I built a Wozeblaster, but running with low volume and a lot of noise !!

By alali.ahmed.t

Expert (105)

alali.ahmed.t's picture

19-11-2022, 05:28

I built a Wozblaster using Eric Boez design, but the volume is low and has a lot of noise (air shshing noise). Where should I start troubleshooting?

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By Wlcracks

Champion (486)

Wlcracks's picture

19-11-2022, 07:40

Assuming you hear a bit of correct audio:

Normally you start with checking all the supply voltages to the i.c.'s.

Could be the output jack, if its not connected correctly you only hear the phase difference between the 2 channels. (same like putting the jack half way)

But the most obvious to me, the output stage is not amplifying. I think its a quad opamp. Check the input v.s. the outputs, normally you would use a oscilloscope for that.

By alali.ahmed.t

Expert (105)

alali.ahmed.t's picture

20-11-2022, 01:05

There is clear volume but it is low and there is a lot of noise too. I installed couple of 604 size capacitors of 100nf since I ran out of the 805 size. I will replace them once the new shipment arrives and see if that will help.

I don't have oscilloscope so I will have to rely on noting down the voltage range of input and output and see.

By meits

Scribe (6527)

meits's picture

20-11-2022, 01:25

could be a flaw I saw in several wozblasters. Can be fixed by placing a few resistors.
The fix looks like this.

By alali.ahmed.t

Expert (105)

alali.ahmed.t's picture

21-11-2022, 18:22

Thanx for this link. I started building the cartridge from scratch again. I will make sure the solder points are done properly and install the same size of the 100nf capacitors where it is needed. I saw on YouTube that the designed worked properly without the need for the resistors modification. But, if the new one I am building had the same problem then I will go ahead and try that modification.

https://youtu.be/Iyx3jNiS84I

By alali.ahmed.t

Expert (105)

alali.ahmed.t's picture

22-11-2022, 21:38

I finished building the new last night, but I got very light smoke around the amplifier IC8 heheheh not good thing. but the cartridge ran and detected. But no sound. I think the amplifier was fried, it is super hot all the time as soon as the machine turns on. I will troubleshoot it tonight. I hope it is just a bad amplifier not something more!

By alali.ahmed.t

Expert (105)

alali.ahmed.t's picture

25-11-2022, 04:35

I have an update:

The wozblaster runs OPL 1, 2, and 3 without any issues but with extreme noise on OPL4. Did extra troubleshooting and ran moontest app by RBSC and the test showed no SRAM installed even thought I have them installed. I am assuming at this moment that the SRAMs are bad!

I would like to thank RBSC team for the moontest app that helped me in troubleshooting.

If anyone knows if having bad SRAM would cause this issue, please let me know.

What are the SRAMs that could give me upto to 2MB? I had KM684000ALG and I am assuming 2 of these would give 1MB unless I am wrong!

By sdsnatcher73

Prophet (3660)

sdsnatcher73's picture

25-11-2022, 05:49

2x 4Mb is 8Mb (Mega bit), which is indeed 1MB (Mega Byte).

Even without SRAM, OPL4 should be able to use wave date from YRM801 chip.

By meits

Scribe (6527)

meits's picture

25-11-2022, 09:39

Iirc last time I checked that tool was not compatible with all OPL4 cartridges. Please confirm with the authors.
I had a situation once where there was only FM. Wave was mute. Turned out the YMF278B was dead.
Might be a silly question, but did you check your soldering on this chip?

By alali.ahmed.t

Expert (105)

alali.ahmed.t's picture

28-11-2022, 18:08

I checked the soldering on the chip, looks good. I will troubleshoot it more this week when I get the time. I might be having a problem from 27C160 rom and burning that I did.

I ran the OPL4 and I could hear the music very well but with a lot of noise. OPL1, 2, and 3 works without any problem.