in advance, my apologies for being a noob on this, but one has to start somewhere.

Ok, I've recently been thinking of selling my 8250, but thinking things over I decided I won't, and instead finally get the friggin' sound right, but I want to do it myself; I feel I should be able to ....I DID switch the keyboards from 2 8235's at one time, so that means I'm not TOTALLY crap on things like this, right? ....RIGHT?
anyway, it's the old well known SCC/PSG balance problem. And I just want to be able to fix something like that myself; I suppose it's fairly simple.
Anyway, I've read a few docs on Hans Otten's site, and in case of the 8250 there seem to be 2 ways to fix it. One's involving replacing some resistors. Well, I guess that's the bad way for me to start; the other one is cutting the cable connecting pin49 and put a "potmeter" between that. That sounds like something even I would be capable of.

I already have a partial fix; an f1 spirit with switch and a 10k potmeter. Repair-Bas made that for me and it works nicely, only thing is of course it only works when I use that specific cart. I'd like to be able to pop in any SCC/FMPAC and have the volume balance right, and I'd rather not have every single one of them modified. I'd rather keep them in original condition
So, having seen a potmeter being placed in a different (broken 8250) before I think I have quite an idea of what to do.
I just want to verify that I'm correct, as I really wouldn't like to waste an MSX like that on such a simple thing.

This is what I gather I have to do:

- cut the correct cable. If I'm not mistaken that's the one completely on the left of the cartridge slot connector (inside the 8250). Is this right?

- put in the potmeter...only, how? those things have more than one connector...+ - , - + or something? What's the right way?

- solder the stuff together (sounds easy)

That should fix things. However, it would be ideal to be able to change the balance on the fly. Now these potmeters are like volume knobs. Guess I'd have to cut a little hole in the MSX'es case to make it look (and work) like that. What would be the best way to do that?

Thanks

Samor

I solve this problem with scc games just pluggin the game on a slot expansor (that brazilian one wich has 4 slots). Doing that, unexpectedly, all sound works ok, so I didn't needed to make any internal modification inside the computer.

How can it happen? I don't know... I'm really rookie on msx hardware/software stuff.

Does anybody knows the answer??

The disadvantage of a volume-knob is its tweakability ^_^ .. the sound should be presented the way it 'is' .. or the way it was at least 'meant to be'. Who tells you that the knob's value is the 'right' value?

@wolf: I'm pretty sure every single MSX will have a slightly different 'mixing balance' when it comes to internal/external sound tho... Heck, I doubt even the different types of FM-PACs output the exact same volume...

Indeed, I have 2 Turbo-R (ST and GT) with MSX-MUSIC inside ; there's a little difference in the sound (it's better on GT, because the FM chip is better isolated from the rest)

Besides, if I use a Dutch FM-PAK on my Philips NMS 8280, it's more different, especially for the treble sounds.

It explains also how it it difficult to emulate MSX-MUSIC and satisfy at the same time everyone (but of course, some improvements are still required on most emulators)

Well, in case of the ST it was idd more of a design-flaw than anything else... Even then, in the end the actual ratio prolly still differs from case to case. I'd rather have it tuned to my taste than to the taste of the original hardware manufacturer tho...

@Samor: a pot on line 49 of the slot would prolly do the trick idd. This only works if the external sound output is too loud tho... if it's the PSG that's too loud, it won't work...

by the way... I have an 8280 and now I wonder: without pointing out to the SCC problem, the PSG is slightly louder compared to other computers??? (how strange if it is so, and with ths SCC is quieter...)

Quote:

The disadvantage of a volume-knob is its tweakability ^_^ .. the sound should be presented the way it 'is' .. or the way it was at least 'meant to be'. Who tells you that the knob's value is the 'right' value?

well, if I leave it like it is now the psg is hardly heard with the scc put in; I guess that was not how it was meant to be; the balance like how it is in a 8235...is that how it's meant to be? And even most MSX emulators don't have it alike either. Aside from that it's already a highly tweaked MSX2 (2+ functionality, turbo switch, in a nutshell all kinds of things that weren't meant to be (probably the most odd part is it being a "PAL MSX2+"). So, I guess a balance knob would be fitting in an msx like that

Now I just need to have two few things verified:

- I have to cut the correct cable. If I'm not mistaken that's the one completely on the left of the cartridge slot connector (inside the 8250). Is this right? I don't want to cut the wrong one

- I have to put in the potmeter...only, how? those things have more than one connector...+ - , - + or something? What's the right way?

thx

you have to cut pin 49 of the cartridge-cable.

and a variable resistor has only 3 pins
take a 10K and use 3 pins

1 2

3

use 1 and 3 or 2 and 3

Quote:

you have to cut pin 49 of the cartridge-cable.

ok, I'm just not entirely sure if that's the one completely at the left or the "one on the left - 1" , if you know what I mean. (are there 50 wires?)

aren't they numbered? it should be in a corner tho, prolly the 'upper right' one, seen from the bottom-print that is... Could be those dutch engineers came up with something whacky instead tho

mostly pin 1 is another colour.
There are 50 wires

sorry, but its still a little confusing...

if I have to place something on pin 49, when there are 50 wires, I guess I dont need the one completely at the left (or right, depending on the perspective), but the one just besides it. Is that right?

If you're gonna grab it at a PIN you would idd be in a corner, since most (all?) slot connectors separate even and odd pins. If you're gonna grab it at a flatcable it would probably be the one next to the last one idd... Just 'intercept' it and put the pot between it. You're not gonna fry anything by putting a 10k resistor over it... Like Bas said, check to see if wire 1 is colored, it should be... There should be some indication as to which line is which... Check the technical databook if you want to be 100% sure.... If not just take a pick and see what happens

ok, I think I know enough to give it a shot now

thx ppl