Hypex UcD180-x assistance

[troystg]

Hi,

I put 4 UcD180's (2xST and 2xAD8620) into a chassis with 2 Connex electronic SMPS500RxE power supplies.

The two ST modules have relatively no DC or AC offset while the AD8620 modules have no AC offset but BOTH have 22V DC offset!!! Measured with open and shorted inputs and no change.

As you can see in the pictures the AD8620's have shorter input and output wiring and share the power supply.



Am I missing something? How do I fix that high DC offset?


Shared album - Troy St.Germain - Google Photos
Shared album - Troy St.Germain - Google Photos
Shared album - Troy St.Germain - Google Photos
Shared album - Troy St.Germain - Google Photos

 

[Davey]

Since both AD8620 modules exhibit the DC offset, this suggests a power supply and/or power supply wiring issue. Or (less likely,) both modules are bad.

Dave.

 

[troystg]

Since both AD8620 modules exhibit the DC offset, this suggests a power supply and/or power supply wiring issue. Or (less likely,) both modules are bad.

Dave.

Thank you for the reply...

All four are wired the same. Same color codes, same power supplies.

Interestingly 22VDC is almost half of the supply rails of +/-45VDC and both AD8620's are exactly the same.

All 4 units are new OLD stock and have never been used. I'm wondering if the AD8620 module is a plugin and the connectors are oxidized due to age..

If I don't get any other replies the next step will be to take the modules out and clean all the contacts with de-oxit..

 

[Eva]

To start tracing the problem measure voltages at AD8620 pins w.r.t. speaker ground. Careful with shorting anything, this is a workbench job.

 

[troystg]

To start tracing the problem measure voltages at AD8620 pins w.r.t. speaker ground. Careful with shorting anything, this is a workbench job.

Unfortunately the ad8620 modules are coated in something from the factory. I don’t think I have access to the opamp or pins.

 

[troystg]

Anyone have a bench that could do testing or repair to these two modules? Unfortunately I don't have those resources.

 

[Baka]

You should take a close picture of installed AD8620.

Also check the supply voltage first.

The absolute maximum for this opamp is +-13V but you shouldn't go above +-12V.

 

[troystg]

I bought a used set of UcD180-AD (not AD8620) and dropped them in the enclosure.

Worked first time. Burning in the four channels of the amp and servo now but it does sound good already.

Anyone want to charge a nominal fee to repair the old modules for me?

An externally hosted image should be here but it was not working when we last tested it.