burnt out... So C11 may not have been the main problem.
Then I removed C11 completely and switched on again, not a good idea, now R84 was burning...
So, can anyone help me out? I also need the values for R50 and R84.
Thanks!

R50 and R84 should be the same value as R51 and R83 which I believe is a 3K32 resistor value.
As the are the same as the others which have not burned out yet, please double check my work.

As for why they are burning up, recap the unit. it will be the 100uF/50V caps. As they are relatively inexpensive, replace all the 100uF and the 10uF lytics. I had many an Avalon resistor burn out when caps had shorted.

If you have any more questions, let me know.
good luck.

 

[Jules123]

Thanks pucho!
R51 and R83 are the same, but they seem to be 10 ohms.
Can you confirm that they are the same as R50 and R84 or does anyone have a pic of them?
I will do a full recap, but only had two 100uf 50V caps at home and couldn’t wait, my fault…

 

[pucho812]

Thanks pucho!
R51 and R83 are the same, but they seem to be 10 ohms.
Can you confirm that they are the same as R50 and R84 or does anyone have a pic of them?
I will do a full recap, but only had two 100uf 50V caps at home and couldn’t wait, my fault…

all four values will be the same for those resistors so if you have 10Ω installed, then I would go with that. I may have my numbers thinking of something else. There may have been a design change at one point. Anyway they should all be the same value which is the core of my previous post.

 

[Jules123]

Thanks!
I'll wait for the parts and then give an update!

 

[Mihobro]

Thanks guys. I got a little impatient waiting for the correct part number earlier today. So I just popped in a green LED I had around the house. It is working fine now. I was going to order the blue one and make it stock but the green one looks sort of cool. So I will keep it.

Yeah and they hurt my eyes too. Did you hear about how they came about? It is an interesting story about corporate politics and research R and D.

 

[pucho812]

Thanks guys. I got a little impatient waiting for the correct part number earlier today. So I just popped in a green LED I had around the house. It is working fine now. I was going to order the blue one and make it stock but the green one looks sort of cool. So I will keep it.

back in the 1990's Avalon used a green LED for power but I don't recall if the U5 ever had that treatment.

 

[Jules123]

Here is the update: Changed Caps and resistors and the U5 came back to life!
So, for the future, if you recap, don't make my mistake. Change ALL caps.

 

[pucho812]

Here is the update: Changed Caps and resistors and the U5 came back to life!
So, for the future, if you recap, don't make my mistake. Change ALL caps.

I normally do not recommend that except in this case as it is the easy option. good job.