Avalon U5 power issues

[Unchained Dman]

Hey all. New to the forums so be gentle please.

I purchased a U5 from "Trusted" party and guess what? So, I am here to get some info on some components. I went through another thread about this unit on a different issue and it help me understand that my unit is blown somewhere.

First of all, visually I can see that R10 is done and I can not identify the color code 100% so if I can start there that would be great.

Second, I have good input power and proper voltage off the secondaries and caps thereafter but thats where it goes haywire. R15 shows 0.99Vdc/ .672Vdc, R9 shows 12Vdc/ 6.5Vdc. From there ZD1 = 6.21Vdc, ZD3 = 0Vdc, ZD2 = 6.5Vdc, ZD4 = 0Vdc. Not really sure where to test the C6-9, C11-14 at for proper measurements but I do know that C11-14 are not getting power at all.

Also, when the U5 is plugged in with an instrument connected, there is no power led or signal leds but the buttons light up and I intermittently get a very distorted signal while listening from the headphones port.

Thanks ahead of time with any help on not having to send in the unit. Burbank may only be 20 miles away but it will take half a day to get there with traffic. Just kidding, id still probably have to ship it (let the postman deal with the traffic).

 

[rock soderstrom]

Hi unchained dman, welcome to the forum!

Unfortunately nobody can't it is hard to help you without schematics or additional info. I think there will be few users here who can intuitively guess the component names and their function.

Your chances for help will increase significantly with more information like service documents, schematics or at least informative photos.

Cheers

 

[pucho812]

ok. R10 is a 4k75 aka 4.75k
secondly the u5 runs off 4 different voltages. The discrete stuff is +/-32vdc the servo stuff runs +/-15vdc.
You should see about 40vdc off the secondaries of the x former.

zd2 and zd4 are in4744a
Zd1 and zd3 are in753a

you should see about 30vdc at one side of r9 and 15vdc on the other end of r9.
You should see about -30vdc at one side of r15 and -15vdc at the other end of r15.

I would bet you either have an issue with a trace coming off the transformer secondaries or you need to recap. If it’s a trace issue, I can show you were to add jumpers and test to ensure the psu is getting the correct ac voltage. If it’s capacitors, Replace the 100uf/50v and the 10uf/63v caps and you should be good. Also insure the zeners are in working order.

 

[rock soderstrom]

Pucho=Avalon U5 whisperer

 

[pucho812]

Pucho=Avalon U5 whisperer

Yes

 

[pucho812]

Hey all. New to the forums so be gentle please.

I purchased a U5 from "Trusted" party and guess what? So, I am here to get some info on some components. I went through another thread about this unit on a different issue and it help me understand that my unit is blown somewhere.

First of all, visually I can see that R10 is done and I can not identify the color code 100% so if I can start there that would be great.

Second, I have good input power and proper voltage off the secondaries and caps thereafter but thats where it goes haywire. R15 shows 0.99Vdc/ .672Vdc, R9 shows 12Vdc/ 6.5Vdc. From there ZD1 = 6.21Vdc, ZD3 = 0Vdc, ZD2 = 6.5Vdc, ZD4 = 0Vdc. Not really sure where to test the C6-9, C11-14 at for proper measurements but I do know that C11-14 are not getting power at all.

Also, when the U5 is plugged in with an instrument connected, there is no power led or signal leds but the buttons light up and I intermittently get a very distorted signal while listening from the headphones port.

Thanks ahead of time with any help on not having to send in the unit. Burbank may only be 20 miles away but it will take half a day to get there with traffic. Just kidding, id still probably have to ship it (let the postman deal with the traffic).

Any update on this.
I am curious as to how things went? probably waiting on a parts order... feel free to DM me if you have any further questions.

 

[Egprod]

hi all
I have the same problem

I need some helps for fix it
Best regards

Greg

 

[pucho812]

View attachment 141607hi all
I have the same problem

I need some helps for fix it
Best regards

Greg

I can't read any of what you wrote there.
What is the issue?

 

[Egprod]

 

[Egprod]

Hi , no Sound , no signal and no power led

 

[pucho812]

Hi , no Sound , no signal and no power led

Ok. If you search here, I have U5 notes. They will tell you where to test for voltage.
Most U5 power issues come down to a couple of things:
1. connection of secondaries into the circuit. The traces can crack over time.

2. The 10uf/63v and the 100uf/50v lytics.

I have broken this down before. A search will help you find it.

Read this thread

https://groupdiy.com/threads/avalon-u5-need-power-led.78399/page-2

 

[Egprod]

Yes many thks
I order new caps for re-caps all for the first time. Somme caps looks more big….

 

[pucho812]

Yes many thks
I order new caps for re-caps all for the first time. Somme caps looks more big….

Yeah, it can’t happen that the physical size is slightly different depending on what you order.

 

[Egprod]

View attachment IMG_4007.jpegBad transfo solder connection ! Many thanks @pucho812

 

[pucho812]

View attachment 142277Bad transfo solder connection ! Many thanks @pucho812

Looks like it should.