Help Debugging Lotharek Stereo install in 1200XL?

[oracle_jedi]

Hey guys,

 

Anyone who has successfully installed a Lotharek Simple Stereo board in a 1200XL, I'd like to check a couple of points:

 

• I get sound on the left channel only.
• Inverting the L/R sound Dupont connector on the board send sound to the opposite channel, so the soldering downstream of the board seems ok.
• Swapping the POKEY chips makes no difference.
• Yoomp detects Stereo.
• Keyboard click, and sound through the five pin audio/video output is normal.
• I have an U1MB installed but I don't have the USwitch installed (yet).
• The 6-pin (3x2) switch headers on the stereo board are all open.

 

The SR pin is not connected to anything (instructions did not say to connect to anything - even though this project http://raster.infos.cz/atari/hw/stereo/stereoen.htm says to connect the SR line to U1B (LM358) pin 6.

 

The A4 line is connected to pin 13 of the CPU (actually a pad under the chip).

 

Yes I did solder that in before posting this...

 

The Bell is taken from the right side of what appears to be R103:

 

 

I think this part is working too, as if I remove the A4/Bell Dupont connector from the Stereo board, Yoomp no longer detects stereo and I get no sound at all.

 

The U1MB ROM adapter was moved to the second ROM socket (as advised by flashjazzcat) and the jumpers moved to just close W1 (otherwise the audio self test does really weird things).

 

 

The Stereo board fits snugly into the POKEY socket and does touch the ROM interface, but this does not appear to inhibit function. I am guessing this is not the cause of single channel sound - otherwise both POKEYs would be non functional.

 

Does this look like a bad Stereo board, or is there something else here that needs to be tested/tried first?

 

Would appreciate any pointers.

 

 

Thanks

 

Graham

[+mytek]

The problem is not having any type of switch connected to the 3x2 header. The switch is responsible for sending either the original Pokey output (mono), or the 2nd Pokey output (stereo) to the 2nd audio output jack.

 

- Michael

[flashjazzcat]

Yeah: just push a jumper over the switch header to test it.

[oracle_jedi]

Okay thanks guys.

 

After testing the 3x2 jumper block a number of different ways, I found that this enables stereo and allows programs to detect it.

 

Moving the two jumpers to the right-hand position disables stereo, and provides two mono channels instead.

 

To me at least that wasn't very clear from the install guide.

 

The USwitch was tricky as I have an early U1MB and so have Dropcheck's MMU adapter board installed. That means I can't solder the USwitch directly to the Stereo Board. I created a rather ugly six-pin jumper cable, and then ran +5V and GND from the motherboard.

 

 

The red wire visible just below the CPU is +5V, the black wire visible just to the right of the CPU is GND.

 

I found space for the stereo RCA jacks behind the rectifier. If you bend the ears flat on the RCA jacks, you can wire them in and still slide the motherboard back into position. That allows for a rather elegant installation from the rear of the machine.

 

 

I going to do some testing with the machine to see if it is stable, but so far so good.

 

Thanks to flashjazzcat and mytekcontrols for the help.

 

 

[Frankie]

I have the same board in my 1200xl, with U1MB as well. The problem I have is that the keyclick sounds through the stereo output come and go. After booting up they are fine, then at some point, even in the middle of typing a command, they just stop. Everything else continues working fine. Stereo sounds in Yoomp work correctly. Just no docks.

 

Anyone know how the key clicks are handled?

[oracle_jedi]

I have had mine on test all day running Zork I. So far no issues with the keyboard click coming and going.

 

I think the keyboard click is done with the Bell line from GTIA pin 15. I would start with checking that connection.

[morelenmir]

To expand on something mentioned here--what is the 'SR' connection for on the SimpleStereo?

 

I have never connected it up and the sound seems to work anyway. I may do so now I know where to solder it though, just for completeness.

Edited August 13, 2018 by morelenmir

[flashjazzcat]

It concerns the RF modulator... but nobody connects it. Unless you're using a TV tuner for a video display, forget about it.

[morelenmir]

It concerns the RF modulator... but nobody connects it. Unless you're using a TV tuner for a video display, forget about it.

 

I've already patched it in, but nothing exploded so now worries! I guess it synchronizes the stereo output to the RF picture maybe?

[flashjazzcat]

I imagine so.

[+Nezgar]

To expand on something mentioned here--what is the 'SR' connection for on the SimpleStereo?.

 

I only have experience with TF_HH's simple stereo board, but connecting SR on that board to the LM358 you get all 8-channels mixed (mono) from RF and Monitor jack too, I presume it's the same with the Lotharek board..