MVS cab. NO SOUND help!!

Hi, this is my first post here so bare with me on the tech stuff.

I just bought a 4-slot mvs cab. The sound doesn't work. I have already had the audio i.c. (Ha13001) changed, and it still doesn't work. I have checked all of the wiring and it seems to be o.k. It also looks as if the "Bridge-rectifier" (sorry I don't know what it is called, it has 3 prongs and a screw right next to the i.c.) has been changed at some point. One more tip, sometimes when playing double dragon strange sounds start coming through the speakers, like the sound is trying to work. any help would be GREATLY appreciated. Thanks so much guys!

Two basic avenues of attack to eliminate a couple of possibilities;

Stick a different pcb in there and see if you get sound.

Try different carts / give your carts and slots a good clean.

it's quite possible that the cab simply isn't wired for stereo. check with the search function for what to check/rewire.

Check for 12 volts on the output IC (pin 10)



Without the 12 volts the board will run with no sound.

The 3 pronged device is a 7805 5 volt regulator IC, it should have 12 volts input and 5 out, the centre pin (and heatsink) are grounded. The 5 volts from the regulator supplies the audio op-amps. Some boards have the op-amps supplied directly from the 5 volt rail.

To check if the problem is related to the output stage or maybe the digital processing; touch the pins of the digital to anolge convertor thats the YM 3012 chip, if you get a buzz/hum from the speakers it confirms that the audio output and op-amp ICs are OK.

WOW! thanks for all the info guys, it's still not working but here's what I tested.
I checked the I.C. It had 12 volts.
I checked the 5 volt regulator it had 12, 5 and the ground pin was making connection.
Where do I go from here? Also if you could "dumb it down " a little bit for me it would be appreciated, I'm not too good with this stuff. Thanks again, and I look forward to more advice.

bump

hufford69 said:

WOW! thanks for all the info guys, it's still not working but here's what I tested.
I checked the I.C. It had 12 volts.
I checked the 5 volt regulator it had 12, 5 and the ground pin was making connection.
Where do I go from here? Also if you could "dumb it down " a little bit for me it would be appreciated, I'm not too good with this stuff. Thanks again, and I look forward to more advice.

Click to expand...

With the volume turned up. If you touch the pins of the digital to analog convertor, thats the YM 3016 chip, located not too far from the HA 13001.
Do you get a hum or buzzing noise from the speakers ?

THANK YOU, I checked the 3016, it DOES hum. where to go now.

That confirms that the audio output pre-amps and output stage are OK. You have a problem around the digital processing stage. It may be an open track somewhere even a dirty or bent pin on the slot socket, make shure the boards cart sockets are squeeky clean.
I take it you have tied different carts in different slots ?
Otherwise it may be a Z80 processor fault (this sometimes gives a Z80 error message, has it displayed this) or associated memory.
Maybe the YM2610 audio processor, but I think that is fairly rare.
Ive had a few problems with open tracks around the Z80, remember the board may have a layer of track sandwiched inbetween the double sided print (there are two versions of the 4 slot one has the other has not).
Im in the process of putting a schematic together for this which may be of help, but dont hold your breath.
Good luck

I did get an error message one time, and I'm pretty sure it started with a Z. But I can't be 100% sure.

Now that I think about it, it was a Z80 error message for sure!
Does that mean, hopefully, that I just need a new z80 chip?

I would check for the obvious first, a continuity problem between the cart and processor may cause this sort of problem.

If you have had the Z80 error message that may be a good place to start. There are also the associated SM1 rom and 6116 ram ICs.

Reasonable desoldering skills are required to pull it off successfully.

thanks again, I just have 1 more question, do the sm1 and 6116 have their own error messages or are they included with the z80?
Anyway thanks, I ordered the z80 but it will take a couple weeks to ship, I'll post again when I know if it works!

That would usually give the Z80 error message