Wadia x64.4 sledgehammer output stage problem

[madskaman]

I have a wadia x64.4 dac that is acting up on me a bit. I have it working well now, but there's an issue with the sledgehammer output stage. Originally, the unit would not play from one channel via RCA outputs. The other channel worked perfectly. I fussed around a little, changed electrolytic capacitors and relays without any change. Then I realized my issue with the positive signal section of the output on one channel. I swapped the positive and negative input signal and the op amps and now it works.

I've been listening to it this way for months, but I'd like to fix it. Comparing side to side, the thing that sticks out is the resistance to ground. On the channel in question, I'm reading open from signal to ground where in the functioning channel I'm reading 220k ohms. It has been this way the entire time. I also swapped out film capacitors from side to side without any change. At this point I'm thinking I have a broken lead somewhere. Any help will be much appreciated.

So, the other part to this is: is this output stage worth fixing or should I put something else in? I'm sure there are better output stages, but not sure which would be a good match for my dac.

 

[madskaman]

I've got this sledgehammer output stage out again and I cannot find this issue. Im checking the output of the op amp to ground and I'm seeing open on the bad channel. On the good one I'm reading 5.8mohm to ground. I cannot find any other location where the output is ties to ground or anything g else for that matter. Does anyone have a schematic or any ideas?

 

[madskaman]

I decided to run 2 stereo discrete jfet buffers in place of the sledgehammer output stage. I built a 15 volt power supply from it and wires it into the same location. I've had it this way for about a week and have been very happy.

 

[RobertS61]

Strange that nobody reacted.
I have probably the same problem with my Wadia 2000 decoder one channel dead. I have few technical skills so I have no idea how to fix it.
You did well to make your own ouput.

 

[madskaman]

I was actually able to fix this board after a while. Ended up being the opamp on one channel after all that. Ha5002 I believe.

 

[RobertS61]

That's great!

The 1000/64.4 and the 2000 are basically the same Decoders I believe. The only thing that differs is the outboard PSU and you need a Digilink 30/40 to connect other sources than the Wadia transports with the 2000.
In that sense the Wadia 1000 is more convenient!

It was an opamp in the Sledgehammer outputchannel that failed I suppose?

 

[RobertS61]

Wadia 2000, one channel down

One of my Wadia's ( with the NON-Sledgehammer output) has a problem with the right channel.
XLR output is very soft volume and RCA total silent.
I could swap the right output from my working Wadia 2000 decoder, the Sledgehammer version, with the right channel of the non working Wadia 2000.
Would the different outputs matter anything? Do not want to damage the good working right output of course.
First I could measure all the voltages at the terminals from the DAC boards of both decoders to the Outputboards of course.
I can establish if they're the same and if the rightchannel of the faulty decoder is very different and the fault lays somewhere else.
What would be the most likely culprit?
NON Sledgehammer:
https://www.diyaudio.com/forums/attachment.php?attachmentid=875089&stc=1&d=1599817613
Sledgehammer output:
https://www.diyaudio.com/forums/attachment.php?attachmentid=875090&stc=1&d=1599817613

 

[madskaman]

I bet you have a similar issue as I had. Probably a blown opamp. You could swap Opamps on the same channel. See if the rca output comes alive? Another location of failure I have seen of these are the internal connections. Make sure the wires are connected to the terminals. It appears as though they are just pressed into place from the factory. I have found that connection loosens or fails over time causing a similar issue. I’d check all of the connectors. Press the wire into the terminal and make sure they’re seated.

 

[RobertS61]

Maybe stupid but which are the opamps on the outputboards of the old Wadia 2000?
I only can see transistors but maybe this opamp has another shape?
https://www.diyaudio.com/forums/attachment.php?attachmentid=875583&stc=1&d=1599985191e

Would be great if it is a connector that's interrupting the signal or current flow.

 

[analog_sa]

Are those painted black cans not opamps?

 

[RobertS61]

These you mean?:
https://www.diyaudio.com/forums/attachment.php?attachmentid=875630&stc=1&d=1599996176

HA5002:
https://www.diyaudio.com/forums/attachment.php?attachmentid=875632&stc=1&d=1599996663

and the other two not pointed to.

 

[diyiggy]

Are rhe little yellow caps at the top of the pictures some decoupling wet tantal ? Shorts?

Or manufacturing problem if a common issue whatever the design...I m thinking about cold joints...?!
Are the red units on both boards some relays that need checking as well?

 

[RobertS61]

To be honest I've no idea.

Those yellow/brown look like tantals (I have no schematic) and those red like indeed like relays that would be worth investing.

My primary question was if I could swap out the boards from the non-sledgehammer outputs with the sledgehammer output boards of my newer working DAC after I made sure all the voltages are alright, connectors etc...
If I swap those outputboards and the unit is working, I know that the right outputboard is the culprit that causes no output in that channel.

 

[RobertS61]

HA5002

I was actually able to fix this board after a while. Ended up being the opamp on one channel after all that. Ha5002 I believe.

Wher did you source that metal can round opamp?
Seems obsolete..
Only available on Ebay

 

[madskaman]

Correct. The painted black cans are opamps. I replaced the bad one with HA2-5002. And yes, had to roll the dice on eBay.

 

[RobertS61]

HA-5002

Okay, clear.
I will investigate first if it is the outputboard and then I will try to investigate further.
How did you find the faulty one?

 

[madskaman]

I would probably just unsolder the opamps on the bad channel and swap them. If it is a bad opamp, then you would have a similar symptom with xlr (low gain) but your rca would output correctly.

You could check voltages and signal before... but if it's playing from the xlr, then voltages are likely good. You could check to see if you have signal at the input to the opamp. I checked mine with a dmm, ac voltage at pin 8. I had something like .6v with it "playing" and nothing on the output. If you have no signal on the input, then that would point to a relay upstream preventing signal to pass through.

 

[RobertS61]

The XLR plays at a low volume indeed.

So just swap the two HA2-5002 opamps in my faulty channel you advise?

All the DC voltages are okay.

 

[RobertS61]

Wadia 2000 ouputboard

These is the Wadia 2000 year 1990 version outputboard:
Leftchannel working:
https://www.diyaudio.com/forums/attachment.php?attachmentid=876152&stc=1&d=1600179335

Rightchannel dead on RCA low level on XLR:
https://www.diyaudio.com/forums/attachment.php?attachmentid=876153&stc=1&d=1600179341

Soldersite of the Left- and Rightchannel:
https://www.diyaudio.com/forums/attachment.php?attachmentid=876154&stc=1&d=1600179341

With a black marker a OK with date and paragraph is written on this site at 1-9-90 being probably an American dateformat meaning the January 9 1990.

It's a bit tricky to get this board out.
There's almost no grip on the RCA nuts at the back and the 6 hexscrews are tightened with 100 lbs torque so I needed to extent the key to get them loose. One slip and you're done...

I think I lack to proper soldering skills to get these HA2-5002 opamps desoldered so I let a more experienced friend of mine desolder them.
I ordered 4 in Hong Kong and hope at least two are good...

 

[analog_sa]

These, being diamond buffers with no voltage gain should be easy enough to troubleshoot even without a scope. Just take them out and jumper IN to OUT.

It may even sound better that way.