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SX-1980 power supply problems

Boards have been ordered

I decided to pull the trigger and place the order.

Thanks again to everyone!!!

I ordered 10, it was the minimum number that made sense. Besides the one that I need a couple are already spoken for, if anyone is interested in one shoot me a PM..

This is the final mod list:


1. 22 ohm 3W resistor for R202, moved to open real estate.

2. Soft-start and speaker protection relays are now LY2-0-DC24, powered from C203 +.

3. Removed R102 and R308. Pads left in place with shorted trace that can be cut if necessary to allow dropping resistors for the relays.

4. Spark killer added across the soft start contacts. .01uf and 100 ohm 1/2W.

5. Contacts for soft start in parallel.

6. All wires are now on connectors for easy install and removal with screw terminals. Screws are on the top of the connector with the wires entering the connector at the side. The entire connector plugs into the board with the wires attached.

7. 80V reg transistors have been moved to the large heat sink. Wires to be soldered to board with female connector at transistor.

8. The large electrolytic caps have mounting provisions for axial or radial.

9. The current source mod has been integrated into the board.

10. All of the substitute devices have been orientated with pad layouts that match the pinout of the device.

11. The board has been silkscreened with components id.

12. The board has an internal ground plane. This is a bit subtle when you look at the layout. This should help with noise and to spread heat.

13. Q203 and Q205 have larger heat sinks. The heat sinks use pins that are soldered to a large isolated pads on the board.

14. The board can be built from 100% new components, most of them from Mouser and digikey. The only exception is the protection IC. There are some available in the market or worst case the IC can be moved.

15. All transistors have been laid out in a circular pattern to allow easy substitution if necessary.

16. Emitter, base and collector are silkscreend for all transistors.



I did think about a small problem, nothing to do with the layout.

When I get the board and build it up the test unit I have may not even work. In fact I am sure the amps need attention. One of the wires that connects to the outputs is not even connected, de soldered. I guess I'll just pull both amps and give them a look over the weekend. I guess I need to look through a few threads! I am a pioneer virgin...
 
Check the outputs.
Your skills may come in handy if they fail the checks.
Amp boards are straightforward.
 
As a first test you also could disconnect the output boards from the rest of the unit and measure the power supply board for correct voltages.
 
markthefixer said:
That was post #1. :yes: :D
Click to expand...

Actually I will be able to disconnect the outputs from the power supply.. :D

It's going to take a week or so for the boards to show up so I will have plenty of time to attend to the amps, except for this weekend...

Just moved my boy from Austin to Tulsa to start school... 500 miles in a U-Haul!
(Actually the wife and I drove his car)

I am going to set up his place with a suck face Luxman and a nice little pair of M&K speakers.. Too bad he has no idea what this stuff is...
 
He'll grow to appreciate it. Especially when the gang at school gets a look. There's always a few that are semi-literate in old gear.
 
Getting close !!!

We received the boards in today..... Mitchel did an awesome job building the board up :beerchug:

We are missing one part that somehow did not get ordered, it's the 12 position header. It looks like the connector is plugged input there is no header. We also need to finish the 80V transistor install. I took a good look at the amp section and cleaned up a bunch on them, they should be ok for a test. Once the power supply is deemed solid I am going to recap the beast.

I can already see a couple things to change on the next board. The connectors on the left side near the relays and big resistor need to be moved inboard a bit. Not a show stopper....

I have some replacement standoffs for the board that were finishing up on the 3D printer when I left work. They should snap in to the sheet metal and have a hole in them so a screw can be used to hold the board down. I used ferrels for the wires because I feel it would be a better connection, especially when more than one wire is put into a connector. This makes the wiring a bit tight on the sides but it's completely serviceable.



We should be able to test it tomorrow. :D:D I sure hope it works!

20559907688_fa2e2ee93d_b.jpg


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20559910318_8f6aabc6b9_k.jpg
 
The mounting of the components, with the leads bent precisely, is exceptional.

Such a fine sight to see.
 
Wow! That looks incredible!! I am not sure how to test the power draw but if someone could explain how to do the test I would be glad to do it. Really incredible looking power supply with such attention to detail. :thmbsp:
 
The original resistors for the current sources were 1/4 watt resistors in an 1/8 watt case size.

660-MFS1/4LCT52R122J

The S following the MF specifies it. Check the data sheet from KOA Speer.

If this is what you are referring to (R1, R3).

1/4 watt would do just fine, at the time I was going for as small as possible and it seems that the part number has lingered.
 
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Totally awesome, after this gets up and running I'm ordering a board even though I do not own a 1980 yet, almost did but not yet..
 
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