Suddenly no tone, just clicks. Please Help !

[snazz]

with the resistor in place
and no buttons pressed

I've got 5.5v on pin8

[guest]

it should be at 5v
with a few volts of oscillating signal on it

[snazz]

it's 5v all right...but it's only got .110v of modulation on it...

[Brassteacher]

it's 5v all right...but it's only got .110v of modulation on it...

snazz, try this, but TURN.THE.VOLUME.DOWN.FIRST.

Run a jumper from the top of R122 to the empty hole for pin 8 of IC15A. See pic:

x0x VCA bypass.jpg (495.26 KiB) Viewed 1773 times

This will take the signal right off the filter and feed it directly (well, through a cap anyway, which is a good thing in this case) into the volume pot, completely bypassing IC15. Power it up and slowly turn the volume up. If you are finally getting sound, IC15 is bad, no doubt.

[snazz]

with or without the 220k resistor jumping pins 9 and 4 ?

[Brassteacher]

with or without the 220k resistor jumping pins 9 and 4 ?

Without. This goes completely around all that.

[snazz]

ok,
I made that jump,
and in my headphones I could definitely hear the osc thru the res, cutoff and so on...louder than it has been thru this troubleshooting for sure..., kinda crunchy, not high fidelity, but I heard it !

[Brassteacher]

ok,
I made that jump,
and in my headphones I could definitely hear the osc thru the res, cutoff and so on...louder than it has been thru this troubleshooting for sure..., kinda crunchy, not high fidelity, but I heard it !

I don't suppose you have another BA6110 lying around to plug in do you? The crunchiness should go away with having a better connection, and by not having a damaged chip on the board still.

[snazz]

nope, if the chip is shot, I don't have one...
if I need a new chip, I'm gonna have to ask if anyone out there in your community has one ?
it's going to be a bummer to replace...

if that is what needs to happen...

[Altitude]

nope, if the chip is shot, I don't have one...
if I need a new chip, I'm gonna have to ask if anyone out there in your community has one ?
it's going to be a bummer to replace...

if that is what needs to happen...

I have spares.

[snazz]

I have spares.

really ? cool.
well if everyone is in agreement that the ba6110 chip is bad then I'd like to find out how to get one sent out so I can replace it...
it looks slightly daunting to remove the old one, but I'm sure you folks know the easiest way to go about doing that.....

[Altitude]

rock it back and forth till it breaks off and desolder the pins one at a time.

[snazz]

that doesn't sound too bad...
I knew you'd have an easier way to do it...

after replacing this...( hopefully that fixes it )
I'd like to know how to do 2 things...
both things are probably already well written about here in this forum somewhere..
1. is it possible to somehow slightly decrease the attack to smooth it out a bit..when it was working I could still kinda hear this "click" fire before the sound of the osc got dominance..
2. I've heard a rumor that there is a bass boost mod


3. any mods you all think are worth looking at, I'll read...

THANKS!

[Altitude]

Ah yes, the dreaded click.

Some reading: viewtopic.php?f=13&t=16764

To sum up: There are 3 sources of this, one is the DC offset thump which can be fixed with the mod in my post, the second is a click from the env triggering on a non-zero crossing point of the free running of VCO (nothing can be done about this), and the other is still a mystery but there is a suitable fix. Look at later pages of the thread, I added a filter cap and a diode to the VCA section which pretty much eliminates it.

Bass boost mod is not really anything to right home about, it works better with some other mods, but just having it on it's own is not worth it IMHO

On a side note, it was brought to my attention the the BCbox fix for the DC offset is actually on the SH-101 which also has a BA662A. It is not on the schematic and the parts are not stuffed, but there is a trimpot marked VCA offset on the board and wired up identically. It looks like the opted to sort BA662s (note the dot) instead of using this fix

[guest]

you might want to socket the ic
just in case you need to do more debugging