Help assembling a FM Blaster

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By thezorry

Resident (63)

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01-02-2021, 07:47

Hi!

I recently purchased a FM Blaster DIY kit from repro factory. I’m having problems getting it 100% working. I’m getting some distorted sounds and I ran moontest to ensure the memory is properly working, getting this result:

I’ve checked my soldering again and again and I’m stuck atm, any guesses on where can be the problem? I's funny that both banks fails the same addresses, so I guess the problem should be some address line not properly soldered (but I rechecked them a lot of times).

Thanks for your help!

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By Meits

Scribe (6456)

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01-02-2021, 11:40

can you check what exactly is wrong with the sound?

  • Internal WAVE
  • External samples
  • FM

I've had a moonsound go dead on just the WAVE/samples part.
Where is that RAM tester, so I can check it on my FM-Blaster? I know it doesn't work quite well with every moonsound clone.

By Pencioner

Scribe (1476)

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01-02-2021, 11:48

Meits wrote:

can you check what exactly is wrong with the sound?

  • Internal WAVE
  • External samples
  • FM

I've had a moonsound go dead on just the WAVE/samples part.
Where is that RAM tester, so I can check it on my FM-Blaster? I know it doesn't work quite well with every moonsound clone.

Get it here: http://msx.in.ua/z/moontest.com
When you run it, disable any Turbo modes (on turboR or 5.6/7MHz computers) because the waiting times i think is not fixed yet to fit turbos

I didn't hear about any compatibility issues iirc, please provide more info if you experience that :)

By Meits

Scribe (6456)

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01-02-2021, 15:15

Pencioner wrote:

I didn't hear about any compatibility issues iirc, please provide more info if you experience that Smile

My personal memory probably went bad.
I'll check the tool on several opl4 cartridges.

Edit: I remember. It had some issues in the beginning :)

By ericb59

Paragon (1047)

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01-02-2021, 13:58

Can you post pictures of both sides of the card you assembled ?

By thezorry

Resident (63)

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01-02-2021, 15:45

ericb59 wrote:

Can you post pictures of both sides of the card you assembled ?

There you go... With pictures I can see some dirty in the OPL4 soldering, is it possible this could be the problem? I've already cleaned with isopopyl alcohol.

Thanks for your help.

By Alexey

Guardian (3235)

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01-02-2021, 18:48

I can clearly see quite a few bad soldering points (especially on SMD elements). Those need to be fixed. Most likely the reason is low temperature or lack of flux. Also it seems that you soldered the left RAM chip after you soldered the EPROM. The joints do not look very secure. I would recommend you to resolder all suspiciously looking elements and then clean the board with 96% spirit (use an old toothbrush) and wipe it with a soft cloth.

It could be a busted RAM chip. I had this problem when I built my own cartridge. I had to replace the RAM chips twice to make it work.

Also did you use the fixed firmware for GAL16V8D? The original firmware has some issues and the chip could be overheating.

By ericb59

Paragon (1047)

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01-02-2021, 17:24

@Alexey : the gal’s program is fixed yes.

引用:

With pictures I can see some dirty in the OPL4 soldering, is it possible this could be the problem?

Sure it can do multiple problems

By thezorry

Resident (63)

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01-02-2021, 23:15

I’ve resoldered all the smd components and throughly cleaned and wiped. now it looks way better... but I’m getting the same result Sad even I’ve tried in my other msx to discard any incompatibility. maybe I’ve damaged something in the process?

@alexey don’t you think it’s strange both banks giving the same result? I doesn’t look an error from a ram chip, I guess if this was the case the error should be shown only in one bank don’t you think?

I’m very tired right now. Tomorrow I will send you pictures again.

By Alexey

Guardian (3235)

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02-02-2021, 02:49

Both RAM chips are connected to the same address and data bus lines, so if there's a problem on one of the lines, both chips will show the same result. Check your soldering of the Yamaha's chip with a microscope, especially the pins connected to MD0-MD7. Some of the pins of the YMF chip don't look well-soldered, especially the pins connected to large ground planes.

Then check how well both RAM chips are soldered and fix all suspicious joints. If you used conductive flux, make sure that none of it is left between the pins of the YMF and RAM chips.

By thezorry

Resident (63)

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03-02-2021, 21:42

This is the result for the rework. Maybe my soldering is not very good looking but I think it's tidier and functional.

In the resolder operation I broke two tantalum capacitors, and my local electronics store doesn't have the SMD capacitors of this size, so I used two spare electrolytic capacitors around.

The memory test outcome is the same as before, I'm pretty sure of one of the memory IC is screwed. Now which one? Also it's difficult to find out replacements, at least cheap ones (the IC's they sell in aliexpress are the cheapest but I'm not sure they will be reliable and the delivery time is too long).

But things are way better after the rework. I'm getting stereo sound (left channel didn't work before) and I think that all the moonsound themes without samples sound perfect! In the 100% sound demo, there are some songs perfect, on others themes like the intro I can hear some strange background clicks and hisses, I guess these artifacts are caused by the memory error.

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