ShibaSoku AM70A service manual needed / problems

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Hi Damien
petertar had sent a PM to me. Meanwhile I saw some one ebay saying that he can fabricate if we send him requirements. I had sent a message for my requirements. Making one on PCB software another learning curve - i cannot do that at this time. However i have one having 22 pins and planning get another one cut to make 28 pin - hopefully i can do that as 22 pin ones are matching
 
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You are probably referring to sparko6079 on eBay. It seems he can fabricate the extenders much easier than making PCB's. He starts with copper clad and CNC's the traces. I'll make drawings for the AM70A and the AD725D analog extenders. I think the same boards could be used for both.

These are very close I think: Sony SVO-5800, SVO-5800P, SVP-5600, SVP-56 Extender Board Riser IN KIT FORM | eBay

The 725D needs one and the AM70A needs 2 for each board extended.

The 725D uses a 2 row Eurocard type connector for the extender. The 3 row type is far more common so these are more of a challenge. The 725C uses more conventional extenders.

The guys is on vacation until Feb. so I don't expect too quick a response. I'll share what I learn.
 
Perhaps the chinese New Year may be the cause of shipment delay

file-0ZNoz7HhYP.png
 
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CNY is worse that posted because of the new corona virus. However the boards have been in the US since 1-13. I would not use the cheap shipping for any important stuff, but this was free shipping so I can't complain.

Here is the tracking:
2020-01-26 20:49:56ARRIVAL DESTINATION DHL ECOMMERCE FACILITY
2020-01-25 04:15:17DEPARTURE ORIGIN DHL ECOMMERCE FACILITY
2020-01-24 23:35:30PROCESSED
2020-01-24 16:26:26ARRIVAL AT DHL ECOMMERCE DISTRIBUTION CENTER
2020-01-13 17:25:00Arrival of goods at destination airport
2020-01-12 18:47:00shipment departed from airport of origin country
2020-01-11 22:30:00Hand over to airline.
2020-01-10 23:34:03EN ROUTE TO DHL ECOMMERCE
2020-01-10 23:29:38ELECTRONIC NOTIFICATION RECEIVED: YOUR ORDER HAS BEEN PROCESSED AND TRACKING WILL BE UPDATED SOON
2020-01-10 17:05:29Depart from facility to service provider.
2020-01-07 21:15:02Shipment arrived at facility and measured.
2020-01-07 21:15:02Fpx picked up shipment.
2020-01-06 14:43:35Picked up by the carrier,Tracking #: 302402595885
 
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Update- been too busy with other distractions but back to the AM70A. I got the boards, fixed my layout errors and some tweaking and it is working. I have a buffered output for the monitor and for the level adjusted input that I can route to a scope. Ill review the layout and share the corrected version soon.

Now to the next issues. The unit is all working but it has noise issues on the distortion and the IM systems. The distortion floor seems to be noise limited compared to the 725D and I'm pretty sure its the opamps around BEF1. Unfortunately they are mostly SMT and really hard to trace out the circuit. Same for the IM plus hum issues in the IM source as well. I believe the same solutions that worked in the 725D will work here IF I can figure out which parts to change and the replacements will fit. Being dense SMT it will be quite nerve-racking to work on these PCB's.

Also the extender boards work for both the AM70A and the 725D.
 
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update- I swapped out the key opamps but no indicated improvements. Not worth doing at this stage. Looking at the monitor out (from my rear addon) it clear that for distortion the notch depth is the big limit and noise is #2. There is some 120Hz in the output but the ripple on the supplies is .5 mV so not likely the source.
The IM floor seems to be noise again. There is a little 60 Hz even when fed from a battery powered source with no 60 Hz added. Finding this may be a major chore since its likely to be noise induced across ground or the like.

Going back to my simulation it seems the LME49990 in the two critical places will get another 10-15 dB of notch depth. Its also clear I need to check all three filters. I'll report back if the system responds like the simulation.
 
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I found an error in my simulations of the notch filters. The updated files are here: ShibaSoku Automatic Distortion Analyzer

I'm still working out how to align the filters etc. The few service instructions that have surfaced completely skirt those questions. Since this is open loop its not a simple "just maximize the notch depth" thing. I still need to figure out at what frequency points the notch switches to the next step.
 
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This unit has had odd behaviors since I got it. Today I touched the memory button and it locked up. It turns out the battery backup for the memory was dead. Its an oddball NIMH battery BUT a generic wireless phone battery is a workable replacement. Picture illustrates. Now everything works.

I'm making some progress on the alignment but still about 6dB higher distortion floor than the 725D.
 

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