74HC04 vs SN7404n notice about opl2lpt-replica HOT 4 OPEN

the extra 470 ohm resister can be used parallelly on the outer two pin of volume control, make volume adjust more smooth.

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I had same issue, that me get almost crazy, but resolution is pretty quite simple :)
Only what you need is change oscilator circuit from this:

, to this:

After that, you get perfectly stable frequency +/-1Hz.

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Interesting i had a batch of SN7404n (ordered 5) ..4x worked with 470R.

..but 1x pcb needed both 470 replaced with a 4.7k.

I suspect anything above 1k will work more consistently.

Note (new builders):

• if building the circuit the first time - becareful and pay attention to the dots and chip orientation (as labels written on the pcb arent necessarily orientated the correct way)

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These values must still be just downright incorrect. This card doesn't work right at all using all original mouser parts linked in the BOM. 1K resistors paired with a 100pf cap generate a TON of random noise and loud glitches and the FM music gets all corrupted at all times. When changing resistors to a higher value, the issue is fixed and I think this card works best with 4.7k resistors. What are these resistors even supposed to achieve and what is the configuration of the original Adlib card?

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