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Getting Pokey sound (Ballblazer) after UAV mod in console with prior composite mod


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I bought a composite modded 7800 on eBay years and years before I ever touched a soldering iron.  I went back to install the UAV kit from brewingacademy.com on it yesterday, following the PDF and the YouTube video in the guide.  I deviated a bit from the video as my 7800 already had some destructive changes made when the eBay seller modified it -- they removed the RF port by breaking it off the RF modulator (but left it in for some reason, I completely removed it), and removed R3, R5, and C10. 


The console before I installed UAV could play sound from Pokey (original Ballblazer cart).  Now after installing UAV I'm not getting this sound.  I did not have the exact 6.8k resistor to replace R5, but combined two that add up to 6.9k (tested w/ meter) and soldered them to the bottom hole of R5, then lifted R6 and connected them to the positive side of a 10uF capacitor as was done in the YouTube video and PDF guides (see attached image, sorry it's a little blurry).


Any idea where I messed up -- do I need to replace R3 and/or C10? 


Edit to add: Everything else works with the mod.  Composite and Svideo, and sound from non-Pokey games.


Edited by rayrayrayraydog
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C10 is why you aren't getting pokey audio. The audio line from the cart ports goes to C10 before moving back down to R5. The capacitor isn't that critical since you added the 10µf cap off the resistors. So you could just jumper that with a cut lead or wire.


Also, I've made UAV installs much easier for me now since I did those videos and made the PDF guide.







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14 hours ago, rayrayrayraydog said:

Wow, that looks great!  I wish the extra mounting bits were part of the kit that I bought.  I have a bunch of those stick-on heatsinks as well -- do you think they are really helping?


To be sure, you are saying that I can just take some wire and bridge the pads in C10 and I should be good?

Yes you can just bodge a wire in place of C10 to restore the external audio back into the circuit and you should be good at that point. Although instead of using 2 resistors to create 6.9 I would have just gone with any value around 6.2k and been good there. Even at 6.8k the Pokey will still frequently be a little quieter by a dB or two as compared to the TIA.


One of those mount boards is actually in the hands of the Brewing academy to see if they are interested in getting more made to be included as part of a new 7800 UAV kit. It would cost more of course but I think the savings in time, the fact it has the audio already being handled, and has the chroma fix in place makes the extra costs work it. It can also be done with the RF in place or not as I designed the board to fit in there since it is only a smidgen larger than the UAV itself. 


The heatsinks I installed a few years ago because I started to get quite a few instances of TIAs seeming to go bad and I figured heat was a large part of the reason for it. As several of the chips on the 7800 are custom like the TIA, I wanted to try and help them live on longer as much as possible. One side effect of the heatsinks is that I don't see as much color drift on the game hues as would otherwise be seen. It is still there but not as drastic of a change as before. So the heatsinks can't hurt. I also stuck with low profile ones as I still reattach the RF shielding on my 7800 and they all fit under it. 

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23 hours ago, rayrayrayraydog said:

Thank you for explaining!  I will rework those resistors and fix C10.  I didn't realize there was a chroma fix board and just watched the install video on YouTube.  I was noticing that the text in games (especially scores at top of Pole Position 2) is a little fuzzy.  How can I get my hands on one of those boards?

Shoot me a PM. I've got just a few of the larger through hole version like in the video available and quite a few of my rev2 SMD version that is about 1/4 the size. The SMD version seems to provide better results but it is a slightly more difficult install given the smaller size. I also sent a handful of the through hole versions like you saw in the video to The Brewing Academy to see if they want to offer those separately to those that already have UAVs installed or want to install UAVs and perhaps not pay the extra for the mount PCB solution. Honestly the chroma fix should be a required part of the kit for the 7800 installs.


In fact, I'm sure it would be possible to add an SMD 4050 to the UAV that could be jumped for use with 5200 installs and allow the original 4050 to be removed and a separate 4050 built into the UAV to keep the RF working. That would make the 5200 installation more universal between the consoles, but also be jumped to allow for the chroma fix on the 7800. The chroma fix only effects 7800 games BTW...so do keep that in mind.


Edited by -^CrossBow^-
Cleaned up my sentence structure a bit at the end LOL!
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